One of the world's top cardiologists says that many of the major nutrition guidelines have no good basis in science.
"I'm not a nutrition scientist and that may be an advantage because every week in the newspaper we read something is good for you and the same thing the next week is bad for you," said (McMaster University), at , a symposium presented by the European Society of Cardiology and the Zurich Heart House.
Yusuf presented evidence that many of the most significant and impactful nutrition recommendations regarding dietary fats, salt, carbohydrates, and even vegetables are not supported by evidence.
Yusuf's talk relied heavily on findings from the , a large ongoing epidemiological study of 140,000 people in 17 countries. Though PURE is an observational study, "its design and extensive data collection are geared toward addressing major questions on causation and development of the underlying determinants of cardiovascular disease."
Much of the data presented by Yusuf has not been published yet and should be considered preliminary, he said. In 2014 .
The results from PURE will likely add fuel to the ongoing fiery debate over carbohydrates and fats. Yusuf displayed data showing that the incidence of cardiovascular disease in the PURE population increases as carbohydrate intake (as a percentage of total calories) rises.
"Previous guidelines said reduce fats and compensate for it by increasing carbohydrates ... and so essentially we've increased carbohydrate intake in most Western countries and this is likely damaging. We were in for a big surprise. We actually found that increasing fats was protective."
The PURE data show a steep increase in CV risk as carbohydrate intake increased beyond 55% of total energy. WHO guidelines state that up to 75% of energy can come from carbohydrates. "But that is wrong," said Yusuf.
Dietary Fat
"We actually found that increasing fats was protective," he said. Low consumption of total fat was associated with increased risk. Very high fat is also "probably bad," Yusuf said, based on earlier studies from Finland with people who had "extremely high fat levels, not the usual fat levels that populations consume."
No clear patterns emerged for different types of fats, Yusuf reported. Trends suggested that saturated fats were not harmful and perhaps even beneficial, while monounsaturated oils appeared beneficial. Polyunsaturated oils had a neutral effect, he said.
"You've got to think about the change in oils that have occurred in the world in the last 30 years," said Yusuf. "It was entirely industry driven. We went from natural fats, which are animal fats, to vegetable fats, because they [industry] can produce it and therefore charge for it, and this was swallowed hook, line, and sinker by the AHA, and the WHO just repeated it."
Yusuf also took aim at milk consumption trends in the US. "Even if you consume milk they want you to consume 2% or 1% of fat" but, he asked, "what is the evidence?" "A big, big, zero," he said. In fact, he said, there "really are no data at all to reduce the fat content of milk."
Yusuf came down squarely in favor of fats over carbohydrates: "Fundamentally, some fats are good, some fats may be neutral, but it's carbohydrates that are the worst thing." He offered a piece of advice: "so when you eat a hamburger throw away the bun and eat the meat."
Yusuf summarized the PURE findings, which found that saturated fats from dairy sources were protective and saturated fats from meats were neutral. White meat from chicken or fish appeared to have a beneficial effect, while red meat in moderate quantities was not associated with harm.
Yusuf volunteered a strong endorsement for , author of The Big Fat Surprise, who has been heavily criticized by the nutrition establishment for her defense of dietary fat. "She shook up the nutrition world but she got it right," said Yusuf.
"Why did we go wrong? We went wrong because of surrogate endpoints."
The demonization of fats -- saturated fats in particular -- stemmed from earlier observations linking saturated fat consumption to LDL levels. Yusuf reported that PURE confirmed this finding, but he also noted that the overall difference in LDL was small and that there was a large amount of variance. More importantly, randomized studies that have looked at fat reduction to reduce cardiovascular events have not shown benefit, except in cases where fat levels were extremely high, he said.
Yusuf said that the ApoB/ApoA ratio is a much more highly sensitive marker of risk. Data from PURE shows that this ratio goes up with carbohydrate consumption but is neutral with saturated fats or polyunsaturated fats and declines with monounsaturated fats.
Regarding salt consumption Yusuf restated findings from and t. He said the low sodium position was based on the well-established relationship between sodium and blood pressure. But, he argued, the benefits of extremely low levels of sodium have never been tested in a randomized controlled trial. Further, since sodium is an essential nutrient it is inevitable that taking sodium levels too low will be harmful. He also pointed out that although reducing blood pressure through sodium reduction may turn out to be beneficial in people with hypertension, it is entirely possible that non-hypertensives will derive no benefits from sodium reduction but they may well be susceptible to the harms associated with low sodium levels.
Fruits and Vegetables
Yusuf also raised questions about fundamental recommendations that are almost never subject to critical scrutiny. "Where on earth did the concept that we should eat 5 servings of fruits and vegetables come from?" asked Yusuf.
"Why not 4, why not 3, why not 6, why not 7? Is it all fruits, is it all vegetables, is it what kinds of fruits, what kinds of vegetables?"
He reported that the PURE data found a neutral effect for vegetables, and that the literature is "really inconsistent." More importantly, he dismissed the idea that foods need to be judged based on their effect on health. "But I have to tell you, when it's regarding diet, neutral is good. You have to eat something. If you like it eat it. Not every food has to be good or bad."
Yusuf then pointed out that it is almost impossible for a large portion of the world to follow these fruit and vegetable recommendations. "Why are fruits and vegetables not consumed? All the guidelines are written by people sitting in Geneva or Dallas who are white, rich, and male. They are male, and so they don't know the cost of foods, they don't go do the grocery shopping. They're white and they only think of what happens in their countries." In high income countries like Canada and Sweden people spend only about 10% of their income on food. But in lower income countries like Pakistan, India, Zimbabwe, 65% of income is spent on food. It is then "no wonder that they're going to buy the cheapest food," he said. The cost of buying 2 servings of fruit and 3 servings of vegetables, as recommended by WHO, is completely unaffordable for many.