Jethalal S. Zaveri
We need continual supplies of foods and water to provide energy for body-activities and building materials for growth and repair. Though we may subsist on a wide variety of diets, optimum growth development, and health require a balance of nutrients. A balanced diet must contain not only proteins, carbohydrates and fats, but also vitamins, minerals and water as well as a certain amount of indigestible fibre to keep the intestinal peristalsis [1 ]stimulated.
Water
About two-third of the total body-weight is water. Besides playing a key role in the body's heating and cooling systems, water acts as a solvent for chemical reactions and a carrier fluid in the body's circulating systems. Water is lost from the body in urine, feces, sweat and exhalation. It must be replaced in the daily food intake. The most obvious source is water and beverages, fruits and vegetables.
Carbohydrates
Carbohydrates—sugars and starches—make up the largest single component of human diet. It is a necessary constituent, because it is the body's preferred energy source. Any available glucose is metabolized first, before proteins or fats. Without sufficient carbohydrates in the diet, proteins will be metabolized for energy and there may be an actual wasting of body-proteins. Carbohydrates, in the form of starches, predominate greatly in products made from flour—breads, biscuits, etc.—cereal products and in vegetables such as potatoes. Sugar is added in most processed foods now available in market. Only the three elements—Carbon (C), Hydrogen (H) and Oxygen (O) combined in the ratio CxH2yOy constitute all carbohydrates; proportion of hydrogen atoms to oxygen atoms being the same as in water (H2O).
Glucose and its variant forms are simple sugars (monosaccharides). Sucrose, maltose and lactose are disacharides i.e. two simple sugars joined together. Starches are more complex sugars consisting of many monosaccharides linked together. Cellulose, a polysaccharide in the vegetable kingdom, is a major constituent of the diet but is not available to the human body as a nutrient, since we lack the appropriate enzymes to digest it. It comes from fruits, vegetables, bran i.e. skin of the whole cereal grains. The cellulose-fibre passes through the digestive tract essentially unchanged, but the 'bulk' helps to satisfy hunger and is important for stimulating bowel function. Substantial proportion of fibre in the diet relieves problems of chronic constipation. Carbohydrates are often regarded as prime culprits in causing obesity (fatness). But a high fibre diet is filling without fattening. Evidence is also accumulating that such a diet may help to lower the rates of both cancer (by speeding the passage of potential carcinogens out of the body) and of heart-disease (bran and other fibres promote the excretion of excess cholesterol). Whole wheat (brown bread and unpolished rice etc.) are more valuable and their value must be reappreciated.
Proteins
Proteins are necessary in the human diet for the amino acids. The proteins available in different foods differ widely in the assortment of amino acids and their proportion, but no one protein contains all of the twenty-three or so, naturally occurring amino acids. Actually the human body is capable of converting certain amino acids to others and even build them up from non-protein sources (carbohydrates and fats). But it is unable to synthesize eight [2] essential ones which must be supplied by the diet to maintain health. Others are not essential in the diet (though essential to the body) since they can be synthesized in the body.
All the amino acids needed for growth and maintenance of the body are available in the protein supplied by milk. Some vegetable notably the legumes (peas, beans), lentils, ground-nuts etc. also supply substantial amounts of high quality protein. One can live healthfully on a vegetarian diet by giving importance to legumes and by combination of other foods that mutually supplement each other's deficiencies. Since the digestion splits the protein molecules into their constituent amino acids, it makes no difference to the body how the amino acids are supplied. Unless sufficient amounts of essential amino acids are provided regularly, even if the diet is quite adequate for caloric requirement, a protein deficiency syndrome may develop. In children, protein-deficiency results in a retardation of growth, lethargy and mental retardation.
Proteins of wheat, corn and peas etc are simple proteins containing only amino acids. Proteins of milk, egg etc. are conjugate proteins i.e. combined with non-protein substances.
Fat: Butter, Oil, etc.
A little fat goes a long way as far as the calories are concerned. Fats are more economical sources of energy for the body (9 calories/gm, vs. 4 calories/gm. for carbohydrates and proteins). Moreover, in most foods, proteins and carbohydrates represent less than 25 percent of the total weight of the food; (the rest is water). But fat is 100 percent fat.
