B‑Complex Unpacked: Roles, Daily Targets, Best Foods & Fixing Deficiencies
From brain‑boosting B12 to energy‑sparking B1, discover why eight water‑soluble vitamins work better together—and how to get enough on any diet.
Hook
**Nearly one in three adults over 50 is low in vitamin B12—jeopardising memory and energy (NHANES 2024).**
TL;DR
- Eight B‑vitamins (B1, B2, B3, B5, B6, B7, B9, B12) act as energy co‑enzymes
- RDA varies: B1 = 1.1 mg, B12 = 2.4 µg, Folate = 400 µg DFE
- Most people meet needs from whole grains, legumes, meat/eggs—except vegans → monitor B12
- Alcohol, metformin and proton‑pump inhibitors deplete key B‑vitamins
B‑vitamin family overview
| Vitamin | Key job | RDA | Upper limit |
|---------|---------|-----|-------------|
| B1 Thiamine | Carb → ATP | 1.1‑1.2 mg | none |
| B2 Riboflavin | FAD/FMN cofactor | 1.1‑1.3 mg | none |
| B3 Niacin | NAD/NADP | 14‑16 mg NE | 35 mg NE |
| B5 Pantothenic | CoA synthesis | 5 mg | none |
| B6 Pyridoxine | Neurotransmitters | 1.3‐1.7 mg | 100 mg |
| B7 Biotin | Gene regulation | 30 µg | none |
| B9 Folate | DNA methylation | 400 µg DFE | 1 000 µg (synthetic) |
| B12 Cobalamin | Myelin, RBC | 2.4 µg | none |
Highlights of individual roles
- **B1**: deficiency → beriberi, Wernicke’s encephalopathy (alcoholics)
- **B6**: lowers PMS symptoms at 50 mg/d (Cochrane 2023)
- **B9 + B12**: synergistic; folate without B12 can mask anaemia but allow nerve damage
Daily requirements & who needs more
- **Pregnancy**: Folate 600 µg DFE to prevent neural‑tube defects
- **Vegans**: 250 µg cyanocobalamin daily or 2 000 µg weekly
- **Smokers**: extra B6 & B9 to counter oxidative stress
Deficiency red flags
- Fatigue, cracked mouth corners → B2
- Tingling hands, memory lapses → B12
- Glossitis, megaloblastic anaemia → B9/B12
Top natural sources (per serve)
| Food | B‑strong vitamins |
|------|-------------------|
| Beef liver 85 g | B2, B3, B6, B9, B12 |
| Chickpeas 1 cup | B1, B6, B9 |
| Eggs 2 pcs | B2, B7, B12 |
| Nutritional yeast 2 Tbsp | B1, B2, B3, B6, B12 (fort.) |
| Salmon 100 g | B3, B6, B12 |
Absorption hacks & blockers
- **B12 needs intrinsic factor**—watch PPI & metformin use
- **Alcohol** impairs B1, B6
- Cooking losses: B1 & folate leach into water—steam or sauté instead of boil
When to supplement & forms
- Vegans → cyanocobalamin or methyl‑B12 lozenges
- Pregnancy → 400 µg methyl‑folate + prenatal B‑complex
- Chronic stress → 50 mg B‑complex (may lower homocysteine 15 %)
Myth vs fact
| Myth | Fact |
|------|------|
| “Energy shots give lasting B‑power.” | Excess water‑soluble Bs are excreted in urine.
| “All B‑vitamins are stored.” | Only B12 (~3 yr stores); others deplete in weeks.
| “Megadose B6 is harmless.” | > 200 mg/d long‑term → nerve toxicity.
Take‑home message
Eat a variety of whole grains, legumes, eggs, seafood—and supplement smartly if vegan, pregnant or on B‑depleting meds to keep energy, nerves and DNA repair humming.
References
1. NIH ODS B‑Vitamin Fact Sheets 2024
2. Cochrane Review. *Vitamin B6 & PMS* 2023
3. ADA. *B12 Status in Metformin Users* 2025