Appendix: Dietary Reference Intakes

The table on the pages that follow lists vitamins, their food sources, and adverse effects of over-consumption. The table gives recommended intake (RDA) and—a feature not available in previous RDA lists—shows tolerable upper levels that readers can use as a guideline to prevent excess consumption.

The reference values are referred to collectively as the Dietary Reference Intakes (DRIs) and include Recommended Dietary Allowance (RDA), Adequate Intake (AI), and the Tolerable Upper Intake Level (UL). A requirement, which can vary depending on age, gender, and life stage, is defined as the lowest continuing intake level of a nutrient that will maintain a defined level of nutriture in an individual. (The nutrient levels published in the DRI reports apply to the healthy general population. They are not expected to be sufficient for individuals who are already malnourished, nor would they be adequate for disease states known to have increased nutrient requirements.)

The table was developed by the Institute of Medicine's Standing Committee on the Scientific Evaluation of Dietary Reference Intakes, in cooperation with Health Canada. In 1995 the Food and Nutrition Board of the Institute of Medicine—part of the National Academy of Sciences—appointed the committee to replace the tenth (1989) edition of the Recommended Dietary Allowances (RDAs) document.

Dietary reference intakes: Vitamins
Nutrient Function Life stage group RDA/AI* UL a Selected food sources Adverse effects of excessive consumption Special considerations
Biotin Coenzyme in synthesis of fat, glycogen, and amino acids Infants (μg/d)   Liver and smaller amounts in fruits and meats No adverse effects of biotin in humans or animals were found. This does not mean that there is no potential for adverse effects resulting from high intakes. Because data on the adverse effects of biotin are limited, caution may be warranted. None
    0–6 mo 5* NDb      
    7–12 mo 6* ND      
    Children          
    1–3 y 8* ND      
    4 –8 y 12* ND      
    Males          
    9–13 y 20* ND      
    14–18 y 25* ND      
    19–30 y 30* ND      
    31–50 y 30* ND      
    50–70 y 30* ND      
    > 70 y 30* ND      
    Females          
    9–13 y 20* ND      
    14–18 y 25* ND      
    19–30 y 30* ND      
    31–50 y 30* ND      
    50–70 y 30* ND      
    > 70 y 30* ND      
    Pregnancy          
    ≤ 18 y 30* ND      
    19–30 y 30* ND      
    31–50 y 30* ND      
    Lactation          
    ≤ 18 y 35* ND      
    19–30 y 35* ND      
    31–50 y 35* ND      
Choline Precursor for acetylcholine, phospholipids, and betaine Infants (mg/d) (mg/d) Milk, liver, eggs, peanuts Fishy body odor, sweating, salivation, hypotension, hepatotoxicity Individuals with trimethylaminuria, renal disease, liver disease, depression, and Parkinson's disease may be at risk of adverse effects with choline intakes at the UL.
    0–6 mo 125* ND      
    7–12 mo 150* ND      
    Children          
    1–3 y 200* 1000      
    4 –8 y 250* 1000      
    Males          
    9–13 y 375* 2000     Although AIs have been set for choline there are few data to assess whether a dietary supply of choline is needed at all stages of the life cycle, and it may be that the choline requirement can be met by endogenous synthesis at some of these stages.
    14–18 y 550* 3000      
    19–30 y 550* 3500      
    31–50 y 550* 3500      
    50–70 y 550* 3500      
    > 70 y 550* 3500      
    Females          
    9–13 y 375* 2000      
    14–18 y 400* 3000      
    19–30 y 425* 3500      
    31–50 y 425* 3500      
    50–70 y 425* 3500      
    > 70 y 425* 3500      
    Pregnancy          
    ≤ 18 y 450* 3000      
    19–30 y 450* 3500      
    31–50 y 450* 3500      
    Lactation          
    ≤ 18 y 550* 3000      
    19–30 y 550* 3500      
    31–50 y 550* 3500      
[continued]
Dietary reference intakes: Vitamins
Nutrient Function Life stage group RDA/AI* ULa Selected food sources Adverse effects of excessive consumption Special considerations
Folate Coenzyme in the metabolism of nucleic and amino acids; prevents megaloblastic anemia Infants (μg/d) (μg/d) Enriched cereal grains, dark leafy vegetables, enriched and whole-grain breads and bread products, fortified ready-to-eat cereals Masks neurological complication in people with vitamin B12 deficiency. In view of evidence linking folate intake with neural tube defects in the fetus, it is recommended that all women capable of becoming pregnant consume 400 μg from supplements or fortified foods in addition to intake of food folate from a varied diet.
