Macadamia Nut Consumption Lowers Cholesterol in Men
Eating macadamia nuts reduces cholesterol levels in men with high cholesterol, according to a new study in the Journal of Nutrition (2003;133:1060–3).
A high cholesterol level has long been known to contribute to cardiac risk; however, the proportions of the types of cholesterol that make up the total cholesterol are of more importance than total cholesterol alone in determining the risk of heart disease. For example, a high proportion of low-density lipoprotein (LDL; “bad”) cholesterol increases the risk of heart disease, while a high proportion of high-density lipoprotein (HDL; “good”) cholesterol is protective.
Levels of LDL, HDL, and total cholesterol in the blood are strongly influenced by diet and exercise, as well as genetic factors. Low-fat diets have been the mainstay of dietary recommendations for preventing and treating high cholesterol. Different fats, however, have been observed to have different effects on cholesterol and its subtypes. Studies have shown that eating foods rich in saturated fats, such as butter and cheese, increases total and LDL cholesterol levels. In contrast, eating foods rich in polyunsaturated fats (PUFAs), such as vegetable oils, and foods rich in monounsaturated fats (MUFAs), such as olives or olive oil and some nuts and seeds, reduces total and LDL cholesterol levels. While eating PUFAs can also cause a drop in HDL cholesterol levels, some studies have found that MUFAs might increase HDL cholesterol, further reducing cardiac risk.
In the current study, seventeen men with high cholesterol levels were given macadamia nuts to incorporate into their regular diet for four weeks. The goal was for each participant to consume 15% of their total daily calories from macadamia nuts. The actual amount of nuts eaten was between 1.5 and three ounces per day. Total cholesterol was 3% lower and LDL cholesterol was 5.3% lower at the end of the trial than at the beginning. A rise in HDL cholesterol of nearly 8% was also observed.
Previous studies examining the effect of nuts and seeds on health have consistently shown a reduced risk of heart disease, heart attack, and death from all causes in people who eat them, even in amounts exceeding recommendations for fat intake. The addition of nuts to the diet has been shown in numerous trials to reduce cholesterol levels. Walnuts, almonds, pecans, and pistachios have all been shown to reduce total and LDL cholesterol levels, and in some, but not all, of these studies, a rise in HDL cholesterol was also observed. In contrast to the findings of the current study, two previous trials of macadamia nut and oil consumption have not found the benefits to include improvements in HDL cholesterol levels.
The beneficial effects of eating nuts have been attributed to their high MUFA content. Macadamia nuts in particular are among the richest food sources of MUFAs, with about 80% of their fat being monounsaturated. In addition, nuts are rich in plant components known as sterols, which reduce levels of cholesterol by preventing its absorption. Fiber, bioflavonoids, and other nutrients in nuts may further contribute to nuts’ beneficial effects. Longer controlled trials to better understand the role of nuts in preventing heart disease are needed. For now, it is reasonable to recommend a diet that includes plenty of nuts and seeds (but is low in other fatty foods) and lots of vegetables, fruits, soy, other beans, and whole grains, along with regular exercise and quitting smoking for people who are trying to reduce their cholesterol levels.
Maureen Williams, ND, received her bachelor’s degree from the University of Pennsylvania and her Doctorate of Naturopathic Medicine from Bastyr University in Seattle, WA. She has a private practice in Quechee, Vermont, and does extensive work with traditional herbal medicine in Guatemala and Honduras. Dr. Williams is a regular contributor to Healthnotes Newswire.
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