Glossary
B Vitamins
Updated February 28, 2026
B vitamins function as coenzymes across energy conversion, methylation, and redox control. Their impact is often underestimated because each one acts at low dose yet shifts how efficiently calories become ATP, how quickly tissues repair, and how stable nervous signaling remains through training and stress.
Biochemical role map
| Vitamin | Name | Role | Common sources |
|---|---|---|---|
| B1 | Thiamin | Carbohydrate processing at entry points | Whole grains, pork, legumes |
| B2 | Riboflavin | Mitochondrial electron flow | Dairy, eggs, mushrooms |
| B3 | Niacin | Energy and oxidative repair | Meats, fish, whole grains |
| B5 | Pantothenic acid | Acetyl transfer and cortisol resilience | Meats, legumes, avocados |
| B6 | Pyridoxine | Amino acid conversion and neurotransmitter support | Poultry, potatoes, bananas |
| B7 | Biotin | Carboxylation and gene-linked metabolism | Eggs, nuts, seeds |
| B9 | Folate | DNA synthesis and cell division | Leafy greens, lentils |
| B12 | Cobalamin | Red blood cell production and myelin stability | Fish, red meat, fortified foods |
Deficiency and excess profiles
| Vitamin | Common deficiency pattern | Functional consequence | Typical risk context |
|---|---|---|---|
| B1 | Low intake and alcohol load | Mental fatigue, reduced exercise tolerance | High carbohydrate intake without micronutrient diversity |
| B2 | Low animal and fortified intake | Cracked lip corners, mucosal sensitivity | Broad low-variety diets |
| B3 | Chronic low quality carb intake | Exercise intolerance, skin and mood shifts | Energy-dense processed eating |
| B6 | Low protein quality and inflammation | Nerve irritation, mood swings, poor recovery | Stress-heavy training blocks |
| B9/B12 | Low bioavailable intake | Macrocytic anemia risk, reduced endurance adaptation | Vegan patterns, malabsorption, gastric hyposecretion |
| B5/B7 | Inconsistent intake over months | Dry skin, brittle hair, poor digestion resilience | Highly restrictive plans |
Excess from isolated supplementation can produce neuropathy signs, flushing, or lab noise. The practical issue is usually not a high dose of one vitamin but an imbalance where one nutrient is high and others remain constrained by intake quality.
Food matrix and coverage
Whole-food matrices matter because absorption and companion nutrients differ. Fermented dairy can support B12 and riboflavin co-presence, while legumes and seeds support B6 and folate with fiber-mediated gut effects. Dark chocolate and seeds may carry niacin but still lack the broader spread needed for sustained training days, so they should support rather than anchor strategy.
For mixed diets, food quality comes from combining:
| Pattern | Strength |
|---|---|
| Mixed omnivore | Broadest direct coverage across B vitamins in a realistic workflow |
| Vegetarian with dairy/eggs | Reliable B12 via fortified foods and dairy but weaker folate from refined reliance |
| Vegan without fortified planning | Needs explicit B12 and B2 redundancy due to common gaps |
Monitoring priorities
Vegetarians, older adults, low-calorie athletes, and people with persistent gut or sleep disruption should monitor status more tightly. Testing should focus on B12, methylfolate relevance, and markers tied to anemia and recovery quality, especially when symptoms persist despite calorie and protein consistency.
Clinical application
In deficit phases, B vitamins should be managed as one support cluster rather than isolated add-ons. Start with food diversity across whole grains, legumes, fish or eggs, and fermented foods, then use lab-directed supplements only where status gaps are identified.