Eating Walnuts and Other Tree Nuts May Lower Cholesterol
In a 2018 meta-analysis and systematic review published in the American Journal of Clinical Nutrition, researcher Marta Guasch-Ferré and colleagues shared their analysis of 26 studies of the effects of diets rich in walnuts on blood lipids and cardiovascular health. The studies included a total of 1059 participants. The walnut-heavy diets were associated with lower total cholesterol, lower LDL (“bad”) cholesterol, and lower triglyceride concentrations. They were also associated with lower apolipoprotein B, a component of LDL.
When walnut-enriched diets were compared to American diets and Western diets, the benefits of the added walnuts on total cholesterol and LDL cholesterol were even more dramatic. The researchers described a Western diet as high in red and processed meats, high-fat dairy products, processed and artificially sweetened foods, and with little intake of fruits, vegetables, fish, legumes, or whole grains.
Compared to control diets, the diets rich in walnuts did not cause weight gain or an increase in body mass index (BMI), and they also did not affect blood pressure.
The studies included in the meta-analysis lasted from four weeks to one year, with a mean length of 8 weeks. The amount of walnuts ranged from 15 to 108 grams per day. In most cases, participants were given whole walnuts to incorporate into whatever daily meal plan they were following, which in some cases was their usual diet and in others was an intervention diet such as a Mediterranean diet or a low-fat diet.
Another meta-analysis published in the American Journal of Clinical Nutrition in 2015 by Liana C. Del Gobbo and colleagues analyzed 61 studies about the effects of tree nuts on cholesterol and related measures, and similarly found that eating tree nuts lowers total cholesterol, LDL cholesterol, ApoB, and triglycerides. Del Gobbo and colleagues wrote, “The major determinant of cholesterol lowering appears to be nut dose rather than nut type.” Tree nuts include walnuts, pistachios, macadamia nuts, pecans, cashews, almonds, hazelnuts, and Brazil nuts.
