Saturated and hydrogenated fats in food in relation to health

The report of the National Cholesterol Education Program (NCEP) expert panel on detection, evaluation, and treatment of high blood cholesterol in adults published in 1988 evoked great interest from the medical profession, the public, and food manufacturers. The merits of different dietary interventions to lower plasma cholesterol are debated in advertising, popular publications, and research publications. The present paper is a review of the contributions of saturated and trans fatty acids (FA) to the US diet, their metabolism, and effects upon plasma cholesterol. Saturated (SFA) and trans FA are metabolized to yield energy. They are not dietary essentials; SFA can be biosynthesized, and trans FA are not naturally occurring in plants, with only very small amounts in animals. Trans FA are produced in hydrogenation of liquid vegetable oils and are estimated to contribute 3-7% of the fat consumed. Most of the SFA in the US diet (35% of total fat consumed) is obtained from meat, poultry, fish, and dairy products (approximately 60%). The fats and oils consumed directly or as components of food products, mostly baked goods, contribute approximately 20% of the SFA. More than 30 years of research led the NCEP to conclude that SFA was the most potent dietary component in increasing plasma cholesterol, and that no more than 10% of the energy (en%) of the diet should be SFA. Trans FA are metabolized similarly to SFA, but no recommendation has been made about their consumption. Reduction of consumption of SFA should be practiced in a prudent manner, by reducing consumption of foods high in SFA, and not by eliminating classes of foods. Some changes in formulations of foods or preparation practices (type of frying fat) can be made. These modifications may decrease the palatability of the food, thereby presenting a challenge to the food industry. Substitution of fats hydrogenated to contain trans FA for fats high in SFA may not be beneficial to health. Labeling of foods would improve the ability of the consumer to make appropriate choices.