Carbohydrate
Carbohydrate foods are energy foods, and include sugars and starches (and indeed dietary fibers as well, see below). They are formed from simple sugar, among which are glucose (found in most foods), fructose (primarily found in fruit) and galactose (dairy produce). Sucrose is refined from cane and beet sugar, and in digestion breaks down to glucose and fructose.
These simple sugars form inter-linking chains, to make complex carbohydrates – the starches, such as grains, cereals and pulses and the foods made from them (bread, pasta, etc.) – plus vegetables and fruits. Complex carbohydrates have to be broken into simple sugars for absorption; the most significant of which is glucose. We require only limited stores of carbohydrate, for any not immediately used by the body is stored as glycogen in the liver and muscles, and anything in excess is converted into fat.
The structure of simple sugars in the food, the soluble fibre and fat content of a food determines the rate at which carbohydrate is metabolised and glucose enters the bloodstream. The more rapidly this occurs the more ‘glycaemic’ the food, with a propensity to raise blood sugar. This is undesirable because as blood glucose levels rise, the pancreas secretes insulin to enable the liver and muscle cells to store the glucose. As insulin levels increase, so blood sugar levels fall. Once they fall below a critical level, the brain, which needs glucose to function, becomes impaired. This is hypoglycemia, an affliction which can cause many unpleasant symptoms, in children particularly.
Of all the simple sugar, only glucose can be released directly into the bloodstream, which is why glucose-rich carbohydrates, such as sugar, and sugary cakes and biscuits, are highly glycaemic. Fructose and galactose must first be converted to glucose and therefore enter the bloodstream at a slower rate. This is a very slow process with fructose especially, which is why fructose-containing carbohydrates, primarily fruits, are low glycaemic foods.
Glycaemic foods are primarily foods that have been refined, and include sugar (honey, sucrose, maltose, glucose, sweets, chocolates), white flour (bread, pasta, biscuits, refined cereals, often with added sugar), and refined rice (white).
Unrefined carbohydrates, those which are not glycaemic, include whole-wheat products (brown bread, brown flours, whole-wheat pasta), maize and other whole grains, wild rice, unpolished brown rice, fruit, vegetables, legumes and pulses such as lentils, beans and peas. These should play a significant part in any healthy diet.
