Those who have been following the carbohydrate quality debate will enjoy a recent feisty review by Professor Tom Wolever from the University of Toronto published in the European Journal of Clinical Nutrition. Wolever is the co-inventor of the glycaemic index concept and is obviously a little peeved that other measures of carbohydrate quality such as wholegrain have gained acceptance in dietary guidelines whereas GI has not.

Wholegrains versus GI

Here is how Wolever weighs up the relative merits of wholegrains and GI as measures of carbohydrate quality (minimally edited).

The evidence for the health benefits of wholegrains comes from epidemiological studies showing strong associations between high intake of wholegrains and reduced risk for cardiovascular disease, diabetes and obesity. Recent large clinical trials in subjects without diabetes showed that increased wholegrain consumption reduced systolic blood pressure, but none showed any significant effect of wholegrains on blood glucose, insulin sensitivity and/or insulin secretion, inflammatory markers or body weight (Tighe 2010, Brownlee 2010, Kristensen 2012). One study found that wholegrains reduced LDL-cholesterol, but another found the opposite.

On the other hand, trials of low-GI diets of similar magnitude in subjects without diabetes showed significant beneficial effects of a low-GI diet on blood lipids,(Jebb 2010, McMillan-Price 2006) inflammatory markers (Gogebakan 2011) body weight (Larsen 2010) and possibly insulin sensitivity. When the results of the four low-GI studies are combined, there is a significant reduction in LDL-cholesterol and C-reactive protein and a strong trend towards weight reduction.

Low-GI diets have at least as many, if not more, statistically significant effects than wholegrain-enriched diets; this does not support the hypothesis that wholegrain is a better marker of carbohydrate quality than GI.

I confess I have struggled to understand how wholegrains could lower risk for diabetes and coronary heart disease for the reasons that Wolever summarises. A small effect on systolic blood pressure really isn’t good enough. There is always the possibility that wholegrains may be operating via a yet-to-be-discovered mechanism, but this appears unlikely. Wholegrains have no effect on the inflammatory marker CRP suggesting no effect on underlying disease processes.

So how can one explain nutritionists’ recent embrace of wholegrains as a measure of carbohydrate quality? Perhaps the decision makers like the message – simple and easy to understand. But then again, if the message has shortcomings should we be broadcasting it? ‘Eat less fat’ was a simplification of ‘eat less saturated fat’ and look where that took us.

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Alternatively, perhaps there is a philosophical dimension to it. Nutritionists like the idea of wholegrains because it fits nicely with our philosophy about nutritional health being a natural consequence of eating simple, whole foods. But we are not philosophers; nutritionists are meant to be scientists and to make recommendations based on the facts.

The facts about GI?

The experts are yet to agree on what the facts relating to GI actually are. If you want to understand the GI debate and the case for and against, Wolever’s review is for you. He lists the criticisms of GI made by its detractors, such as imprecise measurement, lack of reproducibility, inaccurate tables and the notion that GI does not apply to mixed meals. He then addresses the issues one by one and challenges his critics to prove him wrong.

And the politics

As you may have guessed, there is a little politics involved here. In North America several influential nutritionists took a stand against GI early on and have defended their position ever since. They now concede that glycaemic ‘response’ is relevant to health but have reservations about the relevance of the GIs of individual foods. Wolever won’t have an easy task convincing them. Sometimes the acceptance of new approaches in science proceeds slowly, funeral by funeral.

In Europe leading nutritionists have been more accepting of the GI concept, especially following the results of the Diogenes study, which showed beneficial effects on weight management. The European Union is now funding a large new trial, with an Australian arm, into whether a high protein, low GI diet is superior to a conventional healthy diet for the prevention of type 2 diabetes.

It is noteworthy that Wolever doesn’t see GI as an alternative to wholegrains but as a complement to it. They are both measures of carbohydrate quality. I would add the caveat that some wholegrain foods and some low GI foods are nutrient-poor, again highlighting that carbohydrate quality is a complex, multi-faceted concept.

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Although advice to eat less saturated fat has been a fixture in Dietary Guidelines for three decades, the last four years have seen a spirited debate about what should take its place in healthy diets. As saturated fat is a macronutrient, one can’t just ‘eat less saturated fat’ and maintain energy balance. Saturated fat needs to be replaced by something else, such as carbohydrate or unsaturated fats. Carbohydrate is now considered a poor replacement for saturated fat as these two macronutrients confer the same risk for heart disease. This leaves mono- and polyunsaturated fats as the better options to replace saturated fat, but which of these should be preferred?

Until recently, the evidence for polyunsaturates was stronger than that for monounsaturates. Both classes of unsaturated fats have beneficial effects on blood lipids and both appear to be protective against heart disease in observational studies. But the big difference in the evidence bases was that there have been many trials involving the replacement of saturated fat with polyunsaturated fat for the primary prevention of cardiovascular disease and the better trials have recently been subject to meta-analysis, providing a rare degree of confidence in this dietary recommendation.

In contrast, there had not been a single primary prevention trial of mono-rich diets, until now.

The PREDIMED Study

February this year saw the publication of the results of the PREDIMED Study, a randomised controlled trial for the primary prevention of cardiovascular disease using Mediterranean diets. This multi-centre trial conducted in Spain assigned subjects who were at high risk of cardiovascular disease to one of three diets – a control diet low in fat, or one of two Mediterranean diets enriched with either extra virgin olive oil or nuts. Energy intake was not restricted and exercise was not advocated.

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After 4.8 years, both Mediterranean diets significantly lowered the rate of the primary end point (myocardial infarction, stroke and death from cardiovascular causes) by about 30 per cent relative to the low fat control diet. In those following the Mediterranean diets, favourable trends were seen for both myocardial infarction and stroke. No adverse diet-related effects were reported.

