Carotene is a general term describing certain polyene hydrocarbons containing 40 carbon atoms. Three of these, a- , b- , and g-carotene, as well as some closely related oxygen-containing carotenoids, exhibit provitamin A activity. b-carotene is the most active of the carotenes and the only one which is available commercially. It is added to food, chiefly margarine, both as a coloring agent, and for its vitamin A potential. Early studies of the health aspects of "carotene" were performed with preparations of uncertain composition and purity. However, it is apparent from the sources of carotene utilized and the purification procedures adopted, that the active principle in these studies was largely b - carotene, so that the results are relevant to the present review. Since the development or synthetic b - carotene for commercial use in 1954, nearly all research on "carotene" has employed a crystalline and well-defined product.
The average daily intake of carotene from natural sources is estimated to be about 2mg per day which is equivalent to approximately 3300 IU of vitamin A. Substantially larger amounts may be ingested in diets rich in colored vegetables. The Recommended Dietary Allowance of vitamin A from all sources is 5000 IU for adults. Consumption information from various sources, suggests that the per capita daily intake of b - carotene added to foods is 0.2 to 0.3mg.
Doses several orders of magnitude greater than would conceivably be used as additives in food have proved nontoxic to various animal species given b- carotene orally in acute, short and long term studies. A single study suggested some impairment in neonatal skeletal development when 180 mg per kg or more of carotene were administered, daily to rats, but this study has not been confirmed.
When given in moderate amounts, carotene is readily converted to vitamin A. However, this conversion is limited when large amounts of carotene are administered. The regulatory mechanism has not been elucidated. Doses of 180 mg (300,000 IU) daily for 2 or more years have been taken orally by patients suffering from certain types of photosensitivity with no evidence of hypervitaminosis A or other harmful effects.
In the light of these considerations, the Select Committee concludes that: There is no evidence in the available information on carotene (b - carotene) that demonstrates, or suggests reasonable grounds to suspect, a hazard to the public when it is used at levels that are now current or that might reasonably be expected in the future.