Dr. R.L. Bijlani is with the Department of Physiology, All India Institute of Medical Sciences, New Delhi

Diabetes mellitus is a curious condition. It was identified as a disease entity thousands of years ago (called madhumeha in Charaka Samhita) but even today we cannot pinpoint its cause in a given patient. The cause may be diet, lack of exercise, overweight, genes, stress, auto-immunity, a virus, or a combination, which includes some of these factors and perhaps also something which we still do not know. Diabetes has been treated successfully for more than 75 years but it continues to maim and kill even today. The worst paradox is that although we have a good idea of how diabetes may be prevented, the prevalence of the disease is actually rising at an alarming rate. The prevalence of diabetes in India has trebled in the last 20 years and is now more than 10% in urban areas (1). Fortunately the prevalence is only about one-third as high in rural areas: a fact which has also provided valuable clues about lifestyle changes and prevention methods.

Pathophysiology of Diabetes
Diabetes results from an effective deficiency of insulin. The word effective is important because the actual secretion of insulin may not be reduced; it could even be higher than normal. But the secreted insulin may not be able to act due to insulin antibodies, or due to a defect in the cell receptors which mediate the action of insulin. Insulin is a hormone which regulates metabolism, specially facilitating utilization of carbohydrate, both for getting energy and for storage as glycogen. By increasing the fraction of energy which the body gets by oxidation of carbohydrates, insulin reduces the need for getting energy from fatty acids or amino acids. In addition, insulin also directly promotes the synthesis of fats (triglycerides) for storage, and of proteins for anabolic processes. Insulin secretion, and correspondingly substrate utilization, shifts periodically. After a meal, carbohydrate availability is high; hence insulin is secreted and energy is obtained from carbohydrates. Between meals, and during starvation, insulin secretion is reduced and energy is obtained predominantly from fats. During periods of good food supply, on the whole, more fat is stored than utilized: hence the person puts on weight. During periods of poor food supply, the opposite happens, and the person loses weight. In diabetes, since insulin availability is effectively low, the metabolism resembles that of starvation period. Fat stores are mobilized for providing energy. Eventually, even proteins are used as fuel. Hence the person loses weight. But since the person continues to eat, carbohydrate is not actually absent: it is just not being adequately utilized. Hence carbohydrate accumulates in the blood as glucose. The blood glucose level rises, and when it crosses a certain level, glucose appears also in the urine. In order to pass through the urine, glucose has to be accompanied by water. Hence the volume of urine also increases.

Pathophysiological Explanation for Explosive Trends
Any plausible explanation of recent rise in the incidence of diabetes to epidemic proportions should be able to account for at least four observations.

First, the incidence is rising in India. Second, the incidence is higher in urban areas than in rural areas. Third, the incidence is higher than even urban areas among Indians who have migrated to Western countries.
Finally, a similar rise in incidence has been observed in the past among the Maoris of New Zealand and the Australian Aborigines when they turned affluent and adopted a Western life style. One major factor which is common to all populations which have shown a striking rise in the incidence of diabetes is a rapid shift in the life style towards eating more, exercising less and living a more stressful life. Further, the populations which have shown this phenomenon have suffered for centuries from chronic food shortage characterized by alternating periods of sufficiency and scarcity. Based on such facts, Neel proposed in 1962 the thrifty gene hypothesis which has been revived and elaborated upon recently, and experimental work has also generated some evidence which seems to favour it. The hypothesis states that when food supply is unstable and unpredictable, it is helpful to have the ability to store energy in the body as fat during periods of plenty. The stored energy can then be mobilized during periods of scarcity. Under these conditions, natural selection favours the survival of individuals whose genes favour low energy expenditure (low basal metabolic rate) and efficient diversion of surplus energy towards storage as fat.
However, if the same individuals start living in conditions of constant and abundant food supply, they put on weight but do not get an opportunity to lose it. Overweight has a clear association with impaired glucose tolerance, which may eventually manifest as diabetes. The thrifty gene hypothesis was modified and elaborated upon by Hales & Barker in 1992 who proposed the thrifty phenotype hypothesis. This hypothesis emphasizes the role of early (foetal and infant) malnutrition in development of impaired glucose tolerance in adult life. It appears that if the mother is malnourished, the foetus has to share not only some malnutrition but also some endocrine adaptations of the mother to her state of malnutrition. The result is a thrifty phenotype in which insulin resistance and impaired capacity for insulin secretion are useful adaptations. These very adaptations become the cause of diabetes if upon growing up into an adult this child gets overnourished and obese. The umbrella which was useful in rainy weather turns into a burden in sunshine. In terms of the pathophysiology discussed above, one might say that a person adapted to frequent phases of mobilization of fat does not require much action of insulin during these phases. Therefore he cannot cope up with a situation requiring constant and excessive action of insulin for both glucose utilization and fat storage. The result is a breakdown of the insulin mechanism and consequent diabetes.

