The Dietary Inflammatory Index is Lower Among Healthy Older Adults Consuming a Walnut-Supplemented Diet. Ancillary Results from the Walnuts and Healthy Aging Randomized Controlled Trial.

BACKGROUND

Walnuts may lower diet-related inflammation by providing anti-inflammatory compounds and displacing pro-inflammatory nutrients.

OBJECTIVE

To explore the association between daily walnut consumption or abstention for 2 years and the Dietary Inflammatory Index (DII®).

DESIGN

The Walnuts and Healthy Aging (WAHA) study is a dual-center (Loma Linda, California, USA and Barcelona, Spain), randomized trial, comparing a walnut-rich diet with a control diet over 2 years between May 2012 to May 2016, for age-related outcomes in healthy, free-living older adults aged 63-79 y. This ancillary study concerned only the Loma Linda cohort.

PARTICIPANTS/

SETTING

A total of 319 older adults (mean age 69 y, 66% women) from Loma Linda, Ca were randomly assigned to walnut (n = 166) or control (n = 153) diets.

INTERVENTION: The walnut group consumed 1-2 oz walnuts/day (30-60 g/day, ∼15% of energy), while the control group abstained from walnuts and limited other nuts to <2 servings/week. Both groups followed their usual background diet.

MAIN OUTCOME MEASURES: DII scores were calculated from five 24-hour dietary recalls taken at random during the 2-year period.

STATISTICAL ANALYSES PERFORMED: Linear mixed models tested DII differences between the walnut and control groups, adjusting for sex, age, BMI, race, energy intake, smoking status, physical activity, and educational attainment.

RESULTS

The mean DII (SE) score was -0.025 (0.14) in the walnut group and 0.615 (0.14) in the control diet group (p<0.01). At the nutrient level, n-3 PUFAs (ß=-0.291; 95%CI: -0.450, -0.132; p<0.01), magnesium (ß=-0.014; 95%CI: -0.015, -0.013; p<0.01), carbohydrate (ß=-0.009; 95%CI: -0.014, -0.005; p<0.01), fiber (ß=-0.120; 95%CI: -0.133, -0.106; p=0.05), and protein (ß=-0.020; 95% CI: -0.031, -0.008; p<0.01), were associated with a more anti-inflammatory DII score, while intake of total and saturated fat were associated with a higher, more proinflammatory, DII score (ß=0.033; 95%CI: 0.020, 0.045; p<0.01 and ß=0.102; 95%CI: 0.080, 0.125; p<0.01 respectively).

CONCLUSION

Incorporating walnuts into the habitual diet was associated with more anti-inflammatory DII scores compared with a walnut-free control diet. These findings suggest that adding a single whole food may be a feasible complementary strategy for favorably improving the inflammatory potential of a diet.