Older adults consuming one to two ounces of daily walnuts experienced a lower dietary inflammatory index and modestly higher total immunoglobulin G concentrations compared to a control diet over a two-year clinical trial involving 708 participants across the United States and Spain, according to recent findings from Loma Linda University and the Walnuts and Healthy Aging study.
Two-Year Trial Tracks 708 Older Adults Across the United States and Spain
Between May 2012 and May 2014, researchers enrolled 708 cognitively healthy older adults aged 63 to 79 in a major clinical investigation known as the Walnuts and Healthy Aging trial. Conducted by teams at Loma Linda University School of Public Health and the Hospital Clinic of Barcelona in Spain, the study examined whether incorporating tree nuts into daily routines could influence immune and inflammatory markers as participants aged.
Participants who met the baseline criteria were randomized equally into two groups. The intervention group consumed 30 to 60 grams of walnuts daily—roughly one to two ounces—accounting for approximately 15 percent of their daily energy intake. Meanwhile, the control group abstained from walnuts while strictly limiting their consumption of other tree nuts. Neither cohort received instructions to alter any other aspect of their dietary habits.
Out of the initial cohort, researchers successfully analyzed serum samples and data from 474 participants at baseline and after the two-year mark, comprising 240 individuals from the intervention group and 234 controls. Compliance among Spanish participants was verified by measuring alpha-linolenic acid proportions in red blood cell membranes, which dropped by 6 percent in the control group but surged by 426 percent among those assigned to eat walnuts.
Dietary Inflammatory Index Scores Shift Lower Among Walnut Eaters
A post-hoc analysis published in the Journal of the Academy of Nutrition and Dietetics focused on the Dietary Inflammatory Index, a research instrument used to estimate whether an overall diet carries characteristics associated with higher or lower inflammatory potential. At the conclusion of the two-year period, participants who ate walnuts demonstrated slightly but statistically significantly lower Dietary Inflammatory Index scores than the control participants.
Senior investigator Sujatha Rajaram emphasized that the intervention encouraged a beneficial trend without requiring a total dietary overhaul.
The important message is that incorporating walnuts into the diet was associated with a shift toward a less inflammatory dietary pattern. This illustrates how a relatively simple food choice can contribute to the overall quality of the diet.
Sujatha Rajaram, professor in the School of Public Health at Loma Linda University
Co-primary author Lynnley Huey noted that the findings align with public health strategies prioritizing primary prevention and sustainable lifestyle adjustments, describing the intervention as a simple and accessible step people can take as they pursue more inclusive and sustainable approaches to healthier lifestyles
.
Tracking Immunoglobulins and Cardiovascular Biomarkers in Serum Samples
A separate analysis published in JACC Advances examined circulating immunoglobulin concentrations and antibodies targeting malondialdehyde-modified low-density lipoprotein within the trial participants. Over the course of the two years, total immunoglobulin G, total immunoglobulin M, and specific anti-malondialdehyde-modified low-density lipoprotein immunoglobulin M antibodies declined significantly across both the intervention and control groups. Circulating malondialdehyde-modified low-density lipoprotein concentrations remained stable in both cohorts.
When comparing the two arms directly, regular walnut consumption was associated with modestly higher total immunoglobulin G concentrations than the control diet. Baseline immunoglobulin levels also displayed regional variations; total immunoglobulin G and immunoglobulin M concentrations were 25 percent lower among American participants than among Spanish participants.
Researchers pointed out that while previous trials have linked regular walnut consumption to improved lipid profiles and reduced circulating inflammatory markers such as tumor necrosis factor-alpha and interleukin-6, the recent immunological analysis did not track clinical cardiovascular events. Consequently, study authors emphasized that the exact health implications of the observed immunoglobulin differences remain to be established.
Practical Ways to Incorporate Walnuts Into Daily Meals
For individuals looking to replicate the dietary patterns studied by Loma Linda University researchers, co-primary author Jayme Brisco outlined several straightforward methods for adding walnuts to existing meals without disrupting personal routines.
- Crushing walnuts and tossing them into fresh salads.
- Mixing the nuts directly into morning breakfast cereals.
- Eating a simple handful of walnuts as a daily snack in place of processed items heavy in refined carbohydrates and sugar.
These findings add to a body of literature generated by the Walnuts and Healthy Aging trial, which spans more than 20 published research papers. Additional findings and related research on nut consumption and health outcomes are scheduled for presentation at the Eighth International Congress on Vegetarian Nutrition, a hybrid conference set for March 14-16, 2027, in Loma Linda, California.