RESEARCH: Walnuts Preventing Cognitive Decline
Walnuts. Quite coincidental that they look exactly how our brain does. Did you know that adding walnuts to your diet could help protect against age-related cognitive decline? Walnuts contain polyphenols and omega-3 fatty acids, which counteract the oxidative stress and inflammation that contribute to cognitive decline.
Eating walnuts may help slow cognitive decline in at-risk groups of the elderly population, according to a study conducted by researchers in California and Spain.
The Walnuts and Healthy Ageing Study, published this month in The American Journal of Clinical Nutrition, found that walnut consumption by healthy, elderly adults had little effect on cognitive function over two years, but it had a greater effect on elderly adults who had smoked more and had a lower baseline neuropsychological test scores.
The study examined nearly 640 free-living elders in Loma Linda, California, USA, and in Barcelona, Catalonia, Spain. For two years, the test group included walnuts in their daily diet, and the control group abstained from walnuts.
Walnuts contain omega-3 fatty acids and polyphenols, which have previously been found to counteract oxidative stress and inflammation, both of which are drivers of cognitive decline.
Joan Sabaté, MD, DrPH, professor of nutrition and epidemiology at Loma Linda University School of Public Health and the study’s principal investigator, said this was the largest and most well-controlled trial ever conducted on the effects of nuts on cognition.
“While this was a minor result, it could lead to better outcomes when conducted over longer periods,” Sabaté said. “Further investigation is warranted based on our findings, especially for disadvantaged populations, who may have the most to gain from incorporating walnuts and other nuts into their diet.”
Sabaté and his research team at Loma Linda University were the first to discover the cholesterol-lowering effect of nut consumption — specifically walnuts — with lowering blood cholesterol. Findings were first published in the New England Journal of Medicine in 1993.
Subsequently, findings from Loma Linda University researchers have linked nut consumption to lower risk of cardiovascular diseases.
Effect of a 2-year diet intervention with walnuts on cognitive decline. The Walnuts And Healthy Aging (WAHA) study: a randomized controlled trial
Walnut consumption counteracts oxidative stress and inflammation, 2 drivers of cognitive decline. Clinical data concerning effects on cognition are lacking.
The Walnuts And Healthy Ageing study is a 2-center (Barcelona, Spain; Loma Linda, CA) randomized controlled trial examining the cognitive effects of a 2-y walnut intervention in cognitively healthy elders.
We randomly allocated 708 free-living elders (63–79 y, 68% women) to a diet enriched with walnuts at ∼15% energy (30–60 g/d) or a control diet (abstention from walnuts). We administered a comprehensive neurocognitive test battery at baseline and 2 y. Change in the global cognition composite was the primary outcome. We performed repeated structural and functional brain MRI in 108 Barcelona participants.
A total of 636 participants completed the intervention. Besides differences in nutrient intake, participants from Barcelona smoked more, were less educated, and had lower baseline neuropsychological test scores than those from Loma Linda. Walnuts were well tolerated and compliance was good. Modified intention-to-treat analyses (n = 657) uncovered no between-group differences in the global cognitive composite, with mean changes of −0.072 (95% CI: −0.100, −0.043) in the walnut diet group and −0.086 (95% CI: −0.115, −0.057) in the control diet group (P = 0.491). Post hoc analyses revealed significant differences in the Barcelona cohort, with unadjusted changes of −0.037 (95% CI: −0.077, 0.002) in the walnut group and −0.097 (95% CI: −0.137, −0.057) in controls (P = 0.040). Results of brain fMRI in a subset of Barcelona participants indicated greater functional network recruitment in a working memory task in controls.
Walnut supplementation for 2y did not affect cognition in healthy elders. However, brain fMRI and post hoc analyses by site suggest that walnuts might delay cognitive decline in subgroups at higher risk. These encouraging but inconclusive results warrant further investigation, particularly targeting disadvantaged populations, in whom the greatest benefit could be expected.
Source: “Effect of a 2-year diet intervention with walnuts on cognitive decline. The Walnuts And Healthy Aging (WAHA) study: a randomized controlled trial”. Aleix Sala-Vila, Cinta Valls-Pedret, Sujatha Rajaram, Nina Coll-Padrós, Montserrat Cofán, Mercè Serra-Mir, Ana M Pérez-Heras, Irene Roth, Tania M Freitas-Simoes, Mónica Doménech, Carlos Calvo, Anna López-Illamola, Edward Bitok, Natalie K Buxton, Lynnley Huey, Adam Arechiga, Keiji Oda, Grace J Lee, Dolores Corella, Lídia Vaqué-Alcázar, Roser Sala-Llonch, David Bartrés-Faz, Joan Sabaté, Emilio Ros.
American Journal of Clinical Nutrition DOI:10.1093/ajcn/nqz328.