Findings from a randomized controlled trial “Effects of 2-Year Walnut-Supplemented Diet on Inflammatory Biomarkers” 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.
“Robust epidemiological evidence suggests that regular nut consumption is associated with lower cardiovascular disease (CVD) risk. As summarized in a recent meta-analysis of 19 prospective studies, when comparing extreme quantiles of total nut consumption (2.5 to 28 g/day), total CVD and CVD mortality were 15% and 23% lower, respectively. Walnut consumption independent from other nuts revealed similar inverse associations with CVD in 3 studies,” write the investigators.
“Nut consumption may be associated with lower CVD risk because nuts have a consistent cholesterol-lowering effect. A meta-analysis of 24 randomized controlled trials (RCTs) concluded that, compared with control diets, walnut-enriched diets resulted in significant weighted mean differences in low-density lipoprotein cholesterol (−5.5 mg/dl), but had no effect on blood pressure or high-sensitivity C-reactive protein (hs-CRP). Nut-enriched diets also affect endothelial function, with weighted mean differences in flow-mediated dilatation of 0.79% in 8 RCTs. These modest salutary effects of nut diets, however, cannot fully account for the lower CVD outcomes observed in prospective studies. Given the prevailing theory that inflammation is a major driver of atherosclerosis, 1 potential mechanism linking nut consumption to reduced CVD might be diminished inflammation.”
“We hypothesized that incorporating walnuts into the usual diet would improve inflammatory biomarkers. Therefore, we assessed changes in circulating inflammatory molecules in the WAHA (Walnuts And Healthy Aging; NCT01634841) study, a dual-center (Hospital Clínic, Barcelona, Spain, and Loma Linda University, Loma Linda, California) RCT designed to evaluate walnut effects on age-related health outcomes in 708 healthy elders (63 to 79 years of age). Walnut consumption affected cognitive function, the main outcome, only in the high-risk subgroup. Changes in inflammatory markers were a pre-specified secondary outcome.”
In the study, conducted by Emilio Ros, MD, PhD, 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”, says Ros, a lead researcher in the study. “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.”
While existing scientific evidence establishes walnuts as a heart-healthy food, researchers continue to investigate the “how” and “why” behind walnuts’ cardiovascular benefits. According to 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 polyphenols, that likely play a role in their anti-inflammatory effect and other health benefits.”