Palm oil: biochemical, physiological, nutritional, hematological, and toxicological aspects: a review

The link between dietary fats and cardiovascular diseases has necessitated a growing research interest in palm oil, the second largest consumed vegetable oil in the world. Palm oil, obtained from a tropical plant, Elaeis guineensis contains 50% saturated fatty acids, yet it does not promote atherosclerosis and arterial thrombosis. The saturated fatty acid to unsaturated fatty acid ratio of palm oil is close to unity and it contains a high amount of the antioxidants, beta-carotene, and vitamin E. Although palm oil-based diets induce a higher blood cholesterol level than do corn, soybean, safflower seed, and sunflower oils, the consumption of palm oil causes the endogenous cholesterol level to drop. This phenomenon seems to arise from the presence of the tocotrienols and the peculiar isomeric position of its fatty acids. The benefits of palm oil to health include reduction in risk of arterial thrombosis and atherosclerosis, inhibition of endogenous cholesterol biosynthesis, platelet aggregation, and reduction in blood pressure. Palm oil has been used in the fresh state and/or at various levels of oxidation. Oxidation is a result of processing the oil for various culinary purposes. However, a considerable amount of the commonly used palm oil is in the oxidized state, which poses potential dangers to the biochemical and physiological functions of the body. Unlike fresh palm oil, oxidized palm oil induces an adverse lipid profile, reproductive toxicity and toxicity of the kidney, lung, liver, and heart. This may be as a result of the generation of toxicants brought on by oxidation. In contrast to oxidized palm oil, red or refined palm oil at moderate levels in the diet of experimental animals promotes efficient utilization of nutrients, favorable body weight gains, induction of hepatic drug metabolizing enzymes, adequate hemoglobinization of red cells and improvement of immune function. Howerer, high palm oil levels in the diet induce toxicity to the liver as shown by loss of cellular radial architecture and cell size reductions which are corroborated by alanine transaminase to asparate transaminase ratios which are higher than unity. The consumtion of moderate amounts of palm oil and reduction in the level of oxidation may reduce the health risk believed to be associated with the consumption of palm oil. Red palm oil, by virtue of its beta-carotene content, may protect against vitamin A deficiency and certain forms of cancer.