Prevention and Treatment
Since lifestyle, specially in terms of diet and exercise, plays a major role in the causation of the common types of diabetes, it stands to reason that appropriate changes in life style could prevent diabetes. Further, the same measures can also contribute to treatment. However, for prevention only life style changes are enough, but for treatment drugs may also be necessary in addition. What is still more encouraging, but not surprising, is that the same type of life style changes are also useful for preventing several other diseases such as high blood pressure and coronary heart disease. Although life style is an integrated entity, for convenience it is generally split into components as discussed below.

Diet
Diet has two aspects: quantitative and qualitative. The quantity of diet should be just enough to meet the requirements. Overweight persons should take less food than even their requirements till they achieve a desirable weight. A balance between energy intake and expenditure can be achieved not only by altering food intake but also by altering physical activity. It is better to be physically active and eat more, than to be sedentary and eat less, although both alternatives may achieve energy balance.
The quality of desirable diet for prevention and treatment of diabetes should have two main features. First, following its ingestion, the post-prandial rise in blood glucose should be relatively low. Secondly, taken day after day on a long-term basis, the diet should improve sensitivity to insulin. Both these features are common to diets which are high in carbohydrate but provide most of this carbohydrate in a complex form (i.e. as starch, not as sugar). Another feature of these diets is that they are rich in dietary fibre. In terms of foods it means that these diets have more of cereals, pulses, fruits and vegetables, and less of fat, meat and sugar. Further, the cereals and pulses in such a diet are preferably eaten whole, i.e., along with the husk. Apart from these generalizations, a few foods may be specially beneficial due to some characteristic chemical or physical features. For example, our studies at All India Institute of Medical Sciences have found buckwheat (kuttoo), barley (jau) and bengal gram (kala chana) to be promising. Chapaties made from a mixture of wheat, barley and bengal gram, a traditional preparation in Rajasthan, are acceptable and have a favourable influence on carbohydrate tolerance as well as serum lipids. Studies from other centres have reported favourable effects also with fenugreek (methi) and bitter gourd (karela). Plants having a hypoglycemic effect include neem leaves or bark, bamboo seeds, trifla, amaltas and powder from jamun core.
A happy outcome of recent nutritional research has also been a relaxation in some of the unpleasant restrictions imposed on diabetics. First, Indians are accustomed to high carbohydrate diets, providing about 70% of the energy. They can continue to take such diets. Second, if sugar is accompanied by fibre, fat and protein, the glycemic response to the food is quite low. Therefore sugar is not absolutely forbidden. If a cup of tea is sweetened with sugar but is accompanied by milk in the tea and biscuits or some other food, the sugar can be taken. The glycemic response to a high sugar food like ice cream is also quite low because of its fat and protein content. Thus ice cream is not taboo. However, too much of foods containing sugar would have a tendency to increase the energy intake. If this is compensated by reducing energy intake from other sources, the diet may become low in fibre and some essential vitamins and minerals. Thus although sugar is not taboo, sweet foods should be taken only in moderation. What is necessary is prudence, not an absolute ban. That is desirable not only for treatment of diabetes but also for its prevention in apparently healthy persons. Hence we have reached a stage when a diabetic patient can have a diet which is also a healthy diet for the rest of his family. All what the diabetic needs to do in addition is to regulate the quantity of the diet, and size, frequency and timing of meals, more carefully than the rest of the family. If taking insulin or an oral hypoglycemic, the necessity of not missing a meal would obviously still apply. But the degree of relaxation that is now considered rational and scientific is itself a big relief compared to the traditional lop-sided regimens which made the diabetic patient’s diet tasteless and markedly different from that of the rest of the family.

