Nutritional Value of Foods
The modern knowledge of nutrition indicates that foods serve specific functions in the body. Therefore, men need foods of different types in adequate quantities. All materials for building and maintaining strong, active bodies must be secured from the dairy products, eggs, fruits and vegetables, meats, and cereal products which are issued to the mess.
Abnormal supply conditions may make it necessary to substitute some foods for others. It is essential, therefore, to know which nutrients are required and which foods are richest in these nutrients.
The four cornerstones of the diet are proteins, vitamins, minerals, and energy-producing factors, all of which are essential to the maintenance of health.
The substance in foods which are called proteins merit their name which means "to take first place." They furnish essential building and repairing material for muscles and tissues of the body and enter into many, if not all, of the body functions. They also furnish energy.
Protein from animal sources in general is superior to protein from vegetable sources. Best sources: Milk, eggs, meat, fish, poultry. Other sources: Dried peas and beans, cereals, and vegetables.
Vitamins are definite chemical substances present in food in minute quantities. They are necessary for growth and the maintenance of normal body functions. The effects of vitamins on health are spectacular. There are several known vitamins which must be adequately supplied in the diet. All are essential for good health, but each has certain special functions. A brief summary of the functions and sources of the better known vitamins is herewith presented.
An adequate intake of vitamin A is necessary for normal resistance to infections and better vision in dim light. It may therefore be particularly important for all seamen standing night watches and for flyers. Best sources: Butter, liver, egg yolk, cheese, fish liver oils, yellow and green vegetables, and fruits.
Vitamin B1 (thiamin) affects morale and disposition, helps prevent fatigue, maintains appetite, healthy nerves, and normal muscle action. This vitamin is destroyed by excess heat. It is readily soluble in water and therefore is partially lost if cooking water is discarded.
Best sources: Liver and kidney, lean meat, especially pork, beans and peas, cereals with whole grain value, enriched flour, nuts, milk, and eggs.
Vitamin G (riboflavin) is essential to growth and normal nutrition for all ages. Deficiencies may result in digestive disturbances, nervous depression, general weakness, and poor conditions of the eyes and skin. Vitamin G is soluble in water and is destroyed by light. Best sources: Milk, lean meat, eggs, liver, green vegetables, peas, and beans.
Niacin, a third water-soluble vitamin, prevents the deficiency disease called pellagra which is usually manifested by skin disorders, and in severe stages, mental disturbances. Best sources: Liver, lean pork, salmon, whole grain cereals and enriched flour, milk, and eggs.
Vitamin C (ascorbic acid), "the sailor's vitamin" prevents scurvy, that scourge of long voyages in olden days which is now reduced because of better methods of food preservation such as canning and cold storage.
This vitamin is necessary to maintain the health of teeth and gums, to aid in resistance to infections, to prevent listlessness and fatigue and to maintain the strength of the bony structure and of the walls of the blood vessels. It is soluble in water and is partially destroyed by cooking, this loss being less in acid fruits and tomatoes. Best sources: Citrus fruits, raw vegetables, fresh fruits and fruit juices, tomatoes, raw or canned. Other sources: Green vegetables and potatoes, if not overcooked.
Vitamin D is concerned with the efficient utilization of calcium and phosphorous in the normal development and growth of the bones and teeth. Best sources: Fish liver oils, egg yolk, liver, and irradiated food. Sunshine affects the skin in such a way as to produce vitamin D which is utilized in the same manner as vitamin D from food.
Although there may be requirements for other less well known vitamins, a well rounded diet that provides sufficient amounts of the vitamins listed above will in general supply these in adequate quantities.
Certain mineral elements are needed by the body for growth and maintenance of body structure and processes. Some of these are so widely distributed in foods that they are usually supplied in sufficient amounts in any diet. Calcium and iron, however, may be too low unless care is taken in food planning.
Calcium, combined with phosphorous, furnishes the material from which bones and teeth are built, aids in the clotting of blood, and in regulating the action of nerves and muscles. Calcium is not quite as readily lost in cooking as are other minerals. Best sources: Milk, whole or skim (fresh, dehydrated), milk (evaporated), cheese. Other sources: Leafy vegetables, molasses, dried beans, or soy beans.
Iron is required for the formation of the coloring matter of the red blood cells. Unless sufficient amounts of this substance are present, the blood cannot efficiently carry oxygen to all parts of the
body for the continuance of life. Best sources: Eggs, meat, molasses, green vegetables, dried fruits, dried beans, whole grain cereals, and enriched flour.
ENERGY PRODUCING FOODS
Active men need large amounts of energy, 3,000 to 4,500 calories per day. In a well balanced diet it is estimated that approximately 10 to 15 per cent of the calories should be derived from protein; 55 to 70 percent from carbohydrate and 20 to 30 percent from fat. It is evident, therefore, that although protein is useful as an energy-producing food as well as for its muscle building function, the majority of energy is supplied from carbohydrates such as starches and sugars, and from fats. Best sources: Fats and oils; flour (bread, cakes, pastry), spaghetti, macaroni, rice and other cereals; sugar and sirups.
Suggestions for applying the principles of nutrition in a practical manner are presented in the following chapter on planning the menu.