A number of estimations agree that in the economically developed world, roughly 30% of all cancers are associated with nutritional factors and therefore theoretically could be avoided by a better dietary balance, the prevention of overweight and adequate physical activity.
The European Conference on Nutrition and Cancer that will open tomorrow Thursday 21 June in Lyon, France, will allow several hundred researchers to exchange views and results of on-going studies on nutrition, metabolic balance and certain types of cancer. Already, a number of preliminary results from the European Prospective Investigation into Cancer and Nutrition (EPIC)1 , which will be discussed starting tomorrow, are being disclosed concerning three groups of foods (fruits and vegetables, alcohol and animal products).
1- The protective effect of fruits and vegetables
The EPIC study confirms the reduction in incidence of cancers of the colon and rectum and upper aerodigestive tract associated with these. However, the protective effect previously found for stomach and lung cancers does not clearly come out : one should note that the follow-up period is relatively short, just as the number of cancer cases that occurred during that period.
2- The disastrous effects of alcohol and tobacco
The EPIC results confirm, in addition to the obvious effect of tobacco on lung cancer risk, the very strong effect of the consumption of alcohol and tobacco on cancers of the upper aerodigestive tract. For example, the risk for one of these cancers for someone who smokes over a pack per day is 8 times higher than that of a non-smoker.
As far as alcohol is concerned, an intake higher than 60g of ethanol per day (roughly a consumption of a standard .75 liter bottle of wine) will increase the risk of one of these cancers 9 times. One should emphasize the fact that the combination of these will have a multiplier effect which will increase the risk of our smoker-drinker 50 times !
This precisely confirms the results obtained by an IARC team fifteen years ago on the cancers of the larynx, pharynx and esophagus in Southern European countries.
The protective effect of the consumption of fruits and vegetables was also quantified. A daily consumption of approximately 500g or more is sufficient to decrease by 50% the incidence of cancers of the upper aerodigestive tract.
3- Contrasting results for preserved meats and red meats, and protective effect of fish
As far as meat, fish and dairy products (animal products), the analyses focused on cancers of the colon, rectum, stomach and upper aerodigestive tract. The associations that clearly came out of these were an increase of the colon cancer risk with total consumption of preserved meats and a significant reduction of the same risk with fish consumption.
On the other hand, it is clear that consumption of red meat does not seem for the time being to be associated with the risk of developing colon/rectum cancer. However, these analyses have not yet taken into account the method used for cooking. This important question will be carefully analysed at a later stage.
Consumption of poultry is not associated with an increase in cancer risk and is in fact possibly associated with a reduction of that risk.
There was a positive association between total consumption of meat and cancers of the stomach and of the upper aerodigestive tract ; however, this association is weak and non significant and will be studied further.
From a larger preventive perspective, for the general public, the multifactor aspect of the incidence of diet-related cancers should be stressed, along with the importance of physical activity and prevention of obesity.
These, in a nutshell, are the first significant results of this landmark study that will be discussed over the next few days here in Lyon.
1 EPIC is the largest epidemiological study ever conducted on the relationship between diet and cancer, with over 500,000 subjects in 10 European countries. This prospective study aims at elucidating the cause-effect relationships between dietary balance, anthropometric measurements, physical activity and hormonal factors as well as genetic susceptibility factors, and specific types of cancer.