Vitamin A
Retinol, β-carotene
Description
Vitamin A is a fat-soluble vitamin that accumulates within the body's fat stores. It is necessary to maintain the integrity of the skin, immune function and night vision. It also plays an important role in bone growth, reproduction and lactation.
The body can convert β-carotene into vitamin A as needed.
Sources
Vitamin A is most commonly found in dairy products, margarine, liver, eggs, cheese and fish oil. Orange and dark green fruits and vegetables are good sources of β-carotene.
Vitamin A and β-carotene are expressed as mcg of Retinol Activity Equivalents (RAE).
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1 mcg of RAE = 1 mcg of vitamin A = 6 mcg of β-carotene
Recommended Daily Allowance (RDA)
Recommended average daily nutrient intake that is sufficient to meet the nutrient requirements of nearly all (97 to 98%) healthy individuals in each age and gender group. The RDA should only be used as a guide for daily individual intake:
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1 mcg = 3,33 UI
Deficiency
The body can store two years worth of vitamin A in the liver. Deficiencies are virtually nonexistent.
Vitamin A deficiency causes the mucous membranes and skin to dry as well as night blindness and eye lesions.
Toxicity
Unless one ingests large quantities of liver or fish oil, it is practically impossible to have too much vitamin A in one's diet.
Daily doses of 10 mg of vitamin A may cause headache, hair loss, drying of the mucous membranes and skin, bleeding gums, optic atrophy, bone loss and liver damage. Extremely high doses can also cause nausea, vomiting, fatigue and dizziness. Excessive doses during pregnancy may also increase the risk of birth defects.
β-carotene is not the source of these problems since the body only uses it if there is a vitamin A deficiency.
Supplements
Given that taking too much Vitamin A can be toxic, supplements should not be taken unless indicated by your doctor, furthermore, deficiency is rare. The maximum safe dose is 3 mg (10,000 UI) per day. β-carotene however, does not pose any problem.
Vitamin A supplements are contraindicated when taking isotretinoin (Accutane®) and should be used with caution during pregnancy.
Watch what you eat. Nutrition has a significant impact on health!
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