    0–6 mo 65* ND b      
Also known as: Folic acid Folacin Pteroylpoly-glutamates   7–12 mo 80* ND      
    Children       No adverse effects associated with folate from food or supplements have been reported. This does not mean that there is no potential for adverse effects resulting from high intakes. Because data on the adverse effects of folate are limited, caution may be warranted.  
    1–3 y 150 300      
    4 –8 y 200 400      
Note: Given as a dietary folate equivalents (DFE). 1 DFE = 1 μg food folate = 0.6 μg of folate from fortified food or as a supplement consumed with food = 0.5 μg of a supplement taken on an empty stomach.   Males          
    9–13 y 300 600      
    14–18 y 400 800      
    19–30 y 400 1,000      
    31–50 y 400 1,000      
    50–70 y 400 1,000      
    > 70 y 400 1,000      
      Females       The UL for folate applies to synthetic forms obtained from supplements and/or fortified foods. It is assumed that women will continue consuming 400 μg from supplements of fortified food until their pregnancy is confirmed and they enter prenatal care, which ordinarily occurs after the end of the periconceptional period—the critical time for formation of the neural tube.
    9–13 y 300 600      
    14–18 y 400 800      
    19–30 y 400 1,000      
    31–50 y 400 1,000      
    50–70 y 400 1,000      
    > 70 y 400 1,000      
    Pregnancy          
    ≤ 18 y 600 800      
    19–30 y 600 1,000      
    31–50 y 600 1,000      
    Lactation          
    < 18 y 500 800      
    19–30 y 500 1,000      
    31–50 y 500 1,000      
Niacin Coenzyme or cosubstrate in many biological reduction and oxidation reactions—thus required for energy metabolism Infants (mg/d) (mg/d) Meat, fish, poultry, enriched and whole-grain breads and bread products, fortified ready-to-eat cereals There is no evidence of adverse effects from the consumption of naturally occuring niacin in foods. Extra niacin may be required by persons treated with hemodialysis or peritoneal dialysis, or those with malabsorption syndrome.
    0–6 mo 2* ND      
Includes nicotinic acid amide, nicotinic acid (pyridine-3-carboxylic acid) and derivatives that exhibit the biological activity of nicotinamide.   7–12 mo 4* ND      
    Children          
    1–3 y 6 10      
    4 –8 y 8 15   Adverse effects from niacin-containing supplements may include flushing and and gastrointestinal distress.  
    Males          
    9–13 y 12 20      
    14–18 y 16 30      
    19–30 y 16 35      
Note: Given as niacin equivalents (NE). 1 mg of niacin = 60 mg of trytophan; 0–6 months = preformed niacin (not NE).   31–50 y 16 35      
    50–70 y 16 35   The UL for niacin applies to synthetic forms obtained from supplements, fortified foods, or a combination of the two.  
