Daily Recommended Allowances of Vitamins and Minerals
For healthy adults, vitamins and minerals should be consumed at levels approximately equal to the Recommended Dietary Allowance (RDA) established by the Institute of Medicine's Food and Nutrition Board, with intake ideally obtained from natural food sources rather than supplements. 1
Key Vitamins - Daily RDA for Adults
Water-Soluble Vitamins
Vitamin C: 75 mg/day for women, 90 mg/day for men, with a tolerable upper limit of 2,000 mg/day (exceeding this causes diarrhea and gastrointestinal disturbances) 1
B Vitamins:
- Thiamine (B1): 1.1 mg/day for women, 1.3 mg/day for men 1
- Riboflavin (B2): 1.1 mg/day for women, 1.3 mg/day for men 1
- Niacin (B3): 14 mg/day niacin equivalents for women, 16 mg/day for men, with upper limit of 35 mg/day (flushing occurs above this) 1
- Vitamin B6: 1.3 mg/day, with upper limit of 100 mg/day (sensory neuropathy develops at excessive doses) 1
- Vitamin B12: 2.4 µg/day 1
- Folic acid: 400 µg/day of dietary folate equivalents, with upper limit of 1,000 µg/day from fortified foods and supplements 1
Fat-Soluble Vitamins
Vitamin A: 700 µg/day for women, 900 µg/day for men, with upper limit of 3,000 µg/day 1
Vitamin D: Adequate intake varies, but maintenance levels of 2,000-4,000 IU daily may be required to maintain serum 25-hydroxyvitamin D levels of 75 nmol/L or higher 1, 2
Vitamin E: 15 mg/day α-tocopherol, with upper limit of 1,000 mg/day (hemorrhage risk at excessive doses) 1
Vitamin K: No established RDA in these guidelines, but 300 µg/day is suggested for specific malabsorptive conditions 1
Essential Minerals - Daily RDA for Adults
Major Minerals
Calcium: 1,000 mg/day for adults ≤50 years, 1,200 mg/day for adults >50 years, with upper limit of 2,500 mg/day 1
Magnesium: 320 mg/day for women, 420 mg/day for men, with upper limit of 350 mg/day from supplements only (food and water sources excluded from this limit) 1
Iron: 8 mg/day for men and postmenopausal women, 18 mg/day for premenopausal women, with upper limit of 45 mg/day (gastrointestinal disturbances occur at excessive doses) 1
Trace Minerals
Zinc: 8 mg/day for women, 11 mg/day for men, with upper limit of 40 mg/day (interferes with copper absorption at high doses) 1
Copper: 2 mg/day is recommended, particularly important when taking zinc supplements due to their inverse absorption relationship 1, 2
Selenium: 55 µg/day, with upper limit of 400 µg/day (selenosis develops at excessive intake) 1
Chromium: Insufficient data to set RDA; adequate intake is 25 µg/day for women and 35 µg/day for men 1
Critical Clinical Considerations
When Supplementation Is Advisable
Specific populations require supplementation beyond dietary intake: elderly individuals, pregnant or lactating women, strict vegetarians, and individuals on calorie-restricted diets should take a multivitamin preparation 1
Important Safety Warnings
High-dose supplementation should be avoided: Megadoses of vitamins and minerals have not been demonstrated to protect against cardiovascular disease, diabetes, or cancer, and may actually cause health problems including diarrhea, bleeding, and toxic reactions 1
Upper intake levels exist for good reason: Exceeding tolerable upper limits can cause specific adverse effects - vitamin A and D toxicity, niacin flushing, vitamin B6 neuropathy, vitamin C gastrointestinal disturbances, vitamin E hemorrhage, and selenium toxicity 1
Zinc-copper balance must be maintained: A ratio of 8-15 mg zinc to 1 mg copper should be maintained, as high zinc intake interferes with copper absorption 1, 2
Preferred Sources
Natural food sources are superior to supplements for meeting daily requirements, as the evidence does not support routine pharmacological-dose supplementation in healthy individuals without documented deficiencies 1