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- Vitamins are essential micronutrients required for normal metabolism, growth, and development.
- Deficiencies are less common in the Western world, but certain populations are at increased risk.
- Regulations mandating vitamin supplementation in food products, adequate food security, and availability of vitamin supplements make vitamin deficiencies less common in developed countries.
- Toxicity is rare for water-soluble vitamins; toxicity is possible with fat-soluble vitamins (A, D, E, K).
- Predominant age
- Geriatric patients, pregnant women, exclusively breastfed infants, and individuals with certain chronic disease states
- Individuals from Africa and Southeast Asia are at increased risk.
- True incidence is unknown as most vitamin deficiencies are asymptomatic.
- Varies by age groups, comorbid conditions, geography, and setting (i.e., urban, rural)
- The prevalence of vitamin B12 deficiency is ~6% in patients <60 years of age and increases to around 20% after age 60 years (1).
- Vitamin D deficiency has become increasingly recognized and its prevalence is increased in individuals with darker skin pigmentation, obesity, low dietary intake of vitamin D, or low sunlight exposure.
Etiology and Pathophysiology
- Disease-related deficience can develop under healthy conditions, generally due to 1 of 5 mechanisms:
- Reduced intake
- Diminished absorption
- Increased use
- Increased demand
- Increased excretion
- Chronic disease states: HIV, malabsorption (such as celiac sprue and short bowel syndrome), chronic liver and kidney disease, alcoholism, malignancies, pernicious anemia, and rare inborn errors of metabolism
- Bariatric surgeries: gastric bypass, gastrectomy, small or large bowel resection
- Related to certain drugs: prednisone, phenytoin, isoniazid, protease inhibitors, methotrexate, phenobarbital, alcohol, nitrous oxide, H2 receptor antagonists, metformin, colchicine, cholestyramine, 5-fluorouracil, 6-mercaptopurine, azathioprine, chloramphenicol, proton pump inhibitors, chronically used antibiotics, penicillamine, and hydralazine
- Malnutrition, imbalanced nutrition, obesity, fad diets, extreme vegetarianism, total parenteral nutrition, bulimia/anorexia, and other eating disorders
- Parasitic infestation
- Cystic fibrosis
- Hartnup disease
- Rare genetic predisposition
- Autoimmune disease (e.g., pernicious anemia)
- Congenital enzyme deficiencies (e.g., biotinidase or holocarboxylase synthetase deficiency)
- Transcobalamin II deficiency
- Ataxia with vitamin E deficiency (AVED)
Poverty, malnutrition, chronic disease states, advanced age, dietary restrictions, bariatric surgery, and exclusively breastfed infants
- Ingesting large and varied amounts of vitamins increases risk of toxicity and drug–drug interactions.
- Antioxidant supplement use has not been shown to impact cancer incidence and has increased mortality risk in some studies (2).
- Avoiding restrictive diets decreases the likelihood of vitamin deficiency.
- In particular age groups or with certain risk factors, vitamin supplementation may be recommended.
- U.S. Preventive Services Task Force (USPSTF) recommends vitamin D supplementation in community-dwelling adults aged 65 years or older who are at increased risk for falls (3)[B].
- USPSTF recommends against low-dose supplementation with vitamin D (<400 IU) and calcium (<1,000 mg) to reduce fracture risk in noninstitutionalized populations, concluding that data on the effects of higher doses were insufficient (3).
- USPSTF recommends that all women planning or capable of pregnancy take a daily supplement containing 0.4 to 0.8 mg of folic acid (4)[A].
- USPSTF recommends against the use of beta carotene or vitamin E supplements for the prevention of cardiovascular disease or cancer (2).
- All infants should receive 400 IU/day of vitamin D soon after birth whether breast- or formula-fed (5).
Commonly Associated Conditions
Anemia, neuropathies, dermatitis, visual disturbances