Recommended daily intake of vitamin A and carotenoids
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Recommended Daily Intake of Vitamin A: Guidelines and Units
The recommended daily intake (RDI) of vitamin A varies by age, sex, and physiological status. For adults, common recommendations are 1,000 micrograms retinol equivalents (RE) per day for men, 800 micrograms RE for non-pregnant and pregnant women, and 1,300 micrograms RE for lactating women. These values are based on studies of vitamin A depletion and repletion, and are designed to maintain optimal health and prevent deficiency symptoms such as vision problems and immune dysfunction . The European Food Safety Authority (EFSA) recommends a population reference intake of 750 micrograms RE per day for adult men and 650 micrograms RE per day for adult women, with a tolerable upper intake level (UL) of 3,000 micrograms RE per day for adults to avoid toxicity 67.
Vitamin A Sources: Preformed Vitamin A and Provitamin A Carotenoids
Vitamin A can be obtained from animal sources as preformed vitamin A (retinol) and from plant sources as provitamin A carotenoids, such as beta-carotene, alpha-carotene, and beta-cryptoxanthin. In many diets, both forms contribute to total vitamin A intake, with animal products providing preformed vitamin A and fruits and vegetables supplying carotenoids 15810. In Western diets, about 60–65% of vitamin A comes from preformed sources, while 35–40% comes from carotenoids 5910.
Carotenoids: Conversion to Vitamin A and Bioavailability
Not all carotenoids have vitamin A activity. The main provitamin A carotenoids are beta-carotene, alpha-carotene, and beta-cryptoxanthin. Beta-carotene is the most significant, accounting for the majority of provitamin A activity in the diet 510. However, recent research shows that the conversion of carotenoids to vitamin A is less efficient than previously thought. It is now estimated that 21 micrograms of beta-carotene from a mixed diet are needed to provide 1 microgram of retinol equivalent (RE), rather than the older estimate of 6 micrograms 23. This means that the contribution of carotenoids to vitamin A intake may be lower than previously calculated, and dietary assessments should use updated conversion factors for accuracy 23.
Meeting Vitamin A Requirements: Dietary Patterns and At-Risk Groups
Most people can meet their vitamin A requirements through a balanced diet that includes both animal and plant sources. Foods rich in preformed vitamin A include liver, dairy products, and eggs, while carrots, spinach, sweet potatoes, and other colorful fruits and vegetables are good sources of provitamin A carotenoids 4810. However, certain groups are at risk of inadequate intake, such as those with low income, restrictive diets, or limited access to diverse foods 12. In some populations, especially in developing countries, vitamin A deficiency remains a significant public health concern 14.
Safety and Upper Intake Levels for Vitamin A and Carotenoids
Intakes up to three times the RDI (about 3,000 micrograms RE per day) are considered safe for most adults, with no unwanted side effects expected at these levels 16. Chronic excessive intake of preformed vitamin A, especially from supplements or liver, can lead to toxicity, with teratogenic and liver effects being the most critical concerns 16. The EFSA recommends that women who are pregnant or planning pregnancy should not exceed 3,000 micrograms RE per day and should avoid liver products . There is no evidence that dietary beta-carotene from foods causes toxicity, but high-dose supplements should be avoided, especially by smokers .
Conclusion
The recommended daily intake of vitamin A for adults generally ranges from 600 to 1,000 micrograms retinol equivalents, with an upper safe limit of 3,000 micrograms RE per day. Both preformed vitamin A from animal sources and provitamin A carotenoids from plant sources contribute to meeting these needs, but the conversion efficiency of carotenoids is lower than previously thought. A varied diet rich in both animal and plant foods is the best way to ensure adequate vitamin A intake and avoid deficiency or toxicity 12345678+2 MORE.
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