Vitamin a how many iu

The prevalence of vitamin A deficiency in developing countries begins to increase in young children just after they stop breastfeeding [ 3 ]. The most common and readily recognized symptom of vitamin A deficiency in infants and children is xerophthalmia.

Pregnant women need extra vitamin A for fetal growth and tissue maintenance and for supporting their own metabolism [ 18 ]. The World Health Organization estimates that 9. Other effects of vitamin A deficiency in pregnant and lactating women include increased maternal and infant morbidity and mortality, increased anemia risk, and slower infant growth and development. Most people with cystic fibrosis have pancreatic insufficiency, increasing their risk of vitamin A deficiency due to difficulty absorbing fat [ 19 , 20 ].

However, improved pancreatic replacement treatments, better nutrition, and caloric supplements have helped most patients with cystic fibrosis become vitamin A sufficient [ 21 ]. Several studies have shown that oral supplementation can correct low serum beta-carotene levels in people with cystic fibrosis, but no controlled studies have examined the effects of vitamin A supplementation on clinical outcomes in patients with cystic fibrosis [ ].

This section focuses on three diseases and disorders in which vitamin A might play a role: cancer, age-related macular degeneration AMD , and measles. Because of the role vitamin A plays in regulating cell growth and differentiation, several studies have examined the association between vitamin A and various types of cancer.

However, the relationship between serum vitamin A levels or vitamin A supplementation and cancer risk is unclear. Several prospective and retrospective observational studies in current and former smokers, as well as in people who have never smoked, found that higher intakes of carotenoids, fruits and vegetables, or both are associated with a lower risk of lung cancer [ 1 , 23 ]. In the Carotene and Retinol Efficacy Trial CARET , 18, current and former smokers including some males who had been occupationally exposed to asbestos took daily supplements containing 30 mg beta-carotene and 7, mcg RAE 25, IU retinyl palmitate for 4 years, on average [ 24 ].

In the beta-carotene component of the Physicians' Health Study, 22, male physicians took mg aspirin plus 50 mg beta-carotene, 50 mg beta-carotene plus aspirin placebo, mg aspirin plus beta-carotene placebo, or both placebos every other day for 12 years [ 26 ].

In all three of these studies, taking very high doses of beta-carotene, with or without 7, mcg RAE 25, IU retinyl palmitate or mg aspirin, did not prevent lung cancer. In fact, both the CARET and ATBC studies showed a significant increase in lung cancer risk among study participants taking beta-carotene supplements or beta-carotene and retinyl palmitate supplements.

The evidence on the relationship between beta-carotene and prostate cancer is mixed. However, the ATBC study found that baseline serum beta-carotene and retinol levels and supplemental beta-carotene had no effect on survival [ 28 ]. The ATBC and CARET study results suggest that large supplemental doses of beta-carotene with or without retinyl palmitate have detrimental effects in current or former smokers and workers exposed to asbestos.

The relevance of these results to people who have never smoked or to the effects of beta-carotene or retinol from food or multivitamins which typically have modest amounts of beta-carotene is not known. More research is needed to determine the effects of vitamin A on prostate, lung, and other types of cancer. Age-related macular degeneration AMD is a major cause of significant vision loss in older people.

AMD's etiology is usually unknown, but the cumulative effect of oxidative stress is postulated to play a role. If so, supplements containing carotenoids with antioxidant functions, such as beta-carotene, lutein, and zeaxanthin, might be useful for preventing or treating this condition.

Lutein and zeaxanthin, in particular, accumulate in the retina, the tissue in the eye that is damaged by AMD. A follow-up AREDS2 study confirmed the value of this supplement in reducing the progression of AMD over a median follow-up period of 5 years but found that adding lutein 10 mg and zeaxanthin 2 mg or omega-3 fatty acids to the formulation did not confer any additional benefits [ 31 ].

Importantly, the study revealed that beta-carotene was not a required ingredient; the original AREDS formulation without beta-carotene provided the same protective effect against developing advanced AMD.

Measles is a major cause of morbidity and mortality in children in developing countries. About half of all measles deaths happen in Africa, but the disease is not limited to low-income countries. Vitamin A deficiency is a known risk factor for severe measles.

The World Health Organization recommends high oral doses 60, mcg RAE [, IU] of vitamin A for two days for children over age 1 with measles who live in areas with a high prevalence of vitamin A deficiency [ 32 ]. A Cochrane review of eight randomized controlled trials of treatment with vitamin A for children with measles found that 60, mcg RAE , IU of vitamin A on each of two consecutive days reduced mortality from measles in children younger than 2 and mortality due to pneumonia in children [ 32 ].

Vitamin A also reduced the incidence of croup but not pneumonia or diarrhea, although the mean duration of fever, pneumonia, and diarrhea was shorter in children who received vitamin A supplements.

A meta-analysis of six high-quality randomized controlled trials of measles treatment also found that two doses of 30, mcg RAE , IU in infants and 60, mcg RAE , IU in older children significantly reduced measles mortality [ 33 ]. The vitamin A doses used in these studies are much higher than the UL. The effectiveness of vitamin A supplementation to treat measles in countries, such as the United States, where vitamin A intakes are usually adequate is uncertain.

The body needs vitamin A to maintain the corneas and other epithelial surfaces, so the lower serum concentrations of vitamin A associated with measles, especially in people with protein-calorie malnutrition, can lead to blindness. None of the studies evaluated in a Cochrane review evaluated blindness as a primary outcome [ 34 ]. However, a careful clinical investigation of African children with measles revealed that half of all corneal ulcers in these children, and nearly all bilateral blindness, occurred in those with vitamin A deficiency [ 35 ].

Because vitamin A is fat soluble, the body stores excess amounts, primarily in the liver, and these levels can accumulate. Although excess preformed vitamin A can have significant toxicity known as hypervitaminosis A , large amounts of beta-carotene and other provitamin A carotenoids are not associated with major adverse effects [ 36 ].

The manifestations of hypervitaminosis A depend on the size and rapidity of the excess intake. 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.

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No vitamin A, but do contain carotenoids which are partially converted to Vitamin A in the body. Skin changes are another sign of too little vitamin A. The skin becomes dry and rough. This is seen over the shoulders, buttocks, and the opposite side of a joint of the arms and legs. Little bumps may show up around the base of each hair. This causes a sandpaper-like feel to the skin.

Mucous membranes may also change. This may affect the lining of the urinary tract. This may cause burning and bleeding with urination. The lining of the vagina may also get dry and inflamed. Retinol is used to treat vitamin A deficiency. In many undeveloped countries, vitamin A deficiency is common. Because vitamin A can be stored in the body, large doses can be given to children and some adults only 2 or 3 times a year. This is done to prevent xerophthalmia. This is a condition that leads to blindness.

Vitamin A deficiency is rare in the U. Vitamin A in the form of beta-carotene is considered safe. But high doses over a long period of time can lead to carotenemia. In this condition, your skin becomes yellowish orange.

Vitamin A overdose in the form of retinoids from animal sources can be toxic. The conditions of overdose hypervitaminosis are divided into 2 groups: acute and chronic. These are then split into infant and adult. Children are more sensitive than adults to overdoses of vitamin A. The symptoms of an acute overdose in an infant or child include:.

Pseudotumor cerebri. This condition increases pressure around the brain, bulging of the optic disc in the back of the eye, paralysis, or change in function of some of the cranial nerves. This is seen after the soft spot has closed over and the sutures fused. Skin changes such as dryness, roughness, and cracks in the lips and corners of the mouth. This is because high doses may cause malformations in your baby growing in the womb.

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