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Meat consumption and risk of colorectal cancer

 

Clinical bottom line

An association was found between consumption of red meat, particularly processed meat, and risk of colorectal cancer, which corresponds with current advice to limit intakes of red meat and meat products.


Results from studies investigating meat consumption and risk of colorectal cancer have been inconsistent. The following meta-analysis investigates this relationship.

Reference

MS Sandhu et al. Systematic review of the prospective cohort studies on meat consumption and colorectal cancer risk: a meta-analytical approach. Cancer Epidemiology, Biomarkers and Prevention 2001 10: 439-446.

Search

The literature was searched using MEDLINE, Embase and Cancerlit until mid 1999. References from identified articles and literature reviews were examined. Investigators and authors were contacted for unpublished or missed research. Prospective cohort studies investigating meat consumption and colon or colorectal cancer incidence or mortality were included. Meat was defined as including red meat, lamb, beef, pork and processed meats (such as sausages, burgers, ham and bacon), but not including white meat. Excluded were case-control and ecological studies; studies that only classified people as eating meat or not; and early studies whose data had been subsequently re-analysed.

Thirteen papers were identified with a total of 601,133 participants and 3,617 cases. Initial age of participants ranged from 15 to 55 years and length of follow-up ranged from 3 to 24 years. All but one study assessed diet with food frequency questionnaires. Few studies adjusted for other diet, lifestyle or genetic factors. Twelve adjusted for age.

Results

A daily increase of 100 g of meat was associated with a 14% increased risk of colorectal cancer (odds ratio 1.14, 95% confidence interval 1.04 to 1.25).

A daily increase of 25 g of processed meat was associated with a 49% increased risk (odds ratio 1.49, 95% confidence interval 1.22 to 1.81). Processed meat was defined as processed, cured or nitrate meat, or sausages.

Comment

Unfortunately, only a few studies examined the independent effect of meat consumption on the risk of colorectal cancer so the associations found here could be confounded by other dietary, lifestyle or genetic factors.

Nevertheless, the current UK recommendation is that consumption of red and processed meat should not increase for those consuming average levels (about 90 g a day for the UK population; 8 to 10 portions a week) and should decrease for those consuming high levels (above 140 g a day; 12 to 14 portions a week). The advice of the World Cancer Research Fund (WCRF) is to limit intake of red meat to below 80 g a day. This meta-analysis is in agreement with these recommendations which in essence, is to limit or reduce intakes of red meat. For those at higher risk (e.g. with genetic or other lifestyle factors) it may be wise to consider the WCRF's upper limit of 80 g/day; limit consumption of processed meat products in particular; and choose alternatives to red meat, such as poultry, fish, beans and pulses.

High consumption of red and processed meat may increase the risk of colorectal cancer in various ways, including the formation of carcinogenic agents. Heterocyclic amines are formed on the surface of meat when it is cooked in direct flame or at high temperatures. N-nitroso compounds are found in foods containing nitrates, or which have been exposed to nitrogen oxides, such as processed meats.