Changes in serum carotenoids in subjects with colorectal adenomas after 24 mo of β-carotene supplementation

The effect of β-carotene supplementation on major serum carotenoid fractions (lutein/zeaxanthin, β-cryptoxanthin, lycopene, α-carotene, and β-carotene) was investigated in 224 people with colorectal adenomas (139 men, 85 women) recruited for the Australian Polyp Prevention Project (APPP). Each subject was randomly assigned to take either 20 mg β-carotene/d or placebo over 24 mo. Besides the expected increase in serum concentration of β-carotene (1073% in men, 839% in women), lycopene (176% in men) and α- carotene (211% in men and 166% in women) concentrations were also increased after body mass index, baseline concentration, change in respective carotenoid intake, and other confounding factors were adjusted for. The increase in serum concentrations of these carotenoids after β-carotene supplementation suggests that β-carotene may interact biologically with other carotenoids and such interaction would need to be taken into consideration when the protective effect of β-carotene supplementation for cancer or other diseases is examined.