Effect of Moderate Red Meat Intake Compared With Plant-Based Meat Alternative on Psychological Well-Being: A 10-Wk Cluster Randomized Intervention in Healthy Young Adults.

Background: A healthy diet has been proposed to support good mental health, but the addition of either red meat or meat alternatives is nuanced. Objectives: We aimed to determine if psychological and physiological well-being is differentially affected by consuming recommended weekly amounts of either lean red meat or plant-based meat alternatives (PBMAs) supplemented with a plant-rich diet. Methods: The trial was a parallel 2-arm randomized intervention of 10 wk duration. Eighty healthy omnivorous young adults were clustered as 40 cohabitating household pairs. Each pair was randomly assigned to consume 3 weekly servings of either fresh New Zealand beef and lamb or the equivalent PBMA. They maintained an otherwise ovo-lacto vegetarian diet, aided by a weekly meal kit and supported by engaged advice from research dietitians. Psychological measures were well-being (World Health Organization-Five Well-Being Index); depression, anxiety, and stress (depression anxiety stress scales-short form-21); and fatigue (multidimensional fatigue symptom inventory-short form) assessed weekly throughout the trial. Blood biomarkers included neurotransmitter-related compounds, iron status and vitamins B12 and D. Physical activity and sleep were estimated by a fitness wristband. Mixed effect modeling evaluated changes in each outcome over time relative to its baseline and compared the 2 interventions accounting for randomization unit clustering. Results: Thirty-nine household pairs completed the trial. Participants measured as psychologically healthy at baseline. There were no significant differences between groups in the degree of change from baseline for the psychological outcomes, nor for the majority of the circulatory markers. Differences in changes to vitamin B12 status and 3 neurotransmitter-related compounds (adenosine, agmatine, and tyrosine) from baseline to week 10 were observed between groups. Results were similar in all sensitivity analyses when adjusting for physical activity, sleep, and diet quality covariates. Conclusions: There was no effect on the psychological measures and limited change to physiological status when comparing a balanced diet containing either red meat or PBMAs in healthy young adults.