In this study 266 participants with mild cognitive decline aged 70 years old or older were given the B vitamins folic acid, vitamin B6 and B12 or a placebo for 2 years (Oulhaj A, et.al., 2016).
The researchers tested cognitive performance, used a clinical dementia rating scale, and tested the concentrations of total homocysteine, total DHA (docosahexaenoic) and EPA (eicosatetraenoic acids) which are omega-3 fatty acids. Homocysteine relates to the status of folic acid, B6 and B12.
The results showed that scores for verbal delayed recall, global cognition, and clinical dementia rating were better in the B vitamin-treated group according to increasing baseline concentrations of omega-3 fatty acids, while the scores for the placebo group did not change.
When omega-3 fatty acid concentrations are low, B vitamin treatment has no effect on cognitive decline, but when omega-3 levels are in the upper normal range, B vitamins interact to slow cognitive decline.
Oulhaj A, Jernerén F, Refsum H, Smith AD, de Jager CA.
Omega-3 Fatty Acid Status Enhances the Prevention of Cognitive Decline by B Vitamins in Mild Cognitive Impairment. J Alzheimers Dis. 2016;50(2):547-57.