A Mixed Diet Best.--Knowing the proportion of the different food substances required by man, it will be an easy matter to determine from the tables and charts shown you the best foods for use in a mixed diet. Meats contain too much nitrogen in proportion to the other substances. In milk, the proportion of proteins, carbohydrates, and fats is nearly right to make protoplasm; a considerable amount of mineral matter being also present. For these reasons, milk is extensively used as a food for children, as it combines food material for the forming of protoplasm with mineral matter for the building of bone. Some vegetables (for example, peas and beans) contain a large amount of nitrogenous material but in a less digestible form than is found in some other foods. Vegetarians, then, are correct in theory when they state that a diet of vegetables may contain everything necessary to sustain life. But a mixed diet containing meat is healthier. A purely vegetable diet contains much waste material, such as the cellulose forming the walls of plant cells, which is indigestible. It has been recently discovered that the outer coats of some grains, as rice, contain certain substances (enzymes) which aid in digestion. In the case of polished rice, when this outer coat is removed the grain has much less food value. Daily Fuel Needs of the Body.--It has been pointed out that the daily diet should differ widely according to age, occupation, time of year, etc. The following table shows the daily fuel needs for several ages and occupations:-- 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. For 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 Normal Heat Output.--The following table gives the result of some experiments made to determine the hourly and daily expenditure of energy of the average normal grown person when asleep and awake, at work or at rest:--