Benefits of folic acid on cognitive ageing dependent on omega-3 fatty acid status

The efficacy of folic acid supplementation on cognitive function relies on the omega-3 fatty acid status, suggests a study. Individuals with a lower omega-3 fatty acid status at baseline benefit from treatment, while those with a higher status do not.

“Although epidemiological studies suggest a protective role of B vitamins and omega-3 fatty acids in cognitive decline, findings from intervention studies are conflicting,” the authors said. “Mechanistic studies suggest that the omega-3 fatty acid status can modulate the effects of B vitamins on cognitive decline.”

A total of 791 older adults aged 50–70 years with plasma total homocysteine ≥13 µmol/L and ≤26 µmol/L and serum vitamin B12 ≥200 pmol/L were included in this posthoc analysis. Participants received 800 µg folic acid or placebo daily for 3 years.

The authors then assessed global cognitive functioning and domain-specific functioning (episodic memory, information processing speed, executive functioning) at baseline and after 3 years. They also analysed the effect of folic acid supplementation according to tertiles of baseline omega-3 fatty acid concentrations using linear multiple regression.

Participants had a mean age of 60.2±5.6 years and a mean Mini-Mental State Examination score of 28.6±1.5. The effect of folic acid treatment on global cognition was significantly greater in participants in the low vs high omega-3 fatty acid tertile (mean difference in z-score, 0.16±0.059; p<0.01).

In terms of domain-specific functioning, results were similar for information-processing speed (mean, 0.167±0.068; p=0.01). No overall interactions between folic acid treatment and omega-3 fatty acid tertiles were observed for episodic memory (p=0.14) and executive functioning (p=0.21).

“The results potentially explain the inconsistency in outcomes of B-vitamin supplementation trials and emphasize the importance of a personalized approach,” the authors said.