How much of various vitamins do I need?

by Harvard Health Publications
June 17, 2008 05:28 PM EDT (Updated: June 19, 2008 03:50 PM EDT) views: 77 | rating: 10/10 (4 votes) | comments: 4

The below table can give you a better understanding of how particular vitamins and minerals work in your body, how much of each nutrient you need every day, and what types of food to eat to ensure that you are getting an adequate supply. When reading the table, please note the following:

The recommendations vary by age and sex ("M" stands for men, "W" for women). This table applies to adults ages 19 and over. If you are younger, or if you are pregnant or nursing, these recommendations don't necessarily apply to you. Ask your doctor about what's appropriate for you.
Recommended Dietary Allowance (RDA) refers to the average amount of a nutrient needed by almost all healthy people in a particular life stage and gender group. Another value, called Adequate Intake (AI), is used only when experts feel there is not enough information to decide on an RDA.
Pay close attention to the column that lists the "tolerable upper intake level (UL) per day." This is the maximum amount of a nutrient considered safe if consumed regularly. Beyond that limit, there is a rising risk for side effects, some of which can be quite serious. An upper limit hasn't been established for some nutrients; however, it's important to realize that large amounts of these nutrients could still be harmful. Generally speaking, food sources of nutrients are not a problem. People run into trouble mostly through taking high doses of supplements.
The following recommendations are based largely on guidelines from the Institute of Medicine. Recommended amounts may be expressed in milligrams (mg), micrograms (mcg), or international units (IU), depending on the nutrient.


Vitamin (Common names) and Benefits
RDA or AI*
UL (Tolerable upper intake level per day)
Good food sources
Did you know?

Vitamin A (retinol, retinal, and retinoic acid — three active forms of vitamin A in the body — are retinoids, called "preformed" vitamin A; the body can also easily convert beta carotene to vitamin A as needed)

Essential for vision
Keeps tissues and skin healthy
Plays an important role in bone growth
M: 900 mcg (3,000 IU)

W: 700 mcg (2,333 IU)

Some supplements report vitamin A in international units (IU).
3,000 mcg (about 10,000 IU)
Sources of retinoids: beef, liver, eggs, shrimp, fish, fortified milk, Cheddar cheese, Swiss cheese

Sources of beta carotene: sweet potatoes, carrots, pumpkins, squash, spinach, mangoes, turnip greens
Many people get too much preformed vitamin A (retinoids) from food and supplements.
Large amounts of supplemental [preformed] vitamin A (but not beta carotene) can be harmful to bones.
Smokers should avoid beta carotene supplements to avoid increasing their risk of lung cancer.
The carotenoid lycopene may lower the risk of prostate cancer, and possibly the risk of some other types of cancer, although as yet there is no definitive proof.
Foods rich in the carotenoids lutein and zeaxanthin may protect against cataracts.

Thiamin (vitamin B1)

Helps convert food into energy
Needed for healthy skin, hair, muscles, and brain
M: 1.2 mg

W: 1.1 mg
Not known
Pork chops, ham, soy milk, watermelons, acorn squash
Most nutritious foods have some thiamin.

*RDA = Recommended Dietary Allowance, AI = Adequate Intake

Riboflavin (vitamin B2)

Helps convert food into energy
Needed for healthy skin, hair, blood, and brain
M: 1.3 mg

W: 1.1 mg
Not known
Milk, yogurt, cheese, whole and enriched grains and cereals, liver
Most Americans get enough of this nutrient.

Niacin (vitamin B3, nicotinic acid)

Helps convert food into energy
Essential for healthy skin, blood cells, brain, and nervous system
M: 16 mg

W: 14 mg
35 mg
Meat, poultry, fish, fortified and whole grains, mushrooms, potatoes, peanut butter
Niacin occurs naturally in food and can also be made by your body from the amino acid tryptophan, with the help of B6.

Pantothenic acid (vitamin B5)

Helps convert food into energy
Helps make lipids (fats), neuro-transmitters, steroid hormones, and hemoglobin
5 mg
Not known
Wide variety of nutritious foods, including chicken, whole grains, broccoli, mushrooms, avocados, tomato products
Deficiency causes burning feet and other neurologic symptoms.

Vitamin B6 (pyridoxal, pyridoxine, pyridoxamine)

Aids in lowering homocysteine levels; not clear whether it reduces heart disease risk
Helps convert tryptophan to niacin and serotonin, a neurotransmitter that plays key roles in sleep, appetite, and moods
Helps make red blood cells
Influences cognitive abilities and immune function
19–50:

M: 1.3 mg

W: 1.3 mg

51+:

M: 1.7 mg

W: 1.5 mg
100 mg
Meat, fish, poultry, legumes, tofu and other soy products, potatoes, noncitrus fruits such as bananas and watermelons
Many people don't get enough of this nutrient.

