Friday, August 8, 2008

A Fresh Look At The Role Of Insulin.

Insulin is a hormone, which is produced by a part of the Pancreas gland, situated just below the stomach. For more than a century it was believed and this is what we were taught in medical college that principal function of this hormone is to push glucose into the body’s cells, where it is used as fuel for producing energy, which in turn is used for muscular activity and metabolic needs. By & large, this view continues to be held by most of the people concerned though unfortunately this is NOT true. Principal role ordained by nature to Insulin is storage of excess glucose in the form of glycogen and fat and NOT pushing glucose into cells for their metabolic needs. If you cross check for factual correctness with the published literature (references available, on request), you will come across the following hard facts:
1. Principal glucose using tissues in human body are:
a. Central & Peripheral Nervous System (consisting of the brain, spinal cord, and nerves).
b. Contracting muscles.
Mind you: contracting muscles and NOT relaxing muscles. Accordingly, brain and other parts of the nervous system are not dependent upon Insulin to transport glucose inside their cells. Their cell walls are, in a way or so to say, porous/ permeable to glucose and depending upon the cell’s needs, glucose just slips in from the blood stream, independent of Insulin. Similarly, contracting muscles use only glucose (glycogen, to be precise, which is a storage form of glucose) for their energy requirements. The mechanisms involved in releasing energy from fats are just too slow to meet with the need of sudden bursts of energy required for muscular activity. Therefore, during exercise or physical activity, muscles require almost no Insulin or very little Insulin is enough to push glucose into muscle cells. In other words, muscles become freely permeable to glucose during physical activity, even as gentle a physical activity as walking. (therefore lesson No 1: walk, whenever and wherever and howmuchsoever you can: each step counts and the benefits are enormous.)
2. Rest all the tissues in the body, including relaxing muscles; though preferentially use Free Fatty Acids for their metabolic requirements but are capable of using various other substrates also quite freely and are adept at switching between various modes of energy production. Exception to the foregoing is heart, which can use ONLY Free Fatty Acids for its energy needs. Heart muscle is incapable of metabolizing glucose (though it can metabolize Lactic Acid, which is a byproduct of glucose and fat metabolism). All energy requirements of this nature have been clubbed together in the term “Basal Metabolic Rate”, which has been measured quantitatively and works out to be around 1400 Cal. Per day. These 1400 Cals are meant to come from 150 gm of fat, and come from fat they will: whether you consume 150 gm of fat per day, or convert 300 gm of glucose into fat with the help of Insulin (there are evolutionary reasons for this, which are beyond the scope of this article). Don’t you think that this second option is like going from Delhi to Agra via Mumbai? (Therefore, lesson No. 2: consume at least 100 gm of visible fat per day, which should mostly be in the form of monounsaturated fats like Soya-bean, mustard or groundnut oil, with one third coming from milk fat in any form; another 50 gm of invisible form of fat will be there in other food stuffs. This approach will automatically curb carbohydrate consumption by suppressing hunger).
From the foregoing, it is clear that glucose dependent tissues are not dependent upon Insulin for availability of glucose. Then why has nature created Insulin? As Albert Einstein said “God does not play dice”. In nature, nothing happens for nothing. Every little thing has a role and a meaning. Careful scrutiny reveals that the most significant role of Insulin is to push excess (excess, yes!) glucose into fat cells, which store fat. These cells are mainly located in subcutaneous tissue, below the skin. They mop up not only fats from blood for storage but also convert glucose into fat. For this purpose, glucose has to be pushed into these cells by Insulin. Once inside, glucose gets converted into fat and gets stored. Storage capacity of these cells is unlimited, unlike storage capacity for glucose of muscles and liver. Muscles and liver also store excess glucose under the influence of Insulin in the form of glycogen, but the quantum of this storage is limited to between one & two percent by weight for muscles and between two & four percent by weight for liver, amounting to a total of approximately one kg glucose stored in this form. Now, if one is consuming 100 gm carbohydrate in excess of glucose expenditure for energy production, liver and muscles will get saturated with glycogen in just ten days’ time, and progressively larger amounts of Insulin shall be required to push glucose into these storage sites, leading to Insulin resistance, persistently excess circulating Insulin and a plethora of problems collectively called “Dysmetabolic Syndrome”.