These exciting findings stand in contrast to those of the Women’s Health Initiative, a huge US randomised controlled trial for the primary prevention of cardiovascular disease using a low fat diet which showed no benefit whatsoever. Thus PREDIMED provides a strong endorsement of the Mediterranean diet as the basis for healthy diets for the prevention of cardiovascular disease. The Mediterranean diets were also associated with lower risk for diabetes (see my earlier post).

Monos or polys?

In relation to the polys or monos question, the olive oil arm of PREDIMED was richer in monounsaturates than the nuts arm, which included poly-rich walnuts. The key point is that both diets were protective and equally so. Based on these findings it would appear that there is little to be gained from choosing polys over monos or vice versa – both appear to be good substitutes for saturated fat (and carbohydrate for that matter). Let’s confine the monos versus polys argument to history.

In considering the results of PREDIMED it’s important to bear in mind that this is a whole-diet study and that it is difficult to attribute the benefit to just one aspect of the diet. The foods consumed as part of the Mediterranean diets differed from the control diet in several ways – legume and fish intake, as well as nuts and olive oil intake, were higher in the Mediterranean diets. So it’s a package deal – the benefit is associated with the whole diet.

The challenge for nutritionists

A generation of nutritionists (including me) was educated to think that a healthy diet is a low fat diet and the results of PREDIMED, and the Women’s Health Initiative before it, provide further evidence that this is not the case. The PREDIMED investigators provided high fat foods to their subjects to provide benefit. A litre of olive oil per week was given to those in the olive oil arm of the study, an amount that may cause many dietitians to draw breath. And 210g per week of nuts were provided to those in the nuts arm.

The interventions were designed to enrich diets with foods high in unsaturated fats. How many of us think this way when we educate people about healthy eating?

There are only a few opportunities to build unsaturated fats into people’s diets – vegetable oils, unsaturated spreads, salad dressings, mayonnaise, nuts, seeds and avocado come to mind. Yet much of our ‘healthy eating’ advice in recent years has actively discouraged use of some of these foods: ‘avoid fried foods; use just a scrape of margarine on bread; and choose low-fat salad dressing and mayonnaise’. All of this advice has had the effect of withdrawing protective unsaturated fats from the diet. If body weight management is required the targets for energy reduction should be saturated fat and poor quality carbohydrates, not unsaturated fats. You know, baby, bathwater, etc.

But the low fat dogma runs deep. A challenge for nutritionists is to finally shake it off, relax about percent energy from total fat and undo some of the damage we have done over 30 years with poor advice to the general public about the role of unsaturated fats in healthy diets. The public will love us for it – Mediterranean diets actually taste good.

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In the 1980s, human rights lawyer Geoffrey Robertson became a media personality hosting a television series dealing with ‘Hypotheticals’. He would outline a hypothetical situation and then invite prominent citizens to play imagined roles of the key players addressing various aspects of the situation, thereby exposing the various interests at play.

Let’s play ‘Hypotheticals’. I’ll be the moderator. You can play the role of the food company Chief Executive, Public Relations Guru or Ethicist.

Moderator: Imagine you are a chief executive of a food company, with a big problem: your industry’s product is rich in saturated fat. Credible nutrition organisations worldwide recommend that people eat less saturated fat and choose unsaturated fat instead, which is really bad for business. What would you do?

Chief Executive: I’d put it on the agenda of the next meeting of my contemporaries representing the industry in all major markets around the world. I’d argue that it’s imperative that we undertake a long-term, global project to confront this issue once and for all.

Moderator: Hmmm, taking on credible health organisations – you’re a brave woman. How would you go about such a project?

Chief Executive: We would bring in our public relations company – it’s a global firm operating in all our key markets. Their ‘issues management’ team is first class.

Moderator: Would a public relations firm appreciate a challenge like this?

PR Guru: Oh yes. We dream about a brief like this – a global industry, with a major issue that is going to take 10-20 years to address. We’ll make millions.

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Moderator: What strategy would you recommend? How could you confront the nutrition and health establishment?

PR Executive: We wouldn’t confront the nutrition establishment head on. Our strategy would be to by-pass them, taking our message directly to the general public, changing how consumers perceive a healthy diet. We call this process ‘perceptions management’ – we use it all the time. There would be several stages, each one shifting consumers’ perceptions in the ‘right’ direction.

Moderator: Would you enlist credible nutrition scientists to carry the message?

PR Guru: Good heavens no. No matter how well we train them up, nutrition scientists just can’t stay on message. There would always be the chance that they would blurt out something inappropriate about saturated fat being harmful. We need complete control of the message and that means complete control of the messenger.

We’ll start the ball rolling with a trusted health journalist. We’ll place a story in a serious newspaper, maybe the New York Times, aimed at shifting consumers’ focus away from their current concern about fat. This is a safe place to start as leading experts now say the low fat diet was a mistake anyway. But we don’t want the public to revert to ‘moderation’; the objective must be to replace concern about fat with concern about carbohydrates.

In Stage 2 we’ll ramp up the anti-carbohydrate message with a series of books whipping up public hysteria about sugar. We’ll tell them that it’s poison, worse than alcohol, and that it’s addictive, like cocaine. And that it’s making everybody fat. We’ll position sugar as a killer! We’ll get credible people to carry the message, like doctors, lawyers and economists.

Chief Executive: Ha! Anyone but a nutritionist!

PR Guru: The more we can ramp up the hype about sugar the less people will think about saturated fat. During this phase we will subtlety infer that it’s not saturated fat that increases heart disease risk; it’s sugar!

Stage 3 brings home the bacon. Amid the confusion we will turn conventional nutrition advice on its head. We’ll tell the general public that all these credible scientific types have got it wrong – saturated fat is actually really good for you. And we’ll tell them that the polyunsaturated fat these so-called experts all advocate is actually deadly – it gives people heart disease and cancer, and why not, it sends you blind! We’ll target seed oils. The new healthy diet mantra chanted across social media will be ‘No sugar! No seed oils!’

