What role does vitamin A play in my diet?

Vitamin A is a fat-soluble vitamin, also known as retinol because it produces pigments in the eye's retina. The eye needs a specific metabolite -- retinal -- a light-absorbing substance that is crucial for scotopic vision (low-light vision). Vitamin A is also important for healthy teeth, skeletal tissue, soft tissue, the skin, and mucous membranes.

Vitamin A comes from two main types of foods:
  • Retinol -- a yellow, fat-soluble substance. It is the form of vitamin A absorbed when eating animal food sources. Sources include cod liver oil, butter, margarine, liver, eggs, cheese and milk.
  • Carotenes -- such as alpha-carotene, beta-carotene, gamma-carotene, and xanthophyll beta- cryptoxanthin. Carotene is an orange photosynthetic pigment crucial for plant photosynthesis. The orange colors of carrots, sweet potatoes and cantaloupe melons come from its carotene content. Lower carotene concentrations are what give the yellowish coloration to butter and milk-fat. Some omnivores have yellow-colored body fat, such as chickens and humans.
Provided by Medical News Today
Deborah Beauvais
Nutrition & Dietetics
Vitamin A, also known as retinol, is a fat-soluble vitamin that occurs only in animal foods. Carotenoids, however, serve as a great source of alpha-, beta-, and gamma-carotene that our bodies convert into vitamin A and can be found in many vegetables and fruits.

It is indispensable for our health and is especially abundant in foods such as apricots, broccoli, cantaloupe, carrots, kale, liver, mangos, red peppers, spinach and sweet potatoes. Here are six reasons why you should make sure that your diet includes vitamin A.

Not only does Vitamin A strengthen "entry points" into the human body, such as mucous membranes, the lining of the eyes, respiratory, urinary and intestinal tracts, it is also essential for the lymphocytes, or white blood cells, that fight infection once in the body.

Vitamin A, when converted into the retinal (retinaldehyde) form, is vital for healthy eyes. It allows the eye to effectively distinguish between light and dark, thus improving night vision. Furthermore, vitamin A is believed to fight against cataracts, macular degeneration, glaucoma and other age-related ocular diseases.

Bones and Teeth
When converted into retinoic acid, vitamin A effectively maintains healthy bones and teeth. Dentin, which also requires vitamin A, forms the hard layer of material within our teeth, thereby ensuring their strength. Vitamin A also plays an important role in replacing worn out or old tissue with newer tissue to ensure healthy bones and teeth.

Urinary Stones
Urinary calculi, or solid particles in the urinary system, may cause pain, nausea and vomiting when stones are formed. Vitamin A produces a mineral compound within the body called calcium phosphate that prevents the formation of these solid particles.

As a powerful antioxidant, vitamin A fights against oxidative stress, or "cellular rust," within our bodies, thus protecting us from health problems such as cataracts, atherosclerosis, chronic obstructive pulmonary disease, and cancer.

The antioxidant properties of vitamin A combat free radicals that can damage the skin through oxidative stress. By maintaining proper moisture retention, the skin is not only protected from common dryness, but also keratinization (the process in which the epidermis hardens into a heavy material that makes up hair and nails), psoriasis (a skin disease marked by red, itchy or scaly patches), acne, and even wrinkling.

Vitamin A (or retinol) supports healthy vision, gene expression, reproduction, embryonic development, growth and immune function. Vitamin A comes in two forms: preformed vitamin A and provitamin A carotenoid. Preformed vitamin A is found only in animal products and is immediately available to the body upon ingestion. Provitamin A carotenoids are found in fruits and vegetables, and come from a type of antioxidant that can be converted into vitamin A by the body. About half of all Americans fail to get enough vitamin A.

In addition to helping maintain good vision, Vitamin A helps our body to process calcium. Vitamin A comes in two forms: preformed vitamin A, found in animal foods such as milk and eggs, can be used by our bodies immediately while betacarotenes in dark yellow and green vegetables and fruits are converted into vitamin A after we eat them. Because excessive intake of preformed vitamin A may increase the risk of hip fracture, it is best to avoid vitamin supplements that contain the full RDA (5,000 IU) of vitamin A as preformed vitamin A.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.