A nutritionally balanced diet may eliminate the need for vitamin supplementation.

A nutritionally balanced diet may eliminate the need for vitamin supplementation.
Credit: Public Domain; Wikimedia Commons

Understanding the Basics of Vitamins

Your body requires many nutrients and minerals in just the right amount to work properly, among them 13 vitamins are essential. Four of these vitamins -- vitamin A, vitamin D, vitamin D and vitamin K -- are fat soluble vitamins.

There are two types of vitamins:  water soluble and fat soluble. The body readily uses water soluble vitamins; fat soluble vitamins are stored in the fatty tissues and the liver.

With the exception of vitamin D, your body does not manufacture these essential nutrients for health.  Health experts recommend obtaining the vitamins your body needs through a nutritional and balanced diet.  Foods that contain the fat soluble vitamins do not lose these nutrients through cooking.

Some people choose to take vitamin supplements for various reasons. Donald Hensrud, M.D., Preventive Medicine at the Mayo Clinic[1630] recommends that if you choose to take vitamin supplements, stay as close as possible to the Recommended Dietary Allowance (RDA). This will help you to avoid getting too large amounts of vitamins, especially fat soluble vitamins, and causing a vitamin toxicity.

Vitamin A

Role of Vitamin A

Like the other vitamins, vitamin A, also called retinol, performs many functions in your body.  Perhaps the best known function of retinol is its aid in helping your eyes adjust to light changes. Other roles include helping your skin, eyes, mucus membranes, throat and lungs to maintain their moisture.

Vitamin A helps your body develop and maintain healthy teeth and bones.

Vitamin A Deficiency

Vitamin A deficiency is not often seen in the United States. Symptoms of low levels of this nutrient include night blindness; dry, rough skin; decreased resistance to infections; poor tooth and bone development.

Vitamin A Toxicity

Levels of vitamin A that are too high can cause birth defects and hip fractures.  Mild toxicity can cause nausea and blurred vision. Higher levels can result in slowing of growth, loss of hair, bone pain and liver enlargement.

It is difficult to become toxic from vitamin A through food sources alone. Most instances of vitamin A toxicity are related to the use of vitamin supplements.

Food Sources of Vitamin A

Vitamin A fortified milk, liver, butter, dairy products, egg yolk

Orange vegetables and eggs are a good source of vitamin A

Orange vegetables and eggs are a good source of vitamin A
Credit: Biso; Creative Commons; Wikimedia Commons

Vitamin D

Role of Vitamin D

Vitamin D is often referred to as the "Sunshine Vitamin" because the body is able to synthesize this nutrient through the action of sunlight on the skin.  Vitamin D is needed for the absorption of calcium, promoting healthy bones and teeth.

Deficiency of Vitamin D

Again, deficiencies of this nutrient don't occur often in the United States. Low levels of vitamin in children produce a condition known as rickets -- long legs, slightly bowed -- and flattening of the back of the head. In adults, low levels cause weakness of both muscles and bones.

Toxicity of Vitamin D

Too much of this nutrient can lead to increased levels of calcium in the blood, decreased appetite, nausea and vomiting and slowed mental and physical growth.

Food Sources

Vitamin D fortified dairy products, fish oils, egg yolks


Vitamin D is one vitamin that is difficult to get enough of through diet alone, but exposure to the sun makes up the difference. Children should be exposed to 5 to 10 minutes daily of sunlight; adult sun exposure of 10 to 15 minutes three times a week should be sufficient.

Some people supplement their diets with vitamins

Many people supplement their diet with vitamins(74564)
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Vitamin E

Role of Vitamin E

This vitamin plays an important role as an antioxidant; antioxidants neutralize substances called free radicals.  It also functions to protect vitamins A and C and red blood cells from destruction, as well as performing the same function for essential fatty acids.

Recent research indicates that protection from heart disease and cancer from this vitamin is found in people who regularly eat antioxidant-rich fruits and vegetables rather than from taking supplements.[1631] This suggests that it is the "total package" of antioxidants and other nutrients in the fruits and vegetables, along with vitamin E, that provide this protection.

Deficiency of Vitamin E

Deficiency of this vitamin is almost exclusively limited to premature infants and people who are unable to absorb fats as in cystic fibrosis, malabsorption syndromes and others.

Severe deficiency of vitamin E results mainly in neurological symptoms, including an unbalanced gait, poor coordination and muscle weakness.[1635]

Toxicity of Vitamin E

High levels of vitamin E interferes with the ability of your blood to clot that can lead to hemorrhaging.  People who take blood-thinning medication and/or statin drugs to lower cholesterol should consult their health care providers before taking vitamin E supplements.

Food Sources

Vegetable oil, nuts, green and leafy vegetables, eggs, avocado, whole grain products, liver

Green leafy vegetables are good sources of vitamin K.

Green leafy vegetables are good sources of vitamin K.
Credit: Biswarup Ganguly; Creative Commons; Wikimedia Commons

Vitamin K

Role of Vitamin K

Vitamin K plays a vital role in the ability of your blood to clot and aids in promoting bone health.

Deficiency of Vitamin K

Low levels of vitamin K lead to decreased ability of your blood to clot, leading to excessive bleeding.

Toxicity of Vitamin K

No known instances of vitamin K toxicity have been reported.[1631]

Food Sources

Dark green, leafy vegetables and liver.

Bacteria in your intestines naturally produce vitamin K within your body.

Use Caution Taking Dietary Supplements

Many people wrongly assume that medications and supplements that are available over-the-counter or at health stores are safe to consume. This may not be true for everyone, depending on their particular health status and medications taken.

Supplements of fat soluble vitamins can result in toxicity in the body since these vitamins are stored in your body and not flushed out as are water soluble vitamins. Know and understand the RDA of these vitamins, adhering to them as closely as possible.

The Linus Pauling Institute[1629] offers these tips:  Look for supplements labeled USP-verified; this means that the product has met standards of potency, purity and quality. Take fat soluble vitamin supplements with a meal containing fat or oil.

Consult your health care provider before taking vitamin supplements and ask for the provider's recommendations.

This article is informational in nature and not intended to replace or refute information provided by health care professionals. Consult your health care provider with questions or concerns about your particular health situation or status.