All carbohydrates that you eat are eventually broken down into glucose to be used immediately by the cells or stored for later use. However, depending on the type of carbohydrate you eat, the time it takes for it to be digested and for the glucose to hit your blood stream can vary. This will have an impact on how slowly or quickly you notice a glucose spike.
In this article, we’ll discuss different types of carbohydrates and their impact on your glucose (commonly referred to as blood sugar).
What is the glycaemic index?
The most common way that people look at slow-release carbs is by classifying foods as high glycaemic or low glycaemic. The glycaemic index (GI) ranks carbohydrates on a scale of 0-100 based on their potential to raise your blood sugar. Foods with a high GI (>70) are digested quickly and cause a rapid spike in blood sugar and insulin. Foods with a low GI (<55) are digested more slowly and result in a smaller increase in blood sugar and insulin.
High glycaemic foods are often foods that have been highly processed, beverages with lots of added sugar, bakery items, and candy.
High GI foods (≥70)
- Pretzels
- Cornflakes cereal
- Special K cereal
- White potatoes
- Sweet potatoes
- Sodas (Coca Cola, Pepsi)
- Beer
- Scones
- Pancakes
- Muffins
- Croissant
- White bread (GI 100)
- Skittles
- Swedish Fish
Some fruits with more sugar (pineapple, watermelon) are also considered high glycaemic, although they also offer beneficial nutrients and fibre.
Alternatively, low glycaemic foods are often whole foods such as non-starchy vegetables, low-sugar fruits, lean protein sources, whole grains, beans and legumes, dairy, and nuts and seeds.
Low GI foods (≤55):
- Avocado
- Apples
- Berries
- Oranges
- Spinach
- Tomatoes
- Cucumbers
- Broccoli
- Courgette
- Mushrooms
- Steel cut oats
- Whole grain bread
- Quinoa
- Lentils
- Chickpeas and hummus
- Skim, low-fat, and full-fat milk
- Greek yoghurt
- Chicken, turkey, and other poultry
- Beef and pork
- Eggs
- Fish and shellfish
All about slow-release carbs
However, there is another category of slow-release carbs that is worthwhile to consider. Low glycaemic foods fall in several different food categories, but when it comes to starches (think: potatoes, beans, bread, rice, pasta, and cereals), we can further break these down into three main categories:
Slowly digestible starch (SDS)
Rapidly digestible starch (RDS)
Resistant starch (RS)
These categories represent the starches’ impact on glucose after they are consumed as well as the associated hormone response. It has been shown that foods with slowly digestible starch have a lower glycaemic index, independent of other nutrients in the food such as fat and fibre (1).
While fat and fibre also lead to a lower glycaemic index, when eating foods that are pure carbohydrates (rice, pasta, bread), choosing those that have the greatest amount of slowly digestible starch can have a significant impact on blood glucose, insulin, and satiety.
One study found that a breakfast containing slowly digestible starch reduced the glycaemic response not only after the meal, but also into the rest of the morning. This reduced response continued after lunch as well (2), something called the “second meal effect.”
Why would eating a breakfast with slowly digestible starch reduce your blood glucose well after the meal has been consumed and even into the next meal? Research has shown that not only do slowly digestible starches slow the release of glucose into the blood stream and induce a lower secretion of insulin, but they also reduce the amount of glucose produced by the liver as well as stimulate a slower release of gut hormones that help to keep you full. (3, 4)
Slowly digestible starch is highest in starchy foods that have undergone the least processing. This includes beans and legumes, cooked vegetables like potatoes, corn, peas, and squash, grains like stone-ground wheat, quinoa, brown rice, rolled or steel-cut oats, oat bran, and barley. When cooked fresh, these foods contain higher amounts of SDS than more processed versions like potato chips, breads made with enriched flours, white rice, and instant oats.
What is resistant starch, exactly?
Resistant starch is another form of starch and is also known as digestion-resistant starch. This is because it acts similar to soluble fibre as it moves through your digestive tract undigested and can feed your gut with good bacteria, improving your overall microbiome. Because it does not get digested, it also helps reduce the glycaemic response after a meal as well as the same “second meal effect” seen with SDS.
Additionally, it has been proposed that resistant starch may help with weight management as it has a lower energy density and may help promote satiety.
So where do you find resistant starch? Resistant starch has been categorized into 5 different types:
Type 1: Called physically inaccessible starch because it is bound in the fibrous cells walls and is found in foods such as coarsely ground or whole-kernel grains (quinoa, whole grain barley), seeds (pumpkin, flax), and legumes (chickpeas, lima beans).
Type 2: Found in unripe bananas (greener/not fully yellow bananas) and raw potatoes.
Type 3: This type of starch is found in starchy foods once they are cooked and then cooled. The cooling process turns some of the digestible starches into resistant starches.
Type 4: Chemically modified starch.
Type 5: Formed when starch interacts with lipids.
While this sounds complex, the easiest way to get resistant starch in your diet is to go for types 1-3 and opt for foods like cashews or less ripe or green bananas. Another simple and efficient way is to cook and cool certain starchy foods like rice and potatoes before eating them.
Benefits of slow-release carbs and low GI foods
Slow-release carbs are those with a low glycaemic index as well as those that contain high amounts of slow digestible carbs or resistant starch. They have a lower impact on blood sugar and insulin and may even help lower glucose throughout the day into the next meal. Additionally, slow-release carbs may improve satiety by helping you feel fuller after meals.
A final note from Lingo
There are many ways you can include slow-release carbs in your diet. If you’re wearing a Lingo biosensor, you can test your own response to the suggestions below.
Choose whole grains: Opt for whole grains such as whole-wheat pasta, brown rice, quinoa, and rolled oats instead of refined grains. These have a lower GI and provide slow-release carbohydrates.
Legumes and beans: Include lentils, chickpeas, black beans, or other legumes in your meals. They are rich in resistant starch and protein and can provide a sustained source of energy.
Green vegetables: Load up on non-starchy vegetables like broccoli, spinach, peppers, and kale. They are low in overall carbs, rich in fibre and nutrients, and the carbs they do contain are slow digesting.
Nuts and seeds: Snack on nuts and seeds like almonds, chia seeds, and pecans. Not only do they contain slow-release carbs, but they also have healthy fats and protein to help keep you fuller for longer.
Cooling and reheating: Cook, cool, and reheat certain starchy foods such as rice, potatoes, and pasta. This will increase their resistant starch content, making them slower to digest and a more even glucose profile.