Between the first and second WCRF/AICR report (2007) there is a significant difference in the criteria for the judgement of the evidence.

In general, the criteria for weighing the strength of the evidence in the 2007 report, are more stringent than those of the first report. This holds especially for the judgement of a ‘convincing causal’ association. Evidence from at least two independent cohort studies showing strong and plausible experimental evidence that typical human exposures can lead to cancer outcomes, was now considered mandatory for this. Besides these prospective studies, more emphasis was also put on well performed randomized clinical trials (RCT).

Due to new studies and the more stringent criteria, several protective effects that were considered to be ‘convincing’ in the first WCRF/AICR report, have been re-evaluated to ‘probable’. This holds in particular for fruits and vegetables (dietary composition). But re-evaluations of evidence in the opposite direction were also observed, like for some protective effects which were re-evaluated from 'probable' to 'convincing'. In addition, the total evidence for increased cancer risks by overweight and obesity has become much stronger. Furthermore, some new cancer risks or protective effects were also noted.

Food and nutrition

New findings concern the ‘probable’ protective effect of garlic, milk or calcium for colon/rectum cancer, and of lycopene and selenium for prostate cancer.

The evidence for cancer protection by fruits and vegetables is re-evaluated to ‘probable’ for mouth/pharynx, oesophagus, lung, and stomach. For cancer of the bladder, cervix and colon/rectum it has been ranked even lower. A change after re-evaluation of the cancer protective effects to ‘probable’ was observed for vitamin C (oesophagus) and for allium vegetables (stomach).

However, the evidence for an increased cancer risk by red and/or processed meat for colon and rectum was strengthened, and the same holds for the aflatoxins and liver cancer. New is the ‘probable’ carcinogenic risk of arsenic in drinking water (skin cancer) and the higher risk of prostate cancer due to high calcium intake.

Physical activity

Evidence of the protection by physical activity has become consistent and ‘convincing’ for colon cancer (independent of overweight). New are the ‘probable’ protective effects of physical activity against cancer of the endometrium and breast (postmenopause).

Overweight and obesity

The evidence for an increased cancer risk by body fatness and abdominal fatness has become stronger for oesophagus, pancreas (new), colon/rectum, breast (postmenopause), kidney, endometrium and gallbladder. But, body fatness probably protects against premenopausal breast cancer, although the mechanism is largely unknown.

Growth and development

The available data for the cancer protective effect of lactation has been upgraded to ‘convincing’ evidence. The ‘probable’ increased cancer risk by adult attained height for pancreas and ovary is a new finding.