The aforementioned simple observations have enormous scope for clinical applications. We can logically conclude that Insulin is not essential. Our bodies need very little Insulin for metabolic requirements. Insulin was precious for primitive man thousands of years ago, when food scarcity was common and excess intake of food ; when available; had to be stored for use during starvation period (so called “alternative feasting & fasting” pattern of food habits, first propounded a few years ago by the “Thrifty Gene Hypothesis”). But nowadays when abundance is problematic rather than scarcity, Insulin is literally an excess baggage from the past. What was an asset once upon a time is turning out to be a curse now. Therefore, it can be logically concluded that we should consume only that much carbohydrates which is absolutely necessary (which works out to be between 100 and 150 grams per day) and avoid overloading ourselves with starch and sugar. For diabetic patients, there is a lesson in this: control your blood sugar by carbohydrate-intake restriction, and not by excessive dependence upon Insulin (external or internal) for, through the latter route, though blood sugar will come down, but weight will start increasing, consequences of which are no less deadly than those of persistently raised blood sugar. In fact it prompts us to consider changing the very definition of Diabetes Mellitus, which today goes like this: “Diabetes Mellitus is a metabolic disorder, resulting in hyperglycemia due to inadequate secretion or impaired sensitivity or both of Insulin” You see, here the focus of attention is Insulin. A more rational definition should be, to my mind, “Diabetes Mellitus is a metabolic disorder, resulting in hyperglycemia due to excess dietary consumption or inadequate metabolic utilization or both of carbohydrates”. Herein, the focus of attention has shifted to carbohydrates, which is more rational and clinically useful.
The foregoing prompts a logical thought that probably, theoretically at least, it should be possible to live a healthy life with normal blood sugar levels, even in the face of total absence of Insulin or with very little Insulin. Yes, personally I am convinced that this is possible, if carbohydrate intake is totally and completely eliminated or minimized to less than 100 gm per day, with bulk of Calorie requirement coming from fats and proteins. Apprehensions that total absence of or very low content of carbohydrates in diet may lead to hypoglycemia (when blood sugar drops too low) are misplaced, as there is a mechanism called “Gluconeogenesis”, which gets activated in liver when blood sugar goes too low. Gluconeogenesis leads to breakdown of proteins and converts them into glucose. The difference is that earlier; in the face of excess carbohydrate intake; the system was struggling to keep blood glucose low by secreting excessive amounts of Insulin, but now it is struggling to raise blood sugar to keep it above a minimum level. Fears that increased fat intake may lead to excess cholesterol buildup have already been quelled, I hope, with my previous article “Cholesterol Conundrum: A Reality Check” in the same publication dated------------. But to sustain such a diet for prolonged periods, it is very difficult as such diets are rather expensive and a lot of work in the fields of cuisine & culinary refinement needs to be done to bring down costs and to increase palatability & acceptability in accordance with cultural aspects. Our wheat, rice and sugar centric food habits have to be substituted with the ones orientated towards dairy products, edible oils, pulses, vegetables and fruits & nuts, with poultry & fish thrown in for non-vegetarians. Purified proteins (protein hydrolysates) should enter into our cuisines in a big way- economy of scale will bring down the prices, which are very high today. As per available statistics, consumption of Pulses (Dals) in our country is only 32 gm/person/day and that of fats (vegetable oils + milk fat) is only 24 gm/person/day, whereas both should be five times this figure. The reason is poverty- to some extent financial, but largely intellectual. Sugar has to be totally eliminated, substituting it with Aspartame or Stevia as sweeteners which are calorie free and proven food grade substances of plant origin, unlike Saccharine, which is a chemical substance. (Often people say that they feel uncomfortable with protein hydrolysates, Aspartame, Stevia etc. These things are not natural, they say. I would like to remind them that mankind gave up the natural way of living many thousand years ago, when fire and wheel were invented, and since then we have come a very long way. Need of the hour is not to go back to nature but it is to handle our unnatural existence more intelligently and scientifically. With a little imagination, incredibly tasty but healthy (protein rich, moderately fat rich and low on carbohydrates) fare can be dished out, at a very low cost. But who will take up this challenge? Who will fund the research in this field and who will market the products so developed? I have no answer. Any suggestions? In Europe and North America, such diets have spawned a multibillion-dollar industry. Is there someone who is enterprising enough to take up the initiative and create an Indian equivalent, thereby generating health and wealth in one stroke? Wholehearted & unstinted support from my side is assured.