Hurray, we can all eat grease again! On March 17, 2014, after decades of damning evidence that "bad" fat leads to heart disease, certain cancers, and other serious and even fatal health problems, headlines proclaimed the results of a new study, published in a prestigious journal, that seemed to say that "bad" fat wasn't so bad for your heart after all (1).
But before you fry up that bacon, hold the fork. It turned out that the study had some statistical quirks that made "bad" fat look safer than it really is.
The study was a meta-analysis. That is, it combined the results of several prior research studies. Some had shown marked dangers of saturated fat, while others did not, and they were all blended together in a statistical stew. The weak studies tend to dilute the stronger ones, masking real dangers.
The analysis also used results that were statistically adjusted so as to downplay the dangers of saturated fat. One that went into the mix was Harvard's famed Nurses' Health Study (2). In the original study, those who ate the most saturated fat had a 52 percent increased risk of developing heart disease. That's obviously alarming. But the numbers were then adjusted for cholesterol intake, protein intake, and other factors, making the risk vanish. Here's the problem: The foods that have saturated fat are the same ones that have cholesterol and protein. Meat, for example, has all three. So if you adjust the statistics for cholesterol and protein, the dangers of "bad" fat are hard to see.
It's a bit like studying whether cigarettes cause cancer. If you adjust the statistics for whether people carry cigarette lighters and have ashtrays in their homes, the relationship between cigarettes and cancer can be made to disappear.
Other researchers immediately caught the flaws and called for a retraction. But that didn't stop the article from being widely quoted as showing that "bad" fat was "safe."
Even if you bought the myth that lard won't hurt your heart -- not a sensible thing to do -- it pays to remember that "bad" fat poses other risks. In a carefully controlled Chicago study, researchers found that people eating the most saturated fat had a far higher risk of developing Alzheimer's disease, compared with people who avoided "bad" fat (3). And overwhelming evidence shows that meat-eaters have more weight problems, heart attacks, cancer, diabetes, and hypertension, compared with people who avoid meat (4-8).
"Why are we even talking about saturated fat, anyway?" you might ask. A big reason is that, in 1977, the Senate Select Committee on Nutrition and Human Needs recommended that Americans cut back on meat for health reasons. That was good advice. But the beef industry fought back, making it clear that criticizing meat was a serious political no-no. So when the U.S. Dietary Guidelines were published, they danced around ideas like "eating less meat." Instead, they used a sort of nutritional code, recommending that Americans "limit saturated fat and cholesterol."
Americans were confused -- exactly what the meat industry had hoped for -- and meat intake didn't drop one bit. It actually climbed from 178 pounds per person per year in 1970 to more than 200 pounds in 2004. Cheese, oil, and sugar intake rose, too. And Americans got fatter and fatter. No it wasn't those Snackwell's low-fat cookies that broadened our girth; it was the bacon and egg sandwich and the chicken salad.
The tobacco industry is no doubt kicking itself. Had it used the same tactick confusing consumers by focusing on specific parts of tobacco smoke -- say benzo(a)pyrene -- instead of on smoking itself, it could have deflected attention away from overwhelming evidence that smokers get cancer.
So, while researchers debate about saturated fats, monounsaturated fats, dietary cholesterol, and -- yawn -- all the other things that go into burgers and pork chops, it pays to remember one fact: Meat is unhealthy. Whether you blame its "bad" fat, its cholesterol, the vitamins that meat is missing, its lack of fiber, or anything else, meat boosts your risk heart disease, diabetes, hypertension, and colon cancer. So skip the meat. Vegetables, fruits, whole grains, and beans are still exactly what the doctor ordered. There are plenty of cookbooks and plans to get you started.
References:
1. Chowdhury R, Warnakula S, Kunutsor S, et al. Association of Dietary, Circulating, and Supplement Fatty Acids With Coronary Risk: A Systematic Review and Meta-analysis. Ann Intern Med. 2014;160:398-406.
2. Chiuve SE, Rimm EB, Sandhu RK, et al. Dietary fat quality and risk of sudden cardiac death in women. Am J Clin Nutr. 2012; 96:498-507.
3. Morris MC, Evans EA, Bienias JL, et al. Dietary fats and the risk of incident Alzheimer's disease. Arch Neurol. 2003;60:194-200.
4. Craig WJ, Mangels AR, American Dietetic Association. Position of the American Dietetic Association: vegetarian diets. J Am Diet Assoc. 2009 Jul;109(7):1266-82.
5. Tonstad S, Butler T, Yan R, Fraser GE. Type of vegetarian diet, body weight and prevalence of type 2 diabetes. Diabetes Care 2009;32:791-6.
6. Spencer EA, Appleby PN, Davey GK, Key TJ. Diet and body mass index in 38,000 EPIC-Oxford meat-eaters, fish-eaters, vegetarians, and vegans. Int J Obesity 2003;27:728-34.
7. Berkow S, Barnard ND. Vegetarian diets and weight status. Nutr Rev 2006;64:175-188.
8. Yokoyama Y, Nishimura K, Barnard ND, et al. Vegetarian diets and blood pressure: a meta-analysis. JAMA Internal Medicine 2014, Feb 24, epub ahead of print.