Chief Executive: Which is actually code for ‘eat fat, especially saturated fat!’ Brilliant! You’re hired!

Moderator: Have you considered the moral dimension of such a project?

PR Guru: Don’t be daft.

Chief Executive: Umm, sorry, could you repeat the question?

Ethicist: Although all companies have a responsibility to their shareholders, they also have social responsibilities and in this case that includes public health responsibilities. The proposed project … [I’ll let you fill in this bit].

Of course, this is all purely hypothetical. Nothing like this ever happens in real life.

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Discriminating between carbohydrate-rich foods

To illustrate the argument I used the model for discriminating between carbohydrate-rich foods developed by Professor Manny Noakes and myself. For more information on this model please refer to my previous post or the published paper.

In brief, the model is based on nutrient density and glycaemic index (GI). Nutrient density was chosen as it reflects the fundamental nutritional role of foods – the delivery of essential nutrients. And GI was chosen because it relates to the physiological effect of the carbohydrate itself. When carbohydrate-rich foods are run through the model they end up in one of four carbohydrate quality quadrants.

Dairy products – sweetened and unsweetened

Here is what happens when milks and yoghurts are run through the model.

All these products fall into the highest quality quadrant i.e. they are all nutrient dense foods and they all have low GIs. In Dr Alan Barclay’s presentation at ILSI he stated that nutrition dilution (not disease prevention) was the major nutritional negative associated with high sugar consumption and the model demonstrates this effect. Note the positions of reduced-fat milk and flavoured milk, which is essentially reduced-fat milk plus sugar. The flavoured milk is displaced to the left indicating that it has lower nutrient density – fewer nutrients for the same calories. This is the nutrient dilution effect of sugar. The same effect is apparent with natural low-fat yoghurt and sweetened low-fat yoghurt. So sugar is bad, right?

The other thing to note is that the sweetened dairy foods still fall in the highest quality quadrant – they are all nutrient-rich and all have low GIs, irrespective of their sugar content. Why then would nutritionists divide these foods into good and bad on the basis of their sugar content? Aren’t they all good? Including chocolate milk in a child’s diet does not have a nutrient diluting effect. It’s a nutrient-rich food – it has the opposite effect. A recent study showed that Australian children who drink plain or flavoured milk have higher micronutrient intakes but similar body mass index to those who do not drink milk. How can one argue that chocolate milk is an undesirable food?

Grain foods – sweetened and unsweetened

Here are the results when some refined cereal foods and breakfast cereals are run through the model.

Firstly, note that white rice, polenta, couscous, semolina and white pasta tend to cluster in the lowest quality quadrant – nutrient density is very low and GI varies from moderate to very high. Until recently these cereals were referred to as ‘core’ foods and their consumption was encouraged. I wonder why – look at white rice sitting deep in the lowest quality quadrant. Just because a food is a traditional food doesn’t necessarily mean it’s a healthy food. Although these grain foods contain no sugar their nutrient densities are so low that their inclusion in the diet has a nutrient dilution effect.

Compared to the unsweetened ‘core’ grain foods the nutrient densities of the breakfast cereals are consistently high, driven by their fortification. Some of these breakfast cereals have added sugar but in this context there is no nutrient dilution effect of sugar at all. In fact, including any of the breakfast cereals in a diet at the expense of any of the unsweetened ‘core’ cereals would enrich a diet with nutrients. Relying on the old starch-good/sugar-bad paradigm can produce perverse outcomes.

Sugar, energy density and GI

I recently surveyed Australian breakfast cereals to investigate whether their sugar content was associated with energy density or GI. Please take a look at the findings, which are now published. They show that sugar content of breakfast cereals has absolutely no association with either energy density or GI.

Think about this: In the context of breakfast cereals, sugar content has no association with nutrient density, energy density or GI. In other words, the sugar content is not related to any nutritional or physiological parameter that might actually affect health. This is why sugar content is a very poor measure of the nutritional quality of a carbohydrate-rich food.

What’s needed?

Currently, health authorities are considering front-of-pack labelling systems to guide consumer choice. Using sugar, or added sugar, as a criterion for such a system would be a mistake. It would inevitably mislead. In developing front-of-pack food labelling and in nutrition education more generally two things are needed:

1. Meaningful measures of nutritional quality. If nutrient dilution is the concern with sugar, then why not make nutrient density a criterion?

2. Criteria that can be applied universally. If a criterion can’t be applied universally, then it is obviously flawed. If sugar is to be a criterion, it has to be applied to fruits. There is no place for subjectivity.

Nutrient density and GI are meaningful measures that can be applied to all carbohydrate-rich foods, which is why we used them in our model.

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Recommended carbohydrate intakes

A couple of speakers discussed the recommended range for carbohydrate intakes, which is 45-65% of daily calories in both Australia and the United States. In the United States, the major factor that determined the upper boundary of intake was adverse effects of carbohydrate on levels of triglycerides and HDL-cholesterol in the blood. At the lower end of the scale it was argued that fibre requirements are unlikely to be met at intakes of carbohydrate below 45% of energy (in the low fibre US context). It’s interesting that dietary fibre is considered as a carbohydrate-amount issue in the United States. To my mind it is very much a carbohydrate quality issue.

Mean adult intake of carbohydrate in Australia is about 46% of daily calories, right at the lower end of recommended intake range. This was perceived as low by some speakers and a reason for focussing on glycaemic index as the preferred means of lowering the total glycaemic load of the Australian diet. Others saw the current intake as ‘moderate’, pointing out that the beneficial diets in the Diogenes study contained just 43% of calories from carbohydrate – below the lower boundary of recommended carbohydrate intake.

I introduced my talk by arguing that both the upper and lower boundaries of carbohydrate intake were too high. They were framed at a time when it was thought that a higher percentage of dietary energy from fat was detrimental to health. However, the preferred model for healthy eating is now one with more unsaturated fats and less of both saturated fat and carbohydrate – a Mediterranean-type diet.

