Diabetes and low glycaemic index: what to eat?

This article is general information. It does not replace medical advice or the follow-up of a doctor or dietitian, and food does not replace treatment. If you are concerned, quantities and choices suited to you should be decided with your healthcare team.

Type 1 and type 2 diabetes: two different diseases

According to Assurance Maladie,diabetes is a chronic diseasecharacterised by an excess of sugar in the blood, or hyperglycaemia. It distinguishes two main types:

• Type 1 diabetesis due to an absence of insulin secretion by the pancreas.
• Type 2 diabetesis due to poor use of insulin by the body's cells.

These two situations are not managed in the same way. The benchmarks below are general: they do not say what a particular person should do.

What official sources say about diet

The first message is often surprising: according to Assurance Maladie,we no longer speak of a dietfor people with diabetes, but of a balanced and varied diet, with no forbidden foods. The benchmarks it gives are as follows:

• Carbohydrates at every meal, which should provide about half of the day's energy needs. A balanced meal combines complex carbohydrates (starchy foods) and, preferably, simple carbohydrates from fruit.
• Fibre at every meal: found in vegetables, fruit and wholegrain foods, it affects how quickly carbohydrates are absorbed.
• Wholegrain foods: Assurance Maladie notes, for example, that white bread has a higher glycaemic index than wholemeal bread.
• Wateras the recommended daily drink, and limited consumption of sugary drinks.

The International Diabetes Federation takes the same line: choose carbohydrates rich in fibre, limit refined carbohydrates,spread their intake across mealsand monitor portion sizes. It adds that there is no universal eating programme: the diet must be adapted to each person.

The glycaemic index: definition and scale

The glycaemic index (GI) ranks foods containing carbohydrates according to their effect on blood glucose after the meal. According to theUniversity of Sydney, which maintains the reference database, it is a ranking of carbohydrates on a scale from 1 to 100. Pure glucose serves as the reference. The usual benchmarks, according to the database'sFAQ:

• Low GI: 55 or less.
• Medium GI: 56 to 69.
• High GI: 70 or more.

Assurance Maladie sums up the idea this way: the higher the GI, the faster blood glucose rises.

The measurement method is tightly controlled. At least 10 healthy people eat a portion of the food tested containing 50 g of digestible carbohydrates, and their blood glucose is monitored for two hours. The same procedure is carried out with glucose. The ratio between the two responses is calculated for each person, then averaged.

Some GI values from the Sydney database

Here are the values cited in the FAQ of the University of Sydney database, measured using the method above (with glucose as the reference). They are indicative: they vary according to variety, cooking and the products tested.

• White bread: 70.
• Rice: 58 for cooked basmati; 59 to 86 for cooked brown rice, depending on the products tested.
• Cooked pasta: 35 to 54.
• Cooked red lentils: 26.
• Apple: 40.
• Potato: 80 for a small baked potato.

It can be seen that the same type of food can cover a wide range. For a precise value for a given product, it is best to consult theUniversity of Sydney search database.

What makes the GI vary

• Cooking: overcooked pasta has a higher GI, hence the advice to cook it al dente. Assurance Maladie also cites mashed potato, whose GI is higher than that of potatoes boiled in their skins.
• Processing: according to the Sydney database, finely ground cereals are digested quickly, and most ready-to-eat breakfast cereals have a high GI.
• Fibre: soluble fibres thicken the digestive contents and slow digestion, which lowers the GI.
• The meal as a whole: fats and proteins slow the emptying of the stomach, so a mixed meal may have a weaker glycaemic effect than the GI of a food eaten alone would suggest.

Factors such as the variety or ripeness of a fruit are often cited, but we have no quantified official source to present on this subject.

The limits of the GI as a tool

The GI is useful, but it is not enough to judge a food. The International Diabetes Federation states this clearly: choosing a healthy food also depends on portion size, fibre content, nutrients, calories, added sugars, saturated fats, sodium and the overall balance of the meal. The Sydney database also points out several things:

• It says nothing about portion size: a larger portion produces a larger glycaemic response, even if the GI is the same. Theglycaemic loadpartly corrects this: GL = (GI x grams of carbohydrates) / 100.
• It only applies to foods that contain carbohydrates, and a single value does not describe a whole meal.
• It is not a judgement of nutritional quality: the Sydney database cites fatty chips whose GI is lower than that of a baked potato, with a concern about saturated fats.
• Responses vary from one person to another and from one day to the next: the GI is an average.

Fibre and satiety

Fibres slow the absorption of carbohydrates, promote transit and help you feel full, according to Assurance Maladie. Vegetables, fruit, legumes and wholegrain cereals are the main sources. Our article onfoods rich in protein and fibredetails these foods.

Hidden sugars and sweeteners

Sugars are not limited to sweets: they are found in sauces, ready meals, cereals or flavoured yoghurts. To spot them, seehidden sugar and salt: where do they hide?. As for products sweetened with sweeteners, Assurance Maladie classes them as ultra-processed foods and advises choosing those with the fewest additives. The positions of the WHO and ANSES, notably on the absence of proven benefit for blood glucose, are detailed in our articleSweeteners: aspartame, sugar, which to avoid?.

Reading the label

• Nutritional dataare given per 100 g or 100 ml: this is the basis for comparing two products.
• The "carbohydrates of which sugars" line: total carbohydrates include sugars, but also the starch in starchy foods. Both count towards carbohydrate intake.
• "Without added sugars" is not "sugar-free": Assurance Maladie gives the example of a 100% pure fruit juice, without added sugar, which nevertheless contains 10 g of sugar per 100 ml for orange and 15 g for grape. Naturally present sugar remains present.
• The ingredients list: it reveals additives, including sweeteners.

On Yumiq, the product page shows the number of additives detected (harmless, to watch, risky). The Yumiq-Score penalises controversial additives assessed by EFSA and ANSES, and the Yumiq star requires the absence of any risky additive.

What to remember?

No food cures diabetes, and none is miraculous. Official messages remain simple: a varied diet, carbohydrates spread through the day, fibre and wholegrain foods, water rather than sugary drinks. The GI can help compare two starchy foods, provided the portion and the rest of the meal are not forgotten. The treating doctor or dietitian helps define the quantities suited to each situation.

Sources

• Assurance Maladie - What is diabetes?
• Assurance Maladie - Diabetes and everyday diet: the basics
• Assurance Maladie - Diabetes: managing your diet and organising your meals
• Assurance Maladie - Shopping when you have diabetes
• International Diabetes Federation - Healthy eating
• University of Sydney - Glycemic Index: about the GI
• University of Sydney - Glycemic Index: FAQ