Salim Yusuf’s advice on diet

Samir Malhotra
Professor, PGI, Chandigarh 

How would you interpret the statement "This daal is not tasty" that an uncle of mine, approaching 90, but fitter than many in their 50s, frequently makes? "Put a spoon of desi ghee in his daal and it will become tasty,"  says his wife, my aunt. Well, she should know — having been together for six decades.

Saturated fat has been made out to be a villain for as long as I can remember. Of late, dissenting voices are being heard, though. One such voice is that of Salim Yusuf, born in Kerala, MBBS from St John's, Bangalore, and currently at McMaster University, Canada. President of the World Heart Federation, he is among the most cited scientists in the world. According to the Scopus database, he alone has more citations than any of our medical institutions, barring Delhi AIIMS and Chandigarh PGI. His h-index, a research metric, is 185, among the highest in the world.

Although his group's recent research, Prospective Urban and Rural Epidemiological Study (PURE) was published a few months ago, it was wonderful  to listen to him during the recent World Non-Communicable Diseases Congress. PURE was a study of dietary habits, conducted over seven years, in 18 countries, across five continents, and on 1,35,000 people. Its main findings were: 

(i) High fat intake, including saturated fat, was associated with about 23% reduced risk of mortality. 

(ii) High carbohydrate intake was associated with a 28% increased risk of mortality.

This refutes the old guidances as well as recent American Heart Association Advisory recommending replacing saturated fats with poly- and monounsaturated fats and "good carbohydrates" such as whole grains and whole fruits for heart disease prevention. Dr Yusuf categorically stated that such recommendations are not evidence-based. 

PURE also moderated the current recommendation of 5-9 servings per day of fruits/vegetables and showed that their beneficial effect on mortality peaked at three-four servings daily, with no extra benefit of more servings. PURE also showed that there was no association of fat or carbohydrate or fruit/vegetable intake with heart disease.

Before we read too much into these results, let us understand that while such observational studies are quite useful for proposing hypotheses and giving associations, they are not ideal for establishing cause-effect relationships.  For instance, if we study the association between the number of doctors in the PGI with environmental pollution over the past five decades, we will find that there is a direct correlation between the two. Does this mean that the PGI doctors are causing pollution?  

Take a hypothetical example — let us say we do a study and ask one lakh Chandigarhians about their dietary habits and follow them up for a decade to see how many died. Assuming we find that food 'X' was associated with death, we cannot conclude that we have proved 'X' causes death. On the other hand, if we find that 'X' was NOT associated with death, we can say with reasonable degree of certainty that 'X' does not cause excess mortality. Thinking along these lines, what PURE clearly shows is that saturated fat does not cause excess death or heart disease even though we may be sceptical about whether it is beneficial. 

Dr Yusuf was quite clear when he said that this is not a licence to eat excessive amounts of fat, but that in moderate quantities saturated fat may actually be good. Winter is coming — this information will at least let us eat guilt-free our saag & makki di roti with desi ghee. Only in moderation!

Nothing extraordinary about his other advice, as he himself acknowledged — no smoking, regular exercise. And this is what he had to say about weight, "Maintain a reasonable weight. No need to be too overweight nor too skinny."  He further stated, "Eat a balanced diet — a bit of meat, fish, several portions of fruit and vegetables, but you don't have to be vegan or eat an excessive amount of plants to be healthy." 

Now coming back to my uncle. As a scientist, I understant that such anecdotal evidence has even less value than epidemiological studies. But he makes an interesting study — he follows none of Dr Yusuf's recommendations — finishes a box of sweets within hours, his exercise includes just two short walks with his dog, he is never too thrilled with fruits/vegetables. What is the reason for his health? Could it be his optimisim and sense of humour, matched if not exceeded by his wife? None of this was studied in PURE, and I doubt these factors are codifiable.