No speaker advocated very low carbohydrate diets for the general population. Whether the adverse effect on blood vessel function of very low carbohydrate diets is due to low carbohydrate intake per se or due to the typically high saturated fat content of such diets is unclear and is being researched.

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The benefits of carbohydrate intake

Professor Manny Noakes and Dr Alan Barclay gave two excellent talks addressing the benefits and risks of carbohydrate intakes. Provision of micronutrients and dietary fibre were the obvious benefits of carbohydrate-rich foods. Dr Barclay summarised the findings of a recent review showing that a high dietary fibre intake is associated with lower risk for obesity, type 2 diabetes, cardiovascular disease and colorectal cancer at varying levels of evidence. As much dietary fibre comes from wholegrains it’s difficult to clearly attribute the benefit to one or the other. Professor Noakes mentioned ‘intriguing’ data suggesting that wholegrains may affect body composition but also that CSIRO studies were unable to find any effect of wholegrains on other risk markers or risk factors for coronary heart disease.

Dietary carbohydrate also lowers LDL-cholesterol in the blood when it replaces saturated fat, which should provide benefit. However, this exchange also raises serum triglycerides and lowers HDL-cholesterol so whether there is net benefit on blood lipid-related risk for heart disease is an interesting point for debate.

Professor Noakes acknowledged US data showing that those who successfully maintain weight loss tend to be on low carbohydrate diets. However, she said prescriptions for low carbohydrate diets often threw ‘the baby out with the bathwater’, a reference to recommendations to not only restrict intake of nutrient-poor carbohydrate foods such as soft drinks, confectionery, pastries, biscuits and pies but also to restrict nutrient-rich carbohydrate foods such as fruit, bread and breakfast cereals. The benefits of carbohydrate-rich foods in providing essential nutrients and fibre need to be balanced against any risks associated with carbohydrate intake.

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Risks: sugar or GI?

Discussions on the risks associated with carbohydrate intake revolved around sugar and glycaemic index/glycaemic load, reflecting the current international debate. Dr Barclay discussed the latest review on dietary sugars and body weight conducted for the World Health Organization (WHO) by a team from Otago University in Dunedin. They found that intake of free sugars or sugar-sweetened beverages is a determinant of body weight. Like the review for the Dietary Guidelines for Americans, this review found that the best evidence on sugars and body weight is from studies on sugar-sweetened drinks and perhaps the authors of the WHO review should have limited their findings to beverages. Importantly, their other key finding was that exchanging sugars for other carbohydrates was not associated with weight change. That is, sugar and starch have the same effect!

While you are considering the WHO review take a look at the editorial that accompanied it, written by Walter Willett and David Ludwig. Although generally supportive of the WHO review, these authors take a subtle shot at the WHO for previously disregarding evidence suggesting that starchy products have metabolic effects comparable to those of sugar. They state: Efforts to reduce sugar intake are appropriate, but they should form part of a broader effort to improve the quality of carbohydrates …

This is the nub of the current debate. Carbohydrate quality is not a simple concept that can be reduced down to ‘limit sugar’. It’s complicated and has several dimensions, including nutrient density, dietary fibre/wholegrains and glycaemic index.

Dr Barclay argued that glycaemic index was more important that sugar. He cited the Institute of Medicine’s report on sugar which recommends an upper limit on added sugar intake of 25% of daily calories. But he drew our attention to the rationale for this rather high upper limit, which is not the prevention of disease – it’s to limit nutrient dilution. In contrast, Dr Barclay argued, glycaemic index and glycaemic load are predictors of disease, including obesity, type 2 diabetes and coronary heart disease. His key message was to focus on the body’s response to carbohydrate foods, rather than on whether the carbohydrate was in the form of sugars or starch.

Take-home messages

• Very low carbohydrate diets are not recommended for the general public
• Moderate intakes of nutrient-rich carbohydrate foods are recommended
• Lower GI and high fibre/wholegrain foods are protective

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Gillespie says: … the amount of omega 6 oil we consume has exploded … our average polyunsaturated fat intake is currently … 11 per cent of our total calorie intake – more than double what it was in 1996.

This is just plain wrong. Intake of polyunsaturated fat in Australia has never been anywhere near as high as 11 percent of daily calories and rather than ‘exploding’ it has been declining for three decades.

The evidence on this issue is available to all in the two National Nutrition Surveys in 1983 and 1995, two CSIRO surveys and the 2007 Children’s Nutrition and Physical Activity Survey. The overall picture is one of a steady decline in polyunsaturated fat intake from 1983 until the present. Page 17 of the latest survey report shows children’s intake of polyunsaturated fats to be just 4 percent of total calorie intake across both genders and all age groups, about a third of that claimed by Mr Gillespie. Children’s intake of polyunsaturated fat is little different from the mean intake of men and women of 4.5 percent of daily calories observed in the last survey of adults in 1995.

Where did Mr Gillespie get his figures from?

Gillespie says: Just 200 years ago, barely any of these diseases [diabetes, dementia, obesity, cancer and heart disease] existed …These diseases have raced from obscurity to epidemic proportions during a period when our health authorities have told us to replace animal fats with seed oil.

What Mr Gillespie fails to mention is that 200 years ago life expectancy was about 40 years of age and there was little opportunity for these chronic diseases to develop. The dietary change that so concerns Mr Gillespie has been associated with a doubling of life expectancy to over 80 years of age, but of course this is due to many factors. As the human body doesn’t last forever, old age is associated with increased risk for chronic disease.

Gillespie says: Vegetable’ oil makes you exceedingly vulnerable to cancer. Every mouthful of vegetable oil you consume takes you one step closer to a deadly (and irreversible) outcome.

Mr Gillespie had to go back to a study published in 1969 in order to find support for this tired old argument. He cites the Los Angeles Veterans Trial which was intended to test whether replacing dietary saturated fat with polyunsaturated fat would lower the risk for heart disease. Mr Gillespie states that “… there was a dramatic difference in cancer deaths between the two…” which he attributes to an adverse effect of omega 6 fats from seed oils.

