Table 2:

B vitamins, coenzymes, deficiency symptoms, and risk factors for deficiency

Vitamin	Bioactive coenzyme	Deficiency symptoms	Neurologic symptoms of deficiency	Risk factor(s) for deficiency
Thiamine (B1)	TPP	Mild: fatigue, anorexia, and impaired reaction to stress Deficiency: Beriberi, endocarditis, arrhythmia, and sudden death 1	Mild: irritability, sleep disturbance, peripheral neuropathy, and confusion Deficiency: Wernicke-Korsakoff syndrome 1	– Poor intake: chronic alcoholism, carbohydrate loading, IV/PO without adequate thiamine intake, and malnutrition (eg, HIV, chemotherapy) – Impaired absorption: gastrointestinal surgical procedures, including bariatric surgical procedures – Increased utilization: pregnancy, lactation, hyperthyroidism, and refeeding syndrome – Increased loss: diarrhea, diuretics, advanced kidney disease, or dialysis 1,3
Riboflavin (B2)	Flavoproteins: flavin adenine dinucleotide or flavin mononucleotide (redox reactions)	Stomatitis, cheilitis, glossitis, dermatitis, eye irritation, cataracts, and anemia 1,4	Fatigue, migraine, and personality changes 1,4	–Anorexia nervosa –Malabsorptive syndromes –Prolonged use of barbiturates –Uncommon inborn errors of metabolism –Pregnancy –Dialysis or diarrhea 5
Niacin (B3)	Nicotinamide adenine dinucleotide and nicotinamide adenine dinucleotide phosphate	Pellagra: dermatitis, photodermatitis, burning and twitching in extremities, and diarrhea 1	Depression, anxiety, memory loss, and psychotic symptoms 1	–Low tryptophan intake –High corn diet –Carcinoid syndrome –Prolonged use of isoniazid –Hartnup disease 6,7
Pantothenic acid (B5)	Coenzyme A 1	Diarrhea, numbness, burning sensations, and dermatitis 1,8	Encephalopathy, demyelination, insomnia, and behavioral changes 1,2	–Deficiency is rare unless associated with another vitamin B deficiency 1,8
Pyridoxine, pyridoxal, pyridoxamine (B6)	Pyridoxal 5′-phosphate	Anemia 9	Cognitive impairment, irritability, depression, peripheral neuropathy, and convulsion 1,9,10	–Alcoholism, renal insufficiency, rheumatoid arthritis, and malabsorption syndromes 9
Biotin (B7)	Biotin	Dermatitis and tingling in extremities 1,11	Depression, lethargy, and seizures 1,11	–Biotinidase deficiency, alcoholism, epileptic medications, pregnancy, or breastfeeding 12
Folic acid, folate (B9)	Methyltetrahydrofolate	Megaloblastic anemia, peripheral neuropathy, and spinal cord lesion 1	Behavioral changes, affective disorders, psychosis, and dementia 1	–Genetic polymorphism MTHFR C667T –Malabsorption –Poor intake –Hemodialysis –Hemolysis 2
Cobalamins (B12)	Methylcobalamin and 5’-deoxyadenosylcobalamin 1	Same as folic acid deficiency 13,14	Same as folic acid deficiency 13,14	–Pernicious anemia –Malabsorption (eg, gastric bypass, celiac disease, and Crohn’s disease) –Vegan or poor oral intake 13,14

HIV, Human immunodeficiency virus; IV/PO, intravenous-to-oral; TPP, thiamine pyrophosphate.