Walnut Consumption Reduced ‘Bad’ Cholesterol Levels and may Reduce the Risk of Cardiovascular Disease

According to new research published today in the American Heart Association’s flagship journal Circulation, eating about ½ cup of walnuts every day for two years reduced levels of low-density lipoprotein (LDL) cholesterol, also known as “bad cholesterol,” and reduced the number of total LDL particles and small LDL particles in healthy, older adults.

Healthy older individuals who ate a handful of walnuts (approximately ½ cup) each day for two years had a slight reduction in their LDL cholesterol levels. Walnuts lowered the quantity of LDL particles in the blood, which is a predictor of cardiovascular disease risk. Walnuts are high in omega-3 fatty acids (alpha-linolenic acid), which have been demonstrated to improve heart health.

Prior studies have shown that nuts in general, and walnuts in particular, are associated with lower rates of heart disease and stroke.

Emilio Ros

“Prior studies have shown that nuts in general, and walnuts in particular, are associated with lower rates of heart disease and stroke. One of the reasons is that they lower LDL-cholesterol levels, and now we have another reason: they improve the quality of LDL particles,” said study co-author Emilio Ros, M.D., Ph.D., director of the Lipid Clinic at the Endocrinology and Nutrition Service of the Hospital Clínic of Barcelona in Spain.

“LDL particles come in various sizes. Small, dense LDL particles have been linked to atherosclerosis, the buildup of plaque or fatty deposits in the arteries, according to research. Our study goes beyond LDL cholesterol levels to get a complete picture of all of the lipoproteins and the impact of eating walnuts daily on their potential to improve cardiovascular risk.”

Researchers examined whether regular walnut consumption, regardless of a person’s diet or where they live, has beneficial effects on lipoproteins in a sub-study of the Walnuts and Healthy Aging Study, a large, two-year randomized controlled trial examining whether walnuts contribute to healthy aging.

From May 2012 to May 2016, 708 healthy, independent-living people aged 63 to 79 (68 percent women) from Barcelona, Spain, and Loma Linda, California participated in this study.

The participants were split into two groups at random: active intervention and control. Participants in the intervention group consumed around a half cup of walnuts per day, whereas those in the control group did not consume any walnuts at all.

Participants’ cholesterol levels were measured after two years, and nuclear magnetic resonance spectroscopy was used to examine the content and size of lipoproteins. This improved test allows doctors to more precisely detect lipoprotein characteristics linked to cardiovascular disease risk.

The study’s two-year retention rate was 90% (632 participants completed the study). In 628 cases, complete lipoprotein analyses were available. Among key findings of all study participants:

  • Participants in the walnut group had decreased LDL cholesterol levels by 4.3 mg/dL on average after two years, and total cholesterol by 8.5 mg/dL.
  • Walnut eating lowered overall LDL particles by 4.3 percent and small LDL particles by 6.1 percent on a daily basis. Changes in the concentration and makeup of LDL particles are linked to a decreased risk of cardiovascular disease.
  • IDL (Intermediate Density Lipoprotein) cholesterol fell as well. IDL cholesterol is a precursor of LDL and has a density that is halfway between low-density and very-low-density lipoproteins. IDL cholesterol has emerged as a significant lipid cardiovascular risk factor independent of LDL cholesterol in the previous decade.
  • LDL cholesterol decreases in the walnut group differed by gender; men’s LDL cholesterol dropped 7.9%, while women’s LDL cholesterol dropped 2.6 percent.

“While this is not a tremendous decrease in LDL cholesterol, it’s important to note that at the start of the study all our participants were quite healthy, free of major non-communicable diseases. Nearly half of the individuals were being treated for both high blood pressure and hypercholesterolemia, which is to be anticipated in an elderly population. Thanks in part to statin treatment in 32%, the average cholesterol levels of all the people in our study were normal,” Ros said. “The reduction in LDL cholesterol following a nut-enriched diet may be substantially larger for people with high blood cholesterol levels.”

“Eating a handful of walnuts every day is a simple way to promote cardiovascular health. Many people are worried about unwanted weight gain when they include nuts in their diet,” Ros said. “Our study found that the healthy fats in walnuts did not cause participants to gain weight.”

The fact that both participants and researchers knew who was consuming walnuts was a key weakness of this study. The study did, however, involve two quite different groups with extremely different diets.

“The outcomes were similar in both groups, so we can safely apply the results of this study to other populations,” Ros said. More research is also needed to clarify the different LDL results in men and women.

Walnuts are particularly strong in omega-3 fatty acids, the same heart-healthy lipid found in oily fish, according to the American Heart Association. A modest handful of whole nuts, 1.5 ounces of nut butter, or 2 teaspoons of nut butter constitutes one serving. The California Walnut Commission financed the research.