Actually, there was no statistically significant difference in cancer deaths between the intervention and control groups in this study. And when the results of five similar studies, including the Los Angeles Veterans Trial, were combined again there was no statistically significant increase in cancer risk associated with high omega 6 intake.

Mr Gillespie then goes on to quote the findings of a cohort study that found higher breast cancer risk associated with the consumption of polyunsaturated fats. But that’s just one study. There have been many cohort studies into dietary fat and breast cancer and a pooled analysis of seven of the best studies was conducted in the mid-1990s. And the results? There was no suggestion that polyunsaturated fat increased the risk for breast cancer.

No recognised cancer authority anywhere in the world recommends the restriction of polyunsaturated fat for the prevention of cancer, not the Cancer Council, not the World Cancer Research Fund, no-one.

Gillespie on saturated fat, polyunsaturated fat and heart disease risk

Although Mr Gillespie rails against omega 6 fats he appears to be rather partial to saturated animal fats. He questions the accepted wisdom that replacing saturated fats in the diet with polyunsaturated fats lowers the risk for coronary heart disease, citing the ‘French Paradox’ and the ‘Israeli Paradox’ which contradict the argument. This is primitive scientific evidence.

The advice to replace saturated fats with polyunsaturated fats comes from consistent sets of evidence from different types of studies, including a meta-analysis of diet/blood lipid trials, a pooled analysis of 11 prospective cohort studies and a meta-analysis of randomised controlled trials.

Just about every authoritative nutrition organisation in the world agrees that replacing saturated fat with polyunsaturated fat lowers heart disease risk, including the World Health Organisation, the National Health & Medical Research Council (latest Australian Dietary Guidelines), the Heart Foundation, the Baker-IDI Heart and Diabetes Institute, the CSIRO, the American Heart Association and the Dietary Guidelines for Americans.

Gillespie says: I am a lawyer and the only relevant skill I bring to the table is an ability to gather, understand and synthesise evidence… Just like law, science should be all about the evidence.

Public health nutrition recommendations stand or fall on their evidence base. All of the above organisations carefully scrutinise scientific evidence and weave it into dietary recommendations. Their reputations rest on the quality of advice they provide.

What they don’t do is cherry-pick, selectively unearth old studies with atypical results, present these findings as amazing new insights and ignore more recent, better conducted studies that resolved key nutrition debates years ago.

Gillespie says: More recent research is starting to suggest that polyunsaturated fats and in particular the omega-6 fats in seed oils also lie behind the accelerating incidence of … macular degeneration

Two major studies into diet and macular degeneration have been conducted in Australia – the Melbourne Collaborative Cohort Study and the Blue Mountains Eye Study. The findings of both studies were similar:

• Neither study found that total polyunsaturated fat intake affected risk, or that butter or margarine consumption affected risk.
• In both studies it appeared that omega 3 fats from fish offered some protection.

In the Blue Mountains Eye Study the authors explored the idea that omega 6 fats may interfere with the beneficial action of omega 3 fats from fish. However, the statistical test for an interaction between the two was not significant.

Gillespie says: … trans fats are just the tip of the iceberg.

Part of Mr Gillespie’s concern about seed oils appears to be based on the misconception that all oils with high polyunsaturated fat content need to undergo hydrogenation and are therefore full of trans fats. He states “Because canola oil has fewer polyunsaturated fats than soybean oil, it doesn’t require as much hydrogenation and has about half the trans fats of soybean oil.” The truth is that canola oil and soybean oil on the supermarket shelves do not ‘require’ hydrogenation at all and neither contains appreciable amounts of trans fats.

Trans fat intakes are low in Australia and seed oils are certainly not the major source. The meat and dairy fats that Mr Gillespie appears to support contribute about three-quarters of the trans fat in the Australian diet.

Gillespie says: If you do what I suggest, you will be doing all the wrong things, according to our health authorities. You’ll be eating butter, drinking full-fat milk, chomping through bacon and eggs for breakfast and enjoying a meat pie for lunch.

Need I say more?

What Mr Gillespie doesn’t mention

In demonising polyunsaturated fats Mr Gillespie fails to mention one salient point: polyunsaturated fats are the only fats that are essential nutrients for humans. Although the body can make monounsaturated and saturated fats it must get polyunsaturated fats from food. The idea that the only essential fats in the diet are the ones that make us sick defies logic and commonsense, let alone the weight of scientific evidence.

Summing up

Mr Gillespie has presented an alarmist thesis based on inaccurate data, unsound assumptions and rehashed theories from yesteryear. No authoritative nutrition organisation agrees with him.

The first Dietary Guidelines in Australia were released in 1980 and recommended restriction of the total amount of fat in the diet as a strategy for chronic disease prevention. In the following 20 years this piece of dietary advice took precedence over all others and dominated the nutrition landscape. However, the writing has been on the wall for the low fat diet for many years now.

The end of the low fat era

The hypothesis that the percentage of dietary energy from fat was related to chronic disease risk was developed in the 1970s and put to the test in large cohort studies that commenced in the following decade and then in several randomised controlled trials. A string of null results followed in relation to breast cancer, bowel cancer, coronary heart disease and stroke. Perhaps most surprisingly, no association between total fat and obesity was observed in prospective cohort studies, and randomised controlled trials suggested minimal benefit.

In contrast, evidence from mechanistic studies, cohort studies and controlled trials confirmed that fat type was relevant to chronic disease risk, especially in relation to coronary heart disease.

