Dietary Ratio of Carbohydrate, Fat and Protein

As a result of observations of changes in performance records of highly trained athletes on different diets containing various proportions of the food principles, the following generalization has been made: a diet of 150 grams of fat, 700 grams of carbohydrate and 100 grams of protein plus adequate minerals and vitamins daily was recommended for distance events, and 100 to 130 grams of fat, 350 to 400 grams of carbohydrate and 210 grams of protein, mostly meat, was recommended for speed events. 5 These figures must, at best, be considered as representing the order of magnitude only. Further evidence is needed as a basis for the construction of diets with a view toward providing the best nutrition for muscular activity. To this end, the various food principles will be discussed separately.

Carbohydrates

Carbohydrates are essential dietary constituents but are not the exclusive fuel for muscle. The amounts of carbohydrate used are related to the work level. The depletion of blood sugar levels below 70 mg. per cent results in exhaustion. A low blood sugar may interfere with the metabolism of the central nervous system to such an extent that a mild degree of oxygen want brings on symptoms similar to those obtained under conditions of extreme anoxia. This indicates that the fatigue of protracted exhaustive exercise has a cerebral origin. Associated with the fatigue of prolonged work is a loss in mechanical efficiency due to faulty coordination. Theoretically, a diet rich in carbohydrates should contribute to the maintenance of normal blood sugar concentration for longer periods during prolonged physical work. Even though this is not always actually the case and exhaustion often occurs with a high blood sugar concentration and at high R. Q.'s, the theory is supported by observations in which industrial workers are found to work more efficiently on a carbohydrate-rich than on a fat-rich diet. Evidently the blood sugar level does not always reflect the nutritional condition of the muscles, and also conditions other than the type of fuel affect the R. Q. Although the mechanisms of carbohydrate utilization are not entirely clear, there is sufficient evidence to support the principle that the athlete in training should have extra carbohydrate in his diet.

An exception to the superiority of high carbohydrate meals is observed in workers performing strenuous visual tasks requiring the recognition of fine details moving on a conveyor belt. For this type of work either a balanced standard meal or a high fat meal was preferable.