More on chewing the fat: the good fat and the good cholesterol

Article Abstract:

In the December 12, 1991 issue of The New England Journal of Medicine, researchers report the results of a five-week diet study involving Tarahumara Indians of northwest Mexico. The Indians, who have live on a low-fat diet consisting primarily of beans and corn, were given a diet similar to that popular in most industrialized societies. During the short period of the study, cholesterol levels in the blood of the Indians rose; they gained weight as well. However, the results of the study also illustrate how much remains to be learned about the relationship between dietary fat and the risk of atherosclerosis and coronary heart disease. While the total cholesterol rose, so did the high-density lipoprotein (HDL) cholesterol. The ratio between high- and low-density lipoprotein cholesterol actually changed very little. Since HDL is thought to help prevent atherosclerosis, it is uncertain what influence the dietary change would have on the risk of heart attack for these Indians had it been continued. The converse situation applies to may residents of developed nations. Upon switching to a low-fat diet, total blood cholesterol drops, but the apparently protective HDL drops as well. Often, the LDL drops proportionately more than HDL. However, in one major study involving women, a low-fat diet actually increased the ratio of LDL to HDL, which is often considered to be a more important risk factor than total cholesterol. HDL is thought to transport cholesterol back to the liver from deposits in arteries. This protective effect may be most important for those with high blood cholesterol. Therefore, some argue, the protective effects of HDL may simply not be required if the LDL drops sufficiently low. It may be possible to lower LDL cholesterol without lowering HDL cholesterol by avoiding the lauric, myristic, and palmitic acids, the fatty acids that contribute to increased LDL levels. Consuming a diet with 30 to 40 percent of the total calories in fat, while avoiding these saturated fats, may lower LDL cholesterol and leave HDL cholesterol unchanged. In addition, it should be remembered that many of the same societies that have adopted a diet rich in fats have also evolved a more sedentary life style that also contributes to the risk of heart disease and likely exacerbates the effects of the high-fat diet. (Consumer Summary produced by Reliance Medical Information, Inc.)

Health aspects, Editorial, Coronary heart disease, Dietary fat, High density lipoproteins, Low density lipoproteins, Cholesterol, Atherosclerosis

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Cholesterol intake and serum cholesterol level

Article Abstract:

Aspects of the relationship between dietary cholesterol and blood cholesterol are discussed in the context of a case report in the March 28, 1991 issue of The New England Journal of Medicine. The patient was an 88-year-old man who consumed 25 eggs daily without developing elevated blood cholesterol levels. His cholesterol metabolism and related factors were studied. A recent review of the medical literature showed that each 100-milligram increase in dietary cholesterol intake is associated with an increase of approximately two milligrams per deciliter of blood cholesterol. Above a certain level of intake, however, the blood cholesterol level stops rising, indicating that less cholesterol is absorbed from the intestines when intake exceeds 400 to 500 milligrams per day. Dietary cholesterol is an important predictor of coronary heart disease, independent of its effects on blood cholesterol levels, for reasons that are unknown. A description of the catabolism (breakdown) of dietary cholesterol is presented. The patient's blood levels were unaffected by dietary cholesterol, in large part because he absorbed only a small proportion of it (18 percent). Normally, cholesterol absorption and synthesis by the body are in balance, such that increases in absorption lead to decreases in synthesis. Cholesterol absorption is affected by the amount of fat in the diet, the amount of time required for the intestinal contents to pass through the intestine, and the presence of fiber in the diet. Overall, it is likely that only about one-fourth of all people are sensitive to dietary cholesterol. Another compensatory mechanism in cholesterol metabolism is the bile acid level; cholesterol is converted to bile acids, which may then be excreted. Thus, when high levels of cholesterol are consumed, less is absorbed and more is converted to bile acid, and then excreted. Since it is not possible to determine whether an individual has the kind of resistance to high dietary cholesterol displayed by the 88-year-old patient, people should attempt to reduce their cholesterol intake. (Consumer Summary produced by Reliance Medical Information, Inc.)

editorial

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Normal plasma cholesterol in an 88-year-old man who eats 25 eggs a day: mechanisms of adaptation

Article Abstract:

Although the levels of blood cholesterol are affected by diet, regulatory mechanisms exist in the body to keep these levels relatively constant. Approaches developed in the last few years that allow measurement of cholesterol metabolism have not been applied to large numbers of patients. When the opportunity to study an 88-year-old man who habitually consumed 25 eggs each day arose, the authors applied these approaches to his case. The patient was well-educated and healthy, with no signs of atherosclerosis (a disease associated with the deposition of fatty plaques along the walls of arteries). His poor memory was attributed to Alzheimer's disease. The diet of soft-boiled eggs had been followed for at least 15 years, and two dozen were delivered each day to the patient at the retirement home where he lived. This had been identified as a form of compulsive behavior; the patient stated ''Eating these eggs ruins my life, but I can't help it''. His blood cholesterol was measured, as well as his cholesterol absorption (the amount taken up by the body), sterol synthesis, bile-acid production, and other metabolic processes. (Bile acids play an important role in the digestion of fats.) These findings were compared with those from 11 volunteers who were studied on a low-cholesterol and then on a high-cholesterol diet. Results showed the patient had normal levels of blood cholesterol (200 milligrams per deciliter) and lipids (the fats to which cholesterol is conjugated). The patient absorbed considerably less cholesterol than the normal subjects (18 percent, compared with 54.6 percent on the low-cholesterol diet and 46.4 percent on the high-cholesterol diet). His rate of bile-acid synthesis (important for digesting fats) was two times that of the volunteers, and he had greater amounts of bile acids. The patient showed very efficient compensatory mechanisms for his high cholesterol intake, and the normal cholesterol levels resulted mainly from reduced absorption and increased bile acids. A discussion is presented of cholesterol absorption, a complex process. (Consumer Summary produced by Reliance Medical Information, Inc.)

Eggs, Eggs (Food)

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