Prevention of cancer: restriction of nutritional energy intake (joules).
1. The reduction of nutritional energy intake (joules) often reduces the incidence of both spontaneous and induced cancers in humans and experimental animals in an approximately dose-dependent manner. 2. To achieve the best preventive effect, the reduction of dietary intake should begin well before the carcinogen insult, should be intense enough (lowering the intake of joules by at least approx. 25-30%) and should last a long time, preferably even life-long. 3. This preventive effect depends upon the strain, sex and age of animals, the kind of carcinogenic insult and also the susceptibility of the target tissue. 4. The mechanism by which the dietary restriction may exert its protective action may involve changes in the hormonal equilibria, influences upon the immuno-surveillance, changes of activities of enzymes involved in carcinogen metabolism and other factors. 5. Since over-eating and the resulting obesity constitutes a pronounced risk factor for the incidence of cancer and other diseases, lowering the nutritional energy intake represents today the simplest, cheapest and most effective way to prevent cancer in the general population.