NUTRITIONAL EFFECTS 



693 



nancies about the 17th day. Treatment with 

 estrogen and progesterone was preventive 

 (Walker and Wirtschafter, 1956). It is as- 

 sumed, therefore, that lithospermin inter- 

 fered with the production of these hormones. 

 A repetition of the experiment on a species 

 in which the hypophysis and ovaries are 

 dispensable during much of pregnancy 

 would be of interest. 



In retrospect it has been found that a 

 deficiency in protein and the vitamins 

 thiamine, pyridoxine, pantothenic acid, and 

 folic acid individually can interrupt a preg- 

 nancy. Furthermore, a combination of es- 

 trone and progesterone which is adequate to 

 maintain pregnancy after hypophysectomy 

 and ovariectomy, is equally effective in pro- 

 tein or thiamine deficiency. This suggests 

 that the basic physiologic alteration is a 

 deprivation of ovarian hormones. However, 

 protein- and thiamine-deficiency states dif- 

 fer from each other as shown by the re- 

 sponse to estrogen alone (thiamine defi- 

 ciency is less responsive), and these states 

 differ from hypophysectomy in which es- 

 trone alone has no effect. A pyridoxine de- 

 ficiency seems to involve both ovary and 

 hypophysis, for neither steroids nor pitui- 

 tary hormones were more than partially 

 successful in maintaining pregnancy in rats. 

 Lastly, pantothenic acid and folic acid 

 deficiencies may not create a steroid defi- 

 ciency. What is involved is not known; 

 many possibilities exist. Pantothenic acid, 

 for example, participates in many chemical 

 reactions. Furthermore, it is known that 

 thiamine is essential for carbohydrate me- 

 tabolism but not for fat metabolism whereas 

 pyridoxine is involved in fat metabolism 

 and in the conversion of tryptophan to nico- 

 tinic acid. It is clear, though, that much 

 ground must be covered before the formula- 

 tion of fruitful hypotheses may be antici- 

 pated. 



VI. Concluding Remarks 



The development, composition, and nor- 

 mal functioning of the reproductive system 

 is dependent on adequate nutrition. How- 

 ever, the requirements are many and only 

 gradually are data being acquired which are 

 pertinent to the elucidation of the nutri- 

 tional-gonadal relationship. 



The demands for nutrient substances is 

 not always the same. During pregnancy and 

 lactation there is a need for supplemental 

 feeding. A similar need exists in birds and 

 in the many cold-blooded vertebrates in 

 which reproduction is seasonal. Atypical en- 

 docrine states create imbalances and a need 

 for nutrient materials which vary, unpre- 

 dictably, we must acknowledge, until the 

 numerous interrelationships have been clari- 

 fied. 



At many points where determination of 

 cause and effect are possible, an indirect 

 action of dietary factors on reproduction is 

 indicated. No other conclusion seems pos- 

 sible in view of the many instances in which 

 the effect of dietary deficiencies can be 

 counteracted by the administration of a 

 hormone or combination of hormones. The 

 direct action is not immediately apparent; 

 it probably is on the processes by which 

 metabolic homeostasis is maintained, and is 

 in the nature of a lowering of the respon- 

 siveness to the stimuli which normally trig- 

 ger these processes into action. The processes 

 may be those by which pituitary and gon- 

 adal hormones are produced or they may be 

 the mechanisms by which these hormones 

 produce their effects on the genital tracts 

 and on the numerous other tissues on which 

 they are known to act. 



Because of the many interrelationships, 

 some of which are antagonistic and some 

 supportive, determination of the role of spe- 

 cific dietary substances is not easy. For 

 those who work with laboratory species, 

 the problem is further complicated by the 

 many strain differences. For everyone, the 

 problem is complicated by the many species 

 differences which are the result of an evolu- 

 tion toward carnivorous, herbivorous, or 

 omnivorous diets, to say nothing of the 

 countless specific preferences within each 

 group. 



Finally, it is something of a paradox in our 

 culture that much of our effort has been de- 

 voted to investigations of the effects of de- 

 ficiencies and undernutrition rather than 

 to the effects of excesses and overnutrition. 

 Much evidence supports the view that in 

 the aggregate the latter are fully as dele- 

 terious as the former, but the means by 



