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A public attack on diet dogma from fats to vegetable intake got leading cardiologist Salim Yusuf, MD, DPhil, into scalding water with nutrition experts.
Yusuf, speaking at the Cardiology Update 2017 symposium, noted that he was no expert on nutrition but argued some controversial points for heart health, including:
- Greater fat intake (even saturated fat) was protective
- More carbohydrates were harmful
- Higher fat dairy was beneficial
- Saturated fat from meat was neutral
- More vegetable intake wasn't any better
These conclusions were based mainly on unpublished, preliminary results of his group's ongoing PURE study. That epidemiological look at 140,000 people in 17 countries was designed to address causation and underlying determinants of cardiovascular disease, he said in the talk, which has been by the official conference YouTube page but is still .
While Yusuf is no stranger to controversy, having released hotly-debated conclusions on sodium from PURE already, the diet discussion was deemed "irresponsible" this time. Plant-based diet proponent , even called some of the comments and called for an apology.
was the description by , president of the American College of Lifestyle Medicine, writing in Forbes. He argued that "we have no business seeking expert nutrition guidance from non-experts."
Whatever else, Yusuf's "comments are premature and not helpful," , of New York University in New York City, told 乌鸦传媒視頻. "In view of the fact that he is basing his comments on unpublished work, it's not possible to address his specific concerns.
"But in general, it is well established that healthy diets based largely on plant foods are associated with a lower risk of chronic disease. The specific contribution of fats and sugars is more difficult to establish because so much depends on the number of calories consumed with them."
, of the University of Ottawa, agreed. "I'm not sure that trading premature and perhaps dogmatic low-fat advice, for premature and perhaps dogmatic high-fat advice is supported by the medical literature to date. Seems to me that the most evidence-based advice around fats would be to try to replace saturated fats with unsaturated, to avoid trans, and that if the choice is between saturated fats and refined carbohydrates, the fats are the better choice."
More to the science, Katz broke down what he called a in conclusions such as that meat, but not vegetable intake, is protective against heart disease in a post on LinkedIn.
"Poor countries traditionally eat little meat, and have a very high intake of carbohydrate. In some cases, they have a high intake of fat, too, but from plant sources rather than animal; this is true, for instance, in rural Greece and other Mediterranean populations. In almost no instance do they have a high intake of saturated fat. We know, because it's on prominent display, that when countries with traditionally high-plant, high-carbohydrate, low-saturated-fat and low animal food diets switch to the more 'affluent' pattern of eating more meat, their rates of obesity and chronic disease rise. This is perfectly clear in both India and China."
Katz added that "we might ask: well, what happens within a given population, where access to medical care is the same, when diet is changed? We have the answer. Randomized trials including the Lyon Diet Heart Study, PREDIMED, and others have shown, over a span of years and in multiple countries, that shifts to more plant foods, unsaturated oils, and less meat reduce heart disease, other chronic disease, and rates of premature death from all causes."
Vegan diet proponent and prominent cardiologist , of Rush University Medical Center in Chicago, further challenged the conclusions:
"I have the same concerns that Salim Yusuf actually expresses – this is not randomized data, so it can be hypothesis generating but not prescriptive, particularly because many of his statements conflict with existing scale. Some of these dietary issues may simply be distortion of scale – differences that are too narrow to show a clinical difference. For example, the PURE study had the highest category as >4 servings of vegetables and that was only a small fraction of the population (9,000 out of 150,000).
"But a with over 1,000,000 total subjects demonstrated that consuming 10 servings (200 grams per day) has a dramatic reduction in mortality, stroke, and cardiovascular outcomes.
"Thus, the 'dose' in the PURE study may be too small, with alternative food stuffs, such as animal protein, not varied enough between groups to . In other words, if you want to show improvement with vegetables, it may be best to , rather than smaller variations among omnivorous populations."
For an update on this story, click here.