Description

• 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).

Epidemiology

• Predominant age
  • Geriatric patients, pregnant women, exclusively breastfed infants, and individuals with certain chronic disease states have higher incidence
• Individuals from Africa and Southeast Asia are at increased risk.
• True incidence is unknown because 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 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 deficiency can develop under healthy conditions, generally due to one of five 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 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
• Dialysis
• 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)
• A-β-lipoproteinemia

Risk Factors

Poverty, malnutrition, chronic disease states, advanced age, dietary restrictions, bariatric surgery, certain medications, and exclusively breastfed infants

General Prevention

• Ingesting large and varied amounts of vitamin supplements increases risk of toxicity and drug–drug interactions and is not recommended.
• Antioxidant supplements have not been shown to impact cancer incidence and have increased mortality risk in some studies (2).
• Avoiding restrictive diets.
• U.S. Preventive Services Task Force (USPSTF) recommends against low-dose supplementation with vitamin D (<400 IU) and calcium (<1,000 mg) to reduce fracture risk in community-dwelling postmenopausal women (3).
• The USPSTF concludes that there is insufficient evidence to assess the balance of the benefits and harms of daily supplementation with doses greater than 400 IU of vitamin D and greater than 1,000 mg of calcium for the primary prevention of fractures in community-dwelling, postmenopausal women (3).
• The USPSTF also concludes that the current evidence is insufficient to assess the balance of the benefits and harms of vitamin D and calcium supplementation, alone or combined, for the primary prevention of fractures in men and premenopausal women (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 β-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