According to a new US study, low blood levels of vitamins B6 and B12 may be associated with an increased risk of impaired cognition.
The epidemiological study analyzed blood concentrations of vitamin B and measured cognitive functions and symptoms of depression in a total of 1956 adult participants from two ethnically diverse population groups (1). The study results indicated that low vitamin B12 concentrations were associated with higher depression scores and lower cognition scores, while low vitamin B6 concentrations were linked to lower cognition scores. The study did not find any association between impaired cognition or depression and folate concentrations, homocysteine levels or participants with a variation of the gene that encodes methylenetetrahydrofolate reductase (MTHFR), an enzyme involved in folate metabolism.
The researchers noted that these findings support the hypothesis but do not prove that increased B12 and B6 intake improves cognition and lowers the likelihood of depression. The fact that the study did not show a link between folate and homocysteine levels and cognition or depression challenges a well-cited hypothesis that increased concentrations of homocysteine are linked to a higher rate of atrophy, or wasting in the brain, and therefore mild cognitive impairment.
Epidemiological studies have reported that high levels of homocysteine are associated with suspected or confirmed dementia. The Framingham study, for example, reported that people with homocysteine levels above 14 micromoles per liter of serum were twice as much at risk of dementia (2). A recent intervention study found that daily supplements of folic acid, vitamins B6 and B12 were associated with a 30% reduction in levels of the amino acid homocysteine, and improvements in performance on a range of mental tests, including global cognition and episodic memory (3).