Vitamin A and Beta Carotene – What, How, When, Why to Supplement


Sources and Physiologic Functions:

Sources: Foods which might be wealthy in vitamin A are milk, cheese, butter, eggs, liver, and such fish as herring, sardines, and tuna. The richest sources of nutrition A are the liver oils of shark, halibut, and polar bear. Rich sources of pre-vitamin A are spinach, carrots, papaya, oranges, sweet potatoes, and cantaloupes. Poor assets of vitamin A and pre-diet A are vegetable oils, white lard, white corn, cereals, beef, and legumes.

Food Source

Serving Size/Amt

International Units (IU)

Milk 2% 8 fl oz. – 500IU; Cream Cheese 1oz 405IU; Cheddar Cheese 3.5 ounces1059IU; Egg (boiled) 1 medium 280IU; Egg (scrambled) 1 medium 416IU; Liver (red meat braised) three.Five ounces35679IU; Liver (veal braised) three.5 ounces26883IU; Herring (raw) 3.O oz80IU; Herring (kippered) 1 piece 51IU; Sardines (canned/oil) 2 portions 54IU; Tuna (uncooked) three.0 oz.50IU; Tuna (canned) 3.0 oz.16IU; Pre-Vitamin A (b-carotene) Spinach (boiled) ½ cup 7371IU; Spinach (uncooked) ½ cup 1880IU; Carrots (raw) 1 medium 2025IU; Carrots (boiled) ½ cup 19152IU; Papaya (raw) 1 medium 863IU; Oranges 1 fruit 240IU; Sweet potatoes (baked w/pores and skin) 1 medium 24877IU; Sweet potatoes (boiled w/o skin) 1 medium 27969IU; Cantaloupes 1 cup 5158IU; Parsley ½ cup freeze dried 885IU

Biochemistry: Vitamin A is a fat-soluble diet. Vitamin A is a collective term for retinal, retinol, retinoic acid, and b-carotene. The nutrition A in foods of animal beginning, together with eggs, milk, butter, and liver, takes place largely in the form of retinyl esters. A retinyl ester is a molecule of retinol esterified with a molecule of a fatty acid, including palmitic acid. The fatty acid is bound to the hydroxyl group of retinol. Plants do not contain nutrition A; however, a few vegetation are wealthy resources of pre-nutrition A. Pre-vitamin A takes the form of a own family of compounds called the carotenoids. More than 500 carotenoids occur in nature, even though best approximately 50 of them can be used as precursors of nutrition A. The maximum important of those is all-trans-b-carotene. The prefix all-trans shows that all of the double bonds are inside the trans conformation instead of the cis conformation. Vegetables which might be darkish inexperienced, orange, and yellow are rich sources of the carotenoids. Other styles of pre-vitamin A are cryptoxanthine and a-carotene. Some carotenoids can not be converted to nutrition A by using mammals. These consist of lutein, lycopene, and canthaxanthine.

Vitamin A serves 3 lessons of features: aid of epithelial cells (lungs and tracheal integrity), fetal growth and vitality of the testes, and usage within the visual cycle. Dietary retinoic acid can guide handiest the first feature. Retinoic acid cannot be saved within the liver. Retinyl esters, retinol, and retinal are interconvertible. Retinal may be oxidized to form retinoic acid. All 3 features of vitamin A may be supported by means of nutritional retinyl esters, retinol, ocuprime supplement or retinal. Although those bureaucracy may be converted to retinoic acid, retinoic acid apparently cannot be reduced to form retinal. Dermatological troubles like pimples, psoriasis, Darier’s sickness, and skin getting old are efficaciously treated with retinoic acid and topical tretinoin.

Populations at chance: In america, sufferers tormented by chronic intestinal disorder, malignancy, malaria, pneumonia, and anorexia nervosa are deficient in nutrition A. Requirement for this vitamin is increased in sufferers with appendectomy, burns, cirrhosis, and biliary obstruction. Stress can growth excretion. Zinc and protein deficiency can decrease delivery. Premature toddlers and people affected by cystic fibrosis and rheumatic fever are also at risk.

