Carbohydrates (carbs) are digested at different rates and this has an effect on your blood glucose (blood sugar) levels. The Glycaemic Index (GI) is a ranking from 1-100 and relates to how quickly these foods make your blood glucose levels rise after eating them.
Each time you eat or drink something sugary or starchy, the blood glucose level in your body rises. Some of these are quickly digested and cause quick and sharp rises in your blood glucose levels - they are called high GI foods and drinks. Low GI foods and drinks are more slowly digested and will make your blood glucose rise more slowly. These are sometimes called ‘slow release’ carbs.
Starchy and sugary food and drinks contain carbohydrates:
Foods with a high GI are not necessarily bad foods. For example, potato crisps have a medium GI but a baked potato has a high GI. Despite this, a baked potato is better for your health than potato crisps, which are higher in fat and salt. And all lower GI foods are not necessarily healthy – chocolate and ice cream have a low to medium GI rating. If you focus only on the GI of foods, you could end up eating a diet that’s high in fat and calories, making you more prone to weight gain and heart disease.
So, the key is to use GI in the context of balanced eating.
Most recommendations on eating a diet that includes a range of low GI foods are directed at people with diabetes, since this can help to control blood glucose levels. Research suggests that it’s the amount of carbohydrate you eat rather than its GI rating that has the greatest influence on your blood glucose level after a meal. Diabetes UK advises that people with diabetes eat sensible portion sizes of carbs and include low GI foods into everyday meals.
The GI value of a food is tested on the food when eaten on its own, and there are published lists of high, medium and low GI foods. However, it is not helpful to use the GI values in isolation, as we generally eat food in combination with other foods. GI needs to be taken in the context of varied balanced eating for it to be successfully incorporated into a healthy diet.
Here are some everyday examples of lower GI carb choices.
Many low GI foods are a good source of fibre or wholegrains. A healthy way to use the GI principles is to incorporate a range of lower GI carbs that are also rich in fibre and low in saturated fat.
For weight management, you also need to think about reducing your overall calorie intake by incorporating lower calorie foods into your meals and snacks. Consider the overall balance of your meals by looking at labels and choosing foods that are lower in saturated fat, salt and sugar, and keep an eye on your portion sizes.
There is good scientific evidence to suggest that basing your diet on low GI foods and keeping an eye on the total amount of carbs you eat, may help to control blood glucose levels for people with type 2 diabetes. Choosing low GI foods as part of a balanced diet can help to minimise fluctuations in blood glucose levels. In the long term this can help reduce the risk of complications of diabetes such as heart and kidney problems.
There is some research to suggest that slow, steady rises and falls in glucose may help control appetite. Although many low GI foods are filling, there isn’t enough evidence to suggest that all low GI foods can help you to feel full.
For more information, take a look at our BDA Food Fact Sheet on Sugar.
Govindji A, Puddefoot N. The GI Plan Random House Publishing, 2004.
The graph in this food fact sheet was reproduced with kind permission of www.glycaemicindex.com