Food companies hate the idea of being regulated i.e. having the government tell them what to do. However, with freedom in the marketplace comes responsibility. The best way to avoid regulation is for an industry to do the right thing by its customers and health authorities when a problem with the industry’s products is identified.
In the United States, the Food and Drug Administration recently announced that partially hydrogenated oils (containing trans fats) were no longer ‘Generally Regarded as Safe’ and gave the fats and oils industry three years to get them out of the food supply. So, begrudgingly, the US industry will be forced to adopt a position that companies in the rest of the developed world adopted 20 years ago.
One of the more commercially driven myths circulating at present is the idea that somehow saturated fat is better for health than carbohydrate. Virtually all the low carb advocates push this argument, but why would they do that?
The changing science
The science relating to how much of what we should eat for good health has certainly evolved in recent decades, but it’s not a simple story.
• In the early 1980s, most health authorities recommended that saturated fat in the diet should be limited to lower heart disease risk.
• At that time trans fats were thought to be neutral but by the 1990s they were considered be as bad as saturated fats. And by the 2000s trans fats were thought to be worse than saturated fat.
• Three decades ago carbohydrate was thought to be the ideal replacement for saturated fat, which led to widespread support for low fat diets. But by the late 2000s scientific support for low fat diets had dropped away.
• Although the early science indicated that unsaturated fats may be the best option to replace saturated fat in the diet somehow they were less preferred to carbohydrate. Their time has now come.
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.
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.
Credible nutrition scientists have opposing views on whether omega 6 in vegetable oils is good for heart health. But who is right?
Part 1 of this series examined claims that omega 6 in vegetable oils causes ill health by increasing the risk for cancer, macular degeneration, Parkinson’s disease and inflammatory conditions, such as rheumatoid arthritis, ulcerative colitis and asthma. These claims, frequently expressed on the internet and in social media, were found to be baseless.
Part 2 will consider whether omega 6 increases or decreases the risk for coronary heart disease. Unlike the wild social media claims about omega 6, this issue is argued in the scientific literature with credible scientists on both sides. Whose argument is stronger?
The conventional wisdom
Leading heart health agencies such as the Heart Foundation, the American Heart Association and the World Health Organisation assert that polyunsaturated fats (mainly omega 6) are heart healthy and that they may be the ideal replacement for saturated and trans fats in the diet. The case appears to be strong:
• Polyunsaturated fat (mainly omega 6) has a beneficial effect on blood lipids. When saturated fat is replaced by polyunsaturated fat the level of serum LDL-cholesterol and the total cholesterol/HDL cholesterol ratio both fall, which is consistent with lower risk for coronary heart disease.
• Epidemiological studies indicate that polyunsaturated fat (mainly omega 6) is heart friendly. A pooled analysis of 11 prospective cohort studies conducted in Europe and the United States shows that replacing saturated fat with polyunsaturated fat lowers coronary risk more than other macronutrients.
• In randomised controlled trials coronary heart disease risk falls when saturated fat is replaced by polyunsaturated fat (mainly omega 6) – see Harvard’s meta-analysis.
So the conventional wisdom is based on three consistent lines of evidence with a rare meta-analysis of randomised controlled dietary trials sitting on top. Impressive. How could you argue against it?
More than six months after it broadcast two misleading Catalyst programs about diet, medication and heart disease the ABC has admitted there were problems with impartiality and has undertaken corrective action. But there is still something fishy about this.
In October last year ABC television’s science program Catalyst ran two controversial programs purporting to expose myths about diet, medication and cardiovascular disease. In the first program Catalyst presenter Dr Maryanne Demasi challenged the role of dietary saturated fat in affecting risk for coronary heart disease and in the second she questioned the efficacy of statin medication. Essentially, the Catalyst program argued that the world’s leading nutrition organisations and cardiovascular researchers had got it wrong over the last four decades.
Heart Foundation outraged
In an interview on the ABC radio program PM, Maryanne Demasi even stated that the Heart Foundation was ‘certainly supportive’ of the Catalyst program’s evidence. In fact, the Heart Foundation was livid, took offence and submitted a formal complaint. They weren’t alone – the ABC received a total of 146 complaints. To their credit, journalists within the ABC, such as health reporter Dr Norman Swan and Media Watch front man Paul Barry, challenged the accuracy of the programs and the standard of the journalism on display, respectively. For more of detail see my two posts on the Catalyst programs here and here.
