The "good fats" — are you getting enough?

Better Nutrition, August, 2000

In the past decade, high fat intake has been blamed for a host of chronic problems including obesity, cardiovascular disease and cancer. And while curbing your total fat intake is important to staying healthy, avoiding all fats creates its own set of problems. What we need to do is distinguish the health-promoting fats from those that can wreak havoc on our health.

When we think of fat, we usually picture the visible fat under the skin of chicken, around cuts of beef, pork or lamb, and spreads such as margarine or butter. We may also be aware of "hidden" fats in many of our favorite foods, and consequently look for "fat-free" on labels. But, what about oils? These are fats, too, and while they pack the same number of calories as animal fats, they can be "good" fats because they provide more than just calories, but myriad health benefits, too.

What makes the "good" fats good

Oils are distinguished from other fats because they remain liquid at room temperature. All fats are made up of long carbon chains with up to two hydrogen atoms attached to each carbon. However, oils are unsaturated because they have at least one gap where a hydrogen atom is missing, making them "unsaturated." There are two types of unsaturated fats: mono-unsaturated and polyunsaturated. Mono-unsaturated oils, including canola, olive, peanut and almond, have one hydrogen atom missing. Polyunsaturated oils, such as flax, corn, hemp, safflower, sesame and sunflower, have at least two gaps. These gaps are important because they allow the oil molecule to bend and twist -- making them best suited for diverse biochemical roles.

The fat imbalance

Most dietary oils come from seeds, such as those mentioned above, and from leafy greens and sea vegetables. All of these are "good oils," supplying essential fatty acids (EFAs) from three families: omega-3, omega-6 and omega-9 fatty acids. The human body cannot manufacture the first two, so they must be supplied in the diet. They are therefore considered "essential." Omega-9s can be synthesized within the body and are not considered essential, although they have many health benefits. Relative ratios of omega-3s and omega-6s from our diet have shifted dramatically over the centuries. While the hunter/gatherer diet was high in omega-3s and lower in omega-6s, today our diets are higher in omega-6s than in omega-3s. And, according to nutrition experts such as Artemis Simopoulous, MD, president of the Center for Genetics in Washington DC, and a former nutrition advisor to the President's office of consumer affairs, the shift has been most pronounced in the past 40 or 50 years. We eat far too many omega-6 oils and too few omega-3 oils, and we are paying the health consequences.

We are being advised to add more omega-3 rich foods to our diet so that the proper ratios between omega-3s and omega-6s are restored. Omega-3 rich dietary oils and the percent of n-3s each contains are: flaxseed (57 percent), canola (10 percent), soy (8 percent), walnut (5 percent) and pumpkin seed (15 percent). These oils must be converted in the human body into longer chain polyunsaturated fatty acids (LCPs) needed for cell membrane transport and key cellular functions. Fish supply "ready-made" omega-3 LCPs because their bodies have already converted the parent n-3 EFA alpha linolenic acid (ALA) from various food sources. We can also get the preformed LCPs by consuming certain kinds of seaweed and algae, best gotten through supplementation with DHA or docosahexaenoic acid.

The "bad" fats

Foods from animal sources, with the exception of fish, contain saturated fats -- those with the maximum number of hydrogen atoms. The carbon chains in these fats are stiff, and such fats do not function as well as the more fluid unsaturated fats do for cellular, and other, activities. Moreover, high levels of saturated fats interfere with the processing of oils in the body. Saturated fats can also come from vegetable oils that have been "hydrogenated." This also produces "trans fats" as by-products.

Trans fats cause havoc because they are foreign to the body, and they block the enzymes that produce the more highly unsaturated long chain fatty acids. A growing body of evidence supports the idea that lowering current intakes of trans-fatty acids found in margarine, shortening, fried foods and snacks, may lower the risk of coronary heart disease. Americans eat far more saturated and trans fats than healthy oils, leading health experts to recommend we curb our total fat intake to 30 percent, with no more than 10 percent (about one teaspoon) of total daily calories as saturated fat. To do this, we need to avoid meats, butter, commercial baked goods, ice cream and foods containing trans fats. Meanwhile increasing consumption of fish, fish oils and substituting flaxseed, canola and olive oils for butter and margarine may help us avoid developing many chronic diseases.

Disease prevention:

Cardiovascular Disease:

Epidemiological data gathered between 1959 and 1996 have shown a strong connection between diet and heart disease occurrence among Native American peoples. Research on the diets of Inuits (Eskimos), in particular, have generated great interest because these people have low rates of CVD and diabetes, despite a diet high in fat. Eating lots of fish, especially those from deep cold waters, such as salmon, herring, tuna, anchovies, mackerel, lake trout and menhaden, has been shown to raise HDL (good) cholesterol levels, lower total cholesterol, increase blood viscosity and reduce platelet stickiness. These observations have been confirmed through autopsy reports on 104 Inuit natives by Greenland researchers, who found high tissue levels of omega-3s and selenium and low incidence of ischemic heart disease in these people.