Biotin (vitamin B7)

Helps convert food into energy and synthesize glucose
Helps make and break down some fatty acids
Needed for healthy bones and hair
30 mcg
Not known
Many foods, including whole grains, organ meats, egg yolks, soybeans, and fish
Your body needs very little biotin. Some is made by bacteria in the gastrointestinal tract. However, it's not clear how much of this the body absorbs.

Folic acid (vitamin B9, folate, folacin)

Vital for new cell creation
Helps prevent brain and spinal birth defects when taken early in pregnancy; should be taken regularly by all women of childbearing age, since women may not know they are pregnant in the first weeks of pregnancy
Can lower levels of homocysteine; not clear whether it reduces heart disease risk
May reduce risk for colon cancer
Offsets breast cancer risk among women who consume alcohol
400 mcg
1,000 mcg
Fortified grains and cereals, asparagus, okra, spinach, turnip greens, broccoli, legumes such as black-eyed peas and chickpeas, orange juice, tomato juice
Some people don't get enough of this nutrient.
It's easier to absorb folic acid from supplements and fortified grain products than from dietary sources where it occurs naturally.
Some research suggests that women of childbearing age should get 800 mcg per day. You can get this amount through a healthy diet and a daily multivitamin.
Rarely, folic acid masks a B12 deficiency, which can lead to severe neurological complications. That's not a reason to avoid folic acid; just be sure to get enough B12.

Vitamin B12 (cyanocobalamin)

Aids in lowering homocysteine levels; not clear whether it lowers heart disease risk
Assists in making new cells and breaking down some fatty acids and amino acids
Protects nerve cells and encourages their normal growth
Helps make red blood cells
2.4 mcg
Not known
Meat, poultry, fish, milk, cheese, eggs, fortified cereals, fortified soy milk
Many people, particularly older adults, are deficient in vitamin B12 because they have trouble absorbing this vitamin from food.
Vitamin B12 occurs naturally only in animal food sources, so strict vegetarians and vegans should take a multivitamin to get enough.
A lack of vitamin B12 can cause memory loss, dementia, and numbness in the arms and legs.

Vitamin C (ascorbic acid)

Foods rich in vitamin C may lower the risk for some cancers, including those of the mouth, esophagus, stomach, and breast
Long-term use of supplemental vitamin C may protect against cataracts
Helps make collagen, a connective tissue that knits together wounds and supports blood vessel walls
Helps make the neuro-transmitters serotonin and norepinephrine
Acts as an antioxidant, neutralizing unstable molecules that can damage cells
Bolsters the immune system
M: 90 mg

W: 75 mg

Smokers:

Add 35 mg
2,000 mg
Fruits and fruit juices (especially citrus), potatoes, broccoli, bell peppers, spinach, strawberries, tomatoes, Brussels sprouts
Evidence that vitamin C helps reduce colds has not been convincing.

Choline

Helps make and release the neurotransmitter acetylcholine, which aids in many nerve and brain activities
Plays a role in metabolizing and transporting fats
M: 550 mg

W: 425 mg
3,500 mg
Many foods, especially milk, eggs, liver, and peanuts
Normally the body makes small amounts of choline. But experts don't know whether this amount is enough at certain ages.

Vitamin D (calciferol)

Helps maintain normal blood levels of calcium and phosphorus, which strengthen bones
Helps form teeth and bones
Supplements can reduce the number of nonverterbral fractures
19–50: 5 mcg (200 IU)

51–70: 10 mcg (400 IU)

71+: 15 mcg (600 IU)
50 mcg (2,000 IU)
Fortified milk or margarine, fortified cereals, fatty fish
Most Americans, especially African Americans, don't get enough of this nutrient.
While the body uses sunlight to make vitamin D, it cannot make enough if you live in northern climes or don't spend much time in the sun.

Vitamin E (alpha-tocopherol)

Acts as an antioxidant, neutralizing unstable molecules that can damage cells
Protects vitamin A and certain lipids from damage
Supplements may protect against prostate cancer
15 mg

(15 mg equals about 22 IU from natural sources of vitamin E and 33 IU from synthetic vitamin E)
1,000 mg

(nearly 1,500 IU natural vitamin E; 2,200 IU synthetic vitamin E)
Wide variety of foods, including vegetable oils, salad dressings and margarines made with vegetable oils, wheat germ, leafy green vegetables, whole grains, nuts
Vitamin E does not prevent wrinkles; the extent of its benefits, if any, is unclear.
If you want to boost your intake, look for a multivitamin with 200 IU vitamin E, which is more than the RDA but less than the UL.

Vitamin K (phylloquinone, menadione)

Activates proteins and calcium essential to blood clotting
May help prevent hip fractures
M: 120 mcg

W: 90 mcg
Not known
Cabbage, liver, eggs, milk, spinach, broccoli, sprouts, kale, collards, and other green vegetables
Intestinal bacteria make a form of vitamin K that accounts for half your requirements.
If you take an anticoagulant, keep your vitamin K intake consistent.

*RDA = Recommended Dietary Allowance, AI = Adequate Intake