    > 70 y 16 35      
    Females          
    9–13 y 12 20      
    14–18 y 14 30      
    19–30 y 14 35      
    31–50 y 14 35      
    50–70 y 14 35      
    > 70 y 14 35      
    Pregnancy          
    ≤ 18 y 18 30      
    19–30 y 18 35      
    31–50 y 18 35      
    Lactation          
    ≤ 18 y 17 30      
    19–30 y 17 35      
    31–50 y 17 35      
[continued]
Dietary reference intakes: Vitamins
Nutrient Function Life stage group RDA/AI* ULa Selected food sources Adverse effects of excessive consumption Special considerations
Pantothenic Acid Coenzyme in fatty acid metabolism numerous redox reactions Infants (mg/d) (mg/d) Chicken, beef, potatoes, oats, cereals, tomato products, liver, kidney, yeast, egg yolk, broccoli, whole grains No adverse effects associated with pantothenic acid from food or supplements have been reported. This does not mean that there is no potential for adverse effects resulting from high intakes. Because data on the adverse effects of pantothenic acid are limited, caution may be warranted. None
    0–6 mo 1.7* ND b      
    7–12 mo 1.8* ND      
    Children          
    1–3 y 2* ND      
    4 –8 y 3* ND      
    Males          
    9–13 y 4* ND      
    14–18 y 5* ND      
    19–30 y 5* ND      
    31–50 y 5* ND      
    50–70 y 5* ND      
    > 70 y 5* ND      
    Females          
    9–13 y 4* ND      
    14–18 y 5* ND      
    19–30 y 5* ND      
    31–50 y 5* ND      
    50–70 y 5* ND      
    > 70 y 5* ND      
    Pregnancy          
    ≤ 18 y 6* ND      
    19–30 y 6* ND      
    31–50 y 6* ND      
    Lactation          
    ≤ 18 y 7* ND      
    19–30 y 7* ND      
    31–50 y 7* ND      
Riboflavin Coenzyme in Infants (mg/d) (mg/d) Organ meats, milk, bread products, and fortified cereals No adverse effects associated with riboflavin consumption from food or supplements have been reported. This does not mean that there is no potential for adverse effects resulting from high intakes. Because data on the adverse effects of riboflavin are limited, caution may be warranted. None
    0–6 mo 0.3* ND      
Also known as: Vitamin B2   7–12 mo 0.4* ND      
    Children          
    1–3 y 0.5 ND      
    4 –8 y 0.6 ND      
    Males          
    9–13 y 0.9 ND      
    14–18 y 1.3 ND      
    19–30 y 1.3 ND      
    31–50 y 1.3 ND      
    50–70 y 1.3 ND      
    > 70 y 1.3 ND      
    Females          
    9–13 y 0.9 ND      
    14–18 y 1.0 ND      
    19–30 y 1.1 ND      
    31–50 y 1.1 ND      
    50–70 y 1.1 ND      
    > 70 y 1.1 ND      
    Pregnancy          
    ≤ 18 y 1.4 ND      
    19–30 y 1.4 ND      
    31–50 y 1.4 ND      
    Lactation          
    ≤ 18 y 1.6 ND      
    19–30 y 1.6 ND      
    31–50 y 1.6 ND      
[continued]
Dietary reference intakes: Vitamins
Nutrient Function Life stage group RDA/AI* ULa Selected food sources Adverse effects of excessive consumption Special considerations
Thiamin Coenzyme in the metabolism of carbohydrates and branched-chain amino acids Infants (mg/d)   Enriched, fortified, or whole-grain products; bread and bread products, mixed foods whose main ingredient is grain, and ready-to-eat cereals No adverse effects associated with thiamin from food or supplements have been reported. This does not mean that there is no potential for adverse effects resulting from high intakes. Because data on the adverse effects of thiamin acid are limited, caution may be warranted. Person, who may have increased needs for thiamin include those being treated with hemodialysis or peritoneal dialysis, or individuals with malabsorption syndrome.
    0–6 mo 0.2* ND b      
Also known as: Vitamin B1 Aneurin   7–12 mo 0.3* ND      
    Children          
    1–3 y 0.5 ND      
    4 –8 y 0.6 ND      
    Males          
    9–13 y 0.9 ND      
    14–18 y 1.2 ND      
    19–30 y 1.2 ND      
    31–50 y 1.2 ND      
    50–70 y 1.2 ND      
    > 70 y 1.2 ND      
    Females          
    9–13 y 0.9 ND      
    14–18 y 1.0 ND      
    19–30 y 1.1 ND      
    31–50 y 1.1 ND      
    50–70 y 1.1 ND      
    > 70 y 1.1 ND      
    Pregnancy          
    < 18 y 1.4 ND      
    19–30 y 1.4 ND      
    31–50 y 1.4 ND      
    Lactation          
    < 18 y 1.4 ND      
    19–30 y 1.4 ND      
    31–50 y 1.4 ND      
Vitamin A Required for normal vision, gene expression, reproduction, embryonic development and immune function Infants (μg/d) (μg/d) Liver, dairy products, fish Teratological effects, liver toxicity Individuals with high alcohol intake, pre-existing liver disease, hyperlipidemia, or severe protein mal-nutrition may be distinctly susceptible to the adverse effects of excess preformed vitamin A intake.
