Vitamin
Vitamin B-Complex
B6 · B9 (folate) · B12 and co-factors
Moderate evidence
B vitamins are co-factors in the very pathways the brain uses to make neurotransmitters. Deficiencies — especially B12 and folate — are well-known contributors to fatigue and low mood.
If neurotransmitters are the brain’s messages, B vitamins are part of the machinery that prints them. Folate and B12 in particular drive the methylation cycle that produces serotonin, dopamine and norepinephrine precursors — which is why a true B12 or folate deficiency can show up first as flat mood and fatigue rather than anything dramatic.
A B-complex is a low-cost insurance policy, with the clearest payoff for people whose diet or absorption makes deficiency likely.
What to look for
- Methylfolate and methylcobalamin (the active forms) over folic acid/cyanocobalamin if you want premium absorption
- Sensible doses — “mega-B” formulas with 5,000% RDA aren’t better
- Take in the morning; some people find B vitamins too energizing at night