n-3 Fatty acids of marine origin lower systolic blood pressure and triglycerides but raise LDL cholesterol compared with n-3 and n-6 fatty acids from plants

Article Abstract:

Consumption of fish on a regular basis has been associated with reduced mortality from heart disease. This may be related to the presence in fish of two n-3 (omega-3) unsaturated fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Linoleic acid, an n-6 fatty acid which is derived from plants, may be the most effective of any known fatty acid in lowering plasma cholesterol, but its effect on blood pressure has been disputed. To evaluate the role of these fatty acids in cardiovascular disease prevention, the effects of linoleic acid, linolenic acid (an n-3 fatty acid found in plants), and fish oil containing EPA and DHA on blood lipids and blood pressure were studied. Thirty-three men who had normal blood pressure and mildly elevated blood cholesterol were included in this study. All subjects received a supplement of linoleic acid for three weeks, and then for six weeks, 11 subjects per group were given supplements of either fish oil, linoleic acid, or linolenic acid. Care was taken to match the proportions of saturated, monounsaturated, and total polyunsaturated fatty acids and cholesterol in the diets, which is not always done in this type of study. Compared with the effects of the baseline linoleic acid diet, only the fish oil-supplemented diet affected blood pressure or serum lipids. Systolic blood pressure dropped significantly, by 5.1 mm Hg, while plasma triglycerides and VLDL (very low-density lipoprotein) cholesterol decreased by 39 and 49 percent, respectively; also LDL (low-density lipoprotein) cholesterol rose significantly, by 9 percent. The changes in blood pressure, triglyceride, and VLDL levels were beneficial, while the increase in LDL was considered detrimental to cardiovascular health. According to the calculations, the benefit from the decline in blood pressure should outweigh the risk from the LDL increase. This study illustrates the complexity of cardiovascular disease risk factors; further research on the role of fatty acids in the disease process is needed. (Consumer Summary produced by Reliance Medical Information, Inc.)

Standards, Cardiovascular diseases, Physiological aspects, Low-fat diet, Low fat diet, Blood pressure, Human nutrition, Essential fatty acids, Essential fatty acids in human nutrition

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Cardiovascular disease risk factors in free-living men: comparison of two prudent diets, one based on lactoovovegetarianism and the other allowing lean meat

Article Abstract:

Lactoovovegetarians (vegetarians who include milk products and eggs in their diet) are known to have lower measures of blood cholesterol and lower blood pressure than individuals who include meat in their diet. In addition to the obvious differences in a lactoovovegetarian diet there is a reduced intake of saturated fatty acids and cholesterol and a higher dietary intake of polysaturated fatty acids, potassium, magnesium and fiber. It is currently unknown which of these aspects of the lactoovovegetarian diet is responsible for the reduction of blood cholesterol, lower blood pressure and other beneficial effects. This diet is also distinguished by the types of protein that it includes. Attempts using human volunteers to explore the value of the protein sources in the lactoovovegetarian diet have not produced clear results. This study was designed to test whether the benefits of a vegetarian diet for the reduction of cardiovascular risk factors could be replicated by the use of a similar diet that substituted lean meats for vegetable protein. When 60 percent of the plant-derived protein in the lactoovovegetarian diet was replaced with low-fat meats (modified lactoovovegetarian diet) and compared to both a standard diet and to the lactoovovegetarian diet, the beneficial effects on blood pressure were evident. The modified lactoovovegetarian diet was also associated with lower blood cholesterol levels than the standard diet, but the results were not as striking as with the unmodified lactoovovegetarian diet. Thus, substituting lean meat products for a substantial portion of the plant protein in a lactoovovegetarian diet permitted the beneficial aspects of the unmodified diet to be retained and may allow this type of diet to be more widely accepted.

Risk factors (Health), Vegetarianism, Diet, Food habits

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Effect of dietary cholesterol in normolipidemic subjects is not modified by nature and amount of dietary fat

Article Abstract:

The influence of dietary cholesterol on blood cholesterol is still a controversial area despite extensive research efforts over the past 30 years. Studies have found that not everyone responds to cholesterol from the diet in the same way. Some individuals, known as hyperresponders, experience a relatively large increase in blood cholesterol from consuming a certain amount of cholesterol, whereas others, known as hyporesponders, show little or no blood increase. While at first it appeared that individuals could be classified as hyperresponders or hyporesponders, further research showed that individuals are not consistent in their response to dietary cholesterol. Another important issue is how the fat in the diet as a whole affects response to dietary cholesterol. Some investigators found that if saturated fats were reduced in the diet and replaced by polyunsaturated fats, blood cholesterol would rise less. The authors studied 25 healthy men whose blood lipids (fats), including cholesterol, were normal before the study began. The extra cholesterol was added to two different diets: one was high in saturated fat and the other was low-fat with proportionately more polyunsaturated than saturated fats. The group showed no elevation in blood lipids when they consumed the additional cholesterol which was equivalent to two eggs daily; the lipids measured included total cholesterol, LDL cholesterol (low density, the harmful form of cholesterol), and HDL cholesterol (high density, the beneficial form of cholesterol). The authors conclude that the general population should not necessarily be advised to reduce dietary cholesterol. Instead, this restriction should be reserved for persons with elevated blood cholesterol.

Blood cholesterol, Hyperlipidemia

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