O uso contínuo de multivitamínicos pode aumentar o risco de cancro de mama?

Pesquisadores da Suécia relataram um aumento de 19% do risco de aumento de câncer de mama em mulheres que tomam multi vitaminas. Os detalhes deste estudo foram publicados no dia 24 de Março de 2010 no American Journal. É importante lembrar que existem outros grandes estudos que não encontraram qualquer relação entre o consumo de multivitamínicos e o câncer de mama.

A maioria dos estudos têm mostrado que a administração rotineira de multivitaminas não parece desempenhar um papel positivo ou negativo na prevenção do câncer. No entanto, há bons dados sugerindo um papel preventivo com a suplementação de vitamina D para a prevenção do câncer de mama e colorretal.

O estudo mostra um aumento do risco de câncer de mama com o uso de multivitaminas. O estudo envolveu 35.329 mulheres com câncer. O mesmo estudo afirmou que o uso da vitamina fora associada com um risco aumentado de se desenvolver o câncer de mama. O risco estimado fora de 19% em usuários que tomaram as multivitaminas em comparação aos que não tomaram. Os pesquisadores declararam que a associação não diferencia significativamente pelo status dos receptores hormonais do tumor de mama.

Artigo na íntegra: Researchers from Sweden have reported a 19% increased risk of breast cancer in women taking multivitamins. The details of this study were published early online on March 24, 2010 in the American Journal or Clinical Nutrition.1 However, other large studies have not found such an association. Most studies have shown that the routine administration of multivitamins does not appear to play a positive or negative role in cancer prevention. However, there is good data suggesting a preventive role for vitamin D supplementation for prevention of colorectal and breast cancer. The study showing an increased risk of breast cancer with multivitamin use involved 35,329 cancer-free women who were enrolled in the Swedish Mammography Cohort in 1997. After a follow-up of an average of 9.5 years there were 974 cases of breast cancer in this cohort. These authors stated that “Vitamin use was associated with a statistically significant increased risk of breast cancer.” The overall increased risk was estimated to be 19% in users of multivitamins compared with nonusers. They also stated, “The association did not differ significantly by hormone receptor status of the breast tumor.”

Researchers involved in he Women’s Health Initiative have also looked at the role of multivitamin use and risk of cancer.2 This study involved 68,132 women who were followed for a median of eight years. “Multivariate-adjusted analyses revealed no association of multivitamin use with the risk of cancer.” The hazard ratio for breast cancer risk among multivitamin users in this study was 0.98. Researchers from the Netherlands evaluated the impact of multivitamin use and risk of breast cancer in a case-control study.3 This study involved 2,968 cases of breast cancer diagnosed between 2004 and 2007 and an equal number of controls. This study found no association between multivitamin supplement use and breast cancer risk.Comments: This is obviously a very important issue as multivitamin use is widespread among women. The divergent results of the newest Swedish study should prompt an evaluation of other databases to see if these results can be confirmed. Women should also be aware of the fact that there is very little data to substantiate the need for multivitamins if they are eating a healthy diet. However, the popularity of multivitamin use is likely to continue making evaluation necessary.

Reference:
1 Larsson SC, Akesson A, Bergkvist L, et al. Multivitamin use and breast cancer incidence in a prospective cohort of Swedish women. American Journal of Clinical Nutrition [early online publication]. March 24, 2010.

2 Neuhouser ML, Wassertheil-Smoller S, Thompson C, et al. Multivitamin use and risk of cancer and cardiovascular disease in the Women’s Health Initiative cohorts. Archives of Internal Medicine 2009;169:294-304.

3 Meulepas JM, Newcomb PA, Burnett-Hartman AN, et al. Multivitamin supplement use and risk of invasive breast cancer. Public Health Nutrition [early online publication].2009; Dec3:1-6.