Can dietary beta-carotene materially reduce human cancer rates?

@article{Peto1981CanDB,
  title={Can dietary beta-carotene materially reduce human cancer rates?},
  author={Richard Peto and Richard Doll and Jonathan D. Buckley and Michael B. Sporn},
  journal={Nature},
  year={1981},
  volume={290},
  pages={201-208}
}
Human cancer risks are inversely correlated with (a) blood retinol and (b) dietary β-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 β-carotene. If dietary β-carotene is truly protective—which could be tested by controlled trials—there are a number of theoretical mechanisms whereby it might act… 

A note on the role of dietary retinol and carotene in human gastro‐intestinal cancer

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There was no deficit among cases in the intake of retinol‐containing food items whereas several of the main carotene‐containing fruits and vegetables were eaten less often among cases than among controls.

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TLDR
The hypothesis that increasing retinoid intake in humans would reduce the risk of lung cancer must be tested in humans and should be undertaken initially among those at highest risk.

Dietary carotenoids and lung cancer: a review of recent research.

TLDR
Promising areas of investigation include characterizing biologic activities of carotenoids and gaining further insight into whether they may serve primarily as markers for a healthy lifestyle or diet.

Vitamin A: evidence for its preventive role in human cancer.

Both the provitamin beta-carotene and natural vitamin A and its derivatives (the retinoids) are being proposed as potential chemopreventive agents. The biochemistry and pharmacology of vitamin A

Significance of β-Carotene in Cancer

TLDR
The results in human studies where β-carotene has been measured show that it is strongly associated with the consumption of green and yellow vegetables, so other dietary protective factors, such as dietary fiber, low intake of animal protein or fat, and antioxidants other than β-Carotene, cannot be excluded.

Does beta-carotene prevent cancer? A critical appraisal

Nutrition in cancer prevention.

TLDR
Targeting initial intervention studies in those with explicit genetic predisposition to cancer may have both greater cost-effectiveness and fewer ethical difficulties than do similar studies in the general public.

Differences between carotene and retinol

  • R. Peto
  • Medicine
    Proceedings of the Nutrition Society
  • 1983
TLDR
If dietary vitamin A intake is at all relevant to cancer prevention in developed countries it is more likely to act via modification of blood carotene, rather than blood retinol, levels, then although any factors that importantly determine blood Retinol levels may be important modifiers of cancer onset rates, these factors are not yet understood.
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References

SHOWING 1-10 OF 50 REFERENCES

Dietary vitamin a and human lung cancer

  • E. Bjelke
  • Medicine
    International journal of cancer
  • 1975
Five‐year follow‐up results for 8,278 men who in mail surveys had reported their cigarette smoking and dietary habits showed: (1) an index for vitamin A intake to be negatively associated with lung

Low-fiber intake as an etiologic factor in cancer of the colon.

TLDR
Findings support the hypothesis that low-residue foods play an etiologic role in colon carcinogenesis and a mechanism related to the possible potential carcinogenic properties of degraded biliary compounds may be implicated.

Dietary risk factors in human bladder cancer.

TLDR
The findings of this investigation are consistent with tumor inhibition by retinoids in animal studies and the low risk associated with vitamin A in epidemiologic studies of lung cancer.

Vitamin A, zinc and lung cancer.

TLDR
Serum vitamin A concentration was measured in 26 newly diagnosed lung-cancer patients and found to be significantly lower than those of patients of similar age with either non-malignant lung or non-lung diseases, suggesting that low levels of zinc might reduce the synthesis of RBP and thus reduce the mobilization of vitamin A from the liver.

EFFECTS OF β‐CAROTENE ON ULTRAVIOLET INDUCED CANCER FORMATION IN THE HAIRLESS MOUSE SKIN

TLDR
The purpose of this study was to examine the potential influence of 8-carotene on UV induced skin cancer formation under controlled conditions.

Cancers among users of preparations containing vitamin A. A case‐control investigation

TLDR
There was no convincing evidence that regular consumption of Vitamin A preparations protected against the development of cancer, but there was a suggestion of a negative association among men but not among women and the results offer encouragement for further epidemiologic studies of the possible protective role of vitamin A against cancer.

Vitamin A transport in human vitamin A toxicity.

TLDR
Clinical data support conclusions from detailed studies with hypervitaminotic rats, which suggest that vitamin A toxicity occurs when excessive amounts of vitamin A are presented to cell membranes in association with plasma lipoproteins, rather than specifically bound to retinol-binding protein.

The hypercarotenemia in anorexia nervosa: a comparison of vitamin A and carotene levels in various forms of menstrual dysfunction and cachexia.

TLDR
The findings suggest that the hypercarotenemia in anorexia nervosa may be due either to increased carotene and vitamin A intake or an acquired defect in the utilization or metabolism of vitamin A.