Vitamin A Sources, Food sources & Supplements

Vitamins >> Vitamin A Sources

Retinol activity equivalency (RAE)

Different dietary sources of vitamin A have different potencies. For example, beta-carotene is less easily absorbed than retinol and must be converted to retinal and retinol by the body. The most recent international standard of measure for vitamin A is retinol activity equivalency (RAE), which represents vitamin A activity as retinol. Two micrograms (mcg) of beta-carotene in oil provided as a supplement can be converted by the body to 1 mcg of retinol giving it an RAE ratio of 2:1. However, 12 mcg of beta-carotene from foods are required to provide the body with 1 mcg of retinol, giving dietary beta-carotene an RAE ratio of 12:1. Other provitamin A carotenoids in foods are less easily absorbed than beta-carotene, resulting in RAE ratios of 24:1. The RAE ratios for beta-carotene and other provitamin A carotenoids are shown in the table below. An older international standard, still commonly used, is the international unit (IU). One IU is equivalent to 0.3 mcg of retinol.

Retinol activity equivalency (RAE) ratios for beta-carotene and other provitamin A carotenoids

Quantity Consumed Quantity Bioconverted to Retinol RAE ratio

1 mcg of dietary or supplemental vitamin A 1 mcg of retinol* 1:1

2 mcg of supplemental beta-carotene 1 mcg of retinol 2:1

12 mcg of dietary beta-carotene 1 mcg of retinol 12:1

24 mcg of dietary alpha-carotene 1 mcg of retinol 24:1

24 mcg of dietary beta-cryptoxanthin 1 mcg of retinol 24:1

*One IU is equivalent to 0.3 mcg of retinol, and one mcg of retinol is equivalent to 3.33 IU of retinol.

Food sources

Free retinol is not generally found in foods. Retinyl palmitate, a precursor and storage form of retinol, is found in foods from animals. Plants contain carotenoids, some of which are precursors for vitamin A (e.g., alpha-carotene and beta-carotene). Yellow and orange vegetables contain significant quantities of carotenoids. Green vegetables also contain carotenoids, though the pigment is masked by the green pigment of chlorophyll (1). A number of good food sources of vitamin A are listed in the table below along with their vitamin A content in retinol activity equivalents (mcg RAE). In those foods where retinol activity comes mainly from provitamin A carotenoids, the carotenoid content and the retinol activity equivalents are presented. You may use the USDA food composition database to check foods for their content of several different carotenoids, including lycopene, lutein and zeaxanthin.

Food Serving Vitamin A, RAE
Vitamin A, IU Retinol, mcg Retinol, IU

Cod liver oil 1 teaspoon 1,350 mcg 4,500 IU 1,350 mcg 4,500 IU

Fortified breakfast cereals 1 serving 150-230 mcg 500-767 IU 150-230 mcg 500-767 IU

Egg 1 large 91 mcg 303 IU 89 mcg 296 IU

Butter 1 tablespoon 97 mcg 323 IU 95 mcg 317 IU

Whole milk 1 cup (8 fl ounces) 68 mcg 227 IU 68 mcg 227 IU

2% fat milk (vitamin A added) 1 cup (8 fl ounces) 134 mcg 447 IU 134 mcg 447 IU

Nonfat milk (vitamin A added) 1 cup (8 fl ounces) 149 mcg 500 IU 149 mcg 500 IU

Sweet potato 1/2 cup, mashed 959 mcg 3,196 IU 0 0

Carrot (raw) 1/2 cup, chopped 385 mcg 1,283 IU 0 0

Cantaloupe 1/2 medium melon 466 mcg 1,555 IU 0 0

Spinach 1/2 cup, cooked 472 mcg 1,572 IU 0 0

Squash, butternut 1/2 cup, cooked 572 mcg 1,906 IU 0 0

Supplements

The principal forms of preformed vitamin A (retinol) in supplements are retinyl palmitate and retinyl acetate. Beta-carotene is also a common source of vitamin A in supplements, and many supplements provide a combination of retinol and beta-carotene. If a percentage of the total vitamin A content of a supplement comes from beta-carotene, this information is included in the Supplement Facts label under vitamin A. Most multivitamin supplements available in the U.S. provide 1,500 mcg (5,000 IU) of vitamin A, substantially more than the current RDA for vitamin A. This is due to the fact that the Daily Values (DV) used by the FDA for supplement labeling are based on the RDAs established in 1968 rather than the most recent RDAs, and multivitamin supplements typically provide 100% of the DV for most nutrients. Because retinol intakes of 5,000 IU/day have recently been associated with an increased risk of osteoporosis in older adults (see Safety), some companies have reduced the retinol content in their multivitamin supplements to 750 mcg (2,500 IU).