Prediction of serum-cholesterol responses of man to changes in fats in the diet.

January 1, 1957 Human Health and Nutrition Data 0 Comments

Prediction of serum-cholesterol responses of man to changes in fats in the diet.

Year: 1957
Authors: A Keys, J Anderson, F Grande.
Publication Name: The Lancet.
Publication Details: Page 959.

Abstract:

A number of studies conducted by these authors up to the late 1950’s demonstrated that a sharp decrease in the amount of fat in the usual American or Western European diet, without any change in the amount of calories or vitamins, lowered serum cholesterol values. The observed decline appeared to be rapid in the first few days, but approached a new plateau after a few weeks. The responsible agent at this point in time was believed to be attributed to either the quality of fats in the diet, or the ratio of dietary fat to carbohydrates. The purpose of this pioneering study was to review the literature to date (up to 1957), and report the serum-cholesterol responses to different amounts of dietary glycerides of saturated (S), monoethenoid (M), and polyethanoid (P) fatty acids that produced 9-44% of calories derived from fat. The majority of studies used in this analysis were conducted by these researchers (Keys, A, et al) over a six-year period at the metabolic research unit of the Hastings State Hospital. Participants of these studies were stabilized schizophrenic men, aged 32-56 years of age, who were judged physically and metabolically normal. Diets conformed to the general pattern of menus in the US at the time, in which 37-42% of calories were derived from fats, 13-15% from proteins. Diets in this study were carefully designed to provide similar amounts of total proteins, and varied only in the amounts of carbohydrate and fat, as well as type of fat. Types of fats used in these studies included butter fat, hydrogenated coconut oil, olive oil, cottonseed oil, corn oil, sunflower seed oil, safflower oil, fish oil, and mixed food fats of ordinary American diets. Also included in the data analysis was a Japanese study that consisted of 18 Japanese men, aged 22-54 yrs of age, who were also judged clinically healthy based on physical and blood analyses. The majority of these experiments were made from both forward and backward dietary changes (eg. changing from diet X to Y, and vice versa). Standard periods on each diet ranged from 2-9 weeks, with the average being four weeks. Blood samples were drawn at the end of each dietary period for analysis of serum cholesterol values. In reviewing the data, it was observed that saturated fatty acids, particularly those with a chain length of 10-carbons or longer, exert approximately twice as much effect in raising serum cholesterol values as the cholesterol reducing effect of an equal amount of polyethenoids or linoleic acid. Monoethenoids (oleic acid) appeared to have relatively little effect on serum cholesterol levels. Regarding the lack of effect of oleic acid on serum cholesterol values, the researchers do note that because the majority of variation of oleic acid in the experimental diets is correlated to some extent with the variations in saturated fatty acids, further studies are necessary to fully establish the role of oleic acid on serum cholesterol values. Based on these data, the researchers conclude that an excess of dietary saturated fatty acids are positively associated with high serum cholesterol levels. Furthermore, decreasing intake of saturated fat also appears to be more important in reducing serum cholesterol values than increasing dietary intake of linoleic acid or polyethenoids. Substitution of one type of fat for the other is both effective and acceptable for dietetic practice.



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