October 23, 2015

expert reaction to media reports that upcoming IARC classification of processed and red meat is expected to classify them as carcinogenic and probably carcinogenic to humans respectively

The International Agency for Research on Cancer (IARC) of the World Health Organisation (WHO) are soon to publish a report on the carcinogenicity of red meat and processed meat. There has been discussion in the UK media today that the report is likely to class processed meat as ‘carcinogenic to humans’, and red meat as ‘probably carcinogenic’.

Additional comment from Dr Elizabeth Lund:

“In developing countries where meat consumption is much lower the risk of bowel cancer is in the region of 8-10 people per 100,000. (Key et al. 2004)

“An increased risk associated with red meat consumption is in the region of 28%. So perhaps about 3 extra people per 100,000 are diagnosed with bowel cancer in developed countries.

“Data from 2011 indicate lifetime risk for bowel cancer in the UK is about 58 men per 100,000 and 38 women per 100,000. That is an extra 48 men or 28 women so only a small portion of this might be related to meat consumption. A much bigger risk factor is obesity and lack of exercise. Overall I feel that eating meat once a day combined with plenty of fruit, vegetable and cereal fibre plus exercise and weight control will allow for a low risk of CRC and a more balanced diet.”

Dr Elizabeth Lund, Independent Consultant in Nutritional and Gastrointestinal Health and former research leader at the Institute of Food Research, said:

“This is not a surprising outcome but needs to be put in perspective. Very few people in Europe eat sufficient meat to fall into the high meat consumption category although there is also a dose-dependent correlation between meat intake and CRC risk. It will be interesting to see what the report says about how much is safe. Meat is such a good source of iron and zinc and many women are short of these key micronutrients. Half of teenage girls have insufficient iron intake. Iron is much more bioavailable from meat than from vegetables or supplements. A cooked beef steak contains about 2.4mg of iron/100g of meat. Menstruating women should consume 14.8 mg iron per day from a range of foods. In Europe we normally eat a 200g portion of steak so that would make a significant contribution to our iron intake. For other members of the population only just over 7g of iron per day is required but even then meat can be an important source.

“It should also be noted that some studies have shown that if meat is consumed with vegetables or a high fibre diet the risk of CRC is reduced.

“To suggest meat has a probable action as a carcinogen there normally needs to be a convincing mechanism of action. I am not aware of any convincing mechanism although several have been suggested and the report may provide new knowledge. Of course association without mechanism could just be coincidence.”

Dr Ian Johnson, Emeritus Fellow, Institute of Food Research, said:

“It is very difficult to comment on the new IARC classifications without seeing the data analyses on which they are based. However, although there is epidemiological evidence for a statistically significant association between processed meat consumption and bowel cancer, it is important to emphasise that the size of the effect is relatively small, and the mechanism is poorly defined.  It is certainly very inappropriate to suggest that any adverse effect of bacon and sausages on the risk of bowel cancer is comparable to the dangers of tobacco smoke, which is loaded with known chemical carcinogens and increases the risk of lung cancer in cigarette smokers by around 20 fold.”

Declared interests

Dr Elizabeth Lund: I have undertaken consultancy work for BPEX (2010).

Dr Ian Johnson: is an Emeritus Fellow at the Institute of Food Research, and a member of the Science Advisory Board of the British Nutrition Foundation. He currently holds no research grants and has no commercial affiliations.