Results of independent review
Yesterday, the results of a review of the Catalyst programs by the ABC’s Audience and Consumer Affairs Unit were made public and included findings that standards of impartiality had been breached. Here are some excerpts from the review:
Omega 6 in vegetable oils stands accused of causing ill health by increasing the risk for cancer, macular degeneration, Parkinson’s disease, inflammation and heart disease. Sounds bad, but is any of it true?
What is omega 6?
All fats – animal or vegetable – are made up of building blocks called fatty acids which generally fall into three main groups called saturated, monounsaturated and polyunsaturated. There are two classes of polyunsaturated fatty acids – omega 6 and omega 3. The omega 3 in vegetable oils is called α-linolenic acid and the omega 6 is linoleic acid. The concern about omega 6 relates to linoleic acid which is the most common polyunsaturated fatty acid in the diet.
Do omega 6 fats cause cancer?
In the early 1980s it was thought that fat intake may affect the risk for cancer of the breast and bowel. This hypothesis was based on very basic evidence i.e. different cancer incidence in countries with differing fat intakes, but worth investigating nevertheless.
Several prospective cohort studies were commenced around this time. Data from seven of these studies were pooled in the definitive breast cancer study by Hunter and colleagues. Breast cancer risk was not associated with intake of total fat, animal fat, vegetable fat or polyunsaturated fat. Another pooled analysis of cohort studies published five years later confirmed that polyunsaturated fat was not associated with breast cancer. So omega 6 was off the hook.
Although the headlines have got it wrong the science relating to saturated fat and heart disease has evolved considerably. But Australia’s public health nutrition policy makers are blissfully unaware and are implementing science that’s out of date.
In March yet another headline appeared in the mainstream media stating ‘No link found between saturated fat and heart disease’. The media delights in stories about diet that appear to contradict the status quo and, of course, relevant industry groups always put their public relations firms into action whenever an opportunity presents itself. Hence the misleading headlines.
Certainly there have been recent developments in how the coronary risk associated with dietary saturated fat is understood but it has to be said that the significance of these findings has still not fully registered with many nutritionists and policy makers in Australia, let alone the media. So let’s recap.
The way things were
Prior to 2009 many dietary guidelines around the world included a recommendation to eat less saturated fat on the grounds that it increased the risk for coronary heart disease. But there was always an unstated corollary to ‘eat less saturated fat’ i.e. eat more of something else. If your body weight is stable and you just eat less saturated fat you will start to lose weight, because saturated fat contains calories. To maintain weight while eating less saturated fat you have to eat more of other calorie-containing nutrients, such as carbohydrate, monounsaturated fat or polyunsaturated fat. So ‘eat less saturated fat’ really meant replace saturated fat with a healthier macronutrient.
The assumption of the old dietary guidelines was that it didn’t really matter what you replaced saturated fat with – it was thought that all replacements would lower the risk for heart disease. However, we now know that this assumption was wrong.
Coconut oil is not usually recommended in healthy diets because of its high saturated fat content yet the media is awash with reports about the wonderful health benefits of coconut oil. Is this new science or marketing hype?
Among vegetable oils, coconut oil is one of the richest in saturated fat – about 86-87% of all its fatty acids are saturated. Given the latest advice to replace saturated fat with unsaturated fat it would appear that coconut oil is the last vegetable oil a credible nutritionist would recommend. Wouldn’t all that saturated fat just raise blood cholesterol and increase heart disease risk?
The case for coconut oil
Coconut oil advocates argue that not all saturated fat is the same and that the health effects of coconut oil are better than might be expected. It is true that saturated fat is not a single entity – it’s a collection of different saturated fatty acids, each with its own effect on blood lipids. Medium-chain length saturated fatty acids (6-10 carbons) appear to have little effect, whereas the longer-chain saturated fatty acids (12-16 carbons) all raise total blood cholesterol. Stearic acid, which has 18 carbons, is cholesterol neutral but continues to be treated with suspicion (see below).
At last a trial of monounsaturated-rich Mediterranean diets for the primary prevention of cardiovascular disease has been published and the results are impressive. The missing piece of the puzzle is now in place. Mediterranean-type diets, moderate in total fat but enriched with unsaturated fats, are now the preferred model for healthy diets. But will nutritionists pay any attention or cling to the low fat dogma for a little longer?
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?