People who regularly eat and drink dairy products may be at higher risk of developing certain types of cancer, according to a new study.
Data collected on nearly 30,000 cancer cases among 500,000 Chinese adults found that regular consumption of dairy products was associated with significantly higher risks of liver and breast cancer in women. For every 50g taken per day, the risk increased by 12% and 17% respectively.
However, there was no association between dairy consumption and colorectal cancer, prostate cancer, or any other type of cancer studied. The researchers say these results may not be the same for non-Western populations where the amounts and types of dairy consumption and the ability to metabolize dairy differ significantly.
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Scientists believe that eating more dairy products may increase levels of insulin-like growth factor (IGF-I), which promotes cell proliferation and has been linked to higher risks for several types of cancer . Potentially, they claim that the female sex hormones found in cow’s milk, such as estrogen and progesterone, may play a role in the increased risk of breast cancer, while the saturated and trans fatty acids in dairy products may increase the risk of liver cancer.
Dr Maria Kakkoura, nutritional epidemiologist at Oxford Population Health and first author of the study, said: “This was the first major study to investigate the link between dairy products and cancer risk in a Chinese population. Further studies are needed to validate these current findings, establish whether these associations are causal, and investigate potential underlying mechanisms involved. »
Although the average level of consumption of dairy products in China is still much lower than that of European countries, it has increased rapidly over the past decades. Associate Professor Huaidong Du, Principal Investigator at Oxford Population Health and one of the study’s co-lead authors, added: “Although our results suggest there may be a direct link between regular consumption of milk products 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 the consumption of dairy products based on the results of the study alone. present or without ensuring an adequate intake of protein, vitamins and minerals from other sources.
The results of the large-scale study, conducted by Oxford Population Health, Peking University and the Chinese Academy of Medical Sciences in Beijing, have been published in BMC Medicine. The data was collected from more than 510,000 participants in the China Kadoorie Biobank study.
The participants (59% female, 41% male) came from 10 geographically diverse regions across China and joined the study between 2004 and 2008. None had a history of cancer. During recruitment, each participant, aged 30 to 79, completed a questionnaire on the frequency of consumption of different food products, including dairy products.
The researchers classified the participants into three groups: regular dairy consumers (at least once a week), monthly dairy consumers, and people who never or rarely consumed dairy products (non-consumers).
Participants were followed for about 11 years on average, and researchers used data from national cancer and death registries as well as health insurance records to identify new cancer diagnoses. Fatal and non-fatal events were included.
Data analyzes took into account a range of other factors that may influence cancer risk, including age, sex, region, family history of cancer, socioeconomic status (i.e. (i.e. education and income), lifestyle factors (i.e., physical activity, soy consumption, and fresh fruit consumption), body mass index, chronic virus infection hepatitis B (for liver cancer) and female reproductive factors (for breast cancer).