Eating healthy

By on Saturday, January 12, 2008 - 16:21

Maheswari R gives a low down on the essentials of nutrition and dietary patterns

This is the first of the 6 part series. In the next few articles we will talk about essential food for specific age groups of women and phases such as pregnancy and 50+

Human beings need a wide range of nutrients to perform various functions in the body and to lead a healthy life. Nutrition as a science, examines the relationship between diet and health. Diet is the sum of food consumed by a person.  The World Health Organization (WHO) defined health as "a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity".

There are seven main classes of nutrients that the body needs: carbohydrates, proteins, fats, vitamins, minerals, fibre and water. It is important to consume these seven nutrients on a daily basis to build and maintain health.  Proteins, fats and carbohydrates, which are referred to as proximate principles, are oxidized in the body to yield energy the body needs. Vitamins and minerals do not supply energy but they play an important role in the regulation of the metabolic activity in the body and help in the utilisation of the proximate principles.  Fibre (dietary fibre), which is indigestible complex molecules, contributes to the bulk and has some useful function in the digestive tract.  Man needs all these nutrients in different amounts to grow, live and thrive.

Proteins

Proteins are vital to any living organism.  Proteins are
- Important constituents of tissues and cells of the body.
- Important component of muscle and other tissues and vital body fluids like blood.
- In the form of enzymes and hormones that are concerned with a wide range of vital metabolic process in the body.
- Suppliers of body building material and make good the losses that occur due to wear and tear.  
- As antibodies, helps the body to defend against infection.

Dietary proteins are broken down into amino acids and absorbed as such and these amino acids are used by the body to synthesize the protein required for various functions like tissue building, replacement of depleted protein and synthesizing functional molecules like enzymes, hormones and antibodies.  Amino acids that are not used for protein synthesis, are broken down to provide energy, 1 g of protein giving rise to 4.2 kcal.  If the diet does not contain adequate carbohydrate and fat to provide energy, dietary protein may be broken down to provide energy, which is a wasteful way of using proteins. Hence, a balanced diet should contain adequate carbohydrate and fat to provide energy so that the proteins in the diet are most economically used for the formation of body proteins to fulfill other functions essential to life.

Fat

Fat is an important component of diet and serves a number of functions in the body.  It is a concentrated source of energy and it supplies more than twice the energy furnished by either protein or carbohydrate.  Presence of fat in the diet is important for the absorption of fat-soluble vitamins like vitamin A and carotene. Apart from these functions, some fats, particularly those derived from vegetable sources, provide what is known as “essential fatty acids” (EFA).  These EFAs are also important for the structure and function of cells.

Fats in the diet can be of two kinds, the visible and invisible fat.  The visible fats are those derived from animal fats like butter and ghee which are solid fats and those derived from vegetable fats like groundnut, mustard, coconut, safflower and til, which are liquid fats. Animal fats like ghee and butter contain vitamin A and D. Vegetable oils on the other hand contain vitamin E, which protects the oil from oxidation.

Diet containing nuts, oilseeds, soybean, avocado, pear and animal foods have a higher amount of invisible fat.  Excessive intake of fat in diet leads to increasing level of cholesterol in blood. Excess cholesterol in blood gradually leads to its being deposited under the lining of blood vessels, resulting in a condition known as ‘artherosclerosis’ in which the blood vessels are narrowed and hardened.  The coronary arteries supplying blood to the heart are affected and coronary heart disease results.  Another important aspect of dietary fat is the nutritional significance of polyunsaturated fatty acids present particularly in vegetable oils which not only act as a source of essential fatty acids, but helps in the control of blood cholesterol.  Like vitamins, essential fatty acids also play a role in several metabolic reactions, a deficiency of these fatty acids was believed to lead to a skin condition known as ‘Phrynoderma’ (toad skin) in which skin becomes rough, and thin horny papules of the size of a pin head erupt in certain areas of the body, notable thighs, buttocks, anus and trunk. These fatty acids present in fish and fish oils are considered to be essential for the preventing of coronary heart disease.

Carbohydrate

Carbohydrates are a class of energy yielding substances, which include starch, glucose, cane sugar, milk and sugar. Grain foods, roots and tubers are largely composed of starch, a complex carbohydrate. Food ingredients like simple sugars like cane sugar and glucose are pure carbohydrates. Carbohydrates derived from cereals form chief source of energy in Indian diets.   Starches when eaten in a cooked form are completely digested in the gastrointestinal tract and the released glucose is absorbed and metabolized in the body to yield energy.

Vitamins and Minerals

Vitamins are organic substances present in small amounts in many foods. They are required for carrying out many vital functions of the body. Although they are needed in small amounts, they are essential for health and well being of the body.

Vitamins fall into two categories: fat soluble and water-soluble. The fat-soluble vitamins — A, D, E, and K — dissolve in fat and can be stored in your body. The water-soluble vitamins — C and the B-complex vitamins (such as vitamins B6, B12, niacin, riboflavin, and folate) — need to dissolve in water before your body can absorb them. Because of this, your body can't store these vitamins.

While vitamins are organic substances (made by plants or animals), minerals are inorganic elements that come from the soil and water and are absorbed by plants or eaten by animals. Your body needs larger amounts of some minerals such as calcium to grow and stay healthy. Other minerals like chromium, copper, iodine, iron, selenium, and zinc are called trace minerals because you only need very small amounts of them each day.

Vitamins and minerals boost the immune system, support normal growth and development, and help cells and organs do their jobs.  The vitamins and minerals you need are found in the food you eat. It's important to eat a balanced diet that includes fruits and vegetables.

Fibre

Dietary fibre consists mainly of cellulose that is indigestible because we do not have enzymes to digest it. Fruits and vegetables are rich in dietary fibre. It provides bulk to the intestinal contents and stimulates peristalsis (rhytmic muscular contractions passing along the digestive tract). Lack of dietary fibre in the diet leads to constipation.

Water

Water is necessary for your body to digest and absorb vitamins and nutrients. It also detoxifies the liver and kidneys, and carries away waste from the body. Fibre alone cannot aid proper digestive function by itself.  In fact, without water as its partner, good fiber goes bad, causing constipation and extreme discomfort. Specifically, pregnant and breastfeeding women need additional fluids to stay hydrated.

Water improves energy levels, increases mental and physical performance, removes toxins and waste products from the body, keeps skin healthy, helps lose weight, allows proper digestion, and helps regulate body temperature.

Maheswari R is a post graduate in Human Nutrition and Nutraceuticals.  Currently works as Dietician in the NGO supported programs in Madurai