Diet and Nutrition are two of the most important aspects of maintaining good health. Nutrition is the science of food and its relationship to health is concerned with the part played by nutrition in body growth, development and maintenance. The term ‘food factor’ is used for specific dietary constituents such as proteins, vitamins and minerals. Good nutrition means maintaining a healthy nutritional status that enables us to grow well and enjoy good health.

History:

Through centuries, diet and nutrition have been recognized as important for human beings in health and disease. The history of man has been a constant struggle to obtain food. Protein, carbohydrates and fats were recognized early in the nineteenth century as energy – yielding foods and much attention was paid to their metabolism and contribution to energy requirements. The discovery of vitamins at the turn of the twentieth century was a significant achievement in the field of nutritional science. By about 1950, all the presently known vitamins and essential amino acids had been discovered. Nutrition gained recognition as a scientific discipline with roots in physiology and biochemistry.

Great advances have been made during the past few years in the field of nutrition and in its practical application to meet the daily nutritional needs of the human body. Specific nutritional diseases were identified such as protein energy malnutrition, endemic goiter, nutritional anemia and nutritional blindness and technologies were developed to control them.

Classification of foods:

The association of diet and nutrition with infection, immunity, fertility, maternal and child health plays a significant role in the maintenance of good health. A great deal of research has been conducted on the role of dietary factors in the pathogenesis of non-communicable diseases such as coronary heart disease, diabetes and cancer. Foods are classifieds into various categories based on factors such as:

Origin: 

Foods of animal origin
Foods of vegetable origin

Chemical composition:

Proteins
Fats
Carbohydrates
Vitamins

Predominant functions:

Bodybuilding Foods – Milk, Meat, Poultry, Fish,            
                                         eggs, Pulses, Groundnuts.                               
                                        
Energy Giving Foods – Cereals roots, tubers, fats   
                                                   
Protective Foods – Vegetables, fruits, milk.

Nutritional value:

These include cereals, pulses, vegetables, nuts, oil seeds, fruits, animal foods, fats, sugar, condiments and spices etc.   

For maintaining good health we require energy providing nutrients and water in specific quantities. Specific nutrient requirements include nine essential amino acids, several fatty acids, four fat soluble vitamins, ten water soluble vitamins and choline. Several inorganic substances, including four minerals, seven trace minerals, three electrolytes and the ultra-trace elements must be supplied in the diet. The required amounts of the essential nutrients differ by age physiological state, level of activity etc. Conditionally, essential nutrients are not required in the diet but must be supplied to individuals who do not synthesize them in adequate amounts, such as those which genetic defects, pathological states with nutritional implications and immature infants.

Factors altering Nutrient needs:

The recommended allowances of nutrients are affected by age, gender, rate of growth, pregnancy, lactation, physical activity, composition of diet and drugs.

Physiological factors: Growth, Strenuous physical activity, pregnancy and lactation increase the nutritional needs of the body.

Dietary composition: This affects the biological availability and utilization of nutrients. For instance, the absorption of iron may be impaired by high amounts of calcium or lead. Animal foods such as milk, eggs and meat have high biological values with most of the needed amino acids present in adequate amounts. Plant proteins such as corn, soy and wheat have lower biological values and most be combined with other proteins to achieve optimal utilization by the body.

Disease: Specific dietary deficiency diseases include protein-calorie malnutrition, iron, iodine and vitamin A deficiency. The deficiency of vitamin B 12 can lead to megaloblastic anemia, Vitamin D deficiency can result in rickets, scurvy, beriberi and pellagra. Imbalances in nutrient intakes are also recognized as risk factors for certain chronic degenerative diseases such as saturated fat and cholesterol in coronary heart disease, sodium in hypertension and calcium deficiency in osteoporosis.

Recommended dietary allowances:

Human life and well being can be maintained within a fairly wide range of most nutrients. However, the capacity for adaptation is not in finite – too much, as well as too little intake of a nutrient may have adverse effects or alter the health benefits conferred by another nutrient. Therefore, benchmark recommendations on nutrient intakes have been develop for individuals. The RDA is the average daily dietary intake level that meets the nutrient requirements of nearly all healthy persons of specific sex, age, life stage or physiological conditions.

Diet and nutrition play a significant role in the growth, development and maintenance of the human body. It helps fight diseases and keeps the body fit.

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