What is carbohydrate
Our daily meals are made up of different constituents. The major amongst these are carbohydrates, proteins & fats. Of these, constituents carbohydrates form the chief source of energy. This is also so because they are present in most food stuffs & contribute to about 60-70% of an individual’s daily requirement for energy. Each gram of carbohydrates provides 4 kcals of energy. Carbohydrates come from a variety of foods–flour, bread, rice, legumes, potato, cookies, pasta and even corn/glucose syrup. They also come in a variety of types.
The most common are:
Sugars are mainly present in foods as monosaccharides or as disaccharides. Monosaccharides are the simplest form of carbohydrates. Glucose & fruit sugars (fructose) are examples of a monosaccharides form of carbohydrate. The cells of the body are designed to use only glucose as a source of energy. When two molecules of a monosaccharide combine they form a disaccharide. The most commonly known form of sugar is table sugar (sucrose). This is a disaccharide. Other examples of disaccharides form of carbohydrates are maltose & lactose (milk sugar). Together monosaccharides and disaccharides are commonly also known as “simple sugars".
Starches & Fibers are essentially chains of sugar molecules. Polysaccharides or “complex carbohydrates” include everything made of 3 or more linked sugars; examples of polysaccharides are starch, glycogen, cellulose & fiber. Many foods contain non-digestible carbohydrates like cellulose, hemicellulose, gums pectins & lignins. These undigestible carbohydrates are called fibre or “dietary fiber”. Though these do not contribute towards energy requirements of the body (since they cannot be broken down to glucose) their presence in the diet is necessary for the mechanism of digestion and elimination of waste.
On the other hand starches when eaten in a cooked form are completely digested in the gastrointestinal tract & the released glucose is absorbed and metabolized in the body to yield energy. Starch comes in many different configurations. Some are easier to break into sugar molecules than others. The starch in potatoes, for example, is digested and absorbed into the bloodstream relatively quickly, as compared to starch from whole grains.
Foods high in complex carbohydrates are usually lower in calories, saturated fats & cholesterol and are therefore considered to be healthy. When consumed these foods add more fiber, vitamins, and minerals to the diet than foods high in simple sugars. The AHA recommends 25-30 gm of fiber per day. Whole wheat bread & cereals, dals, legumes, cabbage, beets, carrots turnips, cereal brans are all good sources of dietary fibers.
Role of carbohydrates in body
- Carbohydrates supply energy for the immediate use of the body. The main source of energy soon after a meal is carbohydrate. One gram provides approximately 4 kcal (17 KJ). Carbohydrates have the job of providing all the cells in the body with the energy they need. When carbohydrates are consumed, the body converts them into glucose, which provides sufficient energy for everyday tasks and physical activity. If the body produces too much glucose, it will be stored in the liver and muscle cells as glycogen, to be used when the body needs an extra burst of energy. Any left over glycogen that isn't stored in liver and muscle cells are turned into the total body store of carbohydrates is about 300 gm. The body needs certain amount of carbohydrates to function properly, and an insufficient supply can cause fatigue, muscle cramps and poor mental function. A low-carb diet might seem healthy, but if taken to the extreme, can be very dangerous to a persons overall well - being. This is so because the brain has limited ability to use non-carbohydrate energy sources. For its functioning, its requirement for energy is very high - which is met solely by glucose. Thus the vital role of carbohydrates as fuel cannot be undermined. Its minimum requirement is 100 g/day.
- When this supply is met, proteins are spared for growth & repair. In addition to its role as a fuel, carbohydrate serves as a structural element in bacteria, plants, and animals. Cellulose is the principal structural carbohydrate in plants and is the most abundant polysaccharide in nature.
- Inclusion of complex carbohydrates in the diet provides for the requirement of dietary fiber. By retaining absorbed water, dietary fiber has an effect on the fecal volume and transit time, it contributes to the gas production and excretion of bile salts. Thereby having a direct control over body fat deposits as well as blood sugars.
- Another major role of carbohydrates, specifically simple sugars, is to impart sweetness to food. However, starch structural polysaccharides, and various oligosaccharides serve a variety of other functions. For example, polydextrose is an ingredient that can provide the texture of fat in some foods because of its rheologic properties; it adds texture to such food items as puddings, frostings, and frozen desserts and allows a reduction in fat content without sacrificing "mouth feel" and thus palatability. Polysaccharides can be used as thickeners, stabilizers, emulsifiers and gelling agents.
