Table of Contents
What is the glycaemic index?
Carbohydrates, which are commonly found in foods such as bread, fruit, vegetables or dairy products, are an essential part of a healthy diet and an important source of energy. When any carbohydrate is ingested, it is broken down in the body into simple sugars that enter the bloodstream where they are taken up by the cells of our body and used as a source of energy. But not all carbohydrates are the same, their main difference is their effect on blood sugar levels.
The glycemic index (GI) is a measurement system that ranks foods on a scale according to their effect on blood sugar levels. This system was created in the 1980s by Canadian physician David Jenkins
. Individual foods are ranked on a scale according to how they raise blood sugar levels compared to 50 grams of glucose. Pure glucose is used as a reference food having a GI = 100. The scale can then be used to determine three levels of the glycaemic index:
- Low: 55 and under
- Medium: 56-59
- High: 70 and over
Foods with a low glycemic index are preferred because they are digested more slowly by the body and glucose is therefore absorbed more slowly, resulting in a slow and low rise in blood sugar. Foods with a high glycaemic index should then be rather restricted as they are rapidly digested and the rapidly absorbed glucose from these foods then causes a sharp short-term rise in blood sugar.
It should be noted that the glycaemic index is only assigned to foods containing carbohydrates, therefore the rest of the foods cannot be found in the glycaemic index tables. These foods include all kinds of meat, eggs, herbs and spices.
Factors affecting the glycaemic index of foods
There are several factors that affect the glycaemic index value of foods, such as the type of carbohydrate the food contains, the chemical structure of that carbohydrate or the way it is processed.
- Type of sugar: The misconception is that all sugars have a high glycemic index. But the truth is that the range of glycemic index values varies from 23 for fructose to 105 for maltose. Therefore, the glycemic index of foods depends in part on the type of carbohydrate they contain.
- Structure of starches: Starches are carbohydrates that consist of two molecules – amylose and amylopectin. Amylose is slower to digest compared to amylopectin. For this reason, the ratio of amylose to amylopectin in starches affects the glycaemic index value of a food.
- Processing rate of sugars: Processing processes such as milling and crushing disrupt the structure of amylose and amylopectin molecules, increasing their glycaemic index. Higher refined sugar content then increases the GI of the food.
- Nutrient composition: adding other macronutrients to foods increases their digestion time. The healthy fat and protein content of the food therefore lowers the glycaemic index of the food.
- Cookingmethod: Generally speaking, the longer a food is cooked, the faster it will be digested and absorbed and the more the glycaemic index value will increase.
- Maturity: Unripe fruit contains complex carbohydrates that break down into simple sugars as they ripen. The riper the fruit, the higher its GI. For example, the glycaemic index of an unripe banana is 30, while an overripe banana has a GI of 48.
What does a low-glycemic diet have in common with a low-carbohydrate diet?
If we were to be guided solely by the glycemic index of foods, we might get the misconception that it is possible to eat 40 bananas in a day and still have low blood sugar readings. With a low-glycemic diet, then, you need to look at the total amount of carbohydrates consumed, making it very similar to low-carb diets like the low-carb or keto diet.
Therefore, a unit called glycemic load (GL) is introduced to measure the overall effect of foods on blood sugar. This unit takes into account not only the type (GI) but also the amount (grams per serving) of carbohydrate consumed to calculate the effect of a food on blood sugar. Like the GI, the GL is divided into three levels:
- Low: 10 or less
- Medium: 11-19
- High: 20 or more
When following a low-glycemic diet, the most important factor is still the low glycemic index of the food, but at the same time it is good to keep the glycemic load of the food below 100 GL per day and it is not good to consume one serving of food that has a glycemic load higher than 20:
GL = S x GI / 100
GL = glycemic load, S = amount of carbohydrate in the food in grams, GI = glycemic index
Effect of a low-glycemic diet on our health
- Impact on diabetes: Several studies have noted that a low-glycemic diet lowers blood sugar, helping diabetics control blood sugar levels and delaying the onset of complications of the disease, which include heart disease, stroke, and nerve and kidney damage(1). Conversely, other studies have suggested a link between high-glycemic diets and the development of type 2 diabetes(2).
- Effect on cholesterol: Low-glycaemic diets have been shown to reduce cholesterol by up to 9.6% and LDL cholesterol (which in excess causes atherosclerosis) by up to 8.6%. High LDL cholesterol levels are associated with an increased risk of heart disease and stroke.
- Effect on weight loss: following a low-glycaemic diet can lead to weight loss, especially if it is a healthy change in diet. However, there are currently insufficient studies on the long-term effects of this diet.
- Effect on cancer: There are several studies that associate a higher risk of certain cancers (especially uterine, rectal and breast) with eating a high-glycaemic diet.
- Effect on heart disease: Consumption of high GI foods and a high GL eating style leads to an increase in cholesterol, thereby increasing the risk of heart disease.
