Carbohydrates (carbs) are one of the three major macronutrients found in many food and beverages. They are a common source of energy – each gram releases 4 calories of energy. Carbs are mainly obtained from plants such as grains, lentils, fruits, and vegetables. Animal-based products have very little carb. Milk is an exception; 1 litter of cow’s milk contains 40-50 g lactose. Carbs are not essential nutrients in humans; we can obtain all our energy requirement from fats and proteins. There are three groups of carbs: simple, complex and fibres.
What are simple and complex carbs?
What are fibres?
What are resistant and refined starches?
Should we drink glucose water/ health/ energy drinks?
Resistant starch is starch which cannot be digested. It reaches the colon undigested and is fermented there by the bacteria into health promoting SCFAs. Because it is not absorbed in the stomach and intestines, resistant starch helps control blood sugar, blood cholesterol and body weight.
It is found naturally in seeds, lentils, green bananas and unprocessed whole grains such as whole wheat and brown rice (more in long grain than sticky rice). Resistant starch is also formed when certain starchy food are cooked and then cooled such as rice, potatoes, lentils and pasta: cooling these is a fridge for 6-8 hours increases the content of resistant starch. By thus creating resistant starch, diabetics can safely eat small amounts of starchy foods such as potatoes and rice.
One note of caution. Foods that have been converted to resistant starch can be warmed at low temperature prior to consumption. Heating them at high temperatures will convert the resistant starch back to the original soluble state. A slice of whole wheat bread will contain some resistant starch but there will be none in a toasted piece.
In order to enhance their palatability and flavour, complex carbs are refined by stripping out their fibre. Unfortunately, this process removes most of the nutrients. Products which are predominantly refined carbs include white rice, refined wheat flour (maida), bread, biscuits, pasta, most packaged breakfast cereals, and so-called ‘health drinks’ such as Horlicks. Refined carbs raise blood sugars very rapidly which prompts the release of a correspondingly large dose of insulin. The ultimate consequence of this is overweight and obesity. Unrefined or unprocessed carbs are more nutritious, are absorbed slowly, and consequently the blood sugar rises slowly. Therefore, their impact on body weight is muted. Examples of unrefined carbs include fruits, vegetables, lentils, kidney beans, and unprocessed whole grains such as brown rice and whole wheat flour.
When evaluating the impact of a carb food on the body weight, it is the view of many nutritionists that instead of just looking at the carb content, we should look at the food’s glycaemic index, glycaemic load and insulin index. Glycaemic index is a measure of how quickly the food’s carbs are absorbed and raise the blood glucose. Glycaemic load refers to the total absorbable carbs in food and takes into account the glycaemic index. The insulin index is more accurate in reflecting the effect of any particular carb, and refers to the effect of carbs (glucose, starch) on insulin secretion and blood insulin level. For an average person, these factors are difficult to estimate when consuming a carb food. These are basically research tools for specialists to take into account when deliberating on nutritional advice. All that we need to concern ourselves with is that we need to avoid simple and refined carbs such as sugar-sweetened food, glucose, fructose, refined flour, white rice. At the same time we need to ensure an adequate intake of unprocessed whole grains like whole wheat flour, dietary fibers and resistant starch.
Regular consumption of simple and refined carbs has been shown to produce overweight, obesity leading to metabolic syndrome; a substantially increased risk of diabetes, heart disease and stroke; and a detrimental elevation of ‘bad’ LDL-cholesterol and reduction of ‘good’ HDL-cholesterol. The risk of heart disease is substantially increased by a diet high in refined carbs compared with a diet rich in saturated fats (ghee, butter, mutton, beef).