“B-complex” sounds like a single vitamin, but it is actually a family of eight chemically distinct water-soluble vitamins. They often occur together in foods such as whole grains, legumes, eggs, dairy and meat, and they work as a team in energy metabolism, yet each also has its own specific roles, deficiency syndromes and best food sources. This guide walks through each B vitamin individually, so you can see what it does and how to get enough.
Overview of the B Vitamins
| Vitamin | Common name | Primary role | Top food sources |
|---|---|---|---|
| B1 | Thiamine | Carbohydrate metabolism, nerve function | Whole grains, pulses, nuts, pork, sunflower seeds |
| B2 | Riboflavin | Energy production, skin and eye health | Milk, eggs, almonds, mushrooms, leafy greens |
| B3 | Niacin | Energy metabolism, DNA repair | Peanuts, chicken, fish, whole grains, mushrooms |
| B5 | Pantothenic acid | Coenzyme A synthesis, fat metabolism | Eggs, avocado, legumes, mushrooms, whole grains |
| B6 | Pyridoxine | Amino acid metabolism, neurotransmitters | Chickpeas, bananas, potatoes, fish, poultry |
| B7 | Biotin | Fat, carbohydrate and amino acid metabolism | Eggs (cooked), nuts, seeds, sweet potato |
| B9 | Folate / folic acid | DNA synthesis, cell division | Leafy greens, lentils, beans, citrus, fortified grains |
| B12 | Cobalamin | Nerve function, red blood cells, DNA synthesis | Meat, fish, eggs, dairy, fortified foods |
Vitamin B1 (Thiamine)
Thiamine is a coenzyme in the breakdown of carbohydrates and branched-chain amino acids, and it supports nerve conduction. Because refined grains lose thiamine during milling, populations relying on polished white rice historically developed beriberi, which affects the nervous system and heart. In wealthy countries, thiamine deficiency is now seen mainly with chronic heavy alcohol use, where it can cause Wernicke-Korsakoff syndrome. Good sources include whole wheat, brown or parboiled rice, legumes, sunflower seeds and pork.
Vitamin B2 (Riboflavin)
Riboflavin forms the coenzymes FAD and FMN, central to the electron transport chain and to the activation of other B vitamins. Signs of deficiency include cracked lips and corners of the mouth, sore tongue, and light sensitivity. Riboflavin is sensitive to light, so milk stored in clear containers can lose it. Dairy products, eggs, almonds, mushrooms and fortified cereals are good sources.
Vitamin B3 (Niacin)
Niacin is a component of NAD and NADP, coenzymes involved in hundreds of reactions. The body can partly make niacin from the amino acid tryptophan (about 60 mg of tryptophan yields about 1 mg of niacin). Severe deficiency causes pellagra, characterised by dermatitis, diarrhoea and dementia, historically linked with maize-based diets where niacin is bound and unavailable. Traditional alkaline treatment of maize (nixtamalisation) frees the niacin. High-dose niacin supplements can cause flushing and liver problems and should be used only under medical supervision.
Vitamin B5 (Pantothenic Acid)
Pantothenic acid is a building block of coenzyme A, essential for fatty acid metabolism and the citric acid cycle. Its name comes from the Greek for “from everywhere”, reflecting its wide distribution in foods, so deficiency is rare outside severe malnutrition. Eggs, legumes, whole grains, mushrooms and avocado provide plenty.
Vitamin B6 (Pyridoxine)
B6 acts in more than 100 enzyme reactions, particularly amino acid metabolism, and is needed for making neurotransmitters such as serotonin and GABA, as well as haemoglobin. Deficiency may cause anaemia, skin changes and irritability or depression. Rich sources include chickpeas, fish, poultry, potatoes, bananas and fortified cereals. Very high supplemental intakes (often above 100 mg per day over long periods) can cause nerve damage; the US upper limit for adults is 100 mg per day.
Vitamin B7 (Biotin)
Biotin is a cofactor for carboxylase enzymes in fat, carbohydrate and amino acid metabolism. True deficiency is rare, but it can occur in people who eat large amounts of raw egg whites, which contain avidin, a protein that binds biotin. Cooking inactivates avidin. Biotin supplements are marketed for hair and nails, but evidence for benefit in people without deficiency is limited. High-dose biotin can also interfere with certain laboratory tests, including thyroid and troponin assays, so tell your doctor if you take it.