List of foods with a low glycemic index
When following a low-glycemic diet, the emphasis is on replacing high GI foods with low GI foods. It is therefore more of a lifestyle change, which often involves replacing unhealthy foods with healthier options. Typically, this diet does not count calories or the amount of macronutrients (proteins, sugars, fats) in the diet. For some individuals, this change alone may mean weight loss, but it is important to remember that if your goal is to lose weight significantly, you will need to start counting calories.
Foods suitable for this diet include:
- Bread: whole grain, multigrain, rye
- Breakfast cereals: whole oatmeal, bran
- Fruits: apples, pears, kiwi, plums, apricots, peaches, tomatoes, etc
- Vegetables: carrots, broccoli, cauliflower, celery, zucchini, eggplants, sweet potatoes, squash, corn and more
- Legumes: lentils, beans, chickpeas and more
- Pasta and noodles: whole wheat spaghetti and noodles, soba noodles, rice noodles
- Rice: basmati, whole grain, long grain, brown
- Cereals: quinoa, barley, wholemeal couscous, buckwheat
- Dairy products and their vegetable variants: milk, cheese, yoghurt, coconut milk, soya milk, almond milk
The following foods contain no sugar, or such small amounts that they do not have an assigned glycemic index, so they can be included in a low-glycemic diet.:
- Fish and seafood: trout, carp, zander, tuna, salmon, sardines and shrimp
- Other animal products: beef, pork, poultry, eggs
- Nuts: almonds, pistachios, cashews, walnuts, hazelnuts, pecans, etc.
- Fats: avocados, vegetable oils, butter, lard
- Herbs and spices: such as basil, garlic, dill, salt and pepper
This database can help you find the exact glycemic index of your chosen food.
Foods you should avoid
The rules of the low-glycaemic diet do not strictly prohibit any particular foods. However, the following foods should be avoided in favour of the low-glycaemic variants mentioned above.
- Baked goods: wheat bread, toasted bread, rolls and other white bread
- Breakfast cereals: instant porridge, sweet breakfast cereals, muesli
- Pasta and noodles: instant noodles and corn pasta
- Rice: short grain variants (for risotto)
- Vegetable milks: rice and oat milk with added sugar
- Fruit: melon
- Savoury treats: chips, rice crackers, etc.
- Cakes and other sweets
- Other: liquorice
Diet for weight loss
The following sample weekly menu shows what a low-glycemic diet for one week might look like. Feel free to modify the recipes and add low GI snacks according to your needs and preferences.
- Breakfast: porridge with coconut milk and turmeric, garnished with pumpkin seeds and low GI fruit
- Lunch: chicken sandwich with wholemeal bread, salad and tomatoes
- Dinner: roast beef with vegetables and whole grain rice
- Breakfast: whole wheat toast with avocado, tomato and ox eye
- Lunch: cabbage soup with a slice of wholemeal bread
- Dinner: grilled trout with quinoa and green beans
- Breakfast: omelette with mushrooms, spinach, tomato and cheese
- Lunch: turkey slice with whole wheat noodles, salad and yoghurt
- Dinner: pan-fried tofu pieces with mixed vegetables and whole-wheat noodles
- Breakfast: smoothie with blueberries, Greek yogurt, milk and cinnamon
- Lunch: turkey whole wheat tortilla with vegetables
- Dinner: beef burgers with vegetables and whole wheat bun
- Breakfast: almond flour pancakes with forest fruit
- Lunch: tuna sandwich with wholemeal bread and vegetables
- Dinner: chicken curry with chickpeas and basmati rice
- Breakfast: scrambled eggs with avocado tomatoes and beans
- Lunch: fish slice and salad with beluga lentils (black lentils)
- Dinner: grilled pork slices with roasted sweet potatoes and vegetables
- Breakfast: bran porridge with apple and cinnamon
- Lunch: brown rice with chicken salad
- Dinner: turkey meatballs with vegetables and brown rice
Healthy snacks with a low glycemic index
If you find yourself craving a snack in between each of the foods in the sample menu above, prepare the following low glycemic index foods as a quick snack to help you fight off cravings.
- 10 g unsalted nuts
- Fruit with nut butter (almond, peanut, etc.)
- Vegetable sticks with hummus
- Fruit with yoghurt
- Greek yoghurt with sliced almonds
What to look out for on a low glycaemic index diet?
There are many benefits to a low-glycemic diet, but even a low-glycemic diet doesn’t come without some negatives.
Firstly, a low-glycaemic diet does not look at the complete nutritional picture, i.e. it does not take into account the amount of protein, fat, carbohydrate and fibre consumed.
Secondly, it doesn’t take into account the overall GI of a meal, but only of individual ingredients, as the resulting effect of combining different foods on blood sugar levels would be very difficult to determine.
Finally, some unhealthy foods have a low glycemic index (e.g. Twix bar = 44), while some healthy foods have a high glycemic index (watermelon = 75) but a low glycemic load (watermelon GL = 4-5).
In general, then, this diet is a good first step towards a healthy lifestyle and better dietary choices. It may help some individuals lose weight, lower blood sugar levels, and reduce the risk of heart disease and type 2 diabetes.