Nutrition and cancer--a large scale cohort study.

Positive nutritional intervention is considered as a more practical and effective means for cancer prevention than negative intervention such as discarding undesirable habits. Daily intake of green-yellow vegetables (GYV) apparently carry promising effect to reduce cancer risk. Results of a large scale cohort study in Japan showed that the risks of cancer of many sites such as lung, larynx, mouth, pharynx, esophagus, stomach, liver, and urinary bladder were lower in daily intakers of GYV even when other hazardous habits were kept unchanged. In other words the beneficial effects of daily intake of GYV were demonstrated in groups with various life styles such as smoking daily, drinking daily, and eating meat daily. Beneficial effects of daily intake of GYV were also observed in daily smokers, ex-smokers and passive smokers probably through its effects as inhibitors of cancer promoters abundant in cigarette smoke. Those who increased frequency of GYV consumption during the short period of follow-up also showed reduced risk of stomach cancer in subsequent years of observation showing the effectiveness of nutritional intervention even started from adult age. Thus nutritional intervention is believed to be one of the most valuable means of cancer prevention.