The generally accepted recommendation is that people consume between 45-65% of their total calories in the form of carbohydrates per day. However, carbohydrate needs depend on many factors, including body size, activity levels, and blood sugar control.
Carbohydrates are our main source of energy
Until recently, they were classified as being either “simple” or “complex,” Simple carbohydrates are composed of sugars (such as fructose and glucose) which have simple chemical structures. They are easily and quickly absorbed by the body. Complex carbohydrates have a more complex chemical structures, with three or more sugars linked together. Many complex carbohydrate foods contain fiber, vitamins and minerals, and they take longer to digest – causing the sugar level in blood to rise more slowly. But other so called complex carbohydrate foods such as white bread and potatoes contain mostly starch but little fibres so they are as quickly absorbed as the simple carbohydrates.
When you swallow sugar, your body will react to such a rise in blood sugar by secreting a hormone, the insulin. The role of insulin is to get sugar into our cells to lower the sugar level in our blood. Conversely when there is not enough sugar in the blood another hormon, the glucagon produced by the pancreas has the opposite effect of insulin and raises the concentration of glucose and fatty acids in our blood stream.
Unfortunately, these insulin spikes also have a number of deleterious effects:
- In the long term: the repetition of this process can contribute to decrease the sensitivity of cells to insulin, the first step towards type 2 diabetes, and to promote the mechanisms of inflammation, leading to chronic diseases.
- In the short term: insulin promotes fat storage, these peaks contribute to making us fat.
It is therefore important to focus on carbohydrates that do not generate large spikes in insulin, that is to say those that do not induce a sharp rise in our blood sugar: low or moderate GI carbohydrates.
This is the reason why the glycemic index was developed and is considered a better way of defining carbohydrates. The glycemic index is a scale from 0 to 100 based on how quickly and how much they raise blood sugar levels after eating. Foods with a high glycemic index, like white bread, are rapidly digested and cause substantial fluctuations in blood sugar. Foods with a low glycemic index, like whole oats, are digested more slowly, and lead to a more gradual rise in blood sugar.
Healthy carbohydrates are: low or moderate in calories, high in nutrient, without refined sugars and refined grains, high in naturally occurring fibre, low in sodium, low fat.
Non Healthy carbohydrates are: high in calories, full of refined sugars, high in refined grains like white flour, low in many nutrients, low in fibre, high in sodium, sometimes high in fats.
Many factors can affect a food’s glycemic index:
Processing: Grains that have been milled and refined—removing the bran and the germ—have a higher glycemic index than minimally processed whole grains. Physical form: finely ground grain is more rapidly digested than coarsely ground grain. This is why eating whole grains in their “whole form” like brown rice or oats can be healthier than eating highly processed whole grain bread. Fibre content: High-fiber foods slow the rate of digestion and causes a more gradual and lower rise in blood sugar. Ripeness: Ripe fruits and vegetables have a higher glycemic index. Fat content and acid content: meals with fat or acid are converted more slowly into sugar.