NEW SCIENCE KNOWLEDGE ON DIET

“Knowledge is like fish - it goes off”

The medical world, for the past seventy - five years, backed up by powerful governmental and commercial institutions, has unambiguously advocated a low fat diet with an emphasis on the intake of carbohydrates. To this day the Food Pyramid, which represents the dietary policy of the United States Center for Nutrition, recommends carbohydrates of one sort of another to make up the majority of the calories as the source of nutrition.  Pasta, cereals, bread and rice form the bulk, (a minimum of six servings per day) while fruit and vegetables, which are carbs as well, are suggested to make up a further five servings.  Proteins and Fats, dairy produce, meat, poultry, eggs and fish according to this unbending protocol are advocated for only four servings per day. The danger of fats and cholesterol is underlined on the government site with a warning that these nutrients can cause a higher risk of heart disease and certain types of cancer. 

Over the years there have been challenges to this approach, mainly from non medical groups, but only recently has this mantra been seriously confronted in the medical scientific arena. Spurring on the assault on the holy grail has been a paradigm changing study the outcome of which was published in the prestigious British Medical Journal,The Lancet, this month. 

But before elaborating on the findings it needs an explanation on what the medical profession based its recommendations in the first place. 

THE GENESIS OF THE LOW FAT HIGH CARBOHYDRATE DIET

It is fair to argue that the basis of the high carbohydrate low fat diet had a large body of science behind it and it’s advocacy represented a reasonable interpretation of the available evidence at the time. The foundation of the knowledge that lead to the recommendations lay in a unique painstaking scientifically valid epidemiological study which was conducted over decades, entitled the Framingham Study. This pioneering work focussed on observations of a small stable Massachusetts community in a town called Framingham. The group of investigators initial revelations nailed three key risk factors for coronary heart disease - hypertension, cigarette smoking and raised cholesterol. The latter discovery would lead to the medical profession to focus on lowering cholesterol as a means for preventing heart attacks in addition to the aggressive management of hypertension and an anti smoking crusade. 

The next major influence in the genesis of the low fat diet was lead by an American physiologist Ancel Keys who, like the Framingham group, found raised cholesterol to be causative of heart attacks. Spearheaded by Keys’s investigations, the medical establishment made the assumption that decreasing dietary fat intake would lead to lower blood lipids and cholesterol and therefore a decrease in heart disease. In 1956 the American Medical Association made its nutritional endorsement that is still alive and well in the Food Pyramid. The objective was to cut down dramatically on fats intake as they caused heart disease and replace them by carbohydrates. 

THE OPPOSITION TO THE HIGH CARBOHYDRATE LOW FAT DIET

As early as the sixties Keys was challenged by a British physiologist, John Yudkin, who argued that sugar especially fructose was the culprit not cholesterol in the etiology of coronary heart disease. Yudkin published a book entitled “Pure White and Deadly” and became the pariah of the medical profession, lead by Keys. The British nutritionist was laughed out of court. Jay H. Ell, as a medical student, experienced this barrage first hand when Yudkin was a Visiting Professor, in 1965, to his Medical School at the University of Cape Town. He was ignored and poo poohed when he questioned one heart attack victim after the other on their diet. This even so when the victims claimed that their food intake consisted predominantly of carbohydrates. The patients’ lipid panels, however, were raised and the assumption was that that was due to food intake. Keys won the debate and the British Professor was largely ignored. The emphasis on low fats and high carbohydrates was institutionalized by the food industry where it still gleans major backing to this day.

 It was nearly fifty years later that the sugar pioneer was vindicated. In 2012 his book was republished and widely read.  A Californian pediatric endocrinologist gained recognition for corroborating Yudkin’s work as to the dangers of sugar in the genesis of obesity, heart disease and diabetes. In fairness other researchers had backed the sugar and carbohydrate hypothesis but they too were ignored.  

