Blackmores advises consumers not to be alarmed by media reports today on a study claiming multivitamin users have an increased risk of developing breast cancer.
The results of a Swedish observational study[1], published in the American Journal of Clinical Nutrition, suggest that there may be an association between the use of multivitamins and an increased risk of breast cancer.
The results of this study need to be kept in perspective; it is important to remember that this study does not indicate that taking a multivitamin supplement will cause or increase the risk of breast cancer.
“The risk for those women who took supplements more than seven times a week was actually lower than those women who took supplements less than seven times a week, which is difficult to make sense of, and was not mentioned by the authors,” said Blackmores’ Director of Research Chris Oliver.
The body of evidence is not conclusive and these findings conflict with other multivitamin studies. For example, a large epidemiological study[2] conducted by Harvard researchers found that multivitamin use was not related to overall risk of breast cancer and that multivitamin supplement use may, in fact, reduce the risk of breast cancer in some groups of women.
The authors of the Swedish paper noted that not all other epidemiological studies had observed an association between breast cancer and multivitamin use. Even the evidence for an involvement of most single nutrients in breast cancer was contradictory.
The authors themselves noted that there are several limitations associated with their study.
1) Dietary supplement use was assessed by using a self-administered questionnaire which may be subject to difficulty recalling details and can lead to errors in classification by the researchers.
2) Brands of products taken and the composition of these products were not known and therefore the researchers we were not able to identify the components of multivitamins that may be responsible for the possible association with the potential increase in risk.
3) Another limitation is the observational design of the study which cannot prove causation. The researchers tried to account for known breast cancer risk factors, however it is possible that not all factors were accounted for and this may have impacted the findings.
Blackmores advocates that vitamin supplements are part of maintaining good health and not a replacement for a balanced diet and healthy lifestyle.
Blackmores supports the call by the author for further research into nutritional medicine to build on the growing body of evidence on the role of multivitamins in a balanced lifestyle and for maintaining good health.
For further information, please contact Blackmores’ free Naturopathic Advisory Service on 1800 803 760.
1. Larsson et al. Multivitamin use and breast cancer incidence in a prospective cohort of Swedish women. March 24: 10.3945/ajcn.2009.28837
2. Ishitani et al. A prospective Study of Multivitamin Supplement Use and Risk of Breast Cancer. DOI:10.1093/aje/kwn027