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PURE bombshell


By Dr. Upul Wijayawardhana

Close on heels of the terrible terrorist attack in its famous street, Las Ramblas on 17 August, Barcelona had another bombshell this week but, fortunately, it was benign and of a scientific nature. Defying terrorist threats, an art we Sri Lankans perfected over forty years, Cardiologists from all over the world assembled in their thousands for the European Society of Cardiology meeting where many a ground-breaking trial was presented. The most talked about and, perhaps, the most significant is the PURE study; some aspects of this series of studies was presented which dropped a bombshell, media resounding with headlines like "Fat is good for you".

Doctors are often accused of giving differing health advice, sometimes diametrically opposite, at different times and I can well understand the frustration of patients. In a way doctors are helpless; it is simply because they depend on researchers for the latest findings and, fortunately or unfortunately, it is the nature of science that new discoveries challenge long held views. A compounding factor is that even top researchers, once they convince themselves of a notion, become impervious to new data and search for even the flimsiest evidence to cling on to their beliefs. Longest running controversy in my chosen field, Cardiology, has been the role of dietary fat in the causation of atherosclerosis, hardening of arteries. Has PURE finally given the answer?

PURE studies

PURE, which stands for Prospective Urban Rural Epidemiology study, as the term indicates is a long running epidemiological study, led by co-investigators Drs. Salim Yusuf and Koon Teo at McMaster University in Hamilton, Canada. This is the largest global study looking at environmental, societal and biological influences on obesity and chronic health conditions such as heart disease, diabetes and cancer. There are a number of strands to this study and papers on different aspects are presented and published regularly.

The PURE study results presented at the ESC Congress, in two presentations, were from a total of 135,335 adults aged 35 to 70 years recruited between 2003 and 2009 from urban and rural communities in low-, middle-, and high-income regions of 18 countries in five continents. Researchers recorded food intake at baseline, using country-specific food frequency questionnaires, and collected demographic, socioeconomic, lifestyle, family history, individual health history and medication information. During a median follow-up of 7.4 years (5.5-9.3) there were 4,784 major cardiovascular disease events, 1,649 cardiovascular deaths and 5,796 total deaths.

Fruits, vegetables and legumes

One paper was based on the analysis of fruit, vegetable and legume consumption. Researchers found higher consumption of these was associated with a lower risk of non-cardiovascular and total mortality, three to four servings per day (equivalent to 375-500 g/day) providing the maximum benefits. When looked at separately, researchers found fruit intake was associated with lower risk of cardiovascular, non-cardiovascular and total mortality, while legume intake was inversely associated with non-cardiovascular death and total mortality. Raw vegetable intake was strongly associated with a lower risk of total mortality, while cooked vegetables were associated with a modest benefit against mortality.

The significance of this study is that it disproves the widely held belief that more is better, as the benefits seem to plateau out after three or four servings. The current recommendation is at least five portions a day but I have seen some reports recommending ten portions, an unachievable target. The take home message, from this paper, is to have more fruits and uncooked vegetables in salad form, drizzled with virgin coconut oil; that last recommendation being entirely mine, meant to enhance flavour. Anyway, there is enough information to show that virgin coconut oil is harmless, may even be beneficial.

Dietary fats and carbohydrates

The more important paper focused on the association of fats and carbohydrate intake with cardiovascular disease and mortality. I am sure the audience would have waited with bated breath as, just two months ago, the American Heart Association issued a Presidential Advisory on Dietary Fats and Cardiovascular disease which stated: "Taking into consideration the totality of the scientific evidence, satisfying rigorous criteria for causality, we conclude strongly that lowering intake of saturated fat and replacing it with unsaturated fats, especially polyunsaturated fats, will lower the incidence of CVD." The bombshell was that PURE found just the opposite: Total fat and individual types of fat were associated with lower risk of total mortality, but were not significantly associated with risk of myocardial infarction or cardiovascular disease mortality. Interestingly, higher saturated fat intake was associated with lower risk of stroke. What was even more interesting was the finding that high carbohydrate intake was associated with higher risk of total mortality, but not with the risk of cardiovascular disease or cardiovascular disease mortality. In short, it is sugar that kills not fat! Therefore, cut down on sugar and stop feeling guilty about fat consumption.

The lipid hypothesis

In the sixties and seventies, when marked increase of heart attacks was causing increasing concern, two experts disagreed as to the cause of the ‘epidemic’. British Physiologist John Yudkins argued that sugar was the culprit. In fact, he wrote a book in 1972 titled "Pure, White and Deadly" wherein he went to the extent of stating that dietary fats are harmless. He was countered by the American Nutritionist Ancel Keys who, based on the ‘Seven Countries Study’ which showed a linear correlation between the incidence of Coronary Artery Disease and fat consumption in the seven countries, argued that dietary fat was the main culprit. Keys won and the lipid hypothesis held sway for almost fifty years. Supporters of both continue to argue till this day and will continue to do so in spite of the findings in PURE study which seems to have made Yudkin’s views prophetic.

PURE study is a well conducted, very large study but it still has the disadvantage of being an observation study which can only identify an association unlike a Randomised Clinical Trial which can establish causation. But it is the best piece of evidence we have at the moment and based on this, it is inevitable that guidelines from learned societies be revised.

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