Vitamin A (Retinol)

Retinol

Vitamin A is a fat-soluble vitamin that has several important functions in the body.

  • It helps cells reproduce normally, a process called cellular differentiation.
  • It is essential for good vision. The first sign of a vitamin A deficiency is often poor sight at night.
  • It is needed for the proper development of an embryo and fetus.

Vitamin A helps keep skin and mucous membranes that line the nose, sinuses, and mouth healthy. It also plays a role in:

  • Immune system function
  • Growth
  • Bone formation
  • Reproduction
  • Wound healing

Vitamin A comes from two sources. One group, called retinoids, comes from animal sources and includes retinol. The other group, called carotenoids, comes from plants and includes beta-carotene. The body converts beta-carotene to vitamin A. Major carotenoids, including lycopene, lutein, and zeaxantuin, have important biological properties, including antioxidant and photoprotective activities.

It is rare in the developed world to have a serious deficiency of vitamin A. Symptoms include:

  • Dry eyes
  • Night blindness
  • Diarrhea
  • Skin problems

While vitamin A is essential for good health, it can be toxic in high doses. Never take more than the recommended daily allowance without first talking to your doctor.

Acne, psoriasis, and other skin disorders

Prescription creams and pills containing retinoids, a synthetic form of vitamin A, are used to help clear up severe acne and psoriasis. They have also shown promise for treating other skin disorders, warts, and premature aging from the sun. Recent studies show that topical forms along with antioxidants may help minimize the appearance of fine lines and wrinkles. These medications require close supervision by a doctor. Isotretinoin (Accutane), an oral medication for acne, can cause very serious side effects and must not be used by pregnant women or women of child-bearing age who are not taking birth control.

Eye disorders

Getting enough vitamin A in your diet is essential for good vision. Research shows that people who eat more foods with vitamin A are less likely to develop age-related macular degeneration (AMD). In addition, a large population study found that people who got high levels of vitamin A though their diets had a lower risk of developing cataracts. But researchers don't know whether taking vitamin A supplements would work the same way. Vitamin A supplements may help slightly slow down the damage from retinitis pigmentosa, a hereditary disease that causes poor night vision. However, the study used high doses, which can be toxic.

Measles

For children who have vitamin A deficiency, supplements can reduce the severity and complications of measles. Children who are deficient in vitamin A are more likely to develop infections, including measles. In areas of the world where vitamin A deficiency is widespread or where at least 1% of those with measles die, the World Health Organization (WHO) recommends giving vitamin A supplements to children who have measles. However, vitamin A does not seem to help unless a child has vitamin A deficiency. Never give a child vitamin A supplements without a doctor's supervision.

Inflammatory bowel disease (IBD)

People with IBD, either ulcerative colitis or Crohn disease, may have a hard time absorbing all the nutrients their bodies need. Doctors often recommend that people with IBD take a multivitamin, including vitamin A.

Cancer

Whether vitamin A can reduce the risk of cancer is not clear. People who eat a healthy diet with enough beta-carotene and other carotenoids from fruits and vegetables seem to have a lower risk of certain cancers, such as:

  • Breast cancer
  • Colon Cancer
  • Esophageal cancer
  • Cervical cancer
  • Melanoma

Some laboratory studies suggest that vitamin A and carotenoids may help fight certain types of cancer in test tubes.

Few studies have shown that taking vitamin A supplements will help prevent or treat cancer. In fact, there is some evidence that it may be harmful. Taking beta-carotene or vitamin A supplements has been linked to a higher risk of lung cancer in people who smoke or drink alcohol. However, some researchers say more studies are needed to confirm this.

One preliminary study suggests that a topical form of vitamin A may reduce abnormal growth of cells on the cervix, called cervical neoplasia.

Researchers are also investigating retinoids, a synthetic form of vitamin A, for skin cancer. People with certain types of skin cancer tend to have lower levels of vitamin A and beta-carotene in the blood. However, studies that have looked at whether taking higher amounts of vitamin A or beta-carotene would prevent or treat skin cancer have had mixed results.

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