American Journal of Clinical Nutrition, Vol 21, 803-812, Copyright © 1968 by The American Society for Clinical Nutrition, Inc.

Metabolic Aspects of Calorie Restriction: Nitrogen and Mineral Balances and Vitamin Excretion

¹ From the U. S. Army Medical Research and Nutrition Laboratory, Fitzsimons General Hospital, Denver, Colorado 80240

Eight young, healthy adults consumed 420 kcal of carbohydrate per day for a period of 10 days. The men were assigned to two groups of four men each, one group receiving mineral supplementation and the other no additional minerals. Daily energy expenditure was maintained at the 3,200 kcal level.

Nitrogen balances were not as negative as during 10 days of complete starvation; however, nitrogen losses were still marked indicating that the effects of limited carbohydrate upon reducing protein catabolism were minimal. Mineral supplementation did not affect nitrogen balance.

After 3 days of carbohydrate alone, urinary mineral excretion was reduced drastically, showing the rapid adaptation to the absence of dietary minerals. Mineral supplementation maintained mineral balances with the exception of potassium. A possible explanation for the potassium losses under these conditions was discussed.

Urinary vitamin excretions decreased rapidly during the restriction period when no vitamins were being ingested. From the observed data, ketosis was eliminated with only 420 kcal/day and it was apparent that mineral supplementation was very beneficial in maintaining mineral balances and normal EEG patterns. However, protein catabolism was high in both groups suggesting that these low intake levels were inadequate for active individuals, even for short periods of time.