MTHFR Mutations in Aging Men: What the Research Reveals

Abstract Summary

Objective 

To evaluate the sex-specific clinical implications of MTHFR C677T polymorphism in older men, focusing on homocysteine elevation, cognitive decline, cardiovascular risk, hormonal disruption, and cancer susceptibility.

Context 

In North America, Europe, and Australia, approximately 8–20% of the population carry two MTHFR C677T mutations, resulting in only 30% of normal enzyme function. Critically, the frequency of the MTHFR mutation was significantly lower in those aged 85 and over compared to young adults, and this difference in genotype distribution was observed only in men — suggesting excess mortality among male carriers before reaching advanced age.

Methods Used 

A synthesis of population-based cohort studies, Mendelian randomization analyses, longitudinal neuroimaging investigations, and large-scale meta-analyses evaluating MTHFR polymorphisms in relation to cognitive, cardiovascular, hormonal, and oncologic outcomes in older men.

Researchers' Summary of Findings

Impact on Health

The estimated mortality risk up to age 85 in men with the TT genotype was 3.7-fold elevated, increasing 2.0-fold after age 85 — attributable primarily to cancer rather than cardiovascular causes. No such effect was observed in women. 

Among 1,778 older men, those with the MTHFR-TT genotype had 46% greater odds of cognitive impairment, with brain imaging confirming localized atrophy in regions linked to both intellectual and emotional functioning, mediated by elevated plasma homocysteine. 

High homocysteine from MTHFR mutations may impair testosterone production in Leydig cells, affecting muscle mass, development, and fertility — a compounding concern in aging men already experiencing age-related testosterone decline.

On cancer risk, stratified analyses across 446 studies found decreased colorectal cancer risk specifically in the male population carrying the 677TT genotype, though the Leiden mortality data indicates cancer remains the primary driver of excess mortality in older MTHFR-TT men overall.

Health Implications 

A homocysteine level above 15 µmol/L is a major risk factor for Alzheimer's disease, brain atrophy, and vascular damage. Low folate levels are associated with higher cognitive decline risk in older adults with MTHFR. Genotype testing alone is insufficient — plasma homocysteine, RBC folate, and B12 must be assessed alongside medications and renal function.

Sustainability

Not everyone with MTHFR mutations will experience elevated homocysteine or related symptoms, especially with a wholesome diet and active B vitamin supplementation. Decisions should be guided by ongoing biomarker monitoring rather than genotype alone.

DOI

https://doi.org/10.1038/mp.2011.8