Adherence counts
Most participants had “medium” or “high” levels of adherence to the Mediterranean diet, with “no meaningful differences” at baseline between the intervention and control groups in lifestyle characteristics or mean scores in all primary endpoints.
In the ITT analysis, there were no statistically significant differences in primary outcomes between the groups following the intervention. As for secondary outcomes, the RBC ALA significantly increased in the walnuts group but not the control group (coefficient, 0.04%; 95% confidence interval, 0.03%-0.06%; P < .0001).
However, there were differences in primary outcomes between the groups in the per-protocol analysis: The adherence-adjusted effect on improvement in attention score was −11.26 ms; 95% CI, −19.92 to −2.60; P = .011) for the intervention versus the control group.
The per-protocol analysis showed other differences: an improvement in fluid intelligence score (1.78; 95% CI, 0.90 - 2.67; P < .0001) and a reduction in ADHD symptom score (−2.18; 95% CI, −3.70 to −0.67; P = .0050).
“Overall, no significant differences were found in the intervention group in relation to the control group,” Dr. Julvez said in a news release. “But if the adherence factor is considered, then positive results are observed, since participants who most closely followed the guidelines – in terms of the recommended dose of walnuts and the number of days of consumption – did show improvements in the neuropsychological functions evaluated.”
Adolescence “is a time of great biological changes. Hormonal transformation occurs, which in turn is responsible for stimulating the synaptic growth of the frontal lobe,” he continued, adding that this brain region “enables neuropsychological maturation of more complex emotional and cognitive functions.”
“Neurons that are well nourished with these types of fatty acids will be able to grow and form new, stronger synapses,” he said.
Food as medicine
Uma Naidoo, MD, director of nutritional and lifestyle psychiatry at Massachusetts General Hospital, Boston, “commends” the researchers for conducting an RCT with a “robust” sample size and said she is “excited to see research like this furthering functional nutrition for mental health,” as she believes that “food is medicine.”
Dr. Naidoo, a professional chef, nutritional biologist, and author of the book “This Is Your Brain on Food,” said the findings “align” with her own approach to nutritional psychiatry and are also “in line” with her clinical practice.
However, although these results are “promising,” more research is needed across more diverse populations to “make sure these results are truly generalizable,” said Dr. Naidoo, a faculty member at Harvard Medical School, Boston, who was not involved with the study.
She “envisions a future where the research is so advanced that we can ‘dose’ these healthy whole foods for specific psychiatric symptoms and conditions.”
This study was supported by Instituto de Salud Carlos III (co-funded by European Union Regional Development Fund “A way to make Europe”). The California Walnut Commission has given support by supplying the walnuts for free for the Walnuts Smart Snack Dietary Intervention Trial. Dr. Julvez holds a Miguel Servet-II contract awarded by the Instituto de Salud Carlos III (co-funded by European Union Social Fund). The other authors’ disclosures are listed in the original article. Dr. Naidoo reports no relevant financial relationships.
A version of this article first appeared on Medscape.com.