Exercise
Regular physical exercise influences health favourably through many mechanisms. From the point of view of diabetes, exercise helps in losing weight, which in turn improves glucose tolerance. Secondly, exercise promotes glucose utilization independent of the amount of insulin secreted. Finally, exercise releases endorphins in the brain, which may help relieve emotional stress. Because of multiple benefits of exercise, it is better to balance energy intake through adequate physical activity on one hand, and adequate food of the appropriate quality on the other. As in case of diet, the quality of exercise may also have a significance. We shall touch upon it briefly under yoga.

Stress Reduction
Circumstantial evidence strongly favours the hypothesis that stress may precipitate diabetes in susceptible individuals. Pathophysiologically, the link is understandable because stress is associated with release of counter-regulatory hormones, such as adrenalin and corticosteroids, which elevate blood glucose level. That is likely to put the insulin secretory mechanisms, and mechanisms mediating the action of insulin, under strain. In those who are genetically predisposed to diabetes, the strain may lead to the disease manifesting itself. Therefore changes in life style and cultivation of appropriate attitudes may contribute to prevention and treatment of diabetes.

Yoga
Yoga is a much misunderstood and commercially exploited word. Yoga is neither synonymous with postures (asanas) nor is it a system of medicine. It is a way of life directed at perfection of the body and mind with the ultimate aim of union with the Divine. A preparatory purification of daily life should precede any serious pursuit of yoga. Perfection of the body is sought to be achieved by asanas and breath control (pranayama). But since perfection of the body is only part of the practices, the overall aim of which is very lofty, asanas should be performed with an appropriate attitude. While performing asanas the yogi is occupied by thoughts such as "I am performing these exercises so that my body is healthy enough to carry out the Divine Will", or "I am performing these exercises so that my body is fit to be a temple for the Divine within". Without this attitude the asanas are merely ordinary physical exercises, and it is a misnomer to call them ‘yoga’, as is so commonly done. Perfection of the mind is aimed at developing a consciousness which is not limited by the five senses. Only such consciousness can be aware of the Divine within, and the Divine all around in all animate and inanimate objects. In order for such consciousness to manifest itself, the ordinary or surface mind should be silenced as much as possible. For example, to see the bottom of the sea, the superficial waves have to be silenced. An attempt is made to silence the surface mind through meditation. A frequent by product of meditation is stress reduction. Asanas, pranayama and meditation are merely techniques aimed at a higher goal, the pursuit of which colours every activity an individual performs in the course of daily work. The discipline usually also involves a simple vegetarian diet as a facilitating factor. Thus yoga includes diet, exercise and stress reduction - the life style changes discussed earlier - and much more.

That is why, yogis are generally in good health. But yogis do not enter the discipline to stay healthy or to cure a disease: the aim is much higher, and health is only a by-product. With this background, now we can visualize how narrow, limited and erroneous is the approach of research studies, reports on which run somewhat like this: patients of diabetes were trained in yoga (15 asanas and pranayama) for 1 hour per day for 6 months, and the process led to improvement in blood glucose control. Such studies permit one important conclusion, however. If benefit can result from so little performed so half-heartedly, how much healthier would the society be if yoga actually became a way of life.

Conclusion
Diabetes is an enigma which continues to cause concern in spite of all the significant scientific advances during the last 75 years. However, the mysteries surrounding the disease have not prevented us from bringing about considerable improvement in the lot of diabetic patients. While the unknown frontiers are being explored, we should continue to make full use of our current knowledge to make the life of diabetic patients more comfortable and as near normal as possible.

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