Moderate Intake of Red Meat Tied to Higher Colorectal Cancer Risk

Roxanne Nelson, RN, BSN

April 19, 2019

Consuming a moderate amount of red meat and/or processed meat is associated with an increased risk of developing colorectal cancer, according to new findings.

The study authors found that eating an average of 76 grams of red meat or processed meat a day, which is in line with current government recommendations from the United Kingdom, was associated with a 20% higher chance of developing colorectal cancer as compared to consuming only about 21 grams a day.

Alcohol consumption also raised the risk for colorectal cancer, but eating fiber from bread and cereals lowered it.

"Our results strongly suggest that people who eat red and processed meat four or more times a week have a higher risk of developing bowel cancer than those who eat red and processed meat less than twice a week," said coauthor Tim Key, DPhil, deputy unit director and professor of epidemiology, the University of Oxford, United Kingdom, in a statement.

"There's substantial evidence that red and processed meat are linked to bowel cancer, and the World Health Organization [WHO] classifies processed meat as carcinogenic and red meat as probably carcinogenic — but most previous research looked at people in the 1990s or earlier, and diets have changed significantly since then, so our study gives a more up-to-date insight that is relevant to meat consumption today," he said.

The study was published online April 17 in the International Journal of Epidemiology.

Consistent With Previous Data

During the past decade, much has been written on lifestyle — including diet — and the association with cancer risk. A number of studies have found varying associations between the consumption of red meat and cancer.

The American Institute for Cancer Research and the World Cancer Research Fund published several reports during the past 10 years or so on the effect of diet, nutrition, and/or physical activity on risk for several cancer types. Their most recent study, published in 2017, found that consuming red meat and processed meat may increase the risk for colorectal cancer, as may drinking two or more alcoholic beverages per day. On the flip side, eating whole grains daily and ramping up activity levels can reduce the risk.

In 2015, the WHO's International Agency for Research on Cancer (IARC) classified processed meat as carcinogenic to humans (group 1) on the basis of sufficient evidence for colorectal cancer. In addition, said the group, there was a positive association with stomach cancer.

The IARC has also classified red meat as being probably carcinogenic to humans (group 2A). The decision was based on relevant data that show strong mechanistic evidence of a carcinogenic effect. This association was observed mainly for colorectal cancer but also for pancreatic cancer and prostate cancer.

The authors of the current study point out that most previous studies that found an increased risk for colorectal cancer in those who consume high quantities of red meat and processed meat were conducted during the 1990s or earlier, and patterns in meat consumption have since changed. Additionally, few studies have used re-measured intakes to reduce the impact of measurement error.

In the current study, 475,581 individuals who were aged 40 to 69 years at recruitment (2006–2010) filled out a short food-frequency questionnaire. Dietary intake was re-measured in a large subsample of 175,402 persons.

At an average follow-up time of 5.7 years, 2609 cases of colorectal cancer had occurred. Upon multivariable analysis, the hazard ratio (HR) for incident colorectal cancer was 1.20 among persons who consumed an average of 76 g/day of red meat or processed meat in comparison with those who consumed an average of 21 g/day (and per 50-g/day increment, 1.17).

Red Meat Increases Risk

For red meat, the HR was 1.15 for persons who consumed an average 54 g/day compared with those who reported consuming an average of 8 g/day (and per 50-g/day increment, 1.18). For processed meat, the HR was 1.19 for those who consumed 29 g/day compared to those who consumed an average of 5 g/day (and per 25-g/day increment, 1.19).

Key and colleagues also evaluated the impact of other foods and alcohol. They found that fiber intake from bread and breakfast cereals was associated with a reduced risk for colorectal cancer (HR for the highest vs lowest fifth of intake, 0.86; P trend = .005).

Intakes of fruit and vegetable fiber were not associated with risk for colorectal cancer (P trend = .728 and .633, respectively).

With regard to the consumption of alcoholic beverages, beer was associated with an increased risk for colorectal cancer (HR for each 10-g/day increment of alcohol from beer, 1.11). For each 10-g/day increment of alcohol from wine, the HR was 1.05; for each 10-g/day increment of alcohol from spirits, the HR was 1.08.

Commenting on the study, Gunter Kuhnle, PhD, associate professor of nutrition and health at the University of Reading, United Kingdom, told Medscape Medical News that he feels the study primarily confirms previous results that show an association between the intake of red meat or processed meat and colorectal cancer. "This had been shown in a number of observational studies," he said. "By confirming these results, the study obviously strengthens the evidence, especially as it was conducted in a very different cohort from previous studies.

"The more interesting aspect of the study, in my opinion, is the results for fiber," Kuhnle added. "Again, they are not new but confirm and strengthen the evidence we have that show that fiber intake can mitigate the risk of red/processed meat."

The study was supported by Girdlers' New Zealand Health Research Council Fellowship, Cancer Research UK, the UK Medical Research Council, and the Wellcome Trust. The authors have disclosed no relevant financial relationships.

Int J Epidemiol. Published April 17, 2019. Full text

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