First major study to investigate dairy consumption and cancer risk in Chinese adults has found that greater intake was associated with higher risks of liver cancer and female breast cancer.

原创翻译:龙腾网 转载请注明出处

Overall evidence to date on whether eating dairy products affects the risk of cancer has been inconsistent. Studies on Western populations indicate that dairy products may be associated with a lower risk of colorectal cancer and a higher risk of prostate cancer, but have found no clear lix for breast or other types of cancer.* These results, however, may not be the same for non-Western populations, where amounts and types of dairy consumption and ability to metabolise dairy products differ greatly.


For instance, in China there is very little consumption of cheese and butter, and the consumption of milk and yoghurt is also far lower than Western populations. In addition, most Chinese adults cannot properly metabolise dairy products due to lack of lactase, a key enzyme for breaking down the milk sugar lactose.**


To establish whether dairy products affect the risk of cancer differently in Chinese people, researchers from Oxford Population Health, Peking University, and the Chinese Academy of Medical Sciences, Beijing, have today published the results of a new large-scale study in BMC Medicine. This collected data from over 510,000 participants in the China Kadoorie Biobank Study.

为了确定乳制品对中国人患癌症风险的影响是否不同,来自牛津人口健康、北京大学和北京中国医学科学院的研究人员今天在BMC医学杂志上发表了一项新的大规模研究结果。 该研究收集了中国嘉道理生物银行研究的51万多名参与者的数据。

The participants (59% female, 41% male), who came from ten geographically diverse regions across China and joined the study between 2004 and 2008, had no previous history of cancer. When recruited, each participant (aged 30-79 years) completed a questionnaire about how frequently they consumed different food products, including dairy products. The researchers categorised 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-up for an average of around 11 years, and the researchers used data from national cancer and death registries as well as health insurance records to identify new cancer diagnoses. Both fatal and non-fatal events were included. The data analyses took into account a range of other factors that can affect cancer risk, including age, sex, region, family history of cancer, socio-economic status (i.e. education and income), lifestyle factors (i.e. alcohol intake, smoking, physical activity, soy consumption and fresh fruit intake), body mass index, chronic hepatitis B virus infection (for liver cancer), and female reproductive factors (for breast cancer).

研究人员对参与者进行了平均约11年的跟踪调查,研究人员根据国家癌症和死亡登记以及健康保险记录的数据来确定新的癌症诊断。研究收集了所有致命和非致命案例。数据分析考虑了一系列可能影响癌症风险的其他因素,包括年龄、性别、地区、癌症家族史、社会经济地位(即教育和收入)、生活方式因素(即饮酒、吸烟、体育活动、大豆消费和新鲜水果摄入)、身体质量指数、 慢性乙型肝炎病毒感染(肝癌)和女性生殖因素(乳腺癌)。

The study found:


· Overall, around a fifth (20%) of the participants consumed dairy products regularly (primarily milk), 11% consumed dairy products monthly, and 69% were non-consumers. The average consumption was 38g per day overall in the whole study population and 81g per day among regular dairy consumers (compared with an average consumption of around 300g per day in participants from the UK Biobank).


· During the study period 29,277 new cancer cases were recorded, with the highest rate being for lung cancer (6,282 cases), followed by female breast (2,582 cases), stomach (3,577 cases), colorectal (3,350 cases) and liver cancer (3,191 cases).


· People who consumed dairy products regularly had significantly greater risks of developing liver and breast cancer. For each 50g/day intake, the risk increased by 12% and 17% respectively.


· Regular dairy consumption was associated with an increased risk of lymphoma (though this was not statistically significant).


· There was no association between dairy intake and colorectal cancer, prostate cancer, or any other type of cancer investigated.***

原创翻译:龙腾网 转载请注明出处

Both liver and breast cancer are among the most common types of cancer in China, accounting for around 393,000 and 368,000 new cancer cases each year respectively. While these study results do not prove causation, there are several plausible biological mechanisms that may explain these associations, according to the researchers. Greater dairy consumption, for instance, 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. Potentially, female sex hormones present in cow’s milk (such as oestrogen 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. For the majority of Chinese people who do not produce enough lactase, dairy products may also be broken down into products that affect cancer risk.

肝癌和乳腺癌都是中国最常见的癌症,每年分别约有39.3万和36.8万新发癌症病例。虽然这些研究结果没有证明因果关系,但根据研究人员的说法,有几种貌似合理的生物机制可以解释这些联系。例如,更多的乳制品消费可能会增加胰岛素样生长因子- i (IGF-I)的水平,它能促进细胞增殖,并与几种癌症的更高风险有关。牛奶中的雌性激素(如雌激素和孕酮)可能会增加患乳腺癌的风险,而奶制品中的饱和脂肪酸和反式脂肪酸可能会增加患肝癌的风险。 对于大多数不能产生足够乳糖酶的中国人来说,乳制品也可能被分解成影响癌症风险的产品。

Dr Maria Kakkoura, Nutritional Epidemiologist at Oxford Population Health, and the first author of the study, said: ‘This was the first major study to investigate the lix between dairy products and cancer risk in a Chinese population. Further studies are needed to validate these current findings, establish if these associations are causal, and investigate the potential underlying mechanisms involved’.


Although the average level of dairy consumption in China remains much lower than in European countries, it has risen rapidly in recent decades.


Associate Professor Huaidong Du, Senior Research Fellow at Oxford Population Health, and one of the senior co-authors of the study, added: ‘Whilst our results suggest there may be a direct lix 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.’