Vitamin A and ProVitamin A

Funny how some people go to the extreme. I met a woman who consumed five to 10kg of carrot juice a week and she developed a yellow-orange tinge to her skin from excessive carotenoid concentrations or provitamin A. Reduce or take out the carrot juice and the tinge will go over time. This effect is called carotenemia and is thought to be harmless. Vitamin A is an insoluble vitamin needing fat for absorption. Therefore, a person with a high fat content can absorb up to 90 percent of retinoids. Vegetarians will absorb 5 to 50 percent of provitamin A. Other factors such as age and pregnancy may also affect absorption.

Provitamin A are your carotenoids found in plants (green, leafy vegetables, deeper coloured vegetables and fruit have a higher content of beta carotene).

Preformed vitamin A is found in foods of animal origin (liver, the fat in milk or eggs, cod and halibut liver oils) and it is already in its more functional form compared to provitamin A. Absorption of provitamin A is limited because of the binding of the proteins to the carotenoids. Cooking or juicing can disrupt the enzyme and free the carotenoid.

carrots Vitamin A and ProVitamin AVitamin A is vitally important for vision, immune functioning, reproduction, bone development, epithelial lining and gene expression.

However, preformed vitamin A (retinoid) found in animal or supplement forms can have detrimental effects if taken in excessive amounts.

People who are deficient may experience night blindness (impairment of dark adaption), impaired embryonic development, spontaneous abortion, anaemia, impaired immune competence and dry-scaly rough skin.

A deficiency can occur if the dietary intake of preformed vitamin A and provitamin A is inadequate and this occurs if the fat intake is too low in the diet (low-fat or no-fat diets), zinc deficiency, protein-energy malnutrition (since the protein is needed to help the binding process of the vitamin A), problems in the liver, gall bladder, pancreas or gastro-intestinal tract.

In developing countries, an estimated half a million cases of blindness are caused by vitamin A deficiency and a sub-clinical vitamin A deficiency can increase a child’s morbidity and mortality. People who abuse alcohol or who drink more are more likely to store less vitamin A in the liver, which increases their chance of developing vitamin A deficiencies.

Does this mean we need to run out and buy a bottle of preformed vitamin A?

No. Dosages exceeding the RDA for vitamin A should be taken with caution because it could lead to fatigue, anorexia, brittle nails, hair loss, irritability, a decrease in white blood cells, headaches, malaise, bone pain and fragility.

Dietary and supplementary vitamin A, especially during the first trimester of pregnancy, can cause physical defects (teratogenic) in the growing foetus.

Toxicity also increases in the elderly because of the liver’s inability to detoxify certain substances. Toxicity levels occur with preformed vitamin A rather than beta carotene (provitmin A).

About 10 times the actual prescribed dosage can lead to liver toxicity, liver disease, nausea, headaches, dry skin and eyes, hair loss.

Consuming high amounts of beta carotene or carotenoids are controversial.

There is conflicting evidence about consuming high amounts of carotenoids. Beta carotene is known as an anti-oxidant or as some research has shown, high carotenoid contents may increase lung cancer in smokers?

Consuming eggs, milk and the rainbow antioxidant foods (broccoli, spinach, carrots, peppers, peaches, butternut) regularly should ensure you get enough vitamin A and a supplement should not be needed.

If you think you need to take vitamin A, especially the retinoid complex, rather visit a doctor or dietician who can assess your status then monitor your progress if supplementation has been advised. – The Mercury

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