Until recently, beta carotene was not thought to be toxic to humans. High levels of plasma beta carotene (hypercarotenemia) have not been associated with adverse side effects apart form causing a yellowing of the skin (carotenodermia) that eventually resolves.
Beta carotene effects on reproductive health
Beta carotene is a precursor of Vitamin A, a group of retinoids that includes retinol, retinyl esters and retinoic acid. An excess intake of vitamin A or synthesized retinoids has been associated with birth defects such as eye, lung and heart deformities and pregnant women are advised not to take high doses of supplemental vitamin A.
However, the beta carotene precursor for vitamin A has not been associated with reproductive toxicity, even at large doses of 20 to 30 mg per day. Diets high in carotenid-rich foods also have not been associated with toxicity.
High levels of beta carotene do not cause vitamin A toxicity because the level of vitamin A in the body regulates the metabolic conversion of beta carotene to vitamin A. If the levels of vitamin A are high, there is a decrease in the conversion of beta carotene to vitamin A and vice versa.
Animal studies
No side effects of high-dose beta carotene have been observed in standard toxicity studies in experimental animals. Doses for acute toxicity (up to 5000 mg/kg body weight per day) and for chronic toxicity (up to 1000 mg/kg body weight per day for life) showed no ill effects in rats.
Doses for reproductive toxicity (up to 1000 mg/kg body weight per day for 3 generations of rats) also showed no toxic effects.
Further Reading