    0–6 mo 400* 600      
Includes pro-vitamin A carotenoids that are dietary precursors of retinol   7–12 mo 500* 600     Note: from preformed Vitamin A only.
    Children          
    1–3 y 300 600      
    4 –8 y 400 900      
    Males          
Note: Given as retinol activity equivalents (RAEs). 1 RAE = 1 μg retinol, 12 μg β-carotene, 24 μg -carotene, or 24 μg α-crytoxanthin. To calculate RAEs from REs of provitamin A carotenoids in foods, divide the REs by 2. For preformed vitamin A in foods or supplements and for provitamin A carotenoids in supplements, 1 RE = 1RAE.   9–13 y 600 1,700      
    14–18 y 900 2,800      
    19–30 y 900 3,000     β-carotene supplements are advised only to serve as a provitamin A source for individuals at risk of vitamin A deficiency.
    31–50 y 900 3,000      
    50–70 y 900 3,000      
    > 70 y 900 3,000      
    Females          
    9–13 y 600 1,700      
    14–18 y 700 2,800      
    19–30 y 700 3,000      
    31–50 y 700 3,000      
    50–70 y 700 3,000      
    > 70 y 700 3,000      
    Pregnancy          
    ≤ 18 y 750 2,800      
    19–30 y 770 3,000      
    31–50 y 770 3,000      
    Lactation          
    ≤ 18 y 1,200 2,800      
    19–30 y 1,300 3,000      
    31–50 y 1,300 3,000      
[continued]
Dietary reference intakes: Vitamins
Nutrient Function Life stage group RDA/AI* ULa Selected food sources Adverse effects of excessive consumption Special considerations
Vitamin B6 Coenzyme in the metabolism of amino acids, glycogen and sphingoid bases Infants (mg/d) (mg/d) Fortified cereals, organ meats, fortified soy-based meat substitutes No adverse effects associated with Vitamin B6 from food have been reported. This does not mean that there is no potential for adverse effects resulting from high intakes. Because data on the adverse effects of Vitamin B6 are limited, caution may be warranted. None
    0–6 mo 0.1* NDb      
    7–12 mo 0.3* ND      
Vitamin B6 comprises a group of six related compounds: pyridoxal, pyridoxine, pyridozamine, and 5'-phosphates (PLP, PNP, PMP)   Children         Sensory neuropathy has occurred from high intakes of supplemental forms.  
    1–3 y 0.5 30      
    4 –8 y 0.6 40      
    Males          
    9–13 y 1.0 60      
    14–18 y 1.3 80      
    19–30 y 1.3 100      
    31–50 y 1.3 100      
    50–70 y 1.7 100      
    > 70 y 1.7 100      
    Females          
    9–13 y 1.0 60      
    14–18 y 1.2 80      
    19–30 y 1.3 100      
    31–50 y 1.3 100      
    50–70 y 1.5 100      
    > 70 y 1.5 100      
    Pregnancy          
    ≤ 18 y 1.9 80      
    19–30 y 1.9 100      
    31–50 y 1.9 100      
    Lactation          
    ≤ 18 y 2.0 80      
    19–30 y 2.0 100      
    31–50 y 2.0 100      
Vitamin B12 Coenzyme in nucleic acid metabolism; prevents megaloblastic anemia Infants (μg/d) (μg/d) Fortified cereals, meat, fish, poultry No adverse effects have been associated with the consumption of the amounts of Vitamin B12 normally found in foods or supplements. This does not mean that there is no potential for adverse effects resulting from high intakes. Because data on the adverse effects of vitamin B12 are limited, caution may be warranted. Because 10 to 30 percent of older people may malabsorb foodbound vitamin B12, it is advisable for those older than 50 years to meet their RDA mainly by consuming foods fortified with vitamin B12 or a supplement containing vitaming B12.
