After decades of bashing saturated fat, the medical community was stunned by a 2010 study in the American Journal of Clinical Nutrition. In a research analysis, scientists discovered that there wasn’t enough proof to link saturated fat to either heart disease or stroke. It wasn’t the first time this fat had been vindicated: Four years earlier the Women’s Health Initiative study found that eating less saturated fat didn’t result in lower rates of heart disease or stroke. The 2010 analysis, however, was so big and so thorough — involving 21 studies and nearly 350,000 people — that it grabbed experts’ attention. “Everyone had just assumed that the evidence against saturated fat was strong,” says study author Ronald Krauss, MD, a professor of nutritional sciences at the University of California, Berkeley, who was surprised by the finding and the controversy it created. “We had to work hard to get our study published. There was an intrinsic mistrust of this kind of result.”
Researchers say there were even earlier clues that saturated fat didn’t deserve its reputation as top dietary villain. The decades-old “diet-heart hypothesis” — the idea that saturated fat is bad for the heart — was mostly based on animal studies and short-term trials that looked only at people’s cholesterol levels, not at whether they actually had heart attacks. “Those studies are great for making hypotheses but not for making widespread recommendations,” says Dariush Mozaffarian, MD, an associate professor of medicine and epidemiology at Harvard Medical School and a researcher of diet and heart health. “When we started getting evidence from longer trials and observations, we realized that the truth is more nuanced than we thought.”
What researchers discovered was that cutting out saturated fat didn’t make much difference, until you considered what people ate in place of it. Swapping animal fats for vegetable oils — for instance, using soybean oil instead of butter — appeared to lower LDL cholesterol levels and disease risk. But trading your a.m. bacon for a bagel didn’t do the trick. “When you replace saturated fats with refined carbs, your triglycerides can go up and your good HDL cholesterol can go down,” explains Alice H. Lichtenstein, the director of the Cardiovascular Nutrition Laboratory at Tufts University. High triglycerides and low HDL are risk factors for cardiovascular disease and criteria of metabolic syndrome, a cluster of health problems linked to diabetes and heart disease.
Eating less saturated fat doesn’t seem to help your weight, either. A study in The New England Journal of Medicine found that people on a low-carb diet shed pounds faster and had better cholesterol levels than those on a low-fat diet, even though the low-carb group was taking in relatively more saturated fat. This may be because people eating fewer carbs release less insulin, which may reduce fat storage, control hunger, and influence metabolism in a way that helps keep cholesterol in check.
This information was originally posted here on Fitness Magazine