For the first time in 33 years the latest Australian Dietary Guidelines no longer highlight the need to limit or ‘moderate’ total fat intake, completing the evolution of advice in favour of fat type that has gone through several stages. The guidelines now recommend limiting saturated fat and state:

• Limit intake of foods high in saturated fat such as many biscuits, cakes, pastries, pies, processed meats, commercial burgers, pizza, fried foods, potato chips, crisps and other savoury snacks.
• Replace high fat foods which contain predominantly saturated fats such as butter, cream, cooking margarine, coconut and palm oil with foods which contain predominantly polyunsaturated and monounsaturated fats such as oils, spreads, nut butters/pastes and avocado.

These recommendations are well founded. The first point focusses attention on limiting many nutrient-poor foods that are combinations of saturated fat and poor quality carbohydrate, which is now known to confer the same or greater coronary risk than saturated fat. The second point is arguably more important as it highlights the most desirable replacement for saturated fat in the diet – poly- and monounsaturated fats. This is the area where the science is clearest.

Overall, the implication is that the Mediterranean-type diet – moderate in both total fat and carbohydrate but low in saturated fat and enriched with unsaturated fats is now the preferred model for healthy diets. This general approach is also consistent with the latest Dietary Guidelines for Americans, which no longer advocate low fat diets and encourage the replacement of saturated fat with unsaturated fats.

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Change to the food guide

There is only one significant change to the Australian Guide to Healthy Eating – the separation of unsaturated vegetable oils and spreads from the ‘extras’ or junk foods. This corrects a much criticised flaw in the previous guide and has been welcomed by the Heart Foundation. When the previous Australian Guide to Healthy Eating was released in the late 1990s the Heart Foundation contested the positioning of unsaturated vegetable oils and spreads with ‘extras’ and decided that it would not use the national food guide in any of its nutrition education materials, and it never did. The Heart Foundation’s principled stand on this issue has now been vindicated and, after a 15-year stand-off, Australia’s leading nutrition authorities now largely agree on the advice in relation to these foods.

But the new food guide isn’t perfect. The use of the words ‘choose small amounts’ in relation to unsaturated vegetable oils and spreads is a mistake. It implies restriction and reflects a lingering nervousness about dietary fat and its potential to promote obesity, despite the authorities’ own literature review showing no link.

The simple fact is that children’s intakes of unsaturated fats need to increase by 30 percent if they are to approach the ‘total diets’ modelled during the development of the new food guide and this increase needs to come from somewhere. It can’t come from meats and dairy foods as these foods are also rich in saturated fat. That just leaves nuts and seeds, which are only consumed by a small proportion of the population, and unsaturated vegetable oils and spreads. This inconsistency between the science in the Dietary Guidelines and its communication really should have been sorted out. ‘Choose unsaturated oils and spreads’ would have been an appropriate and moderate recommendation.

About 36-41 percent of calories currently come from nutrient-poor foods high in saturated fat and/or poor quality carbohydrate. These foods are the obvious targets for energy restriction for weight management, not the major source of unsaturated fats.

Energy-dense, nutrient-poor foods

The term ‘energy-dense, nutrient-poor foods’ has found its way into the Dietary Guidelines, especially in relation to obesity. Interestingly, none of the evidence statements in the obesity section actually mentions ‘energy-dense, nutrient-poor foods’. It’s just a euphemism for junk foods which are assumed to be a problem. .

I must admit I find ‘energy-dense, nutrient-poor foods’ an imprecise, clunky term. After all, macadamias are energy-dense and nutrient-poor but this doesn’t mean that they have no place in a healthy diet. On the contrary, the inclusion of these nuts in a diet has a potent effect on improving fat quality. White rice is quite energy-dense and certainly nutrient-poor but for some reason it’s positioned as a food for daily consumption rather than with the other junk foods. If terms don’t have a consistent meaning alternatives need to be considered.

The ‘energy-dense, nutrient-poor’ terminology can be expected to evolve further in the years ahead. As calculations of nutrient density are usually based on a fixed amount of calories, energy density and nutrient density are not distinct concepts – they overlap. Contrary to popular belief, energy density is not a useful measure of the healthiness of foods or diets in relation to the prevention of obesity. Nutrient density is a cleaner measure and this concept has already been embraced in the Dietary Guidelines for Americans.

But nutrient density is not sufficient by itself. Future models for classifying junk foods and healthier foods will need to combine nutrient density with measures of fat quality and carbohydrate quality.

Carbohydrate quality: an evolving concept

While fat quality is now well understood, the concept of carbohydrate quality is undeveloped and remains contentious. In the latest Dietary Guidelines carbohydrate quality remains narrowly conceived around added sugar and wholegrains, with no consideration (not even a literature review) of glycaemic index. However, a debate on this topic is now underway internationally and its conclusions will guide the further evolution of dietary advice in the years ahead.

I’ll cover the latest contributions to this debate in my next post.

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Food groups and ‘distinguishing nutrients’

The concept of food groups has been central to nutrition education in many countries for decades. It’s a simple idea: different types of foods make distinctive contributions to the diet so eating a variety of foods from the different food groups should ensure adequate intakes of essential nutrients.

Although all whole foods contain small amounts of a wide variety of nutrients, the distinctive contribution of a food group is due to 4-6 ‘distinguishing nutrients’ found in abundance. As foods in the same food group share distinguishing nutrients they can be exchanged without compromising nutrient intake. This nutritional equivalence allows flexibility in food choice.

Vegetables and fruits: two food groups or one?

In Australia, fruits and vegetables appear in two separate food groups but the rationale for two food groups is not at all clear. The dietary modelling conducted for the latest Australian Guide to Healthy Eating highlights the distinguishing nutrients of fruits and vegetables:

Vegetables: Vitamin C, fibre, folate, vitamin B6, potassium, beta-carotene
Fruit:            Vitamin C, fibre, folate, vitamin B6, potassium.

Aren’t the distinguishing nutrients for both food groups almost exactly the same? Don’t these food groups do the same job? In early versions of the Five Food Groups vegetables and fruits appeared in one food group but separation into two groups was suggested in 1994 in a NHMRC report called The Core Food Groups. The report stated that ‘It was necessary to group fruit and vegetables separately because of their differing nutrient profiles’. Really?

