Walnut Consumption for Two Years and Leukocyte Telomere Attrition in Mediterranean Elders: Results of a Randomized Controlled Trial

Randomized controlled trials on diet and shortening of leukocyte telomere length (LTL) mostly focus on marine-derived n-3 polyunsaturated fatty acids (PUFA). Walnuts are a sustainable source of n-3 PUFA. We investigated whether inclusion of walnuts (15% of energy) in the diet for 2 years would maintain LTL in cognitively healthy elders (63–79 years old) compared to a control group (habitual diet, abstaining from walnuts). This opportunistic sub-study was conducted within the Walnuts and Healthy Aging study, a dual-centre (Barcelona, Spain and Loma Linda University, California) parallel trial. A sub-set of the Barcelona site participants were randomly assigned to the walnut (n = 80) or control group (n = 69). We assessed LTL at baseline and at 2 years and we conducted repeated-measures ANCOVA with 2 factors: time (baseline, 2 years) and group (control, walnut) and their interaction. Adjusted means (95% confidence interval) of LTL (in kb) in controls were 7.360 (7.084,7.636) at baseline and 7.061 (6.835,7.288) after 2 years; corresponding values in the walnut group were 7.064 (6.807,7.320) and 7.074 (6.864,7.284). The time × intervention interaction was nearly significant (p = 0.079), suggestive of a trend of walnut consumption in preserving LTL. This exploratory research finding should be confirmed in trials with adequate statistical power.