As detailed in their study, Lactose intolerance and risk of lung, breast and ovarian cancers, researchers from Lund University and Region Skåne discovered the chance of lung cancer, breast cancer and ovarian cancer were "significantly" lower in people with lactose intolerance.
The risk of cancer in the siblings and parents of the identified lactose intolerant individuals, however, was more similar to those in the general population.
Lactose intolerance occurs when the small intestine does not produce enough lactase, an enzyme essential to digest a natural sugar found in milk called lactose. Up to 75% of the world's population is thought to suffer from lactose intolerance.
Tracking indicence ratios
The three-man research team scoured Swedish registers linked to the Swedish Cancer Registry to calculate standardized incidence ratios (SIR), which are used to determine whether the occurrence of cancer in a relatively small population is high or low.
A total of 22,788 individuals with lactose intolerance were identified in the registers.
A SIR of 0.55 was calculated for lung cancer among the lactose intolerant individuals - indicating a 45% decrease in risk.
They meanwhile calculated a SIR of 0.61 for ovarian cancer and 0.79 for breast cancer.
These findings, according to the researchers, suggest the identified protective effect against the three forms of cancer "may be related to their specific dietary pattern".
“We found that people with lactose intolerance, who typically consume low amounts of milk and other dairy products, have a reduced risk of lung, breast and ovarian cancers,” said Jianguang Ji, associate professor at Lund University.
“The risk of cancer was not reduced in relatives of people with lactose intolerance, which indicates that protection against these cancers is related to diet. However, it would be wrong to conclude that milk is a risk factor for these cancers.”
Source: British Journal of Cancer doi:10.1038/bjc.2014.544
Title: Lactose intolerance and risk of lung, breast and ovarian cancers: aetiological cues from a population-based study in Sweden
Authors: J Ji, J Sundquist, K Sundquist.