Heart Health

What the Research Says

Since 1993, published research has been investigating how eating walnuts affects various heart health biomarkers and risk markers including:

  • LDL and HDL cholesterol
  • Apolipoprotein B and non-HDL cholesterol
  • Blood pressure
  • Inflammation
  • Endothelial function
  • Plaque formation

Due to the evidence supporting the cardiovascular benefits of walnuts, the U.S. Food and Drug Administration approved one of the first qualified health claims for a whole food in March of 2004: “Supportive but not conclusive research shows that eating 1.5 ounces of walnuts per day, as part of a low saturated fat and low cholesterol diet, and not resulting in increased caloric intake may reduce the risk of coronary heart disease.”1

Continue below for a scientific summary of the research to date.

Research Information

The research supporting the role that walnuts can play in heart health began with a Loma Linda University study, showing walnuts may lower total and LDL cholesterol in men by as much as 12 percent and 16 percent, respectively.2 In this eight-week randomized, crossover trial, 18 healthy men (ages 21-43) were assigned to a cholesterol-lowering diet that did not include nuts or a cholesterol-lowering diet that included walnuts. All food was provided by the researchers and the walnut diet contained three servings (equivalent to 3 ounces) of walnuts per day.

systematic review from the Harvard T.H. Chan School of Public Health examined 25 years of evidence for the role of walnut consumption on cardiovascular risk factors, including cholesterol, triglycerides, blood pressure, and weight.3 A meta-analysis was done on 26 randomized controlled trials representing 1059 individuals (ages 22-75), including those with a variety of conditions such as high cholesterol, type 2 diabetes, metabolic syndrome, overweight or obesity, as well as those that were healthy. When compared to control diets, including low-fat, Mediterranean, American or Japanese, a diet supplemented with walnuts in amounts varying from 5-24 percent of total calories per day (equivalent to 0.5-3.9 ounces per day) resulted in a significantly greater percent decrease in total cholesterol (3.25%), LDL cholesterol (3.73%), triglycerides (5.52%), and apolipoprotein B (4.19%). In addition, incorporating walnuts into the diet had no adverse effects on body weight or blood pressure, according to the studies included in the meta-analysis.

Research from the landmark PREvención con DIeta MEDiterránea (PREDIMED) study further demonstrated the potential heart health benefits of walnuts. The study was conducted among more than 7,000 Spanish individuals (ages 55-80) at high risk for cardiovascular disease and found that a Mediterranean diet supplemented with mixed tree nuts (primarily walnuts) was associated with a lower risk of cardiovascular events, including cardiovascular death, myocardial infarction (heart attack), and stroke, when compared to a low-fat control diet.4

Larger and longer-term studies, as well as studies in more diverse populations, are needed to clarify population-wide effects.2,3,4 In some cases, the amount of walnuts consumed in these trials was relatively large and might be difficult to maintain in a non-research setting.2,3 A meta-analysis offers a comprehensive look at findings among patients of various backgrounds, however, it can be limited by the methods, reported outcomes and quality of the individual studies involved.3 In the PREDIMED study, it is difficult to precisely define what part of the Mediterranean diet was associated with cardiovascular benefits.4

American Heart Association Certified

A Heart-Healthy Food

Walnuts are certified by the American Heart Association® with the Heart-Check mark, per one ounce serving.
View peer-reviewed publications supported by the California Walnut Commission.
Walnut Heart Health
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American Heart Association® Heart-Check Mark Certified Recipes

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1One ounce of walnuts provides 18g of total fat, 2.5g of monounsaturated fat, 13g of polyunsaturated fat, including 2.5g of alpha-linolenic acid, the plant-based omega-3.

2Sabaté J, Fraser GE, Burke K, et al. Effects of walnuts on serum lipid levels and blood pressure in normal men. N Engl J Med. 1993;328:603-607.

3Guasch-Ferré M, Li J, Hu FB, et al. Effects of walnut consumption on blood lipids and other cardiovascular risk factors: an updated meta-analysis and systematic review of controlled trials. Am J Clin Nutr. 2018;108(1):174-187. doi: 10.1093/ajcn/nqy091.

4Estruch R, Ros E, Salas-Salvadó J, et al. Primary Prevention of Cardiovascular Disease with a Mediterranean Diet Supplemented with Extra-Virgin Olive Oil or Nuts. N Engl J Med. 2018;378(25):e34. doi: 10.1056/NEJMoa1800389.

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