    0–6 mo 0.4* ND      
Also known as: Cobalamin metabolism; prevents megaloblastic anemia 7–12 mo 0.5* ND      
    Children          
    1–3 y 0.9 ND      
    4 –8 y 1.2 ND      
    Males          
    9–13 y 1.8 ND      
    14–18 y 2.4 ND      
    19–30 y 2.4 ND      
    31–50 y 2.4 ND      
    50–70 y 2.4 ND      
    > 70 y 2.4 ND      
    Females          
    9–13 y 1.8 ND      
    14–18 y 2.4 ND      
    19–30 y 2.4 ND      
    31–50 y 2.4 ND      
    50–70 y 2.4 ND      
    > 70 y 2.4 ND      
    Pregnancy          
    ≤ 18 y 2.6 ND      
    19–30 y 2.6 ND      
    31–50 y 2.6 ND      
    Lactation          
    ≤ 18 y 2.8 ND      
    19–30 y 2.8 ND      
    31–50 y 2.8 ND      
[continued]
Dietary reference intakes: Vitamins
Nutrient Function Life stage group RDA/AI* ULa Selected food sources Adverse effects of excessive consumption Special considerations
Vitamin C Cofactor for reactions requiring reduced copper or iron metalloenzyme and as a protective antioxidant Infants (mg/d) (mg/d) Citrus fruits, tomatoes, tomato juice, potatoes, brussel sprouts, cauliflower, broccoli, strawberries, cabbage, and spinach Gastrointestinal distrubances, kidney stones, excess iron absorption Individuals who smoke require an additional 35 mg/d of vitamin C over that needed by non-smokers.
    0–6 mo 40* NDb      
Also known as: Ascorbic acid   7–12 mo 50* ND      
Dehydroascorbic acid (DHA)   Children         Nonsmokers regularly exposed to tobacco smoke are encouraged to ensure they meet the RDA for vitamin C.
    1–3 y 15 400      
    4 –8 y 25 650      
    Males          
    9–13 y 45 1,200      
    14–18 y 75 1,800      
    19–30 y 90 2,000      
    31–50 y 90 2,000      
    50–70 y 90 2,000      
    > 70 y 90 2,000      
    Females          
    9–13 y 45 1,200      
    14–18 y 65 1,800      
    19–30 y 75 2,000      
    31–50 y 75 2,000      
    50–70 y 75 2,000      
    > 70 y 75 2,000      
    Pregnancy          
    ≤ 18 y 80 1,800      
    19–30 y 85 2,000      
    31–50 y 85 2,000      
    Lactation          
    ≤ 18 y 115 1,800      
    19–30 y 120 2,000      
    31–50 y 120 2,000      
Vitamin D Maintain serum calcium and phosphorus concentrations Infants (μg/d) (μg/d) Fish liver oils, flesh of fatty fish, liver and fat from seals and polar bears, eggs from hens that have been fed vitamin D, fortified milk products, and fortified cereals. Elevated plasma 25 (OH) D concentration causing hypercalcemia Patients on glucocorticoid therapy may require additional vitamin D.
    0–6 mo 5* 25      
Also known as: Calciferol   7–12 mo 5* 25      
    Children          
Note: 1 μg calciferol = 40 IU vitamin D   1–3 y 5* 50      
    4 –8 y 5* 50      
The DRI values are based on the absence of adequate exposure to sunlight.   Males          
    9–13 y 5* 50      
    14–18 y 5* 50      
    19–30 y 5* 50      
    31–50 y 5* 50      
    50–70 y 10* 50      
    > 70 y 15* 50      
    Females          
    9–13 y 5* 50      
    14–18 y 5* 50      
    19–30 y 5* 50      
    31–50 y 5* 50      
    50–70 y 10* 50      
    > 70 y 15* 50      
    Pregnancy          
    ≤ 18 y 5* 50      
    19–30 y 5* 50      
    31–50 y 5* 50      
    Lactation          
    ≤ 18 y 5* 50      
    19–30 y 5* 50      
    31–50 y 5* 50      
[continued]
Dietary reference intakes: Vitamins
Nutrient Function Life stage group RDA/AI* ULa Selected food sources Adverse effects of excessive consumption Special considerations
Vitamin E A metabolic function has not yet been identified. Vitamin E's major function appears to be as a non-specific chain-breaking antioxidant. Infants (mg/d) (mg/d) Vegetable oils, unprocessed cereal grains, nuts, fruits, vegetables, meats There is no evidence of adverse effects from the consumption of vitamin E naturally occurring in foods. Patients on anticoagulant therapy should be monitored when taking vitamin E supplements.
