Vitamin A in food: retinol, beta-carotene and absorption

Why are a carrot and cod liver oil different?

Both can contribute to vitamin A nutrition, but they take different routes. Cod liver oil contains preformed vitamin A. A carrot contains beta-carotene, a pigment the body can turn into vitamin A. Conversion is variable, so a quantity of beta-carotene is not automatically an equal quantity of retinol. Cod liver oil and ordinary fish oil are different products: check the label.12

What is preformed vitamin A?

Preformed vitamin A includes retinol and retinyl esters. It is found in animal foods such as liver, eggs, dairy and some fish, and may be added to foods or supplements. Liver can be particularly rich. Because excess preformed vitamin A can be harmful, the amount and the other products a person uses matter. For pregnancy-specific guidance, see vitamin A and pregnancy.12

Which plant pigments can become vitamin A?

Beta-carotene, alpha-carotene and beta-cryptoxanthin are provitamin A carotenoids: the body can convert some into vitamin A. Carrots, sweet potatoes and leafy greens provide examples. Other carotenoids, including lutein and zeaxanthin, are not converted into vitamin A. They may have other roles, but their presence does not make a product a source of vitamin A.12

What happens after a meal?

Vitamin A and carotenoids are absorbed in the small intestine through a process that involves fat. Much of the body’s vitamin A is stored in the liver. The body uses different forms: retinal participates in the eye’s response to light, while retinoic acid helps regulate cell development. These roles do not show that taking extra supplements improves vision, skin or immunity in people who already have enough.

Absorption and conversion vary with the food, preparation and individual. This explanation cannot establish the best meal or timing for a particular supplement. Read its directions and see the guide to vitamins and meals. For the eye’s role in dim light, continue to vitamin A and night vision.

For a closer look at the transport particles, liver storage and release to tissues, follow vitamin A through the body.12

Does cooking a carrot change what the body can use?

Think of the orange pigment as being held within the carrot’s structure. Chopping, puréeing and cooking can change how easily some carotenoids are released and absorbed. The amount measured in the food, the amount absorbed and the amount converted to vitamin A are related but different measurements. Cooking does not make every nutrient in a meal more available, and raw carrots still contribute nutrients.

Fat in a meal can aid absorption of fat-soluble carotenoids. The food, preparation, meal and person all matter; there is no single amount of oil established by these studies for every meal or person. People with conditions affecting fat absorption may need individual advice.14

What did one carrot experiment actually measure?

In a 2002 study, nine healthy adults ate two different prepared carrot meals on separate occasions: a commercial purée and boiled, mashed carrots. Researchers estimated that absorption of alpha- and beta-carotene was about twice as high from the purée. They did not find a statistically clear difference in estimated vitamin A yield; that result also does not prove the yields were identical.

The products differed in preparation, the sample was small, and the study received support from Gerber Products. It did not compare every cooking method, establish a personal conversion rate or test health outcomes. It is evidence that preparation can matter, not a reason to avoid raw vegetables.3

Was it the cooking, the oil or both?

A separate UK proof-of-principle study followed five healthy adults after a minimally processed carrot preparation and a stir-fried preparation. The carrots in the minimally processed comparison had been blanched and homogenised before storage; they were not an ordinary whole raw carrot. Both meals included a small amount of oil with the study’s tracer doses; the stir-fried preparation had additional oil. The researchers estimated greater beta-carotene availability from that meal, but the design could not separate the effects of cooking and oil. It cannot tell an individual how much fat to eat.

Food studies do not establish instructions for a particular capsule or gummy. For that distinction, see taking vitamins with food; the orlistat guide explains why a medicine that affects fat absorption changes the question.41

How do food and supplement labels compare?

Labels can list preformed vitamin A, beta-carotene or a mixture. In the United States, vitamin A amounts commonly use micrograms of retinol activity equivalents (mcg RAE), a way of accounting for different activity of forms. Older labels may use international units (IU). Conversion depends on the form and source; an IU number cannot be translated correctly without that information. Labels and reference values vary between countries. Learn how to read the complete supplement label. For a worked example and overlapping products, read vitamin A labels and combinations.12

Does more always help?

Too little vitamin A overall, or too much preformed vitamin A, can be harmful. High-dose beta-carotene supplements have a different risk profile, including findings in trials of people who smoked or had asbestos exposure; the trials did not test carrots or other vegetables. Medicines and overlapping supplements can change the question. Return to vitamin A: benefits, risks and interactions for the evidence and practical context. For the difference between supplement trials and vegetables, see beta-carotene, smoking and cancer.12