There has been a great deal of controversy about the possible implication of fats in the development of heart disease. Similarly for some time cholesterol was regarded as the prime villain in the development of atherosclerosis—the build-up of fatty deposits in the artery-walls. Heart patients are strongly urged to drastically reduce and limit their cholesterol intake. Recently it has been realised that cholesterol level is not always correlated with the condition for the artery-walls and even on a cholesterol-free diet the body can synthesize abundant amount. Indeed, cholesterol is a vital substance for the body; it is found in all the cells and fluids of the body and in the blood. Current research seems to indicate that the "prudent diet" should include a certain proportion of unsaturated fats which are naturally found in vegetables and seed oils. Hydrogenation [3] improves their storage-qualities but eliminates their unsaturation. Cholesterol level in the blood is now believed to be more reliable predictor of heart-attack risk than the total cholesterol levels. A diet rich in saturated fat and/or cholesterol contribute to obesity (fatness) and build-up of fatty deposits inside artery walls. Unsaturated fats prevent cholesterol deposition and physical activity removes it from the artery walls.
Vitamins
If you eat a balanced diet, you do not need vitamin pills. Unfortunately, processing and storing of foods often tend to remove or destroy vitamin constituents, e.g. the pasteurisation of milk destroys milk's natural vitamin C content. The manufacture of flour, involving removal of hull and bran from the grains, strips of many of their vital ingredients especially the B-complex vitamins. The discarded hull and bran provide a highly nutritious fodder for livestock.
Vitamins are organic substances that are needed in very small amounts for the normal metabolic processes and cannot be manufactured by the body itself. Most of them act as co-factors for enzymes in the body. At least a dozen vitamins have been established as needed in human nutrition, while many more are suspected to be essential to good health. Most animals can synthesize all the vitamin C they need, whereas human beings need a regular dietary intake of this vitamin. Plants do not need to take in any vitamins. They synthesize all that they need. Plant substances, in fact, provide major sources of vitamins in the human diet.
Vitamins are grouped into two basic categories according to their solubility. Vitamins A, D, E, and K are soluble in fats and oils. They require the presence of bile in the intestines to be absorbed; a defect of fat-absorption thus leads to their deficiencies. They tend to be stored in the body for relatively long periods and thus a steady in-take is not vital. On the other hand, if the levels of intake are high, accumulation may become a problem. The varied group that makes up the B complex and vitamin C are water soluble and are not stored in the body. As excesses are rapidly excreted, cumulative overdoses do not present a problem but a steady daily source must be ensured.
Vitamin A plays an important role in the chemistry of vision and its deficiency results in night blindness. It is also involved in growth processes and the maintenance of the skin and mucous membranes. Massive overdoses produce toxic effects including headache, nausea etc. Carrots are a rich source of precursor of this vitamin, which itself is produced in the body.
Vitamin B Complex: Strange as it may appear, the members of the B complex group are neither chemically similar nor are their effects similar. Their grouping together was merely an accident of history. They are all water soluble and are found together in various foods; some members of this group are:
B1 (Thiamine): Discovery of the first of this group was named B1. Its deficiency initially causes loss of appetite and indigestion; then an involvement of the nervous system, loss of motor-function and ultimately beriberi including enlargement of heart. Nervous system and cardiac muscle are particularly vulnerable to vitamin Bi, (thiamine) deficiency. Yeast, whole grain cereals (especially the hulls and brans), milk, legumes, (beans etc.) and nuts are rich food source of this vitamin. Its minimum daily requirement varies with the body size and calories utilised per day.
Vitamin B2 (Riboflavin) was originally isolated from milk. A good part of the body's requirement of this vitamin is normally produced by the bacteria inhabiting the intestines, but a part must be consumed in food. Its deficiencies are usually mild and result in dermatitis, inflammation of the tongue and cracking of the corners of the mouth. It generally occurs together with a deficiency of other B vitamins. Food sources for this vitamin include ground-nut, wheat-germ and vegetables such as spinach.
