Modern Diet Myth No. 5: The low fat diet was the result of fraud and conspiracy

As new scientific evidence has emerged the low fat diet has slowly fallen from favour. But the myth-makers are suggesting the whole thing was a con, born out of fraud and carried along by a conspiracy.

The origins of the low fat diet

The low fat diet had its origins in 1980 with the publication of the first Dietary Guidelines for Americans. The recommendation to ‘Avoid too much fat, saturated fat and cholesterol’ was intended to lower blood cholesterol and reduce the risk for heart disease. Although the focus was really on lowering saturated fat, it was thought that lowering total fat intake may help prevent some cancers and obesity.

In Australia, the simpler guideline ‘Avoid eating too much fat’ was adopted to aid its communication.

Keys versus Yudkin

The low fat diet had a low key launch. Yet these humble origins are now being re-imagined as the disastrous consequences of a fight to the (professional) death of two of the great nutritionists their era – Ancel Keys and John Yudkin. As an epidemic of heart disease raged in the post-war years Yudkin pointed his finger at sugar. But Keys argued that the effect of different fats on blood cholesterol was the key mechanism affecting heart disease risk, and he won the day.

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Modern Diet Myth No. 4: Fructose turns to fat

Fructose – the dietary villain de jour – is currently giving rise to more myths than anything else and they all seem to relate to fat. Fructose supposedly leads to fatty liver and too much fat in the blood. To top it off, fructose is said to be uniquely fattening! Where do we start?

Fat in your liver

Most of the carbohydrate we eat ends up in the bloodstream as either glucose or fructose. The myth goes that glucose is the good sugar as it is used to power the brain, the muscles and most of the cells in the body. And the fructose is the bad sugar which is quickly taken up by the liver and turned into fat, giving rise to fatty liver.

Unfortunately for the myth-makers, no reputable health authority in the world agrees. Fatty liver is certainly a common problem but the experts see it as part of the metabolic syndrome – a cluster of abnormalities linked to central obesity and insulin resistance, where the cells of the body become less sensitive to insulin.

There is no recommended diet for fatty liver. Instead, health authorities encourage people with fatty liver to lose some weight and increase their physical activity, both of which improve insulin resistance.

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Modern Diet Myth No. 3: Seed oils cause heart disease

There are lots of oils derived from seeds – sunflower, canola, soybean, cottonseed, sesame, flax, grape seed, peanut and safflower to name a few. The first thing that strikes you about these oils is not how similar they are but how different. Traditional sunflower oil is high in polyunsaturated fats, whereas canola has more monounsaturated fats, plus some omega 3. Flaxseed oil has lots of omega 3 and so on.

About the only thing that all these seed oils have in common is that they are relatively low in saturated fat, which is considered to be a good thing by every reputable nutrition and heart health authority in the world.

Of course, things are very different in the curious world of celebrity-driven nutrition advice where for some reason saturated fat is seen as desirable and coconut oil, one of the most saturated of all oils, is promoted a healthy choice.

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Modern Diet Myth No. 2: Legumes should be eliminated from the diet

One of the more baffling pieces of nutrition advice wafting through the internet is that legumes should be eliminated from the diet. This stands in contrast to conventional nutrition advice which encourages intake of legumes. Who would have thought these humble edible seeds, which include beans, peas, lentils and peanuts, would be the centre of a controversy?

At first glance legumes appear to be rich sources of iron and zinc but their critics argue that this is misleading as the absorption of these nutrients is lessened by anti-nutrients, like phytic acid. Phytic acid in legumes binds to these minerals lowering their absorption from the gut. The iron and zinc in meat is more readily absorbed.

The other argument against legumes relates to protein. Compared to traditional ‘protein foods’ such as meat, poultry, fish and eggs, legumes generally have less protein and the protein is of lower quality. That is, some amino acids are in short supply.

So legumes are labelled as inferior foods, compared to red meat.

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Modern Diet Myth No. 1: Eating McDonald’s makes you fat and sick

For years, the food served at McDonald’s restaurants has been used as an example of all that is wrong in modern western diets – it’s simple, fast, cheap and American, and therefore couldn’t possibly be good for us. In his 2004 movie Super Size Me United States film maker Morgan Spurlock set out to demonstrate that McDonald’s food actually makes people fat and sick, using himself as a guinea pig.

