The study, published online in the International Journal of Cancer, said that since a positive correlation between ovarian cancer risk and the consumption of milk products and lactose was first reported in 1989, many epidemiological studies have further examined the relationship. However, these studies have yielded conflicting conclusions.

Susanna C. Larsson, of the National Institute of Environmental Medicine at the Karolinska Institute in Sweden, found case studies of low-fat milk consumption negatively associated, and whole milk consumption positively associated, with the risk of ovarian cancer. However case studies offered no support for the involvement of lactose in the development of ovarian cancer.

Cohort studies revealed a 13 percent increase in ovarian cancer risk with a daily increase of 10 grams of lactose, the approximate amount in one glass of milk. When case-control and cohort studies were considered in combination, yogurt consumption was associated with a non-significant increase in cancer risk, while cheese was not associated with risk.