When correctly understood, the glycaemic index can be helpful to keep glucose levels under control. This system lets you know how quickly each food impact your glucose level, so many people use it to make informed decisions about their diet. As always, you should solely base your decisions under medical advice from your doctor or healthcare provider before making major changes on your diet.
What’s the glycaemic index?
The British National Health System (NHS) explains on their website how glycaemic index works. This rating system is designed for foods that contain carbohydrates. The index measures the speed at which your body breaks down these nutrients, increasing your blood sugar, and assigns a rating. High rated foods are processed faster than low rated ones.
Per the NHS, examples of high GI foods include those loaded with sugar and carbohydrates, such as:
Carbonated or sugary drinks
On the contrary, low and medium foods are processed at a slower pace, so the increase in blood sugar occurs more gradually and over longer periods of time. These are:
some fruit and vegetables
Glycaemic index of a food looks like a number running from 0 to 100 and usually takes pure glucose (with an index of 100) as a reference. According to Diabetes UK, foods are graded using that number the following way:
Low GI foods: 55 or below
High GI foods: 56 and above
Glycaemic index vs glycaemic load
Glycaemic index is not to be mistaken for glycaemic load. The Harvard Medical School website shed some light on the difference. While the former is a value meant to represent how fast or sudden the spike in your blood sugar levels can be, it leaves the actual quantity out of the picture.
This is where glycaemic load steps in, as it’s an indicator that simultaneously describes the bloodsugar-raising potential and the quantity of carbohydrate that food contains.
A clear way to understand this is thinking of foods where absorption speed doesn’t match the actual quantity of carbohydrates. That’s the case for watermelon, a fruit with a high glycaemic index (80) and a very light glycaemic load per serving (5).
Low GI doesn’t equal healthy
Both the NHS and Diabetes UK are quick to mention that you shouldn’t base your entire diet on a single indicator, even if you need to pay attention to your blood sugar levels, as it happens with those suffering from diabetes.
In fact, the NHS claims that systematically eating only foods that low GI may constitute an unbalanced diet and high in fat. While some foods like wholegrain, fruit and vegetables are indeed healthy and low GI, that’s not always the case. Take the aforementioned example of high GI watermelon, as it’s rich in vitamins and low in calories and mostly water.
The opposite happens with chocolates. Diabetes UK notes that most chocolates are low GI, as their content is rich in fat and that slows down the absorption times. However, they can hardly be considered healthy.
Similarly, some people turn to low GI foods to lose weight. Because blood sugar changes more gradually, these can indeed help you feel satiated for longer and keep your appetite under control. However, unhealthy low GI foods could defeat this purpose or worsen your health in other ways.
The rundown is that you should generally aim for a healthy and balanced diet that takes into account many considerations instead of focusing on one indicator limited in scope. Of course, no person is best suited to plan blood sugar conscious diets than a dietician or health professional.