Eating Walnuts Lowers Cholesterol Levels in People with High Cholesterol. Ann Intern Med. 2000;132:538. doi: 10.7326/0003-4819-132-7-200004040-00039
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Published: Ann Intern Med. 2000;132(7):538.
High cholesterol (hypercholesterolemia) is a risk factor for heart disease. Drug treatments are available that can help to lower cholesterol levels. However, diet is a major part of treatment for everyone with high cholesterol levels and is often the only recommended preventive treatment for people who have not yet developed heart disease. One way to lower cholesterol is to change the fat content of diets by substituting polyunsaturated fat (which is mostly from vegetable oils and does not increase cholesterol) for saturated fat (which is mostly from animal sources and does increase cholesterol). Some reports have suggested that people who eat nuts regularly get heart disease less frequently than people who do not eat nuts. Walnuts are particularly high in polyunsaturated fat. A previous small study showed that cholesterol levels decreased when healthy men ate walnuts instead of other fats. However, that study included only men, all of whom had normal cholesterol levels to begin with.
To find out whether men and women who had high cholesterol levels could decrease these levels by replacing a third of the fat content in their diet with walnuts.
The study was done in Spain and included 55 men and women (average age, 56 years) with high cholesterol levels.
At random, the researchers assigned half of the study patients to eat a cholesterol-lowering Mediterranean diet, which limited red meat and eggs, emphasized vegetables and fish, and used olive oil for cooking. It allowed no nuts. The other half of the subjects ate a diet containing similar amounts of calories and fat, but walnuts made up 35% of the fat content. After 6 weeks, the subjects switched to the other type of diet for another 6 weeks. The researchers measured cholesterol levels at the beginning of the study and again after 6 weeks of each type of diet.
Forty-nine people completed the study. Cholesterol levels decreased about 5% after 6 weeks on the Mediterranean diet alone and about an additional 5% after 6 weeks on the diet that contained walnuts.
The study does not prove that eating walnuts will prevent heart disease, only that substituting walnuts for other fats can help to lower cholesterol levels in the short term. Note also that the walnuts were used in a diet that was already healthy in terms of fat content. The benefit of including walnuts in less healthy types of diets is unknown. The California Walnut Commission provided some support for the study but had no control over how the study was done.
Substituting walnuts for other fat sources may help to lower cholesterol in people with hypercholesterolemia.
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Cardiology, Dyslipidemia, Coronary Risk Factors.
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