Foods containing carbohydrates
Sources of Carbohydrates
In the tropics carbohydrates form the staple foods. Rice, wheat, Bajra, Jowar, Pulses, Fruits, Honey and Jaggery are the main sources.
Following is the classification of the various sources of carbohydrates depending on their types.
Sources of Complex Carbohydrates: -
- Starches - Flour, bread, rice, corn, oats, barley, potatoes, legumes, fruits and vegetables.
- Fiber - Insoluble: whole-wheat breads and cereals, wheat bran, cabbage, beets, carrots, Brussels sprouts, turnips, cauliflower and apple skin (pectin)
- Fiber - Soluble: oat bran, oats, legumes, citrus fruits, strawberries, apple pulp, psyllium, rice bran and barley.
Sources of Simple Carbohydrates: -
- Sucrose - Table sugar, brown sugar, confectionery sugar, raw sugar.
- Glucose - Dextrose, corn syrup and glucose syrup.
- Fructose - Fruits, vegetables and honey.
- Sugar Alcohols - Sorbitol, Mannitol, Xylitol.
- Lactose - Milk and Milk products.
- Maltose, dextrose - products made from refined cereals like baked goods.
Carbohydrate counting refers to a method used in maintaining good - sugar control in diabetes. It entails counting the number of carbohydrate in grams of a given meal, then making sure that the total carbs does not exceed the dietary goal for that meal / day.
Carbohydrates are one of the three primary substances in foods, which also include protein and fat. They are also the substances, which turn 100% into glucose in the bloodstream. They include all sugars and starches in the diet. In fact, carbohydrates are actually either simple sugars or complex sugar molecules, such as starches. In a balanced diet, carbohydrates will be included and are necessary for both energy and good health. But for the diabetic, learning to measure the amount of carbohydrate in the diet can be a useful tool in learning to control blood sugars. This is so because the carbohydrates present in food have the richest impact on the blood sugar. Around 90-100% of the digestible starches and sugars that one eats appears in the blood as glucose within a couple of hours of consumption, whereas, proteins and fats do not affect post meal glucose as carbohydrate foods.
This means that in this system of carb counting the carbs that may be consumed may be of any type from pasta to pie, as long as the carb total remains consistent from day to day. For this reason, carb counting can allow people with diabetes greater freedom in their food choices.
Carb counting is based on the idea that all carbs are created equal and it is the total number of carb grams, not the type of carb (i.e. simple or complex; starch or fruit etc.) that is the bottom line for blood sugar control. The key to remember is that the amount of carbohydrate one eats (whether fruit or starch) will determine how high the blood sugar level will be after a meal or a snack.
Foods have been divided into different food groups and each food group provides a certain amount of carbohydrate thus by knowing the amount of carbohydrate content of each food group it is possible to estimate the amount of carbohydrate one will consume at a given meal.
Ideal carbohydrate in diet
Our diet comprises mainly of three components namely protein, fats and carbohydrates. In most diets even in those considered to be high in fat, carbohydrates provide about 50-60% of the total energy consumed. In some cultures especially in Africa and Asia carbohydrates provide up to 80% of the total energy in the diet.
The energy provided by each gram of carbohydrate is about 4 kcals. Since carbohydrates are an important fuel source and because of the vital role they play in providing energy for the brain cells, its minimum daily requirement is that of 100g. This amount supplies enough energy in the form of glucose to meet the need of the obligate glucose using tissues & to minimize the breakdown of body protein. This is true for hospitalized patients or in conditions of illness, wherein the consumption of food is reduced. However in healthy individuals, the diets may comprise of anything between 50-80% of carbohydrates. There are several aspects that rule the composition of diets of individuals. To name a few: health status (illness/disease), economic status, calorie requirement, and cultural norms. For eg: - a person living in rural set up, belonging to a lower income strata may consume a diet very high in carbohydrates to meet his caloric requirements. This is so because foodstuff such as cereals, pulses and legumes, tubers & root vegetables etc. that are predominantly carbohydrate based are also easily available and cheaper than other food items with high protein and fat concentration.
In practical terms when one tries to actually calculate the grams of carbohydrates coming from the diet this is how it is done:
- A person on 1800 kcal diet, who requires 70% of his daily calories coming from carbohydrates, needs an intake of 315 g of carbohydrates (since one gram of carbohydrates provides 4 kcals).
It is important to note that carbohydrate requirement varies in certain conditions like Diabetes and Obesity, where a carbohydrate rich diet is contraindicated.