Open AccessBeta Carotene: From Biochemistry to Clinical Trials
Author(s) -
Pryor William A.,
Stahl Wilhelm,
Rock Cheryl L.
Publication year - 2000
Publication title -
nutrition reviews
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.958
H-Index - 150
eISSN - 1753-4887
pISSN - 0029-6643
DOI - 10.1111/j.1753-4887.2000.tb07810.x
Subject(s) - beta carotene , clinical trial , medicine , antioxidant , physiology , cancer prevention , vitamin , vitamin e , retinol , disease , carotene , randomized controlled trial , cancer , lung cancer , biology , food science , biochemistry
Three large‐scale clinical trials tested the effects of supplemental 8‐carotene on the risk for chronic diseases such as cancer. The populations involved were Finnish male heavy smokers (the Alpha Tocopherol Beta Carotene [ATBC] trial), male asbestos workers and male and female heavy smokers (Beta‐Carotene and Retinol Efficacy Trial [CARET]), and US. male physicians, 11% of whom were current smokers (Physician's Health Study). All three trials concluded that 8‐carotene provided no protection against lung cancer; however, quite unexpectedlK two of the trials found a higher risk for lung cancer for those subjects given 8‐carotene compared with those that were not. Several authors concluded from these 8‐carotene trials that the protective effects of antioxidants against chronic disease are not as great as had been hoped. As reviewed here, however, 8‐carotene may or may not be an antioxidant; it certainly differs in many respects from the prototypical antioxidant, vitamin E. In any case, the majority of 8‐carotene's effects in vivo are probably not derived from any antioxidant properties that it may possess, but rather from its effect on a number of biochemical systems. Whether taking supplemental antioxidants can reduce the risk for chronic diseases remains to be established, although the case for vitamin E and heart disease appears strong. However, the association between eating a diet sufficient in fruits and vegetables and reduced risk for a number of diseases is consistent. There is no evidence at present that consuming small amounts of supplemental 8‐carotene, i.e., amounts in foods or in a multivitamin tablet, is unwise for any population. The role of supplementation, however, particularly at high levels, with compounds that may be antioxidants but that are less well understood than vitamin E (e.g., carotenoids, plant polyphenols, and other phytochemicals), is less clear. The surprising results of the ATBC and CARET trials are a red flag, signaling the need for further research; a number of areas for future work are suggested here. Future research should lead to a clearer understanding of the effects of 8‐carotene and other phytochemicals, as well as to more refined strategies for intervention, with important clinical and public health implications.