Last month we were asked a question that we didn’t know the answer to: “Is sourdough bread better for diabetics? If so, how does a slice of sourdough compare to a slice of brown bread?”
So we asked one of our experts, dietician Toni-Lee Barrett, for her advice.
The difference between sourdough and normal bread
To start with, it’s helpful to understand the difference between the different kinds of bread. Most breads use commercial yeast to rise, but sourdough bread uses a fermentation process. A ‘starter’ is made from a mixture of flour and water, which is left for at least 24 hours to start the fermentation process. The starter contains yeasts and lactic acid bacteria, which, when added to the rest of the sourdough ingredients, causes the bread to rise.
The fermentation process in sourdough bread may also break down some of the particles in the dough which cause gastrointestinal fermentation and gas production (gut problems). This may be helpful for those who suffer from bloating after ‘normal’ bread.
Ask the diabetic
Paul Edmunds has been living with Type 1 diabetes for 36 years, and has researched the effects of sourdough vs. normal bread.
There is a fundamental difference between ‘sourdough’ and other breads that’s missed here. No commercially-produced bread is made with a whole grain. The wheat germ and husk are removed before milling by steel rollers or blades during which fine white flour is produced. Then some of the germ and/or bran, or maybe some other whole grains, is added back into the bread to make it ‘wholewheat’ or ‘brown’. Amongst other things, this stops the flour from going yellow and slightly reduces its shelf-life, which are considered undesirable by industrial bakers.
Sourdough breads, almost exclusively, are produced by smaller bakers using a stoneground flour. In that grinding process, the whole grain is ground at the same time. If it’s ground for longer, a finer, whiter flour is produced. There are enzymatic processes which take place here that can’t be reproduced by adding the bran and/or germ back in afterwards, and which are believed to be beneficial to gut bacteria and to contribute to its reduced GI.
So, even sourdough bread that looks like ‘white’ bread, is still wholegrain. The reason that the crumb in a good sourdough bread is composed of different sized gluten-produced ‘bubbles’ is that the fibre in the stoneground flour actually bursts these bubbles as they form, resulting in their non-uniform size and distribution.Paul Edmunds, living with Type 1 diabetes
Portion control is essential
Remember that different grains are also used for making bread. The more commonly used grains in our commercial breads are wheat and rye. The grains used, the fibre content of the dough, and how the dough was prepared and baked all influence how the bread breaks down and how we absorb the starches. Sourdough bread and breads that are higher in fibre typically have a lower glycaemic index than standard commercial bread. What does that mean? The answer to: Is sourdough bread better for diabetics? is a yes!
Remember, though, that portion control is so important. One to two slices is the max portion for bread. Take a look at our Diabetes Food Guide for advice on portion control, and check your blood sugar after eating anything new to see how it affects you. Everyone is different, and even if sourdough bread is better for diabetics that doesn’t mean it will work for you.
Understanding the GI of different breads
When trying to choose between different types of breads, it can help to pay attention to the glycaemic index, the kilojoules, carbohydrates and fibre. Try to choose a product that has a lower GI, and is lower in kilojoules and carbohydrates, while being higher in fibre. (Here’s a simple explanation of low GI food, if you need it.)
The glycaemic index (GI) helps guide us on how carbohydrate-rich food may affect our blood sugar levels. Low GI foods are considered “slow release” foods and have a GI of less than 55. Intermediate GI foods have a GI value of between 56 and 69. High GI foods are considered “fast release” carbohydrates and have a GI value of above 70 – they are likely to cause blood sugar levels to rise quickly.
According to the South African Glycaemic Index and Load Guide (2017 – 2019 Edition), it’s best to eat low GI foods most of the time and keep intermediate and high GI foods for exercise. Some products have Diabetes South Africa and/or Glycaemic Index Foundation of South Africa (GIFSA) endorsement logos on their labels, which can help guide you on how to fit the product into your diet.
Of course, if you’re eating a low carb diet then all kinds of bread are off the menu – many people with diabetes have found that a low carb diet contributes to more stable blood sugar, so have given up bread.
GI of South African breads
The South African Glycaemic Index and Load Guide by Gabi Steenkamp and Liesbet Delport has a comprehensive table on nearly all of the breads available and their nutritional composition. This book can be ordered directly from GIFSA or from a dietician. The table below indicates the GI and nutritional composition of some of the most common breads in South African stores.
The foods in the table are listed from lowest GI to highest GI. The Artisan Baker’s sourdough bread has the lowest GI in the table above, but it’s highest in carbohydrates and fairly low in fibre. Albany low GI Ultima kJ controlled brown bread has a slightly higher GI, less kJ and more fibre. Blue Ribbon low GI Brown Plus high fibre bread is still low GI but has more fibre than most other breads. Interestingly, some rye breads are low GI and others are intermediate GI. One would think that nutty wheat, whole wheat and brown bread would be low GI but according to the South African Glycaemic Index and Load Guide, they fall into the high GI category.
It is important to note that the GI classification is not to label the food as ‘good’ or ‘bad’. By knowing the GI of different foods, you can put together a lower GI meal by balancing lower and higher GI foods, with lean protein and healthy fats in the right portion sizes. Here’s more information on low GI food.
Final thoughts on sourdough bread for diabetics
The most important thing to remember when making any decisions about your diet is that every person is different, and every person’s diabetes is different. Try new things, test your blood sugar and then decide what is right for you.
What to read next?
The best diabetes specialists in South Africa: A list of the doctors and diabetes educators our community trusts the most.
The diabetes diet: all you need to know: Explains portion control, carb counting and diabetes superfoods in detail.
Meal plans: Whether you’re looking for a budget meal plan, low carb meal plan, vegetarian or easy cooking – we have them all here, for free!