What is the difference between beta carotene and other types of vitamin a

Vitamin A retinol is a vitamin and is essential for life and overall health. It is a family of substances called pro-vitamin A and as pre-formed vitamin A. Preformed vitamin A is already formed as vitamin A and it comprises of various forms of retinol, retinal and retinoic acid. However, the word retinol is frequently used by scientists when referring to vitamin A. Preformed vitamin A is originated in nature only in animal products, such as fish and dairy products.

Several pro-vitamin A includes carotenoids and beta-carotene, and they can be converted into pre-vitamin compounds inside the human body. Vitamin A has numerous functions in the human body. It is significant for the growth and development, for the maintenance of the immune system as well as good vision. Vitamin A is required by the retina of the eye in the form of retinal, which reacts with protein opsin to synthesize rhodopsin, the light-sensitive molecule required for both low-light vision and color vision.

In addition to that, an irreversibly oxidized form of retinol or retinoic acid has a very different which is an essential hormone-like growth factor for epithelial and other cells. Retinol and other pre-forms are metabolized in the body and stored in the liver, principally as retinyl palmitate. Beta-carotene is a very strong colored red-orange pigment plentiful in various edible plants and fruits.

It is an organic complex and is chemically categorized as a hydrocarbon and precisely as a terpenoid , replicating its derivation from isoprene units. It is a tetraterpene and a fellow of the carotenes. Carotenes are synthesized biochemically from eight isoprene units and thus having 40 carbons. Amongst this overall class of carotenes, beta-carotene is the well-known by having beta-rings at both ends of the long chain molecule.

Beta-carotene is rich in carrots, pumpkins, and sweet potatoes that contribute to their orange colour. In addition to that, beta-carotene is a pro-vitamin A and two molecules of retinol pre-vitamin A can be synthesized from one molecule of beta-carotene.

Vitamin A is a fat-soluble vitamin. The symptoms of hypervitaminosis A following sudden, massive intakes of vitamin A, as with Arctic explorers who ate polar bear liver, are acute [ 37 ]. Chronic intakes of excess vitamin A lead to increased intracranial pressure pseudotumor cerebri , dizziness, nausea, headaches, skin irritation, pain in joints and bones, coma, and even death [ 2 , 4 , 5 ]. Although hypervitaminosis A can be due to excessive dietary intakes, the condition is usually a result of consuming too much preformed vitamin A from supplements or therapeutic retinoids [ 3 , 5 ].

When people consume too much vitamin A, their tissue levels take a long time to fall after they discontinue their intake, and the resulting liver damage is not always reversible. Observational studies have suggested an association between high intakes of preformed vitamin A more than 1, mcg daily—only slightly higher than the RDA , reduced bone mineral density, and increased fracture risk [ 1 , 4 , 38 ].

However, the results of studies on this risk have been mixed, so the safe retinol intake level for this association is unknown. Total intakes of preformed vitamin A that exceed the UL and some synthetic retinoids used as topical therapies such as isotretinoin and etretinate can cause congenital birth defects [ ].

These birth defects can include malformations of the eye, skull, lungs, and heart [ 4 ]. Women who might be pregnant should not take high doses of vitamin A supplements [ 2 ]. Unlike preformed vitamin A, beta-carotene is not known to be teratogenic or lead to reproductive toxicity [ 1 ].

The most significant effect of long-term, excess beta-carotene is carotenodermia, a harmless condition in which the skin becomes yellow-orange [ 1 , 23 ]. This condition can be reversed by discontinuing beta-carotene ingestion. Supplementation with beta-carotene, with or without retinyl palmitate, for 5—8 years has been associated with an increased risk of lung cancer and cardiovascular disease in current and former male and female smokers and in male current and former smokers occupationally exposed to asbestos [ 25 , 39 ].

In the ATBC study, beta-carotene supplements 20 mg daily were also associated with increased mortality, mainly due to lung cancer and ischemic heart disease [ 25 ].

The CARET study ended early, after the investigators found that daily beta-carotene 30 mg and retinyl palmitate 7, mcg RAE [25, IU] supplements increased the risk of lung cancer and cardiovascular disease mortality [ 39 ]. The FNB based these ULs on the amounts associated with an increased risk of liver abnormalities in men and women, teratogenic effects, and a range of toxic effects in infants and children.

