Effect of green mediterranean diet on serum folate and its interaction with genetic variation in folate metabolism: The DIRECT PLUS 18-month dietary randomized controlled trial.

BACKGROUND

& Aims: Folate metabolism can be regulated by diet and genetic variation, particularly Methylenetetrahydrofolate reductase (MTHFR) rs1801133 polymorphism. We explored the effect of plant-based green-Mediterranean (green-MED) diet on serum folate and whether this effect varies by genetic variation in folate metabolism over 18-months

METHODS

In the DIRECT-PLUS trial, 294 participants were randomized to healthy dietary guidelines (HDG), MED, or plant-based green-MED diets. Both isocaloric MED groups consumed walnuts (28g/day), while green-MED group also avoided red/processed meat, consumed Wolffia-globosa Mankai green shake (500 ml/day), and green-tea (3-4 cups/day). MRI assessed visceral adipose tissue (VAT). MTHFR rs1801133 single-nucleotide-polymorphism (SNP), and folate-pathway mRNA expression were evaluated.

RESULTS

Participants (age = 50.1years; 90.6% men; body-mass-index = 31.4 kg/m2; serum folate = 7.6 ng/mL; rs1801133 frequencies: CC = 38.5%; CT = 49.8%; TT = 11.7%) had 89% 18-month retention rate. Folate deficiency at baseline was rare (∼3%, n = 8), indicating effects within the normal range. After 18-months of intervention, the green-MED diet significantly increased serum folate (+1.2 ng/mL) compared to MED (+0.41 ng/mL) and HDG diets (+0.1 ng/mL), p < 0.05 between groups, with higher Mankai intake strongly associated with folate elevation (p = 0.003). rs1801133 TT-genotype carriers had lower folate at baseline (p = 0.037) and post-intervention (p = 0.04; recessive mode-of-inheritance), while CC/CT-genotype carriers showed the highest folate increase following the green-MED intervention (p = 0.03). TT-genotype carriers showed lower baseline MTHFD2 mRNA expression (p = 0.005), but an enriched transcription, compared to CC/CT-carriers post-intervention (p = 0.001). Mankai intake interacted with rs1801133 genotype on VAT (p = 0.028) and Framingham risk score (p = 0.024), with CC/CT-carriers showing dose-response benefits.

CONCLUSIONS

The green-MED diet, enriched with Mankai, significantly increased serum folate compared with the MED and HDG diets. The response differed by MTHFR rs1801133-genotype, with CC/CT carriers showing greater increases in folate. These findings support a gene-diet interaction with potential implications for visceral adiposity and cardiometabolic risk.