- Vitamins are essential micronutrients required for normal metabolism, growth, and development.
- Vitamin supplementation in food products, adequate food security, and availability of supplements make vitamin deficiencies less common in developed countries. Certain populations are at increased risk.
- Toxicity is rare for water-soluble vitamins. It is possible for fat-soluble vitamins (A, D, E, K).
- Higher incidence seen in geriatric patients, pregnant women, exclusively breastfed infants, individuals with highly restricted diets or certain chronic disease states
- 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 old and increases to ~20% after the age of 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. This deficiency is seen in ~5% of the general population, with non-Hispanic Blacks having the highest prevalence.
Etiology and Pathophysiology
- Deficiency usually develops from one of five mechanisms: reduced intake, diminished absorption, increased use, increased demand, increased demand or increased excretion
- Chronic disease states: HIV, malabsorption (i.e., celiac sprue, short bowel syndrome), chronic liver and kidney disease, alcoholism, malignancies, pernicious anemia, inborn errors of metabolism
- Bariatric surgeries: gastric bypass, gastrectomy, small or large bowel resection
- Certain drugs predispose to vitamin deficiencies: 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, hydralazine
- Malnutrition, imbalanced nutrition, obesity, fad diets, extreme vegetarianism, total parenteral nutrition, bulimia/anorexia, other eating disorders, parasitic infection
- Cystic fibrosis
- Hartnup disease, A-β-lipoproteinemia
- Rare genetic predisposition
- Autoimmune disease (i.e., pernicious anemia)
- Congenital enzyme deficiencies (i.e., biotinidase or holocarboxylase synthetase deficiency)
- Transcobalamin II deficiency
- Ataxia with vitamin E deficiency (AVED)
Poverty, malnutrition, chronic excessive alcohol intake, chronic disease states, advanced age, dietary restrictions, bariatric surgery, certain medications, and exclusively breastfed infants
- 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; increased mortality risk seen in some studies
- Avoid restrictive diets.
- 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.
- USPSTF concludes current evidence is insufficient to assess benefits and harms of daily supplementation with doses >400 IU of vitamin D and >1000 mg of calcium for primary prevention of fractures in:
- Community-dwelling, postmenopausal women
- Men and premenopausal women
- Note: The above recommendations are not applicable if there is a history of osteoporotic fractures, increased risk for falls or diagnosis of osteoporosis, or vitamin D deficiency.
- USPSTF recommends against using β-carotene or vitamin E supplements for the prevention of cardiovascular disease or cancer.
- Adults without regular, effective sun exposure year round should consume 600 to 800 IU/day of vitamin D3. Elderly confined indoors and other high-risk groups may require higher doses (800 to 1,000 IU/day).
- All infants should receive 400 IU/day of vitamin D soon after birth if exclusively or partially breastfed.
Commonly Associated Conditions
Anemia, neuropathies, dermatitis, visual disturbances
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