The current consensus based on several published meta-analyses is that consumption of red meat (all fresh, minced, and frozen beef, veal, pork and lamb), especially processed meat (any meat preserved by methods other than freezing, including marinating, smoking, salting, air-drying or heating (includes ham, bacon, sausages, pate and tinned meat)), is associated with an increased risk of bowel cancer (Department of Health, 1998; WHO/FAO, 2003; WCRF, 2007). Sandhu et al (2001) observed significant positive associations with all meat and red meat (an increased risk of around 15% per 100g per day intake of red meat), and a stronger increase for processed meat (49% risk increase for a 25-g per day serving). Norat et al (2002) found a significant increase in risk for colorectal cancer with higher consumption of red meat (1.24 per 120g per day) and processed meat (1.36 per 30g per day). Larsson and Wolk (2006) considered 15 prospective studies, and found a relative risk of 1.28 for an increase of 120g per day intake of red meat and 1.09 for an increase of 30g per day intake of processed meat. Consumption of red meat and processed meat was positively associated with the risk of both colon and rectal cancer, although the association with red meat appeared to be stronger for rectal cancer.
There are no dietary guidelines concerning recommended levels of consumption of red and processed meat; as for alcohol, it is assumed that ‘less is better' and that there is no threshold below which consumption presents no risk. In this section, we assume that the optimum (or target) is zero consumption. Currently, about 10% of the adult population are vegetarian, or consume only fish and poultry products (DEFRA, 2007).