Consolidating these similar food groups into one would appear to make sense and would provide more flexibility for those who find it difficult to eat five serves of vegetables each day, which is most of us.

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Grain foods: distinguished by fortification

The dietary modelling for the new food guide demonstrates the distinctive and very substantial nutritional contribution of the grains food group. In the Foundation Diet for women aged 19-30 years, grains provide 62% of the thiamin, 55% of the folate, 46% of the iron, 39% of the iodine, 38% of the fibre, 32% of the niacin and 28% of the riboflavin. That’s impressive. By far the majority of these nutrients come from wholegrain cereals, though I suspect these were actually fortified wholegrain cereals.

Compare the nutritional content of 600kJ of the following grain foods, expressed as a percentage of the relevant Nutrient Reference Value.

Grain          White rice     Brown rice     W/meal pasta     ‘Weetbix’
Thiamin      6%                9%                 31%                     94%
Folate         2%                6%                 3%                       88%
Iron             7%                8%                 32%                     65%
Fibre           2%                6%                 25%                     19%
Niacin         13%              24%               29%                     77%
Riboflavin   1%                3%                 9%                       78%

This table demonstrates some key points:
• refined grains are relatively nutrient-poor
• wholegrains are slightly better, but
• only fortified grains are nutrient-dense.

Fortification strongly shapes the nutritional contribution of the grains food group. As we enter the era of carbohydrate restriction there will be an increased focus on nutrient-rich carbohydrate foods and in the case of grains that means more emphasis on the fortified foods – breads and breakfast cereals – and less on white rice and plain pasta.

Dairy foods: should they be a group?

It has been argued that dairy foods hold a privileged position in Five food Groups and could be grouped with meats with which they share distinguishing nutrients, such as protein and vitamin B12.

The latest Harvard Healthy Eating Plate went even further, excluding dairy products altogether. This seems to be a step too far as the rationale was fairly weak. The Harvard team point out that dairy products are rich in saturated fat, but why not just recommend lower fat dairy foods? They argue that high intakes of calcium do not translate directly into stronger bones and that other factors are relevant, such as vitamin D and physical activity. Fair enough, but aren’t they all pieces of the same puzzle?

Harvard concedes that “Moderate consumption of milk or other dairy products—one to two servings a day—is fine, and likely has some benefits for children.”

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Meats and alternatives: the illogical food group

Unfortunately, the logic of distinguishing nutrients that underpins the Five Food Groups falls apart when we get to the meat, fish, poultry and ‘alternatives’ food group. Our current Dietary Guidelines for Australians report describes the distinguishing nutrients of this food group as protein, bioavailable iron, zinc, vitamin B12 and long-chain omega 3s. This is valid for red meats, poultry and fish but not for legumes and nuts.

The marked lack of nutrition equivalence in the meats and alternatives food group has been documented. Although legumes and nuts contain iron its absorption from these foods is very low, about 1-2%. Phytates, found in abundance in legumes and nuts, are also potent inhibitors of zinc absorption. And legumes and nuts contain no long-chain omega 3s or vitamin B12. However, legumes and nuts contain dietary fibre, unlike the animal-sourced foods in this group. These are very different foods.

Despite these inconsistencies the composition of this food group won’t change because it reflects an ideological view strongly held by some of the nutrition profession. It’s not driven by science; it’s all about us.

Legumes can at least claim to be a protein food, which is more than can be said for nuts. The recent dietary modelling for the next food guide noted that nuts ‘have a different protein to energy ratio compared with other components of the meats group’, a delicate way of saying that the major macronutrient in nuts is not protein, but fat.

Healthy fats: the missing food group?

If nuts and seeds are a poor fit in the meats food group, where do they belong? Is it too radical to suggest that they belong in their own food group, together with the oils that are derived from them and foods made from these oils, such as unsaturated margarines, salad dressings and mayonnaise? Such a food group would certainly have its own distinguishing nutrients – fat-soluble nutrients. The dietary modelling conducted for the latest food guide (p276) highlights that although these foods contributed just 10.2% of dietary energy in a Foundation Diet they provided 47% of the linoleic acid, 50% of the alpha-linolenic acid, 44% of the retinol, 29% of the vitamin E and 26% of the vitamin D. That’s a substantial and very distinctive contribution.

Shouldn’t there be at least one food group designed to encourage adequate intakes of fat-soluble nutrients? Fats were included as a food group in Australia’s Five Food Groups until 1998 when fat phobia overwhelmed our nutrition authorities. They still haven’t quite recovered.

New meta-analysis

A new meta-analysis of the effects of overweight and obesity on all-cause mortality was published this month in the Journal of the American Medical Association. The analysis included data from 97 studies from around the world, providing a combined sample size of more than 2.88 million subjects and more than 270,000 deaths.

The risk of death of all obese subjects (BMI>30) was substantially and significantly higher (18%) than that of subjects of normal weight (BMI 18.5-25) – the sort of finding that we have come to expect. However, the results told a different and perplexing story when narrower weight categories were considered. For example, those who were overweight (BMI 25-30) experienced 6 per cent lower risk of mortality than subjects of normal weight. Subjects with grade 1 obesity (BMI 30-35) had the same mortality risk as subjects of normal weight. Consequently, the mortality risk associated with obesity appeared to be due entirely to higher grades of obesity – BMI greater than 35, which was associated with a 29% increase in risk.

How can it be?

Previously, a J-shaped relationship between body weight and mortality has been observed i.e. very low body weight was linked with higher risk; normal body weight was associated with the lowest risk; and mortality risk climbed again as body weight increased above the normal range. However, the latest study suggests that we may be looking at a long, drawn out J shape with low mortality risk associated with a broad range of body weights, including normal weight, overweight and grade 1 obesity.

