CHINA – New study investigating dairy consumption and cancer risk in Chinese adults has discovered that higher intake was associated with increased risks of liver cancer and female breast cancer.
Previous studies have reported contrasting associations of dairy consumption with certain cancers, including a positive association with prostate cancer and inverse associations with colorectal and premenopausal breast cancers.
To fill in the knowledge gap, researchers from Oxford Population Health, Peking University, and the Chinese Academy of Medical Sciences, Beijing investigated over 510,000 participants in the China Kadoorie Biobank Study between 2004 and 2008.
They have published a new large-scale study in BMC Medicine which gives an insight into the findings and how dairy products affect the risk of cancer differently in Chinese people.
The results show that overall, 20.4% reported consuming dairy at least once per week (are regular consumers), consuming an average of 37.9 g/day and 80.8 g/day among all participants.
Additionally, eleven percent of participants consumed dairy products monthly and 69% never consumed dairy products.
Looking further into the links between dairy products and incidents of cancer cases, the team adjusted findings to family history, education, income, alcohol intake, smoking, physical activity, soy, fresh fruit intake, and body mass index.
During the study period, 29,277 new cancer cases were recorded, with regular consumers having a greater risk of developing liver and breast cancer. For each 50g/day intake, the risk increased by 12% and 17% respectively.
Regular dairy consumption was also associated with an increased risk of lymphoma, although this was not deemed statistically significant. No significant association was found for any other cancer type investigated.
While these study results do not prove causation, there are several plausible biological mechanisms that may explain these associations, according to the researchers.
They suggest that greater dairy consumption may increase levels of insulin-like growth factor-I (IGF-I), which promotes cell proliferation and has been associated with higher risks for several types of cancer.
Another instance is female sex hormones present in cow’s milk (such as estrogen and progesterone) may have a role in the increased risk of breast cancer, whilst saturated and trans-fatty acids from dairy products may increase the risk of liver cancer.
Associate Professor Huaidong Du, said: “Whilst our results suggest there may be a direct link between regular dairy consumption and certain cancers, it is important to be aware that dairy products are a source of protein, vitamins, and minerals.
It would not be prudent to reduce dairy consumption based solely on the results from the current study or without ensuring adequate intake of protein, vitamins, and minerals from other sources.”
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