The Spurlock ‘experiment’

For 30 days Spurlock ate only McDonald’s food and documented the effects on his physical and psychological well-being on film. The effects were dramatic: he gained over 11 kilos in weight; his blood cholesterol went up; fat built up in his liver; and he experienced sexual dysfunction and swings in mood. At last, here was all the proof we needed that eating McDonald’s food makes you fat and sick!

In reality it was nothing of the sort. Proof comes from scientific experiments and Super Size Me bore no resemblance to science. When conducting dietary experiments researchers are careful to control for all the factors that might affect the result. If two things change in a diet, how do you know if an adverse effect is due to one thing or the other?

Spurlock gave his audience the impression that he was testing the QUALITY of McDonald’s food. However, during his 30-day ‘experiment’ he also changed the QUANTITY of food that he ate. In fact, he absolutely stuffed himself, doubling his calorie intake. This binge was why he put on so many kilos and probably why his blood cholesterol and liver fat increased.

The fact that he was eating McDonald’s food actually had nothing to do with his weight gain. Many dietary experiments have shown that diets with widely differing composition have exactly the same effect on body weight if calories are kept constant, and physical activity remains the same. These are the things that determine whether body weight moves up or down. Spurlock actually lowered his level of physical activity during his month-long feast, presumably to ensure the results were as bad as possible.

Image: source

Spurlock’s motive

What was Spurlock’s motive? If the intention had been to inform the general public of the facts Spurlock would have teamed up with some nutrition researchers and filmed a real scientific study into the effects of McDonald’s food. I suspect he was aware that the results would hardly have been big news.

At best, Spurlock’s movie may be an extreme case of white hat bias i.e. bias leading to the distortion of information in the service of what may be perceived to be righteous ends. But the predetermined outcome and the misrepresentation of its cause surely pushes ethics to the limit.

Alternatively, maybe Super Size Me was just a stunt designed to generate a lot of publicity and to tarnish McDonald’s name. Irrespective of what we think about the nutritional quality of McDonald’s food, wouldn’t we all be better off if we just heard the facts?

Declaration: Bill Shrapnel has no association with McDonald’s.

 

Fatty liver

Fatty liver is reaching epidemic proportions in western countries. What causes it and what diet and lifestyle measures can be used to manage it?

About 30% of adult Australians are thought to have non-alcoholic fatty liver disease – fatty liver for short – and its prevalence is increasing. In its early stages fatty liver is of minor concern and there are no symptoms. But it can progress to a stage called NASH where liver cells begin to be damaged and this is associated with inflammation. At the next stage the risk of cirrhosis of the liver increases which may lead to liver failure and even cancer of the liver. Together, fatty liver and NASH are now the number one cause of liver disease in Western countries. However, the major cause of death in people with fatty liver is cardiovascular disease.

What causes fatty liver?

Fatty liver develops when the liver’s normal processes of delivery and removal of fats go awry. Although the exact cause is not known several things could be going wrong:

• Perhaps too much fat is being delivered to the liver
• The liver may have a problem ‘burning’ fats for energy
• Fat (triglyceride) production by the liver may be increased
• The movement of triglycerides from the liver into the bloodstream may be impeded.

But what is the underlying cause?

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False balance: the distortion of nutrition science by the media

What drives the media’s bias when reporting on nutrition? Is it a desire for sensationalism, misguided good intentions, postmodern contempt for facts, or just commerce? Surely the general public deserves better.

The media doesn’t manage nutrition very well. Apparently, fundamental concepts of good nutrition such as variety, balance and moderation just aren’t very sexy so the media is forever souping things up a bit as it attempts to meet the general public’s insatiable appetite for articles about food, nutrition and diets. Instead of old nutrition truism like ‘There are no good and bad foods, only good and bad diets’ we read that some foods are ‘toxic’ while others are superfoods. All quite over the top.

