Effect of a 1‐Year Walnut Supplementation on Blood Lipids among Older Individuals: Findings from the Walnuts and Healthy Aging (WAHA) study

Background In small well‐controlled short‐term feeding studies conducted in middle‐aged adults, nut‐enriched diets have resulted in cholesterol lowering and absence of weight gain compared to control diets. There are no long‐term data on lipid changes when supplementing the diet with nuts in older adults. Objective To assess whether adding walnuts to the daily diet of free‐living healthy older adults for 1 year will result in changes in blood lipids compared to the usual diet without nuts. Design Within the context of the WAHA study, a two‐center clinical trial aimed at determining the effect of a 2‐year walnut diet on age‐related outcomes, we randomized 707 free‐living older but healthy individuals (352 in Barcelona, 355 in Loma Linda; 67% women, mean age 69 y, mean BMI 27.3 kg/m 2 ) to supplementation of the usual diet with daily doses of walnuts at ≈15% of energy or to usual diet without nuts (control). Participants had frequent (once every two months) assessments by dietitians; no advice was given on total energy/macronutrient intake or food substitution for walnuts. At baseline and 1 year serum lipids were analyzed. Between‐group differences in outcomes were analyzed by analysis of covariance with adjustment for sex, age, center and baseline levels; lipid values were additionally adjusted by changes in statin treatment. Results Complete 1‐year data were available for 514 participants (260 walnut diet, 254 control diet). There were 137 participants pending 1‐year assessment and 56 dropouts for various reasons. The walnut diet was well tolerated and the proportion of α‐linolenic acid in red blood cells increased in the walnut group by 0.162% (95% CI, 0.143–0.181) and in the control group by 0.015% (CI, −0.005–0.035) (P<0.001), indicating good compliance with the intervention. Changes in blood lipids were (mean±SEM) −7.5±1.6 versus −0.4±1.6 mg/dL (P=0.003) for total cholesterol, −7.1±1.3 versus −1.1±1.4 mg/dL (P=0.002) for LDL‐cholesterol, and −0.15±0.31 versus −0.05±0.31 (P=0.025) for the total cholesterol/HDL‐cholesterol ratio, in the walnut versus control diets, respectively. No between‐diet differences were observed for triglycerides or HDL‐cholesterol. Lipid effects were similar in the two centers. No differences in body weight was observed between treatments. Conclusion Incorporating daily doses of walnuts to the habitual diet of older free‐living individuals for 1 year was well tolerated and resulted in significant LDL‐cholesterol reduction without adverse effects on body weight. Results were similar with a Mediterranean or a Western background diet Support or Funding Information The WAHA study is funded by the California Walnut Commission