Mortality data from women aged 45-74 who died between 1968 and 1977 in Slovakia, Czechoslovakia, were used to examine the effect of parity (number of live-born children) on risk of dying from each of 20 common cancers. After controlling for the effects of age and year of death, the effect of parity on risk was statistically significant at the p less than 0.001 level, for cancers of the stomach, liver, gall-bladder, breast, cervix, and ovary; and at the p less than 0.01 level for uterine corpus and brain. No effect of parity was seen for cancer of the colon or rectum. Among parous women the trend relating risk to level of parity was significant at the p less than 0.001 level for cancers of the breast, uterine corpus, ovary and brain; and at the p less than 0.01 level for stomach cancer. The findings relating parity to cancers of the breast and reproductive organs are consistent with previous reports. The associations of parity with cancers of the digestive tract deserve further study.

The existence of non-enzymatic thiamin inactivating factors in plant material was first observed by Weswig et al. in 1946' roughly ten years after the structure of this vitamin was established. This short note stated that rats fed bracken fern as 40% of the diet lost weight and developed symptoms suggestive of thiamin deficiency. The term "antithiamine activity" was used in describing this action and the possible relation to "fern poisoning" i n cattle was discussed. Three years later, Evans and Evans2 confirmed these findings using rats fed a standard diet plus bracken leaves. Subsequently, Kundig and Somogyi' analyzed a number of fruit and vegetables for antithiamin activity (ATA) and found highest activity in blueberries, red chicory, black currants, red beetroot, brussel sprouts, and red cabbage. The activity appeared to be associated with colored plants. Plant antithiamin activity was also studied by Japanese workers: Thai: and Indian investigators.6The next investigations concerned the chemical nature of the antithiamin substances in plants. It was soon concluded that the activity was connected with phenolic compounds. Matsukawa and Kawakami' determined the ATA of a number of phenols, quinones, catechol, and tannic acid: the optimal conditions for activity; as well as products of thiamin decomposition. They noted that (a) the ATA in plants was associated with phenol compounds having two OH groups, (b) the optimal pH was above 7.0 (c) the optimal temperature was above 5OoC, (d) the reaction required oxygen, (e) the reaction was inhibited by cysteine, and (f) thiochrome and thiamin disulfide appeared as reaction products of thiamin decomposition. After analyzing over 30 phenolic compounds for ATA, Somogyi and Bonicke' postulated that the number and position of OH groups is of primary importance for antithiamin activity. Compounds having only one OH group had no activity, those with ortho OH groups had the highest activity, those with para OH groups had medium activity, and those having the OH in the meta position had no activity. Caffeic acid (3,4-dihydroxycinnamic acid) was isolated from fern' and blueberries'" as one the the antithiamin factors in these plants. Sarkar and Chaudhuri" isolated and characterized an antithiamin factor from cotton seed as 3,5-dimethoxy salicylic acid. A more complex substance containing glucose and an ortho-hydroxy phenol group with CH3 and COOH radicals has been partially characterized from rice bran." Williams in 1927 described experiments in which pigeons were fed rice mill by-products and developed 137

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Key Words household handling of food, vitamins, minerals, food prep aration, heated food fats, nutritional qualityThe topic of this workshop "Nutritional losses due to food preparation and possibilities of their prevention" is rather important. Such losses occur between harvesting and distribution, during household and industrial handling as well as catering and during storage.Some of the foods have to be processed so that they remain storable for a longer period of time. Only in this way can the population be provided with a regular and constant supply. It is estimated that 60-70% of all foods are handled industrially. There are losses in nutrient content due to these processes, to a lesser or to a greater extent, depending on the manner of production. Industrial procedures are now known which cause only slight changes in quality.Losses in nutritional value can also result from the household handling of foods and even more so from the preparation of meals in catering. Their magnitude depends in both cases on the cooking method.We carried out investigations in this field some years ago which should be briefly summarized. To receive comparable results it is important to standardize the experimental conditions in all phases. It was investigated how various cooking influence the vitamin C and the thiamin content of potatoes and various vegetables. These experiments show that the extent of vitamin C losses in potatoes and vegetables differs according to the method of preparation.The results of the experiments concerning the decrease in vitamin C content of potatoes by various cooking methods are summarized in Table 1.The smallest reduction of vitamin C content was by the steaming method, i.e. cooking with very little water (so called "waterless" cooking) and the highest losses when cooked in a pressure cooker (1).One probably finds the results surprising that the vitamin C losses in potatoes prepared in a pressure cooker are higher than when boiled in water. These findings confirm our previous experiments (2), in which the vitamin C losses in whole, half and one eights potatoes were determined after cooking in much water and in S1