Certain vegetables and fruits have abundant provitamin A and others have very little, as seen in Graph 3-1. Spinach has about six times as much as broccoli. Broccoli has about ten times as much as celery and cabbage. Colored fruits and vegetables, especially the yellow and orange ones, are generally high in provitamin A. Meats are generally low in vitamin A, except for liver which is excessively high. Dairy products contain a medium amount of vitamin A.
The RDA is based on the amount needed to ensure adequate stores of vitamin Ain the body to support pregnancy, gene expression, immune function, and vision. Different dietary and supplemental sources of vitamin Ahave different potencies. For many years vitamin A activity was measured in International Units (IU) The current international standard of measure for vitamin A activity, however, is retinol activity equivalency (RAE). The RAE uses a microgram (mcg) of retinol as a standard to measure the potency of the forms of vitamin A. Three mcg of RAE is equivalent to ten International Units. The RDA for an adult man is 3000 IU, which is equivalent to 900 mcg of RAE. For adult women, the RDA is 2333 IU, which is equivalent to 700 mcg of RAE. Please refer to Table 3-1 for more complete RDA information.
The best dietary supplement of vitamin A consists of generous quantities of fresh fruits and vegetables. Supplemental forms of vitamin A such as retinyl palmitate and retinyl acetate convert readily into retinol and their potency is listed on the packaging. With supplemental beta-carotene, two mcg of beta-carotene are needed by the body for conversion, resulting in one mcg of retinol. This is known as a RAE ratio of 2:1. For beta-carotene in food, the RAE ratio is 12:1, so 12 mcg of beta-carotene in food is needed to provide one mcg of RAE. With alpha-carotene and betacryptoxanthin, the ratio is 24:1, so more is needed to provide the same retinol
Graph 3-1 Vitamin A content of some common foods.
Table 3-1 RDAs for vitamin A for all ages.
equivalency. Still, the highest amounts of vitamin A activity (outside of liver) are found in fruits and vegetables.
The retinol activity equivalency is not relevant to the antioxidant activity of provitamin A carotenes. The carotenes that are not converted to retinol are still valuable for their antioxidant activity. The RDA for vitamin Awas not intended to provide enough provitamin A for antioxidant use. There is general agreement that a diet rich in fruits and vegetables provides abundant vitamin Ato satisfy all needs. As mentioned, the yellow, orange, and green fruits and vegetables are richest in provitamin A.
The RDA is based on the amount needed to ensure adequate stores of vitamin Ain the body to support pregnancy, gene expression, immune function, and vision. Different dietary and supplemental sources of vitamin Ahave different potencies. For many years vitamin A activity was measured in International Units (IU) The current international standard of measure for vitamin A activity, however, is retinol activity equivalency (RAE). The RAE uses a microgram (mcg) of retinol as a standard to measure the potency of the forms of vitamin A. Three mcg of RAE is equivalent to ten International Units. The RDA for an adult man is 3000 IU, which is equivalent to 900 mcg of RAE. For adult women, the RDA is 2333 IU, which is equivalent to 700 mcg of RAE. Please refer to Table 3-1 for more complete RDA information.
The best dietary supplement of vitamin A consists of generous quantities of fresh fruits and vegetables. Supplemental forms of vitamin A such as retinyl palmitate and retinyl acetate convert readily into retinol and their potency is listed on the packaging. With supplemental beta-carotene, two mcg of beta-carotene are needed by the body for conversion, resulting in one mcg of retinol. This is known as a RAE ratio of 2:1. For beta-carotene in food, the RAE ratio is 12:1, so 12 mcg of beta-carotene in food is needed to provide one mcg of RAE. With alpha-carotene and betacryptoxanthin, the ratio is 24:1, so more is needed to provide the same retinol
Graph 3-1 Vitamin A content of some common foods.
Table 3-1 RDAs for vitamin A for all ages.
equivalency. Still, the highest amounts of vitamin A activity (outside of liver) are found in fruits and vegetables.
The retinol activity equivalency is not relevant to the antioxidant activity of provitamin A carotenes. The carotenes that are not converted to retinol are still valuable for their antioxidant activity. The RDA for vitamin Awas not intended to provide enough provitamin A for antioxidant use. There is general agreement that a diet rich in fruits and vegetables provides abundant vitamin Ato satisfy all needs. As mentioned, the yellow, orange, and green fruits and vegetables are richest in provitamin A.
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