On 18 April 2010, research published in the American Journal of Clinical Nutrition prompted media coverage regarding an association between use of multivitamins and breast cancer risk.
In 1997, over 35,000 Swedish women completed a questionnaire about their diet and lifestyle factors, including their use of dietary supplements such as multivitamins. Approximately nine and a half years later, researchers followed up the same group of women and 974 had been diagnosed with breast cancer.
After taking into account a number of risk factors for breast cancer such as age, family history, levels of physical activity, body mass index and alcohol consumption, the researchers found that women who reported using multivitamins had a 19 per cent increased risk of breast cancer compared with women who did not take multivitamins.
The researchers concluded that the use of multivitamins may increase breast cancer risk.
NBOCC* comment
This particular study shows an increased risk of breast cancer associated with multivitamin use. However, other studies in the area have found a decrease in breast cancer risk with multivitamin use. Overall, studies on multivitamin use and breast cancer risk are inconclusive.This Swedish study involves a large sample of women and a long period of follow-up; however it relied on women self-reporting their multivitamin use by a questionnaire. The study design leaves significant room for error in the participant’s reporting of their dietary supplement use.
Further research is needed to determine which vitamins in particular may impact on breast cancer risk, at what dosage and over what period of time, before any association between breast cancer risk and multivitamin use can be determined.
The majority of women should aim to fulfil their daily vitamin needs through a balanced diet that includes plenty of fresh fruit and vegetables. Some women may be advised to take vitamin supplements based on their individual health needs and should continue to take these as prescribed by their doctor. Women concerned about their use of vitamins, including multivitamin supplements, should discuss this with their doctor.
There are some simple lifestyle changes every woman can make, based on well-established evidence, to reduce breast cancer risk. NBOCC* recommends women limit their alcohol intake, maintain a healthy body weight, particularly after menopause, and participate in regular physical activity.
Click here for more information about breast cancer risk factors, and to assess your personal level of breast cancer risk.