|Advice about dietary fat has flip-flopped as much as the stock market recently, so it’s not surprising that people want to throw up their hands and go back to basics?butter. We know that’s not the answer. So, what is?
In an effort to clear up some of the confusion, the American Heart Association (AHA) sponsored a conference of scientific experts last month to discuss dietary fatty acids and cardiovascular disease. Here, EN presents new findings and thinking from the conference.
Fats 101. There are two main types of fatty acids (the individual components that make up the fat we eat)’saturated and unsaturated. Although foods with fat actually contain some of each type of fatty acid, we label them as either saturated, monounsaturated or polyunsaturated based on the predominant fat they contain.
Is Total Fat Important? Recent research reinforces the theory that the type of fat in the diet may be more important than the actual amount of fat eaten. Even so, a diet low in saturated fat and moderate in overall fat?less than 30% of calories?received renewed emphasis as the diet of choice by conference participants.
“There is still some controversy over specific recommendations for the different fatty acids,” admits Sachiko St. Jeor, Ph.D., R.D., professor of nutrition at the University of Nevada. “But, the bottom line is that it’s the intake of saturated versus unsaturated fats in the diet that’s most important.”
Saturated fats, typically found in meat and dairy foods (see chart), are still considered the main dietary culprit in elevating blood cholesterol levels and raising the risk of heart disease.
But not even all saturated fats are created equal. One type, stearic acid, has virtually no effect on blood cholesterol. Foods rich in stearic acid include beef, chocolate and full-fat dairy foods, but they contain other saturated fats that are cholesterol-raising.
The consensus at the AHA conference was that consumers should strive for a balance of poly fats and mono fats.
“The research findings emphasize that mono’s and polys each have benefits, but the trend is toward grouping them together, not advocating one over the other,” says Alice Lichtenstein, D.Sc., a lipids researcher at Tufts University.
Experts have long recommended keeping total fat to less than 30% of total calories. But in recent years, some have okayed a 40% fat diet, as long as the fat was predominantly mono. Results from several population studies demonstrate a heart- protective effect from increased mono fats.
But lipids researcher Margo Denke, M.D., of the University of Texas Southwestern Medical Center, believes the importance of mono fats on cholesterol levels is overrated. “The substitution of saturated fats [with any type of unsaturated fat] is what is key,” she argues.
Some researchers are now actually worried about mono fats having a deleterious effect on health. Lawrence Rudel, Ph.D., of Wake Forest University, presented a provocative study on monkeys. It found that diets high in mono fats increased the buildup of plaque on artery walls in the same way saturated fats do. This clearly runs counter to previous research in humans.
On balance, however, the preponderance of evidence indicates that mono’s reduce the risk of heart disease when they replace saturated fats and aren’t just added. Eating plenty of fruits and vegetables, minimizing dairy and meat and being active are critical components of the lauded Mediterranean lifestyle. You can’t simply dunk bread in olive oil and suddenly be healthier. Plus, a diet high in mono fats coupled with fewer carbohydrates may improve glucose levels for some people with diabetes.
There are two main families of poly fats: omega-3’s and omega-6’s. Each family includes a fatty acid essential to health, so getting both is important.
Omega-3 Fats. Most people don’t get enough omega-3’s, even though numerous studies suggest they can help prevent heart disease. There are two main types: EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). Both are abundant in fish and small amounts can be formed in the body from plant sources, like flaxseed and walnuts. Fish oil supplements are widely available, but many experts believe it is premature to recommend them to protect against heart disease. They advise eating fish instead.
Omega-6 Fats. Omega-6’s, found in nuts, seeds and plant oils, are also heart-friendly. They help lower “bad” low-density lipoprotein (LDL) cholesterol levels. But studies have also shown that omega-6 fats can cause an unfortunate decrease in “good” high-density lipoprotein (HDL) cholesterol levels. Some experts slough off the effect as insignificant, but others urge a higher ratio of omega-3’s to omega 6’s.
Although trans fats are unsaturated, hydrogenation makes them act as if they were saturated. So much so that they raise “bad” LDL levels and lower “good” HDL levels. Currently, trans fats are not listed at all on food labels and foods laden with trans can still be called cholesterol-free, implying a certain healthfulness that is misleading.
EN‘s Bottom-Line Advice. While the fat saga is complex and continually controversial, EN has boiled all the expert advice down to the following rather simple dietary tips:
Balancing Your Fats
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