A number of dietary trends that have advocated for the elimination of a single nutrient from the diet have come and gone over the past few decades. Fat is one such nutrient that has acquired a negative reputation among some health-conscious consumers. However, clinical and population (epidemiological) studies provide growing evidence that severe restriction of dietary fat from the diet isn’t realistic and, more importantly, not necessary. Why? Because fat is an essential nutrient and some types of fats and oils may promote health.
Dietary Fat Basics
The body needs dietary fats to absorb fat-soluble vitamins, produce hormones, maintain a healthy skin, and promote normal growth, among other vital functions.
Fats can either be saturated or unsaturated, as designated by the presence of double bonds. Saturated fats have no double bonds, whereas unsaturated fats do. Unsaturated fats with one double bond are called monounsaturated fatty acids (MUFAs) and those with more than one double bond are called polyunsaturated fatty acids (PUFAs). There are several kinds of PUFAs. Two that are nutritionally important are linoleic acid and linolenic acid. They are also referred to as essential fatty acids because the body cannot produce them; they have to be obtained from food. Certain forms of PUFAs, called omega-3 fatty acids, have gained special attention because of their positive health effects. Studies have shown that eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) from fish and fish oils may reduce coronary heart disease (CHD) risk. In fact, the Food and Drug administration has recently allowed foods with omega-3 fatty acids to carry a qualified health claim on the label about their role in reducing the risk of heart disease.
Unsaturated fats such as liquid oils have a greater tendency than saturated fats to become rancid when exposed to air. To increase their shelf-life and stability, these oils are often hydrogenated. Hydrogenation is the process of making oils more solid through the addition of hydrogen atoms, thus breaking the double bonds, as in the case of shortening.
Complete hydrogenation converts unsaturated fats into saturated fats. Because they are saturated with hydrogen atoms, fully hydrogenated fats contain no trans fatty acids. Partial hydrogenation creates trans fatty acids. Research suggests that trans fats raise blood LDL cholesterol levels, reduce HDL, and increase CHD risk, more than saturated fatty acids.
Health professionals recommend a moderate total fat intake (20 to 35 percent of calories) emphasizing consumption of unsaturated fats (MUFA and PUFA).
Traditional Roots
Epidemiological studies of ethnic groups living in some parts of Asia and Europe—particularly in the Mediterranean region—suggest protective health effects from consuming traditional diets that include food sources rich in MUFAs and PUFAs. Consumption of these unsaturated fats as part of a healthful diet may improve blood cholesterol levels, lower the risk for heart disease and even certain cancers. Today, these cultures remain among some of the world’s healthiest populations.
Here are some examples of traditional food patterns and lessons learned concerning MUFA and PUFA consumption:
Mediterranean Diet: MUFA
Olive oil is rich in MUFA and is a major ingredient of the Greek, Southern Italian, and Spanish culinary traditions. When consumed as a substitute for butter or lard, olive oil appears to lower blood LDL (“bad”) cholesterol levels, increase HDL (“good”) cholesterol, and reduce the risk of heart attack. This may also help explain why CHD death rates are lower among Mediterranean populations. Their diets are higher in vegetables, fruits, and whole grain products than the typical U.S. diet. Furthermore, antioxidants in olive oil, fruits, and vegetables may protect body cells and tissues from damage by oxidation—a process that could set the stage for heart disease.
MUFA may also have other health benefits. In a study of 3,442 Italian women’s dietary habits, those who ate large amounts of olive oil (about 1.5 tablespoons) daily reduced their risk for ovarian cancer by 30 percent. A survey of 5,632 elderly participants called the Italian Longitudinal Study on Aging (ILSA) showed that the higher an individual’s MUFA consumption is, the lower the likelihood for developing age-related cognitive decline—a mild deterioration in memory. However, these results are preliminary. In the US, it is currently recommended that MUFA and PUFA sources should be eaten more frequently than foods rich in saturated fat, trans fat, and cholesterol—but within the parameters of 20 to 35 percent of total calories.
Eskimo & Japanese Diets: Eicosapentaenoic Acid (EPA) and Docosahexaenoic Acid (DHA)
Despite the climatic variations influencing their traditional food patterns, fatty, cold water fish consumption is what the Eskimos and the Japanese share in common.
Fatty, cold-water fish—especially salmon, herring, mackerel, sardines, and swordfish—are high in EPA and DHA. This may help account for the rarity of ischemic heart disease (a condition characterized by narrowed heart arteries) among Eskimos as well as the lower cholesterol levels and blood pressure of Japanese living in Japan compared to that of Japanese-Americans living in Hawaii, who consume lesser amounts of omega-3 fatty acids.
In addition to the heart health benefits described above, omega-3 fatty acids may also protect against some types of cancers. A 14-year study of 5,885 residents in Nagoya, Japan, found a statistically significant trend suggesting that frequent consumption of fish rich in omega-3 fatty acids may lower lung cancer risk—regardless of the cooking method used. Experts in the US have defined a weekly consumption of 1-2 servings of fish (3 oz/serving) as consistent with good health.
South-Asian, Mediterranean-Style Diet: Alpha-Linolenic Acid (ALA). Although studies on ALA are limited, the available evidence indicates potential positive health effects. A large clinical trial known as the Indo-Mediterranean Diet Heart Study demonstrated a significant reduction in LDL-cholesterol, incidence of heart attacks, and death among patients of South Asian origin who had a history of CHD. Those who experienced these health improvements ate a diet rich in mustard oil or soybean oil—traditional sources of omega-3 fatty acids in the rural Indian diet—as well as walnuts, almonds, legumes, and fruits. It should be mentioned, however, that although ALA and cardiac health may be potentially promising, it’s possible that the primary cardioprotective benefit may be derived from EPA and DHA. A recent report from the Agency for Health Quality Research stated that, with regard to heart health effects, the “potential effect of ALA is unknown.”
Other Dietary & Lifestyle Factors
Many interacting dietary components and non-dietary factors may also contribute to the health and well-being of different ethnic groups.
In the case of dietary components, antioxidants and dietary fiber present in the abundant plant foods eaten by ethnic communities may confer additional protective effects. For instance, isoflavones in Japanese soy products like miso and tofu are associated with lower ovarian and breast cancer risk. Vegetables, fruits, whole-grain foods, and tea have been linked to lower risks of certain types of cancer and CHD.
It should also be noted that the traditional way of life in the Mediterranean, India, and Japan is agricultural. People are generally physically active because farming and fishing are common trades. Everyday stresses may be alleviated through adequate rest and supportive social networks within the family and community. These and a host of other influences may play synergistic roles in maintaining health.
Given that fat is an essential nutrient and that certain types of fat confer health benefits, there is no need to severely restrict fat intake. Balance, variety, and moderation of all foods combined with plenty of exercise and proper weight maintenance are the best approaches to a healthful lifestyle.
