Eating less meat associated with reduced cancer risk

• Researchers are exploring diet as a possible factor in the development of cancer.
• Previous research has indicated that eating meat is associated with a higher risk of some types of cancer.
• A new study has found that people who eat less meat have a lower risk of getting all types of cancer.
• The study, however, cannot prove cause, and the association between meat consumption and cancer risk may be due to other variables.

Researchers from the University of Oxford in the United Kingdom recently released the results of a large study that investigated the effect of varying levels of meat consumption on the likelihood of developing cancer.

The study found that vegetarians, pescatarians, and people who eat little meat have a significantly reduced risk of developing cancer.

The authors of the study analyzed statistics regarding cancer cases in general and also took a close look at the effect of meat eating on three of the most common cancers: postmenopausal breast cancer, prostate cancer, and colorectal cancer.

The study’s lead author is Cody Watling, a DPhil student at the Cancer Epidemiology Unit at the University of Oxford’s Nuffield Department of Population Health. He told Medical News Today:

“Our findings add further evidence that following a vegetarian, pescatarian, or low meat eating diet may be associated with a lower risk of being diagnosed with cancer. These findings also suggest that cancer risk for different diet groups may be different by cancer types.”

The study appears in BMC Medicine.

A large study group

The researchers followed 472,377 individuals in the UK Biobank database over an average period of 11.4 years.

None of the participants, who were aged 40–70 years when the team recruited them between 2006 and 2010, had a cancer diagnosis at the beginning of the study period. Over the course of the study, individuals reported their meat intake to the researchers.

The researchers divided the study cohort into four groups:

• Meat eaters reported eating processed meat, poultry, or red meat — including beef, pork, and lamb — more than five times each week. There were 247,571 individuals in this group, representing 52.4% of the total study population.
• Low meat eaters ate the same foods but a maximum of five times each week. Of the study population, 43.5%, or 205,385 people, were in this group.
• Fish eaters, who ate fish but not meat, accounted for 10,696 individuals, or 2.3% of the study population.
• Vegetarians and vegans, who ate neither meat nor fish, constituted 1.8% of the entire cohort, or 8,685 people.

Watling said, “Due to the large number of cancer cases in the UK Biobank, we were able to look at common cancer types in relation to diet groups, despite the low number of vegetarians and pescatarians, and explore this association further.”

At the end of the study period, 54,961 people had developed cancer of some type. The researchers noted 5,882 cases of colorectal cancer, 9,501 cases of prostate cancer, and 7,537 cases of postmenopausal breast cancer.

Lowering the risk of cancer

With the meat eating group serving as a baseline, the researchers calculated the risk of developing cancer for the other three groups.

The data showed that the vegetarian and vegan group was 14% less likely to develop cancer than the other groups.

The fish eaters were 10% less likely to get cancer, and the low meat eaters reduced their risk by 2%.

Postmenopausal women who were vegetarian had an 18% lower risk of breast cancer, while pescatarian and vegetarian men had a 20% and 31% lower risk, respectively, of prostate cancer. When the study authors looked at colorectal cancer, they found that low meat eaters had a 9% lower risk of developing the disease, which, they note, is consistent with prior research.

Behind the data

The authors write:

“It is not clear whether the other differences observed for all cancers and for prostate cancer reflect any causal relationships or are due to other factors, such as residual confounding or differences in cancer detection.”

Among these potential confounders is body mass index (BMI). When the researchers factored in BMI, the reduction in the risk of breast cancer for vegetarian women became insignificant.

Watling explained to MNT, “BMI would be a potential confounder if differences in BMI by diet groups are not due to dietary differences.”

“For example,” said Watling, “maybe vegetarians exercise more than meat eaters and maintain a healthy BMI as a result.”

Watling pointed out that “there are differences in BMI by diet group, and higher BMI is associated with higher cancer risk.”

“However,” he added, “BMI may also be a mediator if differences in BMI by diet groups are, in fact, due to dietary differences. This is hard to disentangle, as you may suspect. As such, we considered BMI as both a potential confounder and a potential mediator in our analyses.”

For now, Watling suggested:

“My recommendations would be for individuals to limit the intake of processed and red meat in their diet and consume a diet rich in whole grains, fruits, vegetables, and beans while maintaining a healthy body weight.”

The study authors found that vegetarians and pescatarians were more likely to be younger and well-educated and less likely to smoke and drink. This suggests that it is possible that the findings might be due to confounding factors.

Also, the UK BioBank volunteers were all aged 40–70 years at recruitment, which means that the findings may not be generalizable to all age groups.

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