Nutritional Well-Being and Length of Life as Influenced by Different Enrichments of an Already Adequate Diet

Abstract

The complete life cycles were studied in from 66 to 77 males and from 101 to 111 females on each of the five diets here compared. Several objective criteria of nutritional well-being as reflected in growth and development, adult vitality, and length of life, were measured quantitatively and the data submitted to critical statistical examination. Several chemical factors are thus found to participate in the enhancement of nutritional well-being and increase in the length of life, which resulted from the improvement of an already adequate diet by increasing the proportion of milk in the food supply. The enrichments here studied were in each case of the same degree as the difference between our diets A and B. Increased intake of calcium, either alone or with butterfat, resulted in definitely more rapid growth; while enrichment with butterfat alone seemed to result in slower growth but larger adult size than on the original diet A (diet 16). The enrichment of the basal diet in butterfat alone had no measurable effect upon the average age at which the females bore their first young, while each of the other dietary enrichments here studied led to an earlier maturity in this respect. Butterfat and calcium, either alone or together, resulted in longer life and an extension of the period of adult vitality as measured by the length of time during which the females were capable of bearing young. The addition of butterfat alone did not increase the size of the young (measured by weight at the age of 28 days, taken as a conventional ‘end of infancy’ in this rat colony); whereas this was increased by addition of calcium either alone or with butterfat. With both males and females, addition of butterfat alone was followed by slower growth and longer life; while in the other six of the eight comparisons, i.e., with both males and females on enrichment of diet 1) in calcium, 2) in calcium and butterfat, and 3) in calcium, riboflavin and protein, there was increase both in the rate of growth and in the length of life. When one-fifth of the wheat of the basal diet was replaced by an equal weight of skim milk powder, i.e., when along with the increase of calcium there was a corresponding increase of riboflavin and a relatively minor increase of protein, growth was significantly more rapid than on any of the other diets; development was expedited and the life cycle extended in essentially the same degree as by enrichment in calcium alone; and larger young resulted than upon any of the other diets studied. Thus it appears that the three factors which were increased in greatest ratio when the already adequate diet A was modified to constitute the nutritionally better diet B, i.e., calcium, vitamin A, and riboflavin, have all contributed to the improvement in nutritional well-being and resultant health and longevity. Further studies of the relation between rapidity of growth and length of life as influenced by different modifications of diet are in progress.