B6 and B12: B6 deficiency can cause anaemia, dermatitis and convulsions. Fortunately its deficiency is rare. Its sources are the same foods that provide abundant supplies of the other B complex vitamins viz. wheat-germ, milk etc. It is also synthesized by intestinal bacteria. B12 is necessary for growth and maturation of red blood cells. Very small quantities—just micro-grams—are needed. Its deficiency causes anaemia, weakness and numbness of limbs and finally in a complete loss of ability to control them.
Niacin: Yeast, groundnut, wheat-germ, legumes and milk are good food sources of vitamin Niacin. It is also synthesized by bacteria in colon. Its deficiency can result in dementia, diarrhea etc.
Pantothemic acid, folic acid and biotin are other members of the group. They are all synthesized by the bacteria in the intestines. Folic acid is also supplied by fresh leafy green vegetables. Yeast, milk, grains, vegetables and nuts are other food sources for these vitamins.
Vitamin C: Human beings are one of the few animal species that need a dietary supply of this vitamin. Some years ago, large doses of vitamin C (one to ten grams daily), as a preventive for the common cold, was proposed by the Nobel Prize winner—L. Pauling. According to the latest evidence, taking large doses of this vitamin does indeed reduce the average incidence of colds and lessens the severity of those that occur. Besides, it has been found to exert a cholesterol-clearing action on hardened arteries. Pauling has also reported an anti-cancer activity and large doses of the vitamin have, indeed, significantly prolonged the lives of terminal cancer patients.
Experiments on treating scurvy victims, (swollen and painful joints, fragile bones, bleeding gums and loosened teeth), with various foods showed that fresh citrus fruits cleared up the condition. The actual vitamin which was isolated and studied in the early 1930s, was named ascorbic acid. A vitamin C deficiency interferes with the healing of wounds and produces weight-loss, weakness and the other symptoms of scurvy just mentioned.
The best sources of this vitamin are fresh fruits and vegetables, specially, the citrus fruits (oranges, lemons, grapefruit), tomatoes and strawberries. Leafy green vegetables are also a good source, provided there is not too great loss of vitamin in cooking. (Heat, combined with exposure to light, causes a breakdown of the vitamin and large quantities of water used in cooking may dissolve it out of foods).
Vitamin D is actually manufactured in the body but only under special condition viz. in skin exposed to sunlight. Being a typical fat-soluble vitamin, it is stored in the body for long periods. People who work outdoors and have a large portion of their skin exposed to sunlight need only minimal amount in diet. Melanin in the dark-skinned people, screen out a large fraction of the sun's rays. Vitamin D2 (calciferol) is the commercial form of vitamin D.
This vitamin increases calcium-absorption from the gastrointestinal tract and also helps to control bone-formation and resorption. Its deficiency in children causes rickets (bones are soft and fragile and the skeleton becomes malformed). In adults, it leads to softening of the bones, skeletal deformities and frequent fractures. Milk and butter are good sources for this vit&min. Since this vitamin is commonly added to processed foods, a possible overdose in quite likely.
Vitamin E: This is so widespread in foods that actual deficiencies are virtually unknown. Children with cystic fibrosis may have it as a result of malabsorption in the intestines. This vitamin acts as an antioxidant, preventing the oxidation of unsaturated fats. It also provides protection against action of radiation and environmental pollution. Food sources of vitamin E are wheat-germ, oil, whole wheat products, lettuce, milk and butter.
Vitamin K: This vitamin is essential for blood-clotting. It is produced by the intestinal bacteria. Taking antibiotic may kill the population of beneficial intestinal bacteria together with the invading pathogens and the body is without its normal supply of vitamins. At such times, a dietary intake of this vitamin, which is otherwise produced in sufficient quantities, is necessary. It is present in most foods, especially spinach and other leafy vegetables and tomatoes. Its deficiency slows the process of blood-clotting and haemorrhage occurs readily. It is often given routinely before surgery and before delivery to control possible haemorrhages.
The table giving information on major vitamins is given in appendix A.
