Scientists from the University of Oxford and elsewhere found that dairy consumption is linked to higher cancer risks.
Dairy products or milk products, also known as lacticinia, are food products made from milk. The most common dairy animals are a cow, water buffalo, nanny goat, and ewe.
Dairy products include common grocery store food items in the Western world such as yogurt, cheese, and butter.
The type of fat found in dairy is saturated and, because we eat dairy foods regularly, this can add up. On average, dairy products make up about a quarter of the saturated fat we eat.
Previous studies of in western countries have found inconsistent links between dairy consumption and certain cancers.
For example, some research showed a positive link with prostate cancer while others found inverse links with colorectal and breast cancers.
However, there are limited data from China where cancer rates and levels of dairy consumption differ importantly from those of people in western countries.
In the study, the team examined half a million adults from ten areas across China during 2004–2008.
They checked how these people consumed major food groups, including dairy products through surveys and interviews.
During a follow-up of 11 years, there were 29,277 incident cancer cases were found among the 510,146 participants who were free of cancer at the beginning.
The researchers found that 20.4% of participants reported consuming dairy products (mainly milk) regularly, with an estimated mean consumption of 80.8 g/day among regular consumers and of 37.9 g/day among all participants.
The team found strong links between dairy consumption and risks of total and certain site-specific cancers, including liver cancer and breast cancer.
They did not find strong associations between dairy consumption and colorectal cancer or other site-specific cancers.
There was a weak link between dairy intake and lymphoma (cancer that begins in cells of the lymph system)
The team concluded that in Chinese people who have lower dairy consumption than western people, higher dairy intake is linked to higher risks of liver cancer, breast cancer, and possible lymphoma.
They suggest several factors may explain the links between dairy intake and cancer risks. First, higher dairy intake may lead to higher insulin-like-growth factor-I, which plays a key role in cancer development.
Second, the relatively high content of branched-chain amino acids, and lactose (which provides galactose) in milk could activate and enhance cancer development.
Third, saturated fat and trans fat in dairy products are linked to insulin resistance and may increase liver cancer risk.
Fourth, dairy products may change gut health in people who are lactose intolerant and may increase the risk of diseases, such as cancer.
The research is published in BMC Medicine and was conducted by Maria G. Kakkoura et al.
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