Table 1.

Causes of B vitamin deficiency.

B Vitamin	Inadequate Intake	Increased Requirement	Malabsorption	Drug–Nutrient Interactions	Other
Folate [19,20,21,22,23,24]	Common Poor cooking techniques	Elderly Pathological conditions	Intestinal diseases  Coeliac disease  Crohn’s disease  Ulcerative Colitis	Phenytoin Phenobarbital/Primidone Trimethoprim Methotrexate Sulfasalazine Metformin	Alcohol abuse Genetic disorders Haemolytic anaemia
B12 [19,21,22,25,26]	Common Vegan diets	Elderly	Intestinal diseases  Coeliac disease  Crohn’s disease Gastric/intestinal resection Atrophic gastritis Bacterial overgrowth  Helicobacter pylori Pancreatic insufficiency Pernicious anaemia Zollinger–Ellison Syndrome	Proton pump inhibitors H2-receptor antagonists Metformin Nitrous oxide Colchicine	Alcohol abuse Genetic disorders Tropical or non-tropical sprue
B6 [21,22,25,26]	Rare Chronic dieters	Elderly	HIV	Isoniazid Anti-Convulsants Steroids	Alcohol abuse Genetic disorders Liver disease Renal dialysis Rheumatoid arthritis
B2 [21,25,26,27]	Common Chronic dieters	Elderly	Diabetes Liver disease Thyroid and renal insufficiency GI and biliary obstruction	Phenothiazines, e.g., chlorpromazine Theophylline	Alcohol abuse Genetic disorders Hypochromic anaemia Metals such as zinc, copper and iron