Minerals: Minerals constitute about 4% of the body weight. As many as 40 elements are critical for the proper functioning of the body. Some, such as calcium and phosphorus of bones, are present in sizable quantities; others are needed only in minute amounts. These are often referred to as trace elements or micronutrients. Minerals are lost daily in the urine, feces and sweat and must be replaced by the intake of foods. As mineral salts help to maintain acid-base balance and participate in various body-functions such as conductivity, coagulation of blood etc., their deficiency can produce disease or poisoning. Some important minerals and their functions are given here.
Calcium is the most abundant element. 99% of it is found in the bones and teeth. Yet the other one percent is vital for cell activities. It is involved in muscle-and-heart-contraction, in nerve-conduction and blood-clotting. A daily intake of 1 gram is needed to maintain an optimum concentration in the body fluids. But children and nourishing mothers have increased requirements. Bones and teeth will be demineralized, if the diet is deficient in calcium. Milk and milk-products are the best food-sources, but it is also supplied by leafy vegetables.
Phosphorus is also an abundant and vital element. About 80 percent is combined with calcium in the bones and teeth. It is also an essential constituent of the nucleic acids, ATP, etc. Daily requirement is about 1.5 gram, but increased amounts (equal to that of calcium) are needed by growing children and nursing mothers. Foods that are rich in calcium (e.g. milk) also provide good supplies of phosphorus. It is also found in beans and nuts.
Sodium is found mainly in the extra-cellular fluid with only traces inside the cells. It plays a major role in the acid base balance and osmotic pressure. Table salt (sodium chloride) is commonly and routinely added to many foods, but the average diet provides ample amounts of sodium even without salting. Person with heart-disease must severely restrict their salt intake as it is believed to be contributing to the development of hypertension (high blood-pressure).
Normally kidneys maintain optimum levels by reabsorbing it from urine. When, however, sodium-loss is copious by sweating, it must be promptly replaced; otherwise, weakness, cramps and diarrhea may result.
Potassium: In contrast to sodium, it is found mainly inside the cells. Beside the water-balance, it plays a role in nerve and muscle-activity. Either high or low levels produce abnormalities of the heart action. Most foods contain potassium and dietary deficiencies are extremely rare.
Iron is key mineral in the body. It is a constituent of the haemoglobin in the red blood cells, myoglobin of skeletal muscles and various enzymes. It is not one of the more abundant elements. Actually the adult body contains only about 4.5 grams (compared to 125 grams of potassium). About half of this is contained in the haemoglobin. Iron is stored in the body, but the storage is limited and a regular intake in the diet is necessary. Women lose significant amount each month in menstrual flow and thus have increased requirements and often suffer from deficiency. Beans, peas, whole wheat, spinach and prunes supply abundant amount of iron.
Magnesium is widely distributed in the body. Most of it is in the bones but it is also present in the cells and blood-serum. It is a key cofactor in the metabolism of glucose and ATP. Excess concentration in the extra-cellular fluid depresses the conduction of nerve impulses and the muscular action. It is chemically similar to calcium. It is widely distributed in foods, green vegetables being especially good sources.
Copper and Manganese are trace elements which are vital to the body, being constituent of or activating a number of metabolic enzymes. Copper participates in the formation of haemoglobin, though it is not an actual part of it. The entire body content of copper is only about 100 mg. and yet its deficiency (as may occur in infants on an exclusive milk diet) will result in anemia and other serious consequences. Normal diet provides adequate amounts of manganese; excess of this mineral is toxic.
Chlorine, Iodine, Fluorine are members of the same chemical family. Chlorine is distributed throughout the body in the form of chloride ions which diffuse into red blood cells to maintain ionic equilibrium. It is also a part of the hydrochloric acid in the stomach. It is supplied by common salt.
Iodine is found mainly in the thyroid gland. It is essential for the synthesis of the hormone thyroxine. In inland areas, the food and water-supply tend to be iodine-deficient resulting in goitre and other problems. Dietary iodine can be provided by the use of iodized salt. Fluorine is deposited in teeth and bones. It is not certain whether it is needed in the diet, but it is commonly used to prevent tooth decay. In excess it can produce mottling of teeth and skeletal deformities. It is natural constituent of drinking water in some localities.
Zinc and Cobalt are found in most food and tap-water. Zinc is an integral part of numerous enzymes and is involved in such vital body-functions as the transport of carbon dioxide in the blood, energy metabolism and digestion.
