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Review
Nature 290, 201-208 (19 March 1981) | doi:10.1038/290201a0
Can dietary beta-carotene materially reduce human cancer rates?
R. Peto*, R. Doll†, J. D. Buckley‡ & M. B. Sporn§
Abstract
Human cancer risks are inversely correlated with (a) blood retinol and (b) dietary 
-carotene. Although retinol in the blood might well be truly protective, this would be of little immediate value without discovery of the important external determinants of blood retinol which (in developed countries) do not include dietary retinol or -carotene. If dietary -carotene is truly protective—which could be tested by controlled trials—there are a number of theoretical mechanisms whereby it might act, some of which do not directly involve its 'provitamin A' activity.
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