In a stunning reversal of nearly four decades of nutrition policy, the 2015 Dietary Guidelines for Americans (DGA) call for big changes in the way we think about the fats in our diets. The 2010 guidelines—they’re issued every five years—called for restricting total fat intake to no more than 35% of daily calories and cholesterol to a maximum of 300 mg per day. The new advice…
• No restriction on total fat intake.
• No worry about dietary cholesterol.
• A new emphasis on the benefits of polyunsaturated fats.
Believe it or not, these are great changes, but they don’t go quite far enough—and some of the other advice on fats still relies on outdated scientific evidence and could put you at risk.
You’ll be hearing a lot about the new government eating guidelines. Read on to find out what they get right…and what they get wrong…
THE MOST SURPRISING ADVICE: POLYUNSATURATED FATS ARE THE BEST
An emphasis on polyunsaturated fats is one strength of the guidelines, according to Dariush Mozaffarian, MD, DrPH, dean of the Tufts University Friedman School of Nutrition Science and Policy. These fats include the omega-3 fatty acids (EPA and DHA) found in fatty fish such as salmon, but also the linoleic fatty acids found in nuts such as walnuts, pecans, pistachios and almonds, as well as cooking oils such as safflower, sunflower, corn, canola and soybean.
“Total monounsaturated fats, which come from both plant and animal sources, appear to have a relatively neutral effect on cardiovascular disease,” he says, “whereas polyunsaturated fats from vegetable oils, nuts and fish are clearly beneficial. The new dietary guidelines recognize this stronger evidence for polyunsaturated fats than monounsaturated fats.”
That may come as a surprise to many people who long ago tossed their corn or safflower cooking oils and stocked up on olive oil. The new research suggests that it’s time to welcome these seed-based oils back to your kitchen—but keep the olive oil. Says Dr. Mozaffarian, “Plant sources of monounsaturated fats, especially those rich in [antioxidant] phenolics such as extra-virgin olive oil, are still a very healthy choice. For instance, the Mediterranean diet, which includes extra-virgin olive oil, fish and nuts, is one of the healthiest dietary patterns ever studied, and both the dietary guidelines and Dr. Mozaffarian recommend it. (For more on the Mediterranean diet, see Bottom Line’s guide.)
THE BEST PART OF THE NEW GUIDELINES: FOOD
Indeed, the best thing is their focus on food rather than individual nutrients, according to Dr. Mozaffarian. In that regard, they encourage a dietary pattern that is rich in vegetables, fruit, whole grains, seafood, legumes, nuts and dairy products, moderate in alcohol (among adults), lower in red and processed meat and low in sugar-sweetened foods and beverages and refined grains.
What you will no longer see in the guidelines is any advice to limit the total amounts of fat and cholesterol that you consume. That’s going to be a real mind-bender for generations of people trained to limit—and essentially fear—these nutrients. This new permissiveness is rooted in new scientific evidence that limiting total fats doesn’t reduce the risk for cardiovascular disease, diabetes, cancers or obesity, explains Dr. Mozaffarian. Plus, experience has shown that limiting fat overall, in real life, has the unintended consequences of reducing people’s consumption of healthy fats while increasing their intake of foods loaded with added sugars, refined grains and starches—which do increase the risk for obesity, diabetes and heart disease. As for dietary cholesterol, it’s been shown that, within the usual diets eaten in the US, eating foods that are high in cholesterol doesn’t have major effects on the levels of cholesterol in the blood. Dr. Mozaffarian praises the new guidelines’ “quiet lack of statements regarding total fat intake” and the “greater focus on the quality of fats.”
Why that matters: “Many of the healthiest dietary patterns are high in healthy fats.”
WHAT THE DIETARY GUIDELINES GET WRONG
So far, so good. But Dr. Mozaffarian says some misguided advice remains—for instance, a mistaken emphasis on reducing saturated fat. These are the fats that are solid at room temperature, such as those in milk and beef. “Rather than simply saying to increase polyunsaturated fats, the guidelines still advise reducing saturated fat—keeping a 10% of total calories limit on saturated fat,” he says.
But saturated fats aren’t dietary demons. “While many people still think there’s strong evidence that saturated fats are harmful, the evidence suggests their health effects are more middle-of-the-road ,” he says. “There are healthier nutrients, such as polyunsaturated fats, and more harmful nutrients, such as refined carbohydrates, sugars and trans fats.”
Most importantly, he says, the focus on saturated fats contradicts the major new advance of the new guidelines—to focus on foods, not individual nutrients. “There are foods that contain saturated fats that are good for you, and foods with zero saturated fats that are harmful. There is also a range of saturated fats. Because of this complexity, focusing on total saturated fat alone can be distracting and misleading.”
How he would fix it…
• Emphasize increasing sources of polyunsaturated fats rather than decreasing saturated fats. Says Dr. Mozaffarian: “It would have been better if they’d said ‘nuts and vegetable oils are healthy—eat more of these whether it’s in place of foods rich in carbs or saturated fats’—without placing a specific cap on saturated fats. Better to place a cap on refined starches and sugars!”
• Give dairy a break. “The proposed guidelines also kept the historical recommendation to consume low-fat dairy, even though there’s no evidence that it’s healthier than whole-fat dairy,” he says. “All our recommendations about dairy have been based on nutrient theory—particularly, that calcium and vitamin D are important for bone health and that saturated fat is harmful for the heart—rather than understanding what happens to your health when you eat cheese, yogurt, milk or butter. Dr. Mozaffarian explains that in children, those who drink skim milk gain more weight than those who drink whole-fat milk, and that among adults, those who eat more yogurt or cheese have a lower risk for diabetes. “Our work suggests that when people eat low-fat dairy, they unconsciously compensate by eating more carbs. It takes time for the policy to catch up to the science.”
DR. MOZAFFARIAN’S TAKE-HOME MESSAGE ABOUT FATS
“Consumers (and clinicians) should not count grams or calories from total fat or saturated fat. They should focus on the types of foods they’re eating. My advice is to avoid processed meats, refined grains and sugars, and processed foods high in sodium and added sugars—and to eat more minimally processed foods including plenty of fruits, vegetables, nuts, beans, vegetable oils, fish, yogurt and cheese. It’s a Mediterranean-style diet. Liberal use of healthy sources of fat have a positive effect on the risks of cardiovascular disease and diabetes. We need healthy fats.”