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| EUPHIX (www.euphix.org) |
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In the WCRF/AICR report (2007), the currently available evidence is reviewed for 17 cancer sites. Together, these sites amount to roughly 80 percent of the incidence of, and deaths from, all cancers worldwide. The selection and sequence of the sites, as presented in the following tables, is roughly in line with the body’s systems, or with sites that have anatomical, metabolic, hormonal, or other features in common. According to the WCRF/AICR report (2007) the causal relationship between food, nutrition, physical activity, body composition, and cancer is and always will be incomplete. New methods of research, and new issues to study, are always being developed. However, the WCRF/AICR report (2007) distinguishes between five different 'grades' of evidence: 'convincing', 'probable', 'limited-suggestive', 'limited-no conclusion', and 'substantial effect on risk unlikely'. This EUphocus mainly focuses on the 'probable' and 'convincing' evidence of a causal relationship, either positive or negative. This because judgements of convincing or probable causal effects generally justify goals and recommendations (also see next chapter) for both prevention and futher research. The exact criteria used for judging whether evidence should be considered 'convincing' or 'probable' can be found in the WCRF/AICR report (chapter 3). Increased cancer risk: convincing evidence There is convincing evidence for an increased cancer risk by certain foods, drinks or food constituents in 6 of the 17 reviewed cancer sites, as shown in the next table. Four cancer sites concern the consumption of alcoholic drinks, while two others relate to specific carcinogenic contaminants in either drinking water or foods. The risk of lung and colorectal cancer, is also increased by the consumption of respectively a specific supplement or type of food (beta-carotene and red meat and processed meat). Increased cancer risk: probable evidence For oesophagus cancer there is probably an increased cancer risk by drinking an exotic hot drink (maté). Alcoholic drinks are probably increasing the risk for liver cancer (both men and women) and for colorectal cancer (only women). Furthermore, a probable cancer risk is found in four additional cancer sites (nasopharynx, stomach, prostate and skin) by the intake of resp. salted fish, salted & salty foods, high calcium, and arsenic in drinking water. Finally, for 7 cancer sites (pancreas, gallbladder, ovary, endometrium, cervix, kidney, bladder), the available experimental evidence indicate neither a convincing nor a probable increased cancer risk by foods, drinks or food constituents. Decreased cancer risk: convincing evidence For none of the reported 17 cancer sites in the WCRF/AICR report (2007) there is convincing evidence of a protective effect on cancer risk by any food, drink or food constituent. Decreased cancer risk: probable evidence The available evidence for a protective effect on cancer risk by certain foods, drinks and food constituents, is at best judged as ‘probable’. In total, this judgement is made for 7 of the 17 cancer sites. Four of these (lung, oesophagus, stomach, and mouth) concern the probable protective effects of non-starchy vegetables, fruits, foods with carotenoids and allium vegetables. The other three cancer sites concern the probable protective effect of foods containing folic acid (pancreas), dietary fibre, garlic, milk or calcium (colon and rectum), and lycopene or selenium (prostate). | Convincing increased cancer risks by foods, drinks or food constituents
* Available evidence not considered to be convincing a Concerns high dose supplements in smokers b On contaminated foods (cereals, grains, legumes, seeds, nuts, some vegetables and fruits) c Red meat refers to beef, pork, lamb and goat; proces-sed meat refers to: smoking,curing, salting, and addition of chemical preservatives | |||||||||||||||||||||||||||||||||||||
Overweight and obesity |  |
Overweight and obesity are the result of continuous weight gain, due to a positive energy balance (energy intake in excess of energy expenditure). The excess energy from food and drinks is stored as fat in the body in adipose tissue. Storage of fat in the body can be underneath the skin in upper arms, buttocks, belly, hips and thighs (subcutaneous storage). But it can also be stored intra-abdominally or viscerally (around the organs). Also a distinction is often made between ‘peripheral’ and ‘abdominal’ fat, i.e. between fat outside the trunk and fat that is more centrally located. The fat storage pattern is determined largely by genetic factors and also differs between the sexes. In women there is a tendency to store fat subcutaneously around hips, buttocks and thighs, while men are more likely to accumulate abdominal fat. As indicator for total body fatness the ‘body mass index’ (BMI) is used with its specific defined cut-off points. For excess abdominal fat the waist circumference is a useful single indicator, also with its specific cut-off points. Modifiers of weight gain, overweight and obesity Factors that modify the occurrence of weight gain and its resulting overweight or obesity have also been studied. In conclusion, there is convincing evidence that physical activity reduces the risk of weight gain etc., while sedentary living increases it. In addition, having been breastfed and intake of low energy-dense foods, will probably reduce the risk of weight gain and becoming overweight/obese. Consuming energy-dense foods, sugary drinks, fast foods or sedentary lifestyle (e.g. watching TV), will probably increase this risk. Physical activity The effect of physical activity itself on cancer risk, besides being protective towards weight gain, overweight and obesity, was investigated as well. Consistent and convincing evidence demonstrates that physical activity of all types protects against colon cancer. It probably also protects against female hormone-related cancers like endometrium and breast cancer (postmenopause). These results are independent of other factors such as body fatness. Nevertheless, they seem to be well in line with the results of the paragraph on overweight and obesity. | Increased cancer risk: convincing evidence The findings of the systematic literature reviews reported in the WCRF/AICR report (2007), indicate that there is convincing evidence that (excess) body fat increases the risk for the following six cancer sites. Convincing evidence of increased cancer risk by body fatness and fat distribution
a Adenocarcinoma only Increased cancer risk: probable evidence In addition, there is probably an increased risk for additional cancer types by body fatness (gall bladder), abdominal fatness (pancreas, breast [postmenopause], endometrium) and adult weight gain (postmenopausal breast cancer). Decreased cancer risk No convincing evidence was found for a decreasing effect on cancer risk by overweight and obesity in any of the 17 cancer sites studied. However, body fatness was found to be probably protective against premenopausal breast cancer. | |||||||||||||||
Growth and development, including lactation | |
The size and shape of the human body, and the rate at which growth take place from conception to adult life, is determined by a strong interaction between genetic and environmental factors, among which nutritional factors. Relevant body parameters studied in relation to cancer risk are birthweight, child growth, adult attained height, and lactation. Lactation is the process by which mothers produce their milk for breastfeeding. All these parameters are unlikely to directly modify the cancer risk. They do serve however as a marker for other genetic, environmental and nutritional factors which affect growth and development. Increased cancer risk: convincing evidence There is strong, consistent and convincing evidence that the risk of cancer at two sites is increased by the factors that lead to greater adult attained height. However, the nature of these factors, as well as the role played by nutrition, is still unclear. Increased cancer risk: probable evidence Furthermore, adult attained height probably also increases the cancer risk in several other sites: ovary, pancreas, breast (premenopause). In addition, the risk of premenopause breast cancer is probably increased by greater birthweight as well. Decreased cancer risk: convincing evidence It has been convincingly shown that women who breastfeed their child have a reduced risk of breast cancer at all ages thereafter (both premenopause and postmenopause). Lactation is likely to influence the lifetime exposure to menstrual cycles, and thereby hormone levels which may influence cancer risk. | Convincing evidence of increased cancer risk by growth and development
Convincing evidence of decreased cancer risk by breastfeeding
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