Daily walnut consumption may reduce the risk of heart disease

Reviewed by Emily Henderson, B.Sc.Nov 10 2020

Findings from a randomized controlled trial recently published in the Journal of the American College of Cardiology, indicate that people in their 60s and 70s who regularly consume walnuts may have reduced inflammation, a factor associated with a lower risk of heart disease, compared to those who do not eat walnuts. The research was part of the Walnuts and Healthy Aging (WAHA) study - the largest and longest trial to date exploring the benefits of daily walnut consumption.

In the study, conducted by Dr. Emilio Ros from the Hospital Clinic of Barcelona, in partnership with Loma Linda University, more than 600 healthy older adults consumed 30 to 60 grams of walnuts per day as part of their typical diet or followed their standard diet (without walnuts) for two years. Those who consumed walnuts had a significant reduction in inflammation, measured by the concentration of known inflammatory markers in the blood, which were reduced by up to 11.5%.

Of the 10 well-known inflammatory markers that were measured in the study, six were significantly reduced on the walnut diet, including interleukin-1β, a potent pro-inflammatory cytokine which pharmacologic inactivation has been strongly associated with reduced rates of coronary heart disease. The study's conclusion is that the anti-inflammatory effects of walnuts provide a mechanistic explanation for cardiovascular disease reduction beyond cholesterol lowering.

Acute inflammation is a physiological process due to activation of the immune system by injury such as trauma or infection, and is an important defense of the body. Short-term inflammation helps us heal wounds and fight infections, but inflammation that persists overtime (chronic), caused by factors such as poor diet, obesity, stress and high blood pressure, is damaging instead of healing, particularly when it comes to cardiovascular health. The findings of this study suggest walnuts are one food that may lessen chronic inflammation, which could help to reduce the risk for heart disease - a condition we become more susceptible to as we age."

Dr. Emilio Ros, lead researcher in the study

Chronic inflammation is a critical factor in the development and progression of atherosclerosis, which is the buildup of plaque or "hardening" of the arteries, the principal cause of heart attacks and stroke. Therefore, the severity of atherosclerosis depends greatly on chronic inflammation, and dietary and lifestyle changes are key to mitigating this process.

While existing scientific evidence establishes walnuts as a heart-healthy1 food, researchers continue to investigate the "how" and "why" behind walnuts' cardiovascular benefits. According to Dr. Ros, "Walnuts have an optimal mix of essential nutrients like the omega-3 alpha-linolenic acid, or ALA (2.5g/oz), and other highly bioactive components like polyphenols2, that likely play a role in their anti-inflammatory effect and other health benefits."

The study findings were also reinforced by an editorial in the same publication entitled "Ideal Dietary Patterns and Foods to Prevent Cardiovascular Disease: Beware of Their Anti-Inflammatory Potential", which concludes that a better knowledge of the mechanisms of health protection by the different foods and diets, mainly their anti-inflammatory properties, should inform healthier food choices (such as including walnuts regularly in the usual diet).

While these results are promising, the research does have limitations. Study participants were older adults who were healthy and free living with the option to eat a variety of other foods in addition to walnuts. Additionally, further investigation is needed in more diverse and disadvantaged populations.

The California Walnut Commission (CWC) supported this research. The CWC has supported health-related research on walnuts for more than 30 years with the intent to provide knowledge and understanding of the unique health benefits associated with consuming walnuts. While the CWC does provide funds and/or walnuts for various projects, all studies are conducted independently by researchers who design the experiments, interpret the results and present evidence-based conclusions. The CWC is committed to scientific integrity of industry-funded research.

The California walnut industry is made up of over 4,800 growers and more than 90 handlers (processors). The growers and handlers are represented by two entities, the California Walnut Board (CWB) and the California Walnut Commission (CWC).