Red meat consumption in higher healthy eating index diets is associated with brain health critical nutritional adequacy, and fecal microbial diversity.

We evaluated whether red meat consumption, within diets of both high and low healthy eating index (HEI) quality, was associated with differences in brain health-critical micronutrient adequacy, mental health, diet quality, or fecal microbiota composition. Using data from 3643 adults in the American gut project, participants were stratified into four groups: high-HEI (≥ 80) with red meat (HH-R), high-HEI without red meat (HH-NR), low-HEI (< 80) with red meat (LH-R), and low-HEI without red meat (LH-NR). HH-R had higher protein intake and lower carbohydrate intake than HH-NR, with saturated fat levels within recommended limits. Brain health-critical micronutrient adequacies (selenium, vitamin B12, zinc, calcium, vitamin D3, choline) were significantly higher in HH-R (p < 0.001) than HH-NR. Higher HEI scores, irrespective of red meat consumption, were associated with reduced odds of depression (logOR = -2.22), PTSD (logOR = -3.80), and bipolar disorder (logOR = -5.90). Fecal microbiota diversity and richness were highest in HH-R, with higher Bacteroides caccae (padj = 0.003) and Clostridium hathewayi (padj < 0.001), while HH-NR showed higher Bifidobacterium adolescentis and Bacteroides eggerthii (padj < 0.001). Therefore, these findings suggest that the inclusion of red meat in a high-HEI diet improves brain health-supporting micronutrient adequacy without adverse effects on mental health or microbial diversity.