Research: VERHOEVEN and colleagues,

Listed in Issue 21

Abstract

VERHOEVEN and colleagues, TNO Nutrition and Food Research Institute, Zeist The Netherlands examined the association between breast cancer risk and intake of vitamins C, E retinol, beta-carotene, dietary fibre, vegetables, fruit and potatoes.

Background

Methodology

The Netherlands Cohort Study involved 62,573 women aged 5569 years. Follow-up was for 4.3 years.

Results

650 incident breast cancer cases were identified. Risk of breast cancer was not influenced by intake of beta-carotene, vitamin E, dietary fibre, vitamin C supplements, vegetables or potatoes. There was a non-significant inverse association between fruit consumption and breast cancer, a small reduction in risk with increasing intake of dietary vitamin C and a weak positive association observed with retinol. In subjects with a high intake of polyunsaturated fatty acids (PUFAs) there was a non-significant inverse association with both beta-carotene and vitamin C intake and risk of breast cancer.

Conclusion

These results do not suggest a strong role, if any, for intake of vitamins C, E, beta-carotene, retinol, dietary fibre, vegetables, fruit and potatoes in the aetiology of breast cancer.

References

Verhoeven DT et al. Vitamins C and E, retinol, beta-carotene and dietary fibre in relation to breast cancer risk: a prospective cohort study. Br J Cancer 75(1): 149-55. 1997.

Comment

The above study highlights how tortured epidemiological research can be, in attempting to obtain a clear-cut answer regarding dietary intake and risk of cancer. Many studies carried out internationally have shown significant reductions in cancer risk, often as high as 50%, in people eating more fruit and vegetables. However, this study did not show any significant effect, apart from some weak associations. Perhaps the difficulty lies with the age of the study participants (5569 years). Cancer usually develops over many years as a result of multi-faceted genetic and environmental events. It may be extremely difficult to detect differences at such an advanced age and of course there is no way of knowing how these subjects ate during the previous 5 or more decades. Another potential difficulty is the relatively short period of follow-up (4.3 years). It could be that if this study had run for 10 years, dietary associations could have been stronger. A further problem may lie in the use of dietary questionnaires to estimate consumption of these foods. I realise that I may have a occupational bias (being a molecular biologist) against using large epidemiological studies to study cancer risk in European populations which are cosmopolitan, have such diverse ethnic backgrounds and dietary habits and do not, in the main, suffer from severe dietary deficiencies and have been exposed to the plethora of environmental contaminants present in the industrialised world.

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