Tropical oils: nutritional and scientific issues

Abstract

Individually and in combination with other oils, the tropical oils impart into manufactured foods functional properties that appeal to consumers. The use of and/or labeling in the ingredient lists give the impression that these oils are used extensively in commercially processed foods. The estimated daily intake of tropical oils by adult males is slightly more than one fourth of a tablespoon (3.8 g), 75% of which consists of saturated fatty acids. Dietary fats containing saturated fatty acids at the beta-position tend to raise plasma total and LDL-cholesterol, which, of course, contribute to atherosclerosis and coronary heart disease. Health professionals express concern that consumers who choose foods containing tropical oils unknowingly increase their intake of saturated fatty acids. The saturated fatty acid-rich tropical oils, coconut oil, hydrogenated coconut oil, and palm kernel oil, raise cholesterol levels; studies demonstrating this effect are often confounded by a developing essential fatty acid deficiency. Palm oil, an essential fatty acid-sufficient tropical oil, raises plasma cholesterol only when an excess of cholesterol is presented in the diet. The failure of palm oil to elevate blood cholesterol as predicted by the regression equations developed by Keys et al. and Hegsted et al. might be due to the dominant alpha-position location of its constituent saturated fatty acids. If so, the substitution of interesterified artificial fats for palm oil in food formulations, a recommendation of some health professionals, has the potential of raising cholesterol levels. A second rationale addresses prospective roles minor constituents of palm oil might play in health maintenance. This rationale is founded on the following observations. Dietary palm oil does not raise plasma cholesterol. Single fat studies suggests that oils richer in polyunsaturated fatty acid content tend to decrease thrombus formation. Anomalously, palm oil differs from other of the more saturated fats in tending to decrease thrombus formation. Finally, in studies comparing palm oil with other fats and oils, experimental carcinogenesis is enhanced both by vegetable oils richer in linoleic acid content and by more highly saturated animal fats. The carotenoid constituents of red palm oil are potent dietary anticarcinogens. A second group of antioxidants, the tocotrienols, are present in both palm olein and red palm oil. These vitamin E-active constituents are potent suppressors of cholesterol biosynthesis; emerging data point to their anticarcinogenic and antithrombotic activities. This review does not support claims that foods containing palm oil have no place in a prudent diet.