The Truth About Saturated Fats
Good Fats Versus Bad Fats
I was a card-carrying skinny-latte-drinking low-fat girl. I ordered frozen yogurt instead of ice cream, grilled chicken instead of steak, and I snacked on low-fat cheese and reduced-fat crackers. With a family history of high cholesterol (my own number hovered slightly beyond the healthy range), I figured that limiting saturated fat was smart.
But in the past couple of years I've made some changes. Inspired by the movement to eat locally, I started shopping at my farmers' market: I bought a quarter of a grass-fed cow and stocked my basement freezer with the beef, which I ate once a week. I also splurged on local bacon sometimes. When my store was out of skim milk, I discovered I preferred creamier 1 percent. I began eating dark chocolate daily. At the same time, I bought fewer packaged crackers, granola bars, and other snacks.
At a recent checkup, I was shocked: Even though I was eating foods rich in saturated fat and a seemingly more indulgent diet, my total cholesterol was down 10 points, my "bad" LDL cholesterol was stellar, and my "good" HDL was the highest it's ever been. And bonus: I hadn't gained any weight! How was that possible? Actually, the health benefits I experienced may be surprisingly common, a growing number of experts say.What We're Told
Since the epic fail of the fat-free craze of the '80s and '90s, we've learned a lot. The hope was that by cutting fat from our diets, we would trim inches from our figures. Instead, the exact opposite happened: Because fat-free cookies, cheese, chips, and crackers were missing the critical fat that makes us feel full, we ate double -- sometimes triple -- the usual portion. And because manufacturers dumped extra sugar into these foods to make them taste better, we took in just as many calories and often many more. "The low-fat message backfired," says Frank Hu, MD, PhD, a professor of nutrition and epidemiology at the Harvard School of Public Health. "It led to a proliferation of products that were loaded with sugar, refined carbohydrates, and calories."
These days, advice about fat has shifted away from "Eat less fat" to "Eat the right fats." Fats are now labeled "good" and "bad." The good guys are unsaturated fats: monounsaturateds (MUFAs), found in foods like olive oil and avocados, and polyunsaturateds (PUFAs), found in sunflower and corn oils, among others, and in the omega-3s in salmon and walnuts. Both types earned gold stars because they've been shown to lower blood cholesterol and the risk for heart disease.
The villain, we've long been told, is saturated fat. The conventional wisdom, which dates to the 1950s, is that saturated fat, which is present in meat, dairy, and some plant products, increases our total cholesterol and chance for heart disease and stroke. Trans fat, a relative newcomer that dominated packaged goods and fast food, is another bad guy: It not only ups our LDL cholesterol but also lowers our HDL cholesterol (the kind that helps sweep bad cholesterol out of the body). The American Heart Association recommends limiting your intake of saturated fat to less than 7 percent of your total calories (if you eat 2,000 calories a day, that's 16 grams, roughly the amount in a chocolate milk shake) and of trans fats to no more than two grams a day.Saturated Fat Is Wrongfully Accused
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.
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