High intake of red and processed meats may raise the risk of lung and colorectal cancer by up to 20 per cent, according to a new study from researchers at the USA's National Cancer Institute.
Half a million people were surveyed for the new study that also reports raised risks of other cancers, including throat and liver cancer, report the researchers in the open access journal the Public Library of Science - Medicine.
"A decrease in the consumption of red and processed meat could reduce the incidence of cancer at multiple sites," wrote lead author Amanda Cross.
The study, published on-line in the open access journal Public Library of Science - Medicine, the study follows hot on the heels of similar findings published last month by the World Cancer Research Fund's (WCRF), which concluded, amongst other things, that high consumption of red and processed meat was associated with a 30 per cent increase in the risk of colorectal cancer.
The researchers used 124-item food frequency questionnaires to assess dietary intakes among 567,169 people aged between 50 and 71 taking part in the National Institutes of Health (NIH)-AARP (formerly the American Association for Retired Persons) Diet and Health Study.
During 8.2 years of follow-up, the researchers documented 53,396 incident cancers. People with the highest intake of red meat (62.7 grams per 1,000 kcal) were associated with a 20 and 24 per cent increased risk of lung and colorectal cancer, respectively, compared to people with the lowest intakes (9.8 grams per 1,000 kcal).
Moreover, people with the highest intake of red meat were calculated to be at a 61 and 51 per cent increased risk of oesophageal and liver cancer.
For processed meat consumption, people with the highest average intake of these meats (22.6 g per 1,000 kcal) were calculated to be at a 16 and 20 per cent increased risk of lung and colorectal cancer, respectively.
In their discussion of the results, the researchers postulated that dietary fat from the meat, compounds like N-nitroso compounds (NOCs), heterocyclic amines (HCAs), and polycyclic aromatic hydrocarbons (PAHs) formed during high temperature cooking, and iron may be behind the potential risk increases.
"Despite abundant biologic pathways linking meat intake to carcinogenesis at numerous anatomic sites, this is the first comprehensive and prospective analysis of meat intake in relation to a full range of malignancies," wrote Cross.
In an accompanying comment, Jeanine Genkinger and Anita Koushik from Georgetown University and Université de Montréal, respectively, stated that the strongest risk factors for cancer in the US remain obesity and smoking.
"However, understanding the complex interaction of diet with smoking and obesity, and how specific foods and nutrients are metabolized, may provide further clues into the etiology and, most importantly, the prevention of cancer," they concluded.
For future areas of research, Genkinger and Koushik recommended examining particular nutrients within meats, most notably iron, and other potentially carcinogenic components, like heterocyclic amines and nitrosamines produced during cooking.
They also noted that animal feeding habits should be taken into account, stating that exogenous sex steroids are employed in the US. Such hormones are banned in Europe, however.
Last month's WCRF study was met with a noisy response from the global food industry.
Julian Hunt, director of communications at the UK's Food and Drink Federation, said that balance is the key to a healthy lifestyle.
"This report confirms what most of us already knew: the secret of a healthy lifestyle is to enjoy a balanced diet, coupled with moderate amounts of exercise," he said.
"The food and drink industry has long been committed to playing a positive role in improving the health of the nation, focusing on those areas where we can make the biggest difference. Our industry is now widely recognised as leading the world when it comes to reformulating products."
The American Meat Institute (AMI) took a different stance, calling the WCRF panel recommendations on meat consumption "extreme" and "unfounded". The institute said the advice to limit red and processed meats reflected their anti-meat bias.
AMI foundation vice president of Scientific Affairs Randy Huffman, said: "No health groups should be dispensing clear-cut recommendations on specific foods when studies continue to contradict each other time after time…Given the complexities and conflicting research findings, it is inconceivable that WCRF could draw definitive conclusions and make such precise recommendations about specific food categories."
Source: Public Library of Science - Medicine
Open access on-line. 4(12): e325 doi:10.1371/journal.pmed.0040325
"A Prospective Study of Red and Processed Meat Intake in Relation to Cancer Risk"
Authors: A.J. Cross, M.F. Leitzmann, M.H. Gail, A.R. Hollenbeck, A. Schatzkin, R. Sinha
Comment: Public Library of Science - Medicine
Open access on-line. 4(12): e345 doi:10.1371/journal.pmed.0040345
"Meat Consumption and Cancer Risk"
Authors: J.M. Genkinger, A. Koushik