Dr Kostas Tsilidis is a Senior Lecturer in Cancer Epidemiology at Imperial College London. He also holds an Associate Professor position in Epidemiology at the University of Ioannina School of Medicine in Greece. Since January 2020, he is the co-Principal Investigator of the World Cancer Research Fund Continuous Update Project at Imperial College London.
Why was this research done?
Breast cancer is the most common cancer in women with an estimated 2.1 million new cases and over half a million deaths worldwide in 2018. Established risk factors for breast cancer in postmenopausal women include overweight and obesity, levels of oestrogens and androgens in blood, and reproductive factors such as menstruation starting at a younger age, late menopause, late age at first pregnancy, and hormone replacement therapy.
However, the role of nutrition in breast cancer development is unclear except for the link between drinking alcohol and an increased risk of breast cancer. To date, there has been little research on how the levels of minerals and vitamins in blood affects the risk of breast cancer.
So, we looked for associations between blood levels of 11 minerals or vitamins (beta-carotene, calcium, copper, folate, iron, magnesium, phosphorus, selenium, vitamin B6, vitamin B12 and zinc) with breast cancer risk using a technique called Mendelian Randomisation. This technique estimates an individual’s tendency to have low or high blood levels of these minerals and vitamins based on his/her own genome.
What did we find?
Our research was conducted using information from the Breast Cancer Association Consortium. We looked at the genetic tendency of vitamins and mineral levels of 122,977 women diagnosed with breast cancer and 105,974 women without this disease.
We found that having a genetic tendency for higher blood levels of magnesium was linked to a higher risk of developing breast cancer. None of the other minerals and vitamins were associated with breast cancer risk.
What do the results mean?
Previous research on the link between either dietary or blood magnesium and the risk of breast cancer is scarce and inconclusive. Some studies in animals suggest that magnesium has a protective effect in the early phases of cancer development but may promote tumour growth in later phases of the disease. While our research seems to suggest higher levels of magnesium increases the risk of breast cancer, future studies are warranted to replicate this finding and to disentangle the potential underlying biology of why magnesium may increase the risk.