B vitamins include a group of eight essential water-soluble vitamins that must be consumed regularly from food, including animal-based protein, dairy products, leafy greens, and legumes.
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Vitamin form and food sources |
Bioactive form |
Risk factors for deficiency |
Symptoms of insufficiency/ deficiency |
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B1 Thiamine Fish Fortified foods, e.g., cereals, breads, dairy products Pork Whole grains Yeast Thiamine is found naturally in many foods and added to processed foods via fortification. |
Thiamine pyrophosphate (TPP) TPP production is magnesium-dependent. TPP is required for acetylcholine and myelin production. TPP is essential to maintaining aspartate, glutamate, and GABA levels and avoiding delirium and neuronal excitation due to their deficiency. Alcohol inhibits the phosphorylation of thiamine and the production of TPP. |
Alcoholism Carbohydrate loading, high-carb diet Decreased intake Diarrhea Hemodialysis Hyperthyroidism Impaired absorption Increased utilization Increased losses Malnutrition due to pathology, chemotherapy, etc. Pregnancy Refeeding syndrome Use of: diuretics, 5-fluorouracil |
Anorexia Arrhythmias Beriberi: wet beriberi (characterized by edema, cardiomyopathy, heart failure, pleural effusion) and dry beriberi (characterized by peripheral nervous system complications, paresthesia, foot drop, muscle wasting, numbness, and absence of ankle reflexes) Confusion Endocarditis Fatigue Impaired stress reaction Irritability Mitochondrial dysfunction, decreased energy production Oxidative stress Peripheral neuropathy Sleep disturbances Sudden death Wernicke-Korsakoff syndrome (characterized by altered mental status, ataxia, ophthalmoplegia, delirium, and permanent memory loss). |
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B2 Riboflavin Almonds Dairy products Eggs Green vegetables Meat Mushrooms Riboflavin is added to processed foods via fortification. |
Flavoproteins utilized in redox reactions: Flavin adenine dinucleotide (FAD) Flavin mononucleotide (FMN) The active form of riboflavin is required to metabolize niacin, folate, B6, and heme proteins; convert carbohydrates, fats, and protein into glucose for energy; cellular respiration; and immune system function. |
Anorexia nervosa Barbiturate use Hemodialysis Diarrhea Liver disease Malabsorptive syndromes Pregnancy Use of: anticonvulsants, anticholinergics, contraceptive pills, tricyclic antidepressants, antipsychotics, and tetracyclines |
Anemia Cataracts Cheilitis Depression Dermatitis Eye irritation Fatigue Glossitis Hair loss Liver dysfunction Migraine Nervous system complications Personality changes Sore throat Stomatitis |
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B3 Niacin Grains Legumes Nuts Seeds Soy Niacin is found in many animal and plant-based foods and is added to processed foods via fortification. Tryptophan is converted to niacin in the body. |
Nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP) NAD and NADP are required for cholesterol synthesis and DNA repair The conversion of tryptophan to niacin depends on adequate iron, riboflavin, and B6. |
Alcohol use Carcinoid syndrome Hartnup disease High-corn diet Low tryptophan intake Use of azathioprine, isoniazid, nicotine patches, 5-fluorouracil, 6-mercaptopurine |
Anxiety Apathy Burning and twitching in extremities Depression Disorientation Fatigue Memory loss Pellagra (the 4 Ds: dementia, dermatitis, diarrhea, and death) Photodermatitis, scaly rash on skin exposed to the sun Psychotic symptoms Swollen mouth Vomiting |
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B5 Pantothenic acid Avocados Beef Chicken Eggs Fish Lentils Mushrooms Pork Sunflower seeds Sweet potato |
Coenzyme A Acyl-CoA is essential to acetylcholine, cholesterol, and fatty acid synthesis. |
Use of antibiotics (especially tetracyclines), cholinesterase inhibitors, and memantine. Isolated pantothenic acid deficiency is rare and usually associated with other B vitamin insufficiencies. |
