I take a multivitamin every day in addition to supplements. Lately, I've been wondering if I'm not overdoing it, so I started researching the benefits of vitamins as well as the proper dosage. Here's what I've found out about vitamins A-K.

Vitamin A

Recommended daily dosage: 5,000 IU to high safe limit of 10,000 IU

Food sources: orange and green vegetables/fruits; tuna fish

Vitamin A aids in providing an effective immune system. Deficiencies can cause infections and an increased risk of blindness due to macular degeneration. Most will get enough of this vitamin through diet; however cancer and infectious diseases can increase the body's demand for Vitamin A.

Too much Vitamin A can be dangerous and even fatal. 25,000 IU can cause spontaneous abortions in early pregnancy. >10,000 IU during pregnancy has been linked to birth defects.


Vitamin B12

Recommended daily dosage: 6 mcg to high safe limit of 3,000 mcg

Food sources: seafood, ham

B12 is essential in producing myelin, the sheath that insulates nerve fibers and keeps electrical impulses moving through the body. It is also important to the production of blood cells. Deficiencies can cause memory loss, tingling in the arms and legs, tinnitus, hearing loss, low energy. Deficiencies have been linked to dementia and Alzheimer's.

Most people receive enough of this vitamin through diet. However, vegetarians may want to investigate the need for a supplement. High doses of this vitamin are considered safe.


Vitamin B6

Recommended dosage: 2 mg to high safe limit of 100 mg

Food sources: bananas, chicken, beef, eggs, peanuts, walnuts, brown rice

Vitamin B6 aids in fat and protein metabolism and in creating neurotransmitters, the chemicals that allow brain cells to communicate between one another. Deficiencies can cause nerve damage to the hands and feet and impair memory. Those with carpal tunnel syndrome, premenstrual syndrome, and aches of arthritis find it helpful. Speaking from experience, I took this upon the advice of my doctor to help with hot flashes. Gone!

B6 can be dangerous if taken in excess and has been linked to serious nerve disorders and oversensitivity to the sun.


Vitamin C

Daily dosage: 78 mgs. (women) 90 mgs. (men) up to high safe limit of 2000 mg.

Food sources: green vegetables, fruits

Vitamin C helps in arresting free radicals which cause disease and protecting against heart disease. Also helps protect against certain cancers. It may also neutralize the cancer-causing preservatives used in foods (nitrites) and those found in drinking water and some vegetables (nitrates). It may also help asthmatics or those suffering from allergies, as it reduces the body's level of histamine. Diabetics will find this vitamin beneficial in minimizing damaging effects on the nerves, kidneys, and eyes. It has been linked to inhibiting the replication of HIV in virus-infected cells.

High doses are safe; however doses exceeding 2000 mg. can cause diarrhea.


Vitamin D

Daily dosage: 400 IU up to high safe limit of 2000 IU

Food sources: fortified cereal and milk, eggs, fish

Vitamin D aids in bone growth and building bones. Ten minutes in the sun during the summer will provide enough of the vitamin, which is stored in the fat cells. Usually, you will receive enough of the vitamin during the summer that it will last you through the winter.

Since the vitamin is stored in fat cells, therein lies the danger. Irreversible damage to the kidneys and cardiovascular system can occur after long-term high dosage.


Vitamin E

Daily dosage: 22 IU natural, 33 IU synthetic to high safe limit of 1500 IU natural and 1100 IU synthetic

Food sources: spinach, safflower and soybean oils, whole grains

Vitamin E prevents cancer, boosts the immune system, alleviates respiratory problems, and fights heart disease. It also is helpful in easing the symptoms of Alzheimer's. Diabetics will find it helpful in preventing damage to the body's organs, particularly the eyes.

This vitamin is safe at high doses; however it can prevent normal blood clotting, so those on anticoagulants should not take it.


Vitamin K

Daily dosage: 80 mcg to high safe limit of 30,000 mcg

Food sources: green vegetables, liver, wheat bran

Vitamin K helps the blood to clot subsequent to injury. The body requires only tiny amounts of this vitamin, so you probably will get enough via diet. The only people who need supplemental vitamin K are babies, who are given a shot at birth because they lack the bacteria necessary to produce it, and those who suffer from cystic fibrosis.

As a note, vitamin E works against vitamin K, so people with blood-clotting disorders should not take vitamin E.