Signs and Symptoms of Deficiency: Night blindness is the earliest symptom.Severe vitamin A deficiency results in xerophthalmia, which could result in corneal ulceration, Bitot’s spots, and blindness. Thickening of the bone, loss of lung elasticity, epithelial keratinization, impaired hearing, urinary calculi, and keratinization of salivary glands are also seen. In males, sperm production ceases. In women, fetuses are reabsorbed.


The hazards of excess diet A are nicely mounted with ingestion of excessive amounts of preformed vitamin A. Intake of 7,500-15,000 mg preformed retinal equivalents (RE) daily for periods of months to years can produce detrimental consequences including liver toxicity and possible beginning defects. Prolonged every day intake of <7,500 RE (<25,000 IU) is considered safe in the age group of 18-54. For the liver, it had to be taken for 6 years to become toxic. There has been one report of toxicity for doses in ranges as low as 1,500 – 3,000 mgm (5000-10,000IU), but these results were not reproducible and are contrary to the vast majority of the medical literature. There is no evidence that supplements of 3,000 mg RE (10,000 IU) are harmful to normal adults, including pregnant women and the elderly.

There is no evidence that conversion of beta-carotene to vitamin A contributes to vitamin A toxicity, even when beta-carotene is ingested in large amounts. The only consistent adverse effect of high beta-carotene intakes has been coloration of the skin related to hypercarotenemia. The possibility that beta-carotene causes lung cancer will be discussed later. A review of all published evidence on beta-carotene shows two studies, the ATBC trial and the CARET which suggest adverse effects. The rest of the evidence has shown beta-carotene to be safe.

Hypervitaminosis: Early signs of chronic hypervitaminosis are reflected in the skin, which becomes dry and pruritic, the liver, which becomes enlarged and cirrhotic, and in the nervous system, where a rise in intracranial tension mimics the symptoms of a brain tumor. Hypervitaminosis in pregnancy may cause congenital malformations like precocious skeletal growth and transient hydrocephalus. Anorexia, vomiting, loss of hair, nystagmus, gingivitis, glossitis, lymph node enlargement, and delayed clotting time are other symptoms. Isotretinoin is teratogenic and is absolutely contra-indicated in women with childbearing potential unless they have unresponsive, disfiguring acne. Hyperlipidemia occurs with prolonged use of isotretinoin. Hypervitaminosis can lead to vitamin neurotoxic effects. Closely related to the neurological symptoms of hypervitaminosis are symptoms including headache, pseudotumor cerebri, and embryotoxic effects reported in patients given vitamin A analogs or retinoids. Because vitamin A and analogs enter the CNS better than most vitamins, and because retinoids have many effects on enzyme activity and gene expression, Vitamin A neurotoxicity is more likely than all other vitamins. Megadose vitamin therapy may cause injury that is confused with disease symptoms. A study showed that after 49 months of follow up, ingestion of retinol caused a 7% increase in alkaline phosphatase, 11% increase in triacylglycerol, 3% increase in cholesterol and 1% decrease in HDL. The participants were randomly assigned to receive retinol (7,576 retinol equivalents RE, or 25,000 IU) or a placebo daily. Because a 1% increase in cholesterol concentrations has been reported to be associated with a 2% increase in coronary artery disease risk, long term ingestion of 7,576 RE vitamin A should be considered with caution.

Consuming too much vitamin A could increase your risk of osteoporosis. Two studies showed that a daily vitamin A intake > 1.Five mg resulted in a 6% lower in standard bone density and doubled the danger of hip fracture. Excess tiers of this nutrition weaken bones through growing its fee of resorption.


Vitamin A is important for ordinary replica and development. Doses > 10,000 IU/d as dietary supplements have been stated to purpose malformations in a single epidemiologic look at. Nonhuman primate information display no teratogenicity at doses of 30,000 IU/d. Because no look at reviews unfavourable effects of 10,000 IU/d preformed vitamin A supplements, and this dose is extra than the Recommended Dietary Allowance throughout pregnancy (2670 IU or 800 RE/d), it is suggest that girls residing in industrialized international locations or who otherwise have nutritionally good enough diets might not want to ingest greater than the RDA of preformed nutrition A as supplements. If periconceptional diet A exposures to degrees as much as 30,000 IU/d (nine,000 μg RE/d) do occur by accident, multiple animal research do aid only very low threat. Teratogenicity nor