Sources of Provitamin A

Provitamin A or beta-carotene can be confused with vitamin A, which is known as retinol. Provitamin A and other carotenoids are formed into vitamin A by our body and then used for various functions like our vision, skin health, and healthy bone development. Provitamin A and vitamin A can be found naturally in many different foods.

Function

Provitamin A is a carotene or carotenoid, which is a substance synthesized by plants but cannot be made by animals. This is why our body converts provitamin A into vitamin A that can be used. Vitamin A, or retinol, is a fat-soluble vitamin. Around 90 percent of retinol is stored in the liver and the rest is stored in the intestines and kidneys.

Food Sources

Beta-carotenes are mainly found in yellow-orange and dark green vegetables. They are also found in some fruits, like oranges, limes, pineapples, cantaloupes and prunes. Also, fortified margarine contains beta-carotene. Retinol can be found in certain animal products like liver, butter, cheese, egg yolks, fish liver oils and fortified milk. Retinol is found mainly in animal foods and carotenoids are found in most plant foods.

Importance

Vitamin A and provitamin A are required for many of our body's functions. Vitamin A assists in maintaining our skin's pigment and mucous membranes. It also helps with normal development of bones and teeth. It is needed for normal reproductive capabilities. It has recently been discovered to have antioxidant effects that may help prevent cancer, according to the BC Cancer Agency.

Deficiency

Having a vitamin A deficiency can present many symptoms and conditions. Night blindness is a common first sign of people with a vitamin A deficit. Dry skin and hair, skin sores, dry conjuctiva, and clouding of the cornea are also symptoms. An increased occurrence of respiratory, digestive and urogenital infections can also be a sign of a vitamin A deficiency.

Excess Intake

Vitamin A and provitamin A can be toxic at a level greater than 10 mg a day for a long period, over months at a time. Symptoms of excess levels are nausea, vomiting, headaches, hair loss, bone and joint pain, fragile bones, or an enlarged liver and spleen. Other signs include some mild skin conditions, like peeling of the skin.

Did You Know?

Vitamin A gets stored in your body in large amounts. Your liver can hold the required amount of vitamin A your body needs for an entire year! Also, eating a serving of animal liver can equal up to 1,000 times the recommended daily amount of vitamin A.

References

• "Nutrition for Health, Fitness, and Sport;" Melvin H. Williams; 2007
• "Human Anatomy and Physiology;" Elaine N. Marieb, Katja Hoehn; 2007
• BC Cancer Agency: Vitamin A / Retinol