344 BIOLOGY FOR BEGINNERS 



Carbohydrates (starches, sugars, and cellulose) comprise the bulk 

 of man's nourishment. They are found in all vegetable foods, 

 grains, potatoes, fruits, and nuts. Milk furnishes an important 

 animal sugar. Though occupying so large a place in our menu, 

 carbohydrates compose hardly one per cent of the body's weight. 

 This is because they are easily oxidized, furnishing much heat and 

 energy and if any excess is taken, it is changed into fat and stored 

 as such. 



Thus it is seen that while proteid, fat, or carbohydrates may 

 all supply energy, neither of the latter can perform the proteid's 

 function in growth and repair of tissues. However, the fats and 

 carbohydrates serve to protect the valuable proteids by being first 

 oxidized and saving the proteids for tissue building which they 

 alone can perform. (See " Summary of Nutrients " at end of 

 chapter.) 



Measurement of Food Values. There is no way of measuring 

 the tissue-building value of foods. But, since all may produce heat 

 and energy, they may easily be measured and their value as food 

 computed in terms of heat produced. The unit of measurement is 

 the " calorie " which is the amount of heat required to raise the 

 temperature of one pound of water four (4) degrees Fahrenheit. 

 Very careful experiments have shown that a man in an average 

 day's work requires food enough to produce 2800 calories of energy. 



The amount of energy (number of calories) required varies with 

 age and occupation as shown in this table. 



TABLE I 

 DAILY CALORIE NEEDS (APPROXIMATELY) 



1. For child under 2 years 900 calories 



2. For child from 2-5 years 1200 calories 



3. For child from 6-9 years 1500 calories 



4. For child from 10-12 years 1800 calories 



5. Fof child from 12-14 (woman, light work, also) 2100 calories 



6. For boy (12-14), girl (15-16), man sedentary 2400 calories 



7. For boy (15-16), (man light muscular work) 2700 calories 



8. For man, moderately active muscular work 3000 calories 



9. For farmer (busy season) 3200 to 4000 calories 



10. For ditchers, excavators etc 4000 to 5000 calories 



11. For lumbermen, etc 5000 and more calories 



