What was not mentioned, however, was that the vast majority of meat is already a threat to our health, whether contaminated with dioxin or not. There is evidence that processed meat-such as bacon, sausages, hot dogs, packaged ham, pepperoni, sandwich meat and salami-can all increase the risk of cancer.
Bowel cancer and more
The link between processed meat and bowel cancer is especially compel-ling. When the World Cancer Re-search Fund (WCRF) reviewed 12 studies showing an increased risk of colorectal (bowel) cancer in people with the highest intakes compared with those who ate the least, its report concluded: "Processed meatis a convincing cause of colorectal cancer."
More alarming, there is a dose- response relationship: the more processed meat eaten, the higher the cancer risk. In general, consuming 50 g/day of processed meat-equal to one sausage-increases the risk of bowel cancer by 20 per cent (see www.dietandcancerreport.org).
Subsequent French and US reviews also reported that people consuming the highest amounts of processed meat were 20-per-cent more likely to develop bowel cancer compared with those eating small amounts or none at all (Nutr Cancer, 2008; 60: 131-44; PLoS Med, 2007; 4: e325). According to the American study, one in 10 colorectal cancers could be avoided by simply reducing processed meat in the diet.
Other cancers are also associated with processed meat. Of more than 61,000 women, those who ate the most bacon, sausages, ham, salami and hot dogs had a 66-per-cent greater risk of stomach cancer. Red meats, fish and poultry had no such link (Int J Cancer, 2006; 119: 915-9).
In the US study already mention-ed, involving more than 500,000 people, those who ate the most processed meat had a 16-per-cent higher risk of lung cancer, as wellas greater chances of cancers of the prostate, cervix and bladder, and myeloma (PLoS Med, 2007; 4: e325).
Particularly worrying is the link between processed meat eaten when pregnant and childhood brain cancer. Pregnant women who regularly ate cured meats such as hot dogs and sausages were 68-per-cent more likely to have a child with a brain tumour (Neuroepidemiology, 2004; 23: 78- 84). Other studies have found higher risks of twofold or more among the highest processed-meat consumers (Nutr Cancer, 1999; 34: 111-8).
Yet more evidence suggests that processed meat may also play a role in cancers of the breast, pancreas, oesophagus and kidney (Br J Cancer, 2007; 96, 1139-46; J Natl Cancer Inst, 2005; 97: 1458-65; Eur J Cancer Prev, 2000; 9: 257-63; Cancer Causes Control, 2007; 18: 125-33).
Why is processed meat bad?
According to the WCRF, there are several plausible ways in which processed meat can cause cancer. For starters, processing produces cancer-causing substances such as N-nitroso compounds (NOCs), derived from sodium nitrite, a common preserva-tive found in processed meat. The nitrites or NOCs from processed meat have been positively associated with a variety of cancers (Int J Occup Environ Health, 2008; 14: 193-7; World J Gastroenterol, 2006; 12: 4296-303).
Processed meat can also contain heterocyclic amines (HCAs) and polycyclic aromatic hydrocarbons (PAHs), which are formed when meat is cooked at high temperatures. These compounds have been shown to produce tumours and damage DNA in animal studies, while human research has linked them to colorectal neoplasia, squamous cell oesophageal cancer, and cancers of the lung and prostate (PLoS Med, 2007; 4: e325).
Finally, processed meat is a source of saturated fat and iron, each of which is associated with carcino-genesis (PLoS Med, 2007; 4: e325).
These possible mechanisms, combined with the sizable body of evidence related to cancer, have led the WCRF to conclude that processed meat is simply not fit for human consumption. As no amount of processed meat can be confidently shown not to increase cancer risk, the WRCF recommends avoiding it altogether
Here is yet another reason to choose fresh, organic, non-processed food whenever possible.
What is processed meat?
'Processed meat' generally refers to meats preserved by smoking, curing, salting or the addition of preservatives. Meats preserved only by refrigeration-however they are cooked-are usually not classified as 'processed meat'.
However, although cancer risks generally do not apply to fresh, unprocessed meat, there is convincing evidence that red meats such as lamb, pork or beef-processed or not-may also contribute to cancer (PLoS Med, 2007; 4: e325). For this reason, the World Cancer Research Fund recommends limiting intake of red meat to less than 500 g (cooked weight, or 700-750 g raw weight) per week.