Essential to good health, vitamin A is readily available in a variety of plant- and animal-based foods. For healthy individuals who eat a balanced diet, vitamin A deficiency is very unlikely. However, if you have a condition that interferes with the absorption of nutrients, your risk for vitamin A deficiency increases. Conditions such as celiac disease, Chron's disease and pancreatic disorders, for example, increase susceptibility for vitamin A deficiency. Consult with your doctor or a registered dietitian about your nutritional needs to design an eating and supplementation plan if you are at risk for inadequate vitamin A intake or absorption.
Recommendations
Vitamin A supplements are generally measured in international units, which indicate potency rather than weight. To meet the recommended intake of vitamin A, men need 900 mcg, the equivalent of 3,000 international units -- or IU -- daily. Women need 700 mcg, or 2,310 IU, daily, with the exception of pregnant and lactating women, who require 770 mcg and 1,300 mcg daily, respectively, according to the National Institutes of Health. Although it's important to get enough vitamin A, too much can be toxic, potentially leading to birth defects and reduced bone density, as well as liver problems and disorders of the central nervous system. Adult intake should not exceed 3,000 mcg, or 10,000 IU, daily, unless taken on the recommendation of your doctor as a result of specific health problems.
Function
Adequate intakes of vitamin A -- also called retinol -- promote healthy vision, skin, teeth and mucous membranes, according to MedlinePlus. Carotenoids, such as beta-carotene, that your body converts to vitamin A, may help reduce your risk for cancer. However, food sources of beta-carotene are more effective than supplements. Certain antioxidants, including beta-carotene, may also limit damage from free radicals, which are thought to play a role in the onset of some chronic diseases.
Deficiency
Without enough vitamin A, night blindness, reduced immunity and disruptions to reproductive functions may occur. Because symptoms are more severe in children, young people experience greater health risks as a result of vitamin A deficiency. Insufficient intakes by children in developing countries result in 250,000 to 500,000 cases of childhood-onset blindness annually, according to the National Institutes of Health. Although the risk for vitamin A deficiency is minimal in the United States, certain factors increase your risk. Excessive alcohol consumption and strict diets that limit zinc may affect your body's ability to process and store vitamin A.
Sources
Food sources of the retinol form of vitamin A include organ meats, cheese, fortified milk, eggs, meat, cod and fish oil. Orange and yellow fruits and vegetables are generally good sources of beta-carotene. Options include sweet potatoes, carrots, winter squash, apricots and cantaloupe. Broccoli and dark-green leafy vegetables, such as spinach and turnip greens, also help ensure an adequate vitamin A intake. Certain foods, including chicken liver, carrots and kale provide more than 100 percent of the daily recommended intake of vitamin A per serving.
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