About 600 carotenoids have been identified, but so far only about 50 are known to have provitamin A activity and efficiently convert into Vitamin A. It is likely that there are many more. The conversion can be enhanced with Vitamin E.
Some of the most common carotenoids are:
One of the most common carotenoid is beta-carotene. We only absorb about one third of ingested beta-carotene and not all of it is converted into Vitamin A. Absorption also decreased with higher doses which makes it impossible to reach toxic levels. However, your skin, hands and feet might turn yellow-orange (hypercarotenemia), but this is reversible by simply reducing the intake. High supplement doses have been reported to occasionally cause diarrhoea, dizziness, or joint pain.
Unlike Vitamin A, carotenoids are powerful antioxidants. However, they are not quite so powerful in their synthetic form. High synthetic doses can also have the opposite effect by turning into pro-oxidants. What’s more, in combination with smoking or high intakes of alcohol, it has been associated with an increased risk of lung cancer.
Carotenoids protect our DNA (deoxyribonucleic acid), support our immunity, and help to maintain our body tissue. Beta-carotene is also said to increases lung capacity. Please also refer to Vitamin A for further benefits.
We can find carotenoids in many fruits and vegetables, particularly if yellow or red in colour, but also in green leafy vegetables. They are easily destroyed if exposed to air or light. However, light cooking can increase their bioavailability. We can find high levels in:
There are no RDI’s (Recommended Dietary Intakes) established for carotenoids. However, the NHMR (National Health and Medical Research Council) published “Nutrient Values for Australia and New Zealand” in September 2005, suggesting 5,800mcg of carotenes for adult males and 5,000mcg for adult women.