Vitamin B9 (Folate)
Folate is required for synthesising DNA and RNA and for cell division, making it critical during pregnancy and growth. Adequate folate before conception and in early pregnancy substantially reduces the risk of neural tube defects such as spina bifida, which is why women who could become pregnant are advised to consume 400 µg of folic acid daily from supplements or fortified foods in addition to food folate. Deficiency also causes megaloblastic anaemia. Natural folate is found in leafy greens, lentils, beans, citrus fruit, and asparagus; folic acid is the synthetic form used in supplements and in fortified flour in many countries. Folate is easily lost by prolonged boiling.
Vitamin B12 (Cobalamin)
B12 is required for myelin maintenance in nerves, red blood cell formation, and DNA synthesis. It is found naturally almost only in animal foods, so vegans must rely on fortified foods or supplements. Absorption requires intrinsic factor from the stomach, and deficiency may arise from pernicious anaemia (an autoimmune condition), atrophic gastritis in older adults, bariatric surgery, or long-term use of metformin or acid-reducing drugs. Symptoms include fatigue, pale skin, tingling in the hands and feet, memory problems and mood changes. Prolonged deficiency can cause irreversible nerve damage, so early detection matters. The adult recommended intake is 2.4 µg per day.
Daily Needs at a Glance (Adults, US RDA or AI)
| Vitamin | Men | Women |
|---|---|---|
| B1 | 1.2 mg | 1.1 mg |
| B2 | 1.3 mg | 1.1 mg |
| B3 | 16 mg NE | 14 mg NE |
| B5 (AI) | 5 mg | 5 mg |
| B6 (19 to 50 years) | 1.3 mg | 1.3 mg |
| B7 (AI) | 30 µg | 30 µg |
| B9 (DFE) | 400 µg | 400 µg (600 µg in pregnancy) |
| B12 | 2.4 µg | 2.4 µg (2.6 µg in pregnancy) |
NE = niacin equivalents; DFE = dietary folate equivalents; AI = adequate intake.
Who Is at Risk of B Vitamin Shortfalls?
- Vegans and some vegetarians: B12 especially.
- Older adults: reduced B12 absorption.
- Pregnant women: increased folate, B6 and B12 requirements.
- People with alcohol use disorder: thiamine, folate, B6.
- Those with gastrointestinal disorders or bariatric surgery: multiple B vitamins.
- People on certain medications: metformin, proton pump inhibitors, some anticonvulsants.
Cooking and Storage Tips
- Avoid discarding rice or dal cooking water when it is meant to be consumed; use minimal water.
- Steam or microwave vegetables instead of long boiling to retain folate and B6.
- Store milk and grains away from direct light.
- Choose whole or parboiled grains over highly polished ones.
- Do not add baking soda to vegetables, as alkaline conditions destroy thiamine.
Common Misconceptions
- “B vitamins give you energy.” They help release energy from food, but supplements energise only if you are deficient.
- “Excess water-soluble vitamins just wash out.” This is largely true for some, but B6 and niacin in high doses can cause harm.
- “Spirulina and fermented foods provide reliable B12.” Many plant sources contain inactive B12 analogues; fortified foods and supplements are more dependable.
- “B vitamins are interchangeable.” Each has distinct roles, deficiency syndromes and food sources.
Summary
The B-complex vitamins are partners in metabolism and individuals in function. From B1’s role in carbohydrate use to B12’s role in nerve health, each has its own job and deficiency signs. A diet rich in whole grains, legumes, vegetables, dairy or eggs (or fortified alternatives), supplemented where needed, ensures the entire B-team is present.
References and Further Reading
- NIH Office of Dietary Supplements. Fact sheets for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Biotin and Pantothenic Acid.
- National Academies. Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline.
- WHO. Guidelines on folic acid and neural tube defects.
- Harvard T.H. Chan School of Public Health. The Nutrition Source: Vitamins.
- ICMR-NIN. Nutrient Requirements for Indians.
This article is educational and not personalised medical advice.