Vitamin A // Retinol

Intake recommendations

The intake recommendations for vitamin A are based on the amount needed to ensure adequate stores (four months) of retinol in the body to support normal reproductive function, immune function, gene expression, and vision.

In 1993, the European Scientific Committee for Food set population reference intakes (PRI) for vitamin A in micrograms (mcg) of preformed vitamin A (Retinol Activity Equivalents, RAE, see below) and international units (IU) per day (22):

 Age   Males: 
mcg/day (IU/day)
Females: 
mcg/day (IU/day
6–12 months 350 (1,166 IU) 350 (1,167 IU)
 1–3 years 400 (1,333 IU) 400 (1,333 IU)
 4–6 years 400 (1,333 IU) 400 (1,333 IU)
 7–10 years 500 (1,667 IU) 500 (1,667 IU)
 11–14 years 600 (2,000 IU) 600 (2,000 IU)
 15–17 years 700 (2,333 IU) 600 (2,000 IU)
 18 years and older 700 (2,333 IU) 600 (2,000 IU)
 Pregnant - 700 (2,333 IU)
 Breast feeding - 950 (3,167 IU)

Many European nutrition societies such as the German Nutrition Society (DGE) recommend a daily intake of 0.8 mg vitamin A (retinol) for women and 1 mg for men (23). As vitamin A plays an important role for the healthy development of the embryo and the new-born, pregnant women should take 1.1 mg vitamin A per day from the 4th month on. For breastfeeding women the recommended daily intake is 1.5 mg.

In 2015, the European Food Safety Authority (EFSA) set Population Reference Intakes (PRIs) of 750 mcg RE/day for men and 650 mcg RE/day for women. PRIs for infants and children were set in a range from 250 to 750 mcg RE/day. For pregnancy and lactation, additional vitamin A requirements related to the accumulation of retinol in fetal and maternal tissues and transfer of retinol into breast milk were considered and PRIs of 700 and 1,300 mcg RE/day, respectively, were set (11).

In 2001, the U.S. Food and Nutrition Board (FNB) established recommended dietary allowance (RDA) values for vitamin A in both micrograms (mcg) of preformed vitamin A (Retinol Activity Equivalents, RAE, see below) and international units (IU) (24):

Life Stage Age Males: 
mcg/day (IU/day)
Females: 
mcg/day (IU/day)
 Infants (AI) 0–6 months 400 (1,333 IU) 400 (1,333 IU)
 Infants (AI)  7–12 months 500 (1,667 IU) 500 (1,667 IU)
 Children  1–3 years 300 (1,000 IU) 300 (1,000 IU)
 Children  4–8 years 400 (1,333 IU) 400 (1,333 IU)
 Children 9–13 years 600 (2,000 IU) 600 (2,000 IU)
 Adolescents 14–18 years 900 (3,000 IU) 700 (2,333 IU)
 Adults 19 years and older 900 (3,000 IU) 700 (2,333 IU)
 Pregnancy 18 years and younger - 750 (2,500 IU)
 Pregnancy 19 years and older - 770 (2,567 IU)
 Breast-feeding 18 years and younger - 1,200 (4,000 IU)
 Breast-feeding 19 years and older - 1,300 (4,333 IU)

A consumption of excess preformed vitamin A (retinol) during pregnancy is known to cause birth defects (see Safety).

For a detailed overview of recommended daily intakes (PRIs/RDAs) of vitamins and minerals for adults derived from different countries and organizations see PDF.

Provitamin A intake – Retinol Activity Equivalents

Different sources of vitamin A such as food, supplements, and provitamin A carotenoids have different potencies. Beta-carotene is less easily absorbed than retinol and must be converted to retinal and retinol by the body; other provitamin A carotenoids in foods (e.g., alpha-carotene) are even less easily absorbed than beta-carotene.

The international standard of measure for vitamin A is ‘retinol activity equivalents’ (RAE), which considers the conversion ratio and represents vitamin A activity as retinol. According to the U.S. Food and Nutrition Board, the conversion factors are the following (24):

 Quantity consumed Quantity converted to retinol RAE ratio
 1 mcg dietary or supplemental vitamin A 1 mcg of retinol* 1:1
 12 mcg dietary beta-carotene  1 mcg of retinol 12:1
 24 mcg dietary alpha-carotene  1 mcg of retinol 24:1

* An older international standard, still commonly used, is the international unit (IU): One IU is equivalent to 0.3 microgram (mcg) retinol, and one mcg of retinol is equivalent to 3.33 IU retinol.

The conversion factors for dietary beta-carotene to vitamin A have changed over time and have not always been the same in different studies and surveys. Nowadays many researchers suggest a conversion factor of 1:12 ─ to produce 1 mcg retinol from fruits and vegetables, although there is a large difference in bioefficacy within the natural sources. For dietary supplements (capsules and tablets) a conversion factor of 1:2 is applied.

Authored by Dr Peter Engel in 2010, reviewed by Dr. Adrian Wyss on 31.08.2017.