What may have heralded a revolutionary institutional change in this domain is a recent major nutritional epidemiological study organized by a vast team of Canadian researchers. The latter has solidified the Yudkin sugar theory on a sound scientific basis.

THE LATEST NUTRITIONAL STUDIES

A series of seminal papers emanating from the McMaster University in Canada and published, this month, in the British Journal, The Lancet, is bound to trigger a revision of the high carbohydrate low fat diet. They resulted from the Prospective Urban Rural Epidemiology, (PURE) study which was conducted in eighteen countries. A 135,000 patients were enlisted and observed, on average, for seven years. Their diets were analyzed and their health outcomes recorded. During the study 5,796 patients died and 4,784 cardiovascular incidents were recorded. 

The key findings revealed that those patients who had a high intake of carbohydrates had a thirty percent greater chance of dying while those who had a high diet of fats had a twenty three percent less chance of succumbing. In addition the positive effect of a high number of servings of fruit, legumes and vegetables was not borne out in the findings. The benefit of these nutrients was maxed out at only three to four servings per day as opposed to the minimum of five demanded by the Food Pyramid. The study also indicated that a high carb diet in fact increased the blood lipids rather than the conventional wisdom that it was fats. All this finally vindicated the many groups that have been advocating variations of diets that emphasize a high fat content.

CONCLUSIONS

* To understand the PURE result it is obvious that dietary intake of fat has not the, long touted, effect of increasing the blood lipids including cholesterol. In fact the opposite occurs. The source of the high cholesterol that Framingham famously found to be associated with heart disease, in the middle of the twentieth century, is produced by the body endogenously, and not by fat food intake, which theory had been pioneered by Keys.  

* The PURE study will give an impetus to the advocates of high fat low carbohydrate diets and the dieting industry generally There are several versions on the market and in the literature including the Atkins diet and a more severe example - the Ketogenic diet. The latter limits carbohydrates dramatically mainly to leafy greens and  above ground grown vegetables. This turns the conventional food pyramid on its head with all the meats, fish, poultry, eggs and dairy at the base and the carbs at the apex. 

• One fact for sure is that John Yudkin has been vindicated although the medical profession has been resistant to accept the reversal of the former theory that had been written in stone. In fact the leading proponents of this approach including  Dr. Tim Noakes of South Africa have faced challenges from those in control of the profession. Noakes even faced a disciplinary action for advocating management not consistent with conventional guidelines and for inappropriately giving advice on social media. Not surprisingly Noakes was abandoned by his University colleagues who stuck to the conventional hymns. The hearing turned out to be an international platform for those supporting the status quo and those backing the latest science. Noakes was found not guilty, striking a blow for his preferred Banting low carbohydrate/high fat diet.

• While the high fat /low carbohydrate diet is steadily gaining acceptance there are two key factors that there is no consensus on -  how much fat in the diet is best and high low should the carbohydrate intake be.  Also there needs to be greater clarification on the differing effects, if any, between unsaturated and saturated fats.

• There is also evidence that that the fractions of cholesterol such as LDL and HDL may not be the most useful in measuring cardiac risk and other parameters will be introduced. The current understanding will change and be developed as times goes on. Remember however no scientific knowledge is necessary the ultimate truth. Many a sacred cow has been toppled by advances and as the Chinese proverb reminds us - Knowledge is like fish….it goes off. 

• The application of the latest knowledge might take decades to take hold. The food industry revolves around the Food Pyramid and, if it needs reminding, it took half a century for the tobacco industry to officially call it quits and even then they are still going strong.

PAUSE FOR A MINUTES SILENCE

Finally, the very least the institutions could do would be stand in silence out of empathy for those of us who, for three score and ten years, have had a hearty eggless cereal breakfast, learned to love skim milk and butterless bread, resisted meat, avoided cheese, ate guiltless pasta and dutifully took our statins. Still the baby boomers can take heart, pardon the pun, they are still around and seventy is the new forty.