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Date of release: 10 May, 2010

Five-colors-a-day and cancer prevention


It has been long debated whether the quantity of fruits and vegetables ingested is associated with cancer risk. A new article brings the results of a multi-national, prospective European study, based on the EPIC cohort, which examined this issue in 143,000 men and 336,000 women who were followed for 8.7 years [1]. Dietary habits were estimated by questionnaires only once, at enrolment to the study. A total of 9600 men and 21,000 women were diagnosed with cancer during the follow-up period. The intake of fruits and vegetables was higher in Southern Europe than in Northern Europe: 231 g/day in Sweden, 511 g/day in Spain. Overall, quintile 5 of vegetable intake (> 307 g/day) was associated with a statistically significant 7% reduced risk for total cancer compared to quintile 1 (< 97 g/day). The corresponding figure for fruits was a 6% reduction in cancer risk in quintile 5 (> 367 g/day) compared to quintile 1 (< 90 g/day). Each increase of 100 g/day of total fruit and vegetable intake led to a 2% decreased risk for cancer. Note that the crude cancer rates differed from country to country, but the risk was comparable in men and women.

Comment

Twenty years ago, the National Cancer Institute developed the concept of ‘five-a-day’, quickly receiving the nickname ‘five-colors-a-day’, which was based on the belief that eating vegetables and fruits in adequate amounts (five servings, around 400 g/day) has beneficial effects on health and prevents major illnesses. While the association with cardiovascular diseases was well established [2], that for cancer was not. Based on its magnitude, the current study was aimed at resolving the dispute, but actually has left us with the same doubts. On the one hand, and due to the huge numbers, statistically significant results were recorded. However, from the clinical, practical aspect, a decrease in risk of just a few percentages may be meaningless. The investigators [1] and an Editorialist [3] rightly stated that potential limitations and biases should be taken into account, which may weaken the results or make the associations casual. For example, the assessment of ingested fruits and vegetables was based on a single, self-reported questionnaire at enrolment; thus no account was allowed for possible changes in eating habits during the follow-up. The study did not address specific cancers, although previous data indicated that certain fruits or vegetables might protect against certain types of cancers. Lycopene (tomatoes) and prostate cancer [4] serve as a good example. In conclusion, the ‘eat healthy’ campaigns and educational measures to promote the consumption of fruits and vegetables (especially green, leafy vegetables) are very important for the prevention of coronary heart disease, yet there might also be some cancer-related benefits for such a diet, although the results of the above-presented EPIC study should be interpreted with caution.

Comentario

Amos Pines
Department of Medicine T, Ichilov Hospital, Tel-Aviv, Israel

    References

  1. Boffetta P, Couto E, Wichmann J, et al. Fruit and vegetable intake and overall cancer risk in the European Prospective Investigation into Cancer and Nutrition (EPIC). J Natl Cancer Inst 2010;102:529-37. Published April 21, 2010.
    http://www.ncbi.nlm.nih.gov/pubmed/20371762

  2. Hung HC, Joshipura KJ, Jiang R, et al. Fruit and vegetable intake and risk of major chronic disease. J Natl Cancer Inst 2004;96:1577-84.
    http://www.ncbi.nlm.nih.gov/pubmed/15523086

  3. Willett WC. Fruits, vegetables, and cancer prevention: turmoil in the produce section. J Natl Cancer Inst 2010;102:510-11.
    http://www.ncbi.nlm.nih.gov/pubmed/20371763

  4. Kavanaugh CJ, Trumbo PR, Ellwood KC. The U.S. Food and Drug Administrations evidence-based review for qualified health claims: tomatoes, lycopene, and cancer. J Natl Cancer Inst 2007;99:1074-85.
    http://www.ncbi.nlm.nih.gov/pubmed/17623802