The FNB also considered levels of preformed vitamin A associated with decreased bone mineral density, but did not use these data as the basis for its ULs because the evidence was conflicting. The FNB advises against beta-carotene supplements for the general population, except as a provitamin A source to prevent vitamin A deficiency.

However, many dietary supplements such as multivitamins do not provide all of their vitamin A as retinol or its ester forms. For example, the vitamin A in some supplements consists partly or entirely of beta-carotene or other provitamin A carotenoids.

In such cases, the percentage of retinol or retinyl ester in the supplement should be used to determine whether an individual's vitamin A intake exceeds the UL. That amount is above the UL for children from birth to 8 years but below the UL for older children and adults.

Vitamin A can interact with certain medications, and some medications can have an adverse effect on vitamin A levels. A few examples are provided below. Individuals taking these and other medications on a regular basis should discuss their vitamin A status with their healthcare providers. The manufacturers of Alli and Xenical recommend encouraging patients on orlistat to take a multivitamin supplement containing vitamin A and beta-carotene, as well as other fat-soluble vitamins [ 41 , 42 ].

Several synthetic retinoids derived from vitamin A are used orally as prescription medicines. Retinoids can increase the risk of hypervitaminosis A when taken in combination with vitamin A supplements [ 40 ]. The federal government's Dietary Guidelines for Americans notes that "Because foods provide an array of nutrients and other components that have benefits for health, nutritional needs should be met primarily through foods.

In some cases, fortified foods and dietary supplements are useful when it is not possible otherwise to meet needs for one or more nutrients e. For more information about building a healthy dietary pattern, refer to the Dietary Guidelines for Americans and the U. Department of Agriculture's MyPlate. This fact sheet by the Office of Dietary Supplements ODS provides information that should not take the place of medical advice.

We encourage you to talk to your healthcare providers doctor, registered dietitian, pharmacist, etc. Any mention in this publication of a specific product or service, or recommendation from an organization or professional society, does not represent an endorsement by ODS of that product, service, or expert advice. Updated: March 26, History of changes to this fact sheet.

Find ODS on:. Strengthening Knowledge and Understanding of Dietary Supplements. Health Information Health Information. Encyclopedia of Dietary Supplements. London and New York: Informa Healthcare; Ross CA. Vitamin A.

Ross A. Vitamin A and Carotenoids. Modern Nutrition in Health and Disease. Solomons NW. In: Bowman B, Russell R, eds. Present Knowledge in Nutrition. Institute of Medicine. Food and Nutrition Board. Tanumihardjo SA. Vitamin A: biomarkers of nutrition for development. Food and Drug Administration. Department of Agriculture, Agricultural Research Service. FoodData Central , Dietary supplement use in the United States, J Nutr ; What We Eat in America, World Health Organization.

Geneva: World Health Organization; Vitamin A supplements for preventing mortality, illness, and blindness in children aged under 5: systematic review and meta-analysis. BMJ ;d Vitamin A deficiency and clinical disease: An historical overview. Vitamin A and preterm infants: what we know, what we don't know, and what we need to know.

Vitamin A supplementation to prevent mortality and short and long-term morbidity in very low birthweight infants. Vitamin A supplementation for postpartum women. Vitamin A supplementation during pregnancy for maternal and newborn outcomes.

Elevated vitamin A intake and serum retinol in preadolescent children with cystic fibrosis. Am J Clin Nutr ; Vitamin A supplementation for cystic fibrosis. Consensus report on nutrition for pediatric patients with cystic fibrosis. Generally, vitamin A deficiency symptoms also include pale, dry skin , development of conjunctivitis , hypersensitivity to infection , slowing of growth , and reproductive issues.

Some people may be at a higher risk for provitamin A deficiency, including: pregnant women; smokers; elderly people; chronic alcoholics; people with cancer, AIDS, diabetes, and allergies; people exposed to the sun; and people sensitive to skin disorders. Unlike an excess of vitamin A, a precursor excess is not toxic , causing only yellow skin , which is reversible and not dangerous.

Furthermore, as the body does not absorb it fully, there is no real risk of overdose. Vitamin A excesses can be toxic , but this is a very rare situation.

However, it is wise to be careful during pregnancy. An excess of vitamin A is associated with birth defects. That is why it is not recommended for pregnant women to consume liver the food highest in vitamin A. However, beta-carotene intake through food presents no danger.

Fermer Home. Inscription EN What's your name? Skip to content Home Nutrients Beta-Carotene. Beta-carotene is a precursor to vitamin A.