Cobalt is an essential constituent of vitamin B2 which is necessary for the maturation of red blood cells.
The table giving information on major minerals is given in appendix B.
Other mineral elements which are also essential for normal body-functions include sulphur (a constituent of proteins), chromium (participates in glucose metabolism), molybdenum (plays a role in enzyme activity), selenium (important in liver function), and vanadium (necessary for growths).
Some trace minerals that find their way into food or drinking water can be dangerous to health. Industrial water pollution has been adding to the problem. Mercury-residues can cause severe neurological damage. Cadmium (leaking out of water-pipes into drinking water) has been implicated in the development of heart-disease. It is naturally present in wheat but the grain also contains zinc, which prevents the absorption of cadmium. When bran is removed to refine wheat flour, most of the zinc is removed, altering the mineral balance and leaving the cadmium.
A Balanced Diet
Knowledge of complex interaction of nutrients as discussed above help us in choosing a balanced diet and in fostering the development of better nutrition. Whatever the diet may be, it should provide adequate calories to supply the body's energy needs. Carbohydrates (starches and sugars) with some fat are thus essential. Enough protein must be provided for tissue-building and repair—65 to 100 grams of proteins daily intake is recommended for adults. Besides all the necessary vitamins and minerals, the adequate diet should also provide sufficient water and enough fibre to promote good bowel-function.
A variety of foods helps to ensure that all the dietary needs of the body will be met. Each of the major food groups should be adequately represented by one or more members: (a) cereal and grain products (b) milk and milk products (c) fruits and vegetables (d) legumes (beans, peas) (e) nuts and dry fruits.
Caloric Requirement
No matter how inactive one may be, rate of energy-expenditure will not fall below a certain basic value. This is the minimum level of energy expenditure required to maintain the basic cell and body functions—basal metabolic rate (BMR). Energy-consumption will rise sharply when one moves round and does physical work. Energy-consumption is measured in Calories. Just existing at a minimal level, energy-consumption is about 1600 to 1800 Calories a day for man on the average and 1300 to 1500 for a woman. Slightest exertion—sitting up, standing, walking [4], exercising—uses up additional Calories. Thus the amount of physical exertion a person normally does is an important determinant of caloric requirement. For example, a sedentary worker (student, office-clerk, typist etc.) would need 2200 to 2500 Calories a day. One engaged in more strenuous activity (metal-worker, painter) has a daily expenditure of about 3000 Calories. A hard worker may use as many as 8000 Calories in a day. If the food-intake does not supply this requirement, weight will be lost as body's reserves are utilised; if more Calories are taken in than are used, the residue will be stored as fat, and weight will be gained. Mental exertion, no matter how intense and tiring, does not use up many Calories. Emotional stress does cause some increase in energy expenditure through a speeded up heart rate, increased breathing-rate etc.
Physical activity is a primary factor but not the only one determining caloric requirements. Body-size is an important factor. Age is also another one: growing children need far more calories in proportion to their size than adult and the caloric requirement gradually decreases throughout adulthood. Thus a person of middle age will put on weight if he continues to eat the same diet as in earlier years.
Obesity and Dieting
Obesity (fatness) or overweight is a major health problem of the modern times. It is caused by consistently taking in more calories than one uses. The excess is converted to fat and stored in the body. Obesity can develop gradually and insidiously. We not only eat too much, not only eat the wrong foods but often eat too much of the wrong foods. Abundance of food combined with a sedentary way of living contributes to the problem. In a new cases, the problem may have a specific organic cause—a disorder involving thyroid, pituitary or other glands. When it also tends to run in family, it suggests that a hereditary factor may be involved. Since the hunger and satiety centres which regulate the food intake is in the hypothalamus, its abnormality may be involved. Children who are overfed by anxious mothers, develop more fat cells and have problems when they are adults.
A compelling reason to avoid overweight is that it increases the probability of a premature death. Excess body-weight puts a constant strain on the heart in several ways. It must pump harder to supply enough blood to the muscles which must work harder to move the extra weight. The fat deposits require copious blood supply. Millions of extra capillaries are formed adding resistance to the circulation and raising the blood-pressure. Fat persons are more prone to the hardening of arteries, gall stone formation, kidney-inflammation and other diseases.
