Consider these two headlines published in the last couple of days:
New Zealand Herald: Major research finds link between multi-vitamin pills and breast cancer
BusinessWeek: Supplements might reduce breast cancer risk
Both are top search results on Google News, but don’t they seem to contradict each other? Let us look a little more closely at the stories. Here’s the intro for the Herald story:
Women who regularly take multi-vitamin pills face a much higher risk of breast cancer, a study has found.
And here’s BusinessWeek‘s intro:
Women who take multivitamin tablets along with calcium supplements seem to have a reduced risk of developing breast cancer, new research suggests.
Okay, so they definitely seem to contradict each other – or does the “along with calcium supplements” mentioned in the BusinessWeek story make all the difference: ie is taking calcium supplements along with multivitamin tablets rather than just multivitamin tablets alone really the difference between a woman increasing or decreasing the risk of her developing breast cancer?
The answer is no. BusinessWeek continues:
Taking a multivitamin tablet reduced the risk of tumors by about 30 percent, while calcium supplements reduced the risk by 40 percent, the study authors noted.
So calcium is a breast cancer fighter according to this research, but so too are multivitamins, which the Herald suggests can increase the risk of developing breast cancer. The study referred to by BusinessWeek, Associated Press and others is from researchers at Ponce School of Medicine in Ponce, Puerto Rico. It involved the authors comparing “vitamin and calcium intakes of 268 women with breast cancer and 457 women without breast cancer, all in Puerto Rico”. The research was presented at the American Association for Cancer Research annual conference in Washington, D.C. over the weekend.
The Herald report and numerous others refer to a different piece of research conducted by Sweden’s Karolinska Institute and published in the American Journal of Clinical Nutrition. This 10-year study involved more than 35,000 women, and researchers discovered those who regularly took a multi-vitamin pill “increased the risk of developing a tumour by 19 per cent”.
Lack of context
What appears to have happened here is two pieces of research emerged over the same weekend with contradictory conclusions. One is a very large study, the other relatively small. But I haven’t found a story on Google News that refers to both stories, weighing up the results and putting each in context alongside the rival study. As a result, anyone browsing the web is likely to see directly contradictory stories examining the same issue – whether multivitamins impact the risk of a woman developing breast cancer.
Just posted, by the ABC News in Australia, this piece which quotes head of surgical oncology at Newcastle’s Calvary Mater Hospital, Professor John Forbes”
He says the results of the Swedish study are barely statistically significant and do not indicate what the outcome might be for women taking fewer vitamin tablets.