In the journals
Heart experts recognize the benefits of daily omega-6s
Omega-6 fatty acids are an important part of a heart-healthy diet, and lowering your intake from current levels could increase your risk of heart disease, according to a science advisory from the American Heart Association (AHA). Omega-6s are a type of polyunsaturated fat found in certain vegetable oils (corn, sunflower, safflower, and soybean), seeds, and nuts. Compared with the well-known benefits of omega-3s — found in cold-water fish such as salmon and tuna — the role of omega-6s in heart health has been less clear-cut. There's been concern in some nutrition circles that omega-6s may be harmful, based on the belief that they promote inflammation (a key factor in atherosclerosis, and thus cardiovascular disease). On this basis, several popular diet books and Internet sites have urged people to limit their intake of omega-6s.
To address the controversy, the AHA undertook a review of the scientific literature on the benefits and harms of omega-6s. A panel of nutrition experts analyzed the results of several randomized controlled trials and more than two dozen observational and other types of studies. Their findings, published in the journal Circulation (Feb. 17, 2009), exonerate omega-6s and indicate that getting at least 5% to 10% of calories from omega-6s can reduce the risk of heart disease, compared with lower intakes. The panel also concluded that higher intakes appear to be safe and may provide even greater benefits as part of a diet low in saturated fat and cholesterol.
Although omega-6s aren't as well known as omega-3 fats, both are crucial to heart and brain function. Our bodies don't produce them, so we need to get them from food. The main omega-6 fatty acid in food is linoleic acid (LA), which makes up 85% to 90% of our omega-6 intake. Linoleic acid lowers LDL (bad) cholesterol levels and reduces insulin resistance (a precursor to diabetes). The confusion about omega-6 intake and inflammation stems from the fact that LA can be converted into arachidonic acid (AA), a substance involved in the synthesis of inflammatory molecules during the early stages of inflammation. However, as the authors explain, AA and LA also give rise to anti-inflammatory molecules, and these help to suppress the production of several key players in the atherosclerotic process.
The AHA reviewers found that higher levels of omega-6 fatty acids — in particular, AA — either reduced inflammatory markers or left them unchanged. Some research showed an inverse relationship between LA content and heart disease risk (and found no risk associated with AA). A combined analysis of six randomized trials found that replacing saturated fat with omega-6 fatty acids led to a 24% reduced risk of heart attacks and other coronary events.
So how many daily servings of omega-6s should we get? The general recommendation is 5% to 10% of total calories. The actual amount varies depending on gender, age, and physical activity level, but ranges from 12 to 22 grams per day, according to the AHA. To learn more about fats and to calculate the number of fat calories that's right for you, visit our Fats Resource Center at www.health.harvard.edu/fats. Of course, no single nutrient is a magic bullet. The best dietary strategy for staving off heart disease and other chronic conditions is to eat sensible portions and to follow a meal plan that minimizes saturated fat, avoids trans fats, emphasizes whole grains, fruits, and vegetables, and includes a couple of servings of fish each week.