Vitamin A

The best known function of vitamin A is in vision. Vitamin A also plays an important role in control of gene expression for differentiation of epithelial cells such as skin, lung, and intestinal tissue.

Deficiencies: Night blindness is one of the early signs of vitamin A deficiency, because of the role of vitamin A in vision. Bacterial invasion and permanent scarring of the cornea of the eye (xerophthalmia) is a symptom of more profound deficiency. Profound vitamin A deficiency also results in altered appearance and function of skin, lung, and intestinal tissues. Children are most at risk of vitamin A deficiency because they have not yet developed adequate vitamin A stores.

Food sources: Liver, eggs and fortified foods, and provitamin A carotenoids such as beta-carotene, which are found in green leafy vegetables as well as in orange and red fruits and vegetables.

2000-Calorie Diet Recommendations

Shown below are the reference numbers used to compute the Daily Value percentages that appear on the Nutrition Facts labels on foods sold in the U.S. These numbers are meant to approximate the nutrients needed for the average person consuming 2000 calories per day.

Click any of the vitamin or nutrient names below to learn more about the importance of each element, and to see detailed dietary allowances for specific population groups.

***Daily Value recommendations are based on a 2000-calorie diet. Recommendations for individuals will vary depending on gender, age, weight, and other factors.