Fortunately, every now and then a health journalist will examine a nutrition topic in depth, potentially providing the general public with an opportunity to gain some real understanding of nutrition and to hear the views of leading experts.

But with the opportunity there is also a threat – false balance.

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Carbohydrate and triglycerides: do low-carb advocates have a point?

According to advocates of low carbohydrate diets a key benefit is the effect on triglycerides in the blood. The argument goes that a high level of triglycerides is linked to increased risk for coronary heart disease; low carb diets lower triglycerides; so low carb diets should lower the risk for heart disease. Sounds plausible enough, but is it true?

Blood lipids and heart disease risk

The approach to managing blood lipids to lower heart disease risk has evolved over time as our understanding of this complicated field has grown. Decades ago the focus was on lowering total cholesterol but this was later narrowed down to LDL-cholesterol – ‘bad’ cholesterol for the lay person. ‘Good’ HDL-cholesterol was considered protective and the balance between the bad and the good – the LDL/HDL ratio – came into use. More recently, the total cholesterol/HDL ratio has been considered to be a better measure as all non-HDL-cholesterol appears to increase heart disease risk.

What about triglycerides?

If you are interested in how triglycerides affect the risk for heart disease and how diet affects blood triglycerides look no further than the American Heart Association’s scientific statement Triglycerides and Cardiovascular Disease. You may need to allocate an afternoon as the paper is very comprehensive and has over 500 references.

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Who is funding Low Carb Downunder?

Pete Evans, Sarah Wilson and some international speakers were involved in the recent series of Low Carb Downunder presentations. It was a very slick exercise. And very expensive, but who footed the bill?

In August and September the Low Carb Downunder road show came to Sydney and Melbourne. I went along to the Sydney presentation and was certainly impressed by the organisation of the event. Great venue, a big audience, big celebrities and an international speaker – the Melbourne program had three!

Pete Evans is quite a performer. He moved confidently around the stage engaging his lay audience with his passion for The Paleo Way of eating and they lapped it up. If you have ever seen one of those American motivational speakers at work and their star struck audiences hanging off every word, it was a bit like that.

But something was not quite right. The usual rhythm of things is that nutrition professors sell nutrition messages and celebrities sell products. So what were these celebrity presentations on nutrition all about?

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What’s more important – glycaemic load or fructose?

As the focus of public health nutrition switches from fats to carbohydrates there is uncertainty about how carbohydrates actually affect the risk for chronic diseases, such as type 2 diabetes and coronary heart disease. Early dietary advice on fats was based on effects on blood cholesterol but what mechanisms are driving the risk associated with carbohydrate?

Glycaemic response or fructose?

One view is that the key driver of carbohydrate-related risk is glycaemic response i.e. the degree to which carbohydrates raise blood glucose and insulin levels. If glycaemic response is the critical factor then the dietary measure of interest would be glycaemic load, which takes into consideration both the amount of carbohydrate consumed and its potential to raise blood glucose.

An alternative view is that fructose drives the chronic disease risk associated with dietary carbohydrate. If so, we should expect fructose or perhaps sucrose (the major dietary source of fructose) to be associated with risk for chronic disease in large population studies. And, importantly, glycaemic load would not be linked with risk.

Let’s look at the epidemiology and see if it supports one argument or the other.

Glycaemic load and coronary heart disease risk

Four meta-analyses of prospective cohort studies of glycaemic load and risk for coronary heart disease have been published in the last couple of years (Dong 2012, Fan 2012, Ma 2012, Mirrahimi 2012). The findings are essentially the same – glycaemic load is associated with heart disease in women but not men. In two of the meta-analyses the links between glycaemic load and heart disease were stronger in overweight subjects. Fan (2012) also found an association with stroke incidence, as did Sieri (2013) in a recent cohort study. In all four meta-analyses the relative risks for heart disease in men were positive – they just failed to reach statistical significance, perhaps due to smaller numbers.

A study in a Chinese cohort published last year found glycaemic load was associated with coronary heart disease risk in both genders (Yu 2013). Compared to studies in western populations carbohydrate intake was high (68% of calories) but sugar intake was relatively low. Most of the carbohydrate was starch, 87% of which came from white rice and refined wheat products.

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