(Humans fed small beta-carotene supplements do not experience reduced mortality rates. This is line with animal studies which have also found no benefit for such small supplements.
The case is different with very large supplements in experimental animals A human consuming about 2000 calories/day of the hamster chow used below would be ingesting about 5 grams of beta-carotene/day. The 98% survival at 69 weeks is a record for male Syrian golden hamsters.)
Carcinogenesis 15(1): 133-136 1994
The study described in this paper was primarily conducted to identify the cell types involved in the formation, progression and regression of metaplastic changes in the repiratory tract epithelium of hamsters after intratracheal intubations with benzo[a]pyrene. Furthermore, the role of vitamin A and beta-carotene in these processes was studied. In the course of the study a remarkable effect of dietary beta-carotene on survival of hamsters became a subject of investigation. Hamsters were fed diets with various levels of vitamin
A or beta-carotene and were treated intratracheally with a suspension of benzo[a]pyrene with ferric oxide in saline. The tumour response of the respiratory tract was very low (2.8%) and hyper- and metaplasia of respiratory epithelium were virtually absent. However, an interesting observation was an exceptionally low mortality of only 2% after 69 weeks in the group of hamsters fed a high beta-carotene diet (1% w/w), whereas in the other groups mortality after 69 weeks amounted to 25%. Although the exact cause of death of most of the hamsters could not be established, a 40% reduction of lipid peroxidation in the livers was found in the high beta-carotene group. Moreover, in this group the degree and incidence of nephrosis and of focal mineralization of kidneys and heart were lower than in the other groups. These favourable effects of the high beta-carotene diet may have contributed to the unusually high survival rate in hamsters fed this diet. Further studies are planned to verify and study this observation.