The most reliable way to lose weight and to keep it off is to make a drastic change in eating habits. Our food today is not what our ancestors normally ate. Not only has a great deal of its value been removed, but almost all the food we buy has been processed and contains some kind of preservative.
The diet of our ancestors contained a relatively small amount of sugar supplied mainly by fruits. Refined cane sugar (sucrose) did not become a significant factor in the human diet, until about 200 years ago; since then sugar consumption has risen steadily. According to some researchers, sugar may be the main culprit in the development of atherosclerosis. For those who have not been fortunate enough to inherit a strong pancreas, continual high intake of sugar can "burn out" glandular cells of this organ [5], leaving it unable to regulate the body's carbohydrate metabolism.
A reduction in total caloric intake, enough to produce a small but steady weight loss (1/2 to 1 kg. per week) is more effective than food dieting. Sudden introduction of any radically new diet can cause stomach upset. A severe reduction of total calories or a restriction to just one or few specific foods, seems to show results at first but the initial weight loss is mainly a loss of water and soon the weight stops at a constant value. By this time the dieter is chronically hungry, irritable and thoroughly fed up. His resolution usually goes by default the next time he sees somebody eating a cream cake. Dieting is abandoned and the lost weight regained quickly. Incorrect diet (incorrect both in quantity and content) can cause as many problems of ill health as can the tensions of modern living. True, it is difficult to depart from one's eating habits and plan, unfortunate though they may be. There are, however, great many ways in which we can improve our nutritional picture without radically changing our way of life. A few easy tenets with regard to eating combined with a gradual change in the diet will improve our health considerably. An increase in physical activity and regular exercise will also contribute to the weight-loss by increasing energy-expenditure. This again should be a permanent change in habits rather than crash programme of strenuous exercises that may put too great a strain on the unconditioned heart. Regular exercise also lowers the risk of heart-attack. Crash reduction of the total food intake also reduces the intake of vitamin, minerals and water. Leafy vegetable are usually low in calories, high in vitamins and minerals. They satisfy hunger and promote good bowel function.
Tenets for eating
- Eat moderately: leave one quarter of your stomach empty. The slight feeling of hunger will disappear after a few days' regular practice.
- Make maximum use of the food intake. Chew mouthful thoroughly before swallowing. Properly masticated food attains a soft paste-like consistency and slips easily down the throat.
Stage by Stage Plan for Healthier Diet
First Stage: Avoid all food containing preservatives. Eliminate the use of refined white sugar. Avoid sweets, jams and such other foods which contain white sugar. Demarara (unprocessed brown) sugar, jaggery (gur) and honey can be used to sweeten instead of white sugar. Substitute brown bread in place of white. Avoid white flour products as far as possible.
If you are not a vegetarian, discontinue or drastically reduce (if your are unable to avoid it altogether at once) meat and meat-products.
If you are using chemical salt, discontinue it and substitute sea-salt.
Second Stage: Eliminate use of pepper, chillies and other hot spices. (Turmeric and other condiments can be used). Discontinue tea and coffee; substitute them with milk and fruit, juice or fresh fruits. Further reduce meat from your meals.
Third Stage: Avoid meat completely. Increase the use of cereals, dry fruits, nuts, vegetables and salads and milk to give a full nutritional picture.
Substitute fresh fruits for sweet desserts and pastries.
Eliminate deep-fried foods.
When you have completed the last stage, food has assumed its proper place in your life. This does not, however, mean that you cease to enjoy your meals. In fact you may develop a keener sense of taste. An occasional meal, outside the above plan of diet, does little damage, so long as you remember to eat moderately and chew thoroughly.
Disastrous results of bad habits of drinking and smoking have been dealt with in chapter VII of this book.
Peristalsis is the name given to the slow automatic wave like movement along the whole of the alimentary canal propelling the contents onwards.
Vegetable oils are subjected to the process of hydrogenation so that they can be preserved. The process, unfortunately changes the appearance to that of ghee without, however, bestowing the values of real 'ghee'.
