Vitamin A deficiency is especially dangerous for infants, children, pregnant and lactating mothers. From 2012 more than 250 millions pre-school children were affected each year, and around 670.000 children under five were dying. Rare in the Western world, one of the most common cause of blindness in developing countries from Africa and South-East Asia, vitamin A deficiency claims between a quarter to one half a million children's sight. The earliest symptom is impaired dark adaptation or night blindness, caused by insufficient retinol availability for the retina (on the back of the eye). Severe deficiency causes xerophthalmia (Greek name for dry eye), leading to corneal ulcer, scarring and blindness.
As a child, even mildly deficiency in vitamin A will make you more prone to respiratory disease and diarrhea. There are some diseases like liver and gastrointestinal diseases, interfering with the absorption and utilization of vitamin A. If vitamin A values are lower than normal during pregnancy, this can lead to malformations during the fetal development phase.
Vitamin A can be also acutely and chronically toxic, as hipervitaminosis A (vitamin A overdose) - more than a single dose in excess of 300 mg - can cause nausea, vomiting, headaches for few days. A very large dose can cause drowsiness, malaise, skin exfoliation and even death. Single doses of 60 mg retinol are given to children in developing countries to meet 4-6 months needs. Almost 1% of them suffer from toxicity, but preventing xerophthalmia is considered to be more important. Prolonged or regular intake on 7-9 mg daily for adults and even less for children can cause toxicity symptoms, affecting the skin, nervous system, enlarging the liver and making the bones more fragile.
Excessive vitamin A during pregnancy increases the risk of birth defects. High intake of vitamin A before the 7th semester is the most damaging, so pregnant women must avoid liver, vitamin A supplements, acne drugs (isotretinoin) and any other retinol related drugs (skin condition drugs). Some animal liver has too much vitamin A and can be lethal (polar bear, seal), but this is known by the Inuit population, even if the Arctic explorers learn it the hard way.
Excessive beta-carotene intake can induce carotenemia, harmless condition when the skin becomes yellow orange, once you stop having beta-carotene, the condition will be reversed.
Next post will be about vitamin D.
Yours truly,
George
P.S. If you are Romanian, you can also publish your post link in the Publish0x Romanian Community Facebook group for others to read it.
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