    0–6 mo 4* NDb      
Also known as: α-tocopherol   7–12 mo 5* ND      
    Children          
Note: As α-tocopherol. α-Tocopherol includes RRR-α-tocopherol, the only form of α-tocopherol that occurs naturally in foods, and the 2R-stereoisomeric forms of α-tocopherol RRR-, RSR-, RRS-, and RSS-α-tocopherol) that occur in fortified foods and supplements. It does not include the 2S-stereoisomeric forms of α-tocopherol SRR-, SSR-, SRS-, and SSS-α-tocopherol), also found in fortified foods and supplements.   1–3 y 6 200   Adverse effects from vitamin E containing supplements may include hemorrhagic toxicity.  
    4 –8 y 7 300      
    Males          
    9–13 y 11 600      
    14–18 y 15 800      
    19–30 y 15 1,000      
    31–50 y 15 1,000   The UL for vitamin E applies to any form of α-tocopherol obtained from supplements, fortified foods, or a combination of the two.  
    50–70 y 15 1,000      
    > 70 y 15 1,000      
    Females          
    9–13 y 11 600      
    14–18 y 15 800      
    19–30 y 15 1,000      
    31–50 y 15 1,000      
    50–70 y 15 1,000      
    > 70 y 15 1,000      
    Pregnancy          
    ≤ 18 y 15 800      
    19–30 y 15 1,000      
    31–50 y 15 1,000      
    Lactation          
    ≤ 18 y 19 800      
    19–30 y 19 1,000      
    31–50 y 19 1,000      
Vitamin K Coenzyme during the sythesis of many proteins involved in blood clotting and bone metabolism Infants (μg/d) (μ/d) Green vegetables (collards, spinich, salad greens, broccoli), brussel sprouts, cabbage, plant oils and margarine No adverse effects associated with vitamin K consumption from food or supplements have been reported in humans or animals. This does not mean that there is no potential for adverse effects resulting from high intakes. Because data on the adverse effects of vitamin K are limited, caution may be warranted. Patients on anticoagulant therapy should monitor their vitamin K intake.
    0–6 mo 2.0* ND      
    7–12 mo 2.5* ND      
    Children          
    1–3 y 30* ND      
    4 –8 y 55* ND      
    Males          
    9–13 y 60* ND      
    14–18 y 75* ND      
    19–30 y 120* ND      
    31–50 y 120* ND      
    50–70 y 120* ND      
    > 70 y 120* ND      
    Females          
    9–13 y 60* ND      
    14–18 y 75* ND      
    19–30 y 90* ND      
    31–50 y 90* ND      
    50–70 y 90* ND      
    > 70 y 90* ND      
    Pregnancy          
    ≤ 18 y 75* ND      
    19–30 y 90* ND      
    31–50 y 90* ND      
    Lactation          
    ≤ 18 y 75* ND      
    19–30 y 90* ND      
    31–50 y 90* ND      
[continued]
Dietary reference intakes: Vitamins
Note: The table is adapted from the DRI reports, see www.nap.edu. It represents Recommended Dietary Allowances (RDAs) in bold type, Adequate Intakes (AIs) in ordinary type followed by an asterisk (*), and Tolerable Upper Intake Levels (ULs) a. RDAs and AIs may both be used as goals for individual intake. RDAs are set to meet the needs of almost all (97 to 98 percent) individuals in a group. For healthy breastfed infants, the AI is the mean intake. The AI for other life stage and gender groups is believed to cover the needs of all individuals in the group, but lack of data prevent being able to specify with confidence the percentage of individuals covered by this intake.
aUL = The maximum level of daily nutrient intake that is likely to pose no risk of adverse effects. Unless otherwise specified, the UL represents total intake from food, water, and supplements. Due to lack of suitable data, ULs could not be established for vitamin K, thiamin, riboflavin, vitamin B12, pantothenic acid, biotin, or carotenoids. In the absence of ULs, extra caution may be warranted in consuming levels above recommended intakes.
bND = Not determinable due to lack of data of adverse effects in this age group and concern with regard to lack of ability to handle excess amounts. Source of intake should be from food only to prevent high levels of intake.
SOURCE:: Dietary Reference Intakes for Calcium, Phosphorous, Magnesium, Vitamin D, and Fluoride (1997); Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline (1998); Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids (2000); and Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc (2001). These reports may be accessed via www.nap.edu.
Reprinted courtesy of the National Academy of Sciences.