Heart disease: Is sugar the real killer?

As the link between fat, cholesterol and heart disease has fallen apart, ever more studies are linking heart disease to carbohydrates - and specifically sugar.

What can be done to stop the UAE's biggest serial killer, responsible for more than 1,000 deaths in Abu Dhabi last year alone?

This month saw the launch of a year-long campaign by the Zayed Giving Initiative to protect the population from premature death from heart disease.

Along with early diagnosis and treatment, the volunteers taking part will be giving out basic advice about how to avoid getting heart disease in the first place.

Even if we don't take much notice of it, most of us think we know what this advice is: stop smoking, cut back on fatty food and get more exercise.

But just how reliable is it? Within the medical profession, there's growing concern that when it comes to arresting this mass killer, a key accomplice has been overlooked. Sugar.

Since the 1970s, dietary advice for fighting heart disease has focused on avoiding saturated fat. And again, most of us know why: eating fatty foods leads cholesterol-packed "plaques" to clog our arteries like gunk in water-pipes, with potentially lethal effects on our heart and circulation.

It's a striking image - which may explain why it persists despite being known to be nonsense. As long ago in the 1930s, autopsy studies had shown there was no correlation between the cholesterol levels of patients and the state of their arteries.

This has since been underlined by epidemiological studies involving huge numbers of people, which have found no correlation between the risk of heart disease and dietary cholesterol or that other bete noire, saturated fat.

Ironically, as the link between fat, cholesterol and heart disease - never strong - has fallen apart, ever more studies are linking heart disease to the food group we were told to consume instead of fat, carbohydrates. And one specific carbohydrate is emerging as especially dangerous. Sugar.

Earlier this month, the British Medical Journal (BMJ) summed up the current state of play by saying that, "the sugar versus fat debate is far from over, but the pendulum is now definitely swinging away from fat as the root of all evil".

So how has the fat hypothesis survived so long in the face of so much contradictory evidence, while the role of sugar in heart disease has been overlooked?

In a fascinating article in the same issue of the BMJ, the medical writer Dr Geoff Watts delves into the story of the two rival theories. His account casts an unflattering light on the claims of nutrition to be an evidence-based science.

In the 1950s, a researcher at the University of Minnesota named Ancel Keys began a personal campaign to highlight what he saw was the obvious connection between dietary fat, cholesterol and heart disease.

For several decades Prof Keys used a potent mix of hand-picked data, denigration of critics and sheer force of personality to persuade official bodies in the US to promote carbs over fat in dietary advice.

So strong was the spell woven by Prof Keys and his followers that repeated failure of large clinical studies to back their claims made little difference.

Only now is the grip of that thesis starting to loosen. Yet back in 1972, Prof Keys and his claims faced a major challenge from the nutritional researcher Professor John Yudkin of the University of London.

In an internationally successful book entitled Pure, White and Deadly, Prof Yudkin made the case for sugar being the major culprit in a host of diseases.

Drawing on re-analysis of existing data plus some of his own, he argued that the link between heart disease and sugar was stronger than that for fat.

The evidence was far from conclusive. The huge epidemiological studies that now implicate sugar over fat had yet to be done.

Yet Prof Yudkin found his contrarian views had landed him in trouble not only in academia, but also within the multibillion-dollar food industry.

Positions and research grants started to evaporate; conferences likely to support the case against sugar were suddenly cancelled. Meanwhile, the low-fat, high- carb lobby went from strength to strength.

Prof Yudkin died in 1995, disappointed by his lack of success in getting his message across. But he was at least aware of the mounting evidence to support his claim about sugar and heart disease.

As the BMJ states, the final verdict is not yet in, but the signs are that Prof Yudkin will be seen to have been closer to the truth than his nemesis at the University of Minnesota.

An overview of the debate has been put together by Prof Robert Lustig of the University of California, San Francisco, in a new introduction for Pure, White and Deadly, re-issued last month on the 40th anniversary of its publication.

The story of how the pendulum of nutritional evidence has swung away from dietary fat and towards sugar should be required reading in any course on the history of science. For it highlights the fact that, for all its supposed objectivity, scientific progress can be hijacked by strong personalities and the "marketing" of ideas.

The softer sciences have been notably susceptible to such shenanigans. Sigmund Freud, the domineering founder of psychoanalysis, showed little interest in the lack of evidence for his nonsensical ideas about the analysis of dreams.

Similarly, the celebrated paediatrician Dr Benjamin Spock caused thousands of cot-deaths through his "expert" but lethally evidence-free advice in the 1950s to put babies to sleep on their front.

But even the more quantitative sciences have not been immune. For years biochemists refused to believe humans possess 23 pairs of chromosomes because it contradicted the claims of an influential American zoologist. Many ignored the evidence of their own eyes rather than challenge their "guru".

Fortunately, the current campaign to prevent heart disease in the UAE does include some advice about reducing sugar consumption. Time will tell whether it goes far enough.

In the meantime, whenever we hear advice from experts we could do worse than to apply the motto of the Royal Society of London, the oldest scientific academy in the world: nullius in verba. Take no-one's word for it.

Robert Matthews is visiting reader in science at Aston University, Birmingham, England