Arthritic pain Behavioral changes Demyelination Dermatitis Diarrhea Encephalopathy Fatigue Gastrointestinal complications Headaches Insomnia Irritability Numbness, burning sensations |
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B6 Pyridoxine Beef Fortified cereals Poultry Starchy vegetables Non-citrus fruits |
Pyridoxal 5′-phosphate (P5P) P5P supports immune function and brain health; metabolism of carbohydrates, fats, and protein; synthesis of serotonin and dopamine; and maintenance of normal homocysteine levels. |
Alcoholism Autoimmune disorders Malabsorptive states, e.g., IBD, celiac, and bariatric surgery Obesity Pregnancy, preeclampsia, eclampsia Renal insufficiency Rheumatoid arthritis Use of levodopa, penicillamine, hydralazine, isoniazid, cycloserine, and some anticonvulsants (e.g., valproic acid, carbamazepine, phenytoin) |
Cheilosis Cognitive impairment Confusion Convulsions Dermatitis Depression EEG abnormalities Glossitis Idiopathic carpal tunnel syndrome (possibly) Immune insufficiency Irritability Microcytic anemia Peripheral neuropathy |
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B7 Biotin Eggs Fish Nuts Organ meats Seeds Soybeans |
Biotin Catalyzes the metabolism of glucose, fatty acids, and amino acids and is essential to gene regulation, cell signaling, and cell replication |
Alcoholism Biotinidase deficiency Epileptic medications Pregnancy or breastfeeding Use of anticonvulsants. Note: high-dose biotin can interfere with thyroid function, and 25-OH vitamin D tests |
Ataxia Depression Dermatitis Hair thinning Lethargy Nail changes Paresthesia, tingling in extremities Scaly rash around eyes, nose, mouth Seizures Skin infections |
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B9 Folate Beans Brussels sprouts Dairy products Dark leafy greens Grains Nuts Poultry Vegetables |
Methyltetrahydrofolate Methyltetrahydrofolate is essential to RBC production, nucleic acid synthesis, and conversion of homocysteine to methionine. Individuals with the MTHFR gene variants should be supplemented with L-methylfolate (5-MTHF) instead of synthetic folic acid. B12 insufficiency must be ruled out before supplementing with folate. |
Genetic polymorphism MTHFR C667T Hemodialysis Hemolysis Malabsorption Poor intake Use of methotrexate, metformin, cholestyramine, sulfasalazine, antibiotics, and antiepileptics e.g., gabapentin |
Affective disorders Behavioral changes Birth defects Dementia Headaches Megaloblastic anemia Oral ulcerations Palpitations Peripheral neuropathy Poor concentration Psychosis Skin, hair, and fingernail changes Spinal cord lesions |
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B12 Cobalamin Animal-based protein foods Fortified foods |
Methylcobalamin and 5’-deoxyadenosylcobalamin Cobalamin is required for myelin synthesis, neurological function, RBC production, RNA and DNA synthesis, and hormone, lipid, and protein synthesis and metabolism. |
Intrinsic factor deficiency Gastrointestinal surgery Malabsorption (e.g., gastric bypass, celiac, and Crohn’s disease) Poor oral intake Vegan diet Use of antacids, antibiotics, and colchicine |
Decreased appetite Irreversible neurological damage Fatigue Megaloblastic anemia Neuropsychiatric disorders Pernicious anemia Many symptoms are the same as folate deficiency symptoms. |
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Note: Excessively high doses of vitamins can cause toxicity, so supplementation should be initiated and monitored accordingly. |
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B vitamins are essential to health and should be consumed daily as they are not stored in significant amounts. The B vitamins work closely together in a number of metabolic functions.
Insufficiencies should be identified early to prevent progressive loss of function and potentially irreversible damage.
B vitamin supplementation should be individualized depending on genetic factors, diet, and health history.
B vitamins participate in:
Hanna, Mary et al. “B Vitamins: Functions and Uses in Medicine.” The Permanente journal vol. 26,2 (2022): 89-97. doi:10.7812/TPP/21.204