But how come? Isn’t obesity supposed to be associated with increased risk for type 2 diabetes, coronary heart disease, stroke and some cancers? Maybe relying on BMI alone is just not accurate enough. As highlighted in the accompanying editorial, BMI is crude measure of health status. People with the same BMI can have widely differing metabolic health depending on their fitness, the amount of fat on their bodies and, importantly, the distribution of that fat. Waist circumference has been suggested as a better measure of risk than BMI as it is more likely to capture central obesity and its associated risks.

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An obesity paradox?

More challengingly, the editorial suggests that there appears to be an ‘obesity paradox’ i.e. a protective effect of overweight or grade 1 obesity in old age and in the presence of chronic conditions, such as heart disease and diabetes. They speculate that small excess amounts of adipose tissue may provide energy reserves needed during acute catabolic illnesses, have beneficial mechanical effects with some types of traumatic injuries and convey other effects that need to be investigated. The implication is that it can’t be assumed that the life expectancy of all overweight subjects, even those with chronic disease, will increase with weight loss. Another paradox – that’s just what we need!

What about morbidity?

Another recent study found no association between overweight, obesity and mortality though it was a different story when the researchers looked at the risk for disability. Being overweight was associated with a 33% increase in the risk for becoming disabled and the risk was doubled for those with obesity. Furthermore, recovery from disability was negatively associated with obesity.

So, although being overweight may not kill you, it could make you sick.

‘Tampering with the food supply’

One popular dietary myth is that the consumption of simple, minimally processed foods automatically translates into a healthy diet. As a consequence, any ‘tampering with the food supply’ by faceless scientific types is treated with suspicion and resisted.  The defense of naturalism may be logical to a naive audience but it ignores the history of nutrient deficiency in humans. Even today in parts of Tibet a high percentage of the population, consuming a diet of simple, minimally processed foods, suffers from serious intellectual impairment due to iodine deficiency. One of the simplest dietary interventions of all – the addition of iodine to the salt used in food preparation – is all that it takes to solve this crippling problem.

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Let’s remind ourselves of the WHO/FAO definition of food fortification: “the practice of deliberately increasing the content of an essential micronutrient … so as to improve the nutritional quality of the food supply and to provide a public health benefit with minimal risk to health”. You can see why the debate never went very far. By definition, food fortification does more good than harm.

The use of the emotive word ‘tampering’ in the argy bargy of food activism is intended to steer the fortification debate down a philosophical/emotional path, ensuring that the rationality of science takes a back seat.

Making junk food look good?

One of the recent arguments against food fortification is that it may be applied to junk foods, effectively making unhealthy foods look better than they are. Putting the difficulty in defining junk foods to one side, this argument does not really stand up to scrutiny. Fortification has always been about improving the nutritional properties of staple foods, many of which have been nutritionally poor – junk foods if you like.

A couple of hundred years ago when the cultivation of corn became widespread a peculiar thing happened to the communities that adopted it as the staple of their diet – they got sick. At the time it was thought that corn contained some kind of toxin but the real problem was a deficiency of the vitamin niacin – the people were suffering from pellagra. Early in the 20th century pellagra reached epidemic proportions in the south of the United States and thousands of people died.

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No modern junk food wreaks the sort of havoc that corn did a hundred years ago. However, once vitamin deficiency was understood and fortification of cereal foods with niacin became routine in modern societies pellagra virtually disappeared. Only after its nutritional shortcomings were overcome did corn shake off its junk status and take its place as a healthy staple food.

If we take the ‘don’t fortify junk food’ argument to its logical conclusion, only healthy foods would be fortified, which is simply wrong-headed. If implemented it would ensure that the only people who would benefit from fortification are those who already consume healthy foods – those that need the benefit the least.

Undermining nutrition education?

Another criticism of fortification is that it undermines nutrition education. This view states that all people should be educated about nutrition; fortification blurs the boundaries of what’s healthy and what’s not-so-healthy; and everyone finds it too confusing. The ambition to educate people about good nutrition drives all dietitians and nutritionists but we need to be careful: establishing education as the only gateway to nutritional health tends to pitch good nutrition at the educated (well nourished) middle class. It does little for the most disadvantaged and the least educated who are more likely to suffer nutritional deficiencies, less likely to be aware of their health problems and less likely seek information or professional help to address them.

The purpose of food fortification is to ensure that the least educated person, living in the most difficult of circumstances, making poor dietary choices by necessity doesn’t suffer a vitamin deficiency disease. It’s a safety net for the disadvantaged and to succeed the foods chosen for fortification need to be the foods that this group chooses to eat.

Case study: Aboriginal people in Bourke

Max Kamien was a man ahead of his time. As a young doctor working with Aboriginal people in the Bourke area of New South Wales in the 1970s Kamien was confronted with their poor nutritional status – more than 30% had clinical signs of vitamin deficiency. Their staple diet was (unfortified) white bread eaten with golden syrup, jam or honey, washed down with large quantities of sweetened tea. This was a junk diet composed almost entirely of junk foods.

Kamien thought the quickest method of improving the health of this disadvantaged group was to fortify their bread with thiamin, niacin and riboflavin. In a forerunner of more recent criticism of food fortification Kamien was attacked in the media for treating the Aboriginal people as ‘the guinea pigs of Bourke’ with his ‘secret bread tests’ (mustn’t tamper with the food supply Max). But within a short period of time, blood levels of B vitamins in the Aboriginal people increased and physical signs of deficiency virtually disappeared. This simple strategy cobbled together by a doctor and the local baker involved no education, just the fortification of a staple food of the target population. And it worked.

The complacency of success

Anti-food fortification arguments are a bit like arguments against vaccination. The success of both public health strategies is so profound and so well established that the wellbeing they create is assumed to be the norm. Complacency sets in, followed by ill-informed questioning of the worth of these public health initiatives.

Maybe we need a good old fashioned pellagra epidemic to remind us why we fortify foods with essential nutrients.