Challenging conventional wisdom
Those readers who follow The Cape Times will have seen the recent articles and letters by a group of cardiologists in response to Tim Noakes’ challenge to the conventional wisdom on the cause of the current global epidemic of cardiovascular disease.
In their original letter, Professor Commerford and several other renowned and highly respected cardiovascular specialists strongly criticised Noakes for his rejection of the so-called ‘prudent’ diet – low in saturated fats and high in carbohydrates. Noakes’ diet of protein and fat, they said, may have helped him lose weight and run faster, but it was potentially dangerous for many people, and his approach has misled lay people into abandoning the ‘prudent’ diet and in some cases giving up medication such as statins. What they failed to mention was that this diet has not just allowed Noakes to lose weight and run faster – he was never overweight in the first place – but it normalised seriously deranged blood chemistry. And Noakes is not the only person who has experienced this.
Now the ‘plural of anecdote is not data’ in the words of the great Ben Goldacre, but at least this particular anecdote should make people sit up and take notice. In Noakes’ rebuttal letter the following day he cites two large multicentre trials that show no convincing link between dietary saturated fats and heart disease. So what is causing heart disease and obesity? As long ago as the 1990s my friend and colleague Mike Burger (also a lipid researcher) pointed out an article in Science questioning the link between heart disease and dietary saturated fat. The argument was epidemiological – since the advent of the low-fat, high-carbohydrate diet the incidence of heart disease and obesity was rising rapidly in the USA. That trend is now global. And the evidence is that, at least among the middle classes, people are trying their level best to follow the conventional wisdom and eat a diet low in saturated fats and high in carbohydrates. Statins, once used only for those with seriously deranged lipids, are now ubiquitous, with some authorities advocating their use by everyone over the age of 50.
Noakes is correct. What we should now be doing is questioning ‘conventional wisdom’ and looking hard at the current dietary guidelines. Most people are now starting to think that the epidemic of obesity is largely caused by a diet high in refined carbohydrates. The first thing that should be done – and urgently – is altering the food pyramids that appear on every web site, every pamphlet about nutrition and in every school textbook. Most of these show that between 60% and 80% of our daily intake should be from carbohydrates. These carbohydrates are separated out from vegetables and fruit. In my humble opinion this is the first error. This misleads people into thinking that they should be eating pasta, bread and rice as the bulk of their diet. The more prudent among them will opt for wholegrain choices, but this is still refined carbohydrate. The average lay person probably does not realise that vegetables and fruit are carbohydrates – and that this would probably be a more prudent approach to carbohydrate intake. A public health campaign to warn people about the dangers of refined carbohydrates would be a good start, although unpopular with the food industry. What people do not realise is that low-fat products, such as fruit yogurts, are high in sugars such as fructose.
We also need to think about the fact that statins have been a huge money-spinner for pharmaceutical companies struggling to introduce new classes of drugs for an ageing world population. Most of the research into their use is backed by large pharmaceutical companies. I have no doubt that they are necessary for those with genetic lipid abnormalities, but I seriously question their current widespread use.
There is also a small but growing body of evidence suggesting that the so-called chronic diseases of lifestyle are not uniform across the population. I have recently come across interesting studies suggesting that those who develop type 2 diabetes and heart disease at a normal body weight are a lot sicker and die younger than those who develop the diseases as a result of obesity. So we are not looking at a metabolically uniform population. As Noakes says, his diet is for ‘carbohydrate-resistant’ people and I would be willing to bet that this is the vast majority of the population. So why does ‘conventional wisdom’ insist that the prudent heart diet is for everyone?
What Noakes is doing is challenging belief. We need to stop and question, even if what we are questioning are ideas that have been held dear for decades. That is the very nature of science.
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