Carbohydrates are one of three essential nutrient groups necessary for survival. The other two are proteins and fats. Carbohydrates are the primary source of energy for the body. The body converts carbs into the sugar glucose, which then enters the bloodstream to fuel the body's cells.

Not all carbohydrates release energy at the same rate. The Glycemic Index (GI) is a scale that measures how quickly specific foods release glucose into the bloodstream.

Fast-release carbs, or high-GI foods, release glucose into the bloodstream rapidly, causing a spike in blood sugar levels. Slow-release, or low-GI, carbs provide a slower and more sustained release of energy.

This article focuses on some of the slow-release carbs within common food groups. It also provides information on the health benefits of low-GI foods, as well as some important considerations when following a low-GI diet.

Benefits of low-GI foods

Foods on the GI scale range from 0 to 100, with 0 representing the lowest GI and 100 representing the highest. Pure glucose has a GI of 100.

According to the American Diabetes Association (ADA), low-GI foods score less than 55 on the index, medium GI foods score between 56–69, and high-GI foods score 70 or above.

A diet that consists primarily of low-GI foods can help people maintain blood glucose levels and sustain energy levels. A low-GI diet can also lead to improvements in:

• Weight management: Low-GI foods decrease feelings of hunger and increase fat metabolism
• Cardiovascular health: Improved blood flow due to increased elasticity of the blood vessels
• Cholesterol levels: High-fiber, low-GI foods help decrease levels of low-density lipoprotein (LDL), or bad cholesterol
• Cognitive performance: Slow-release carbs help to sustain energy levels, leading to increased alertness and better cognitive performance

Low-GI cereals

According to the ADA, many types of breakfast cereals, such as corn flakes, bran flakes, or puffed rice, contain added sugars and are high on the GI scale. Try replacing these cereals with a slow-release option, such as rolled oats porridge, which has a GI score of 55, according to a detailed list of the glycemic values of a wide variety of foods compiled by the University of Sydney in Australia. Try serving low-GI cereals with other low-GI foods, such as unsweetened plant milk, yogurt, nuts, or low-GI fruits.

Quinoa

Quinoa is a seed harvested from the goosefoot plant. Quinoa is technically a pseudo-cereal, which is a food that has similar nutrients to grains and requires a similar cooking process.

In addition to a low-GI of 53 per 150 gram (g) serving, quinoa is an excellent source of protein and contains a lot of potassium, iron, and vitamin B. It is a particularly nutritious option for people following a gluten-free diet.

Quinoa is a highly versatile food. People can try adding it to salads or soups or making a quinoa porridge to serve with low-GI fruits and nuts. Make sure to rinse quinoa well until the water runs clear to remove the bitter saponin compounds. Pressure cooking is an excellent cooking method for this pseudo-cereal and can help people tolerate it well.

Vegetables

Most vegetables on the glycemic index have a low GI. According to the University of Sydney, examples include:

Vegetable (per 80 g unless otherwise stated) GI score

• Carrots 35
• Sweet potato (150 g) 44
• Butternut squash 51
• Parsnips 52
• Yam (150 g) 54
• Sweet corn 55

Starchy vegetables, such as pumpkin and parsnips, tend to have a higher GI. The following factors can also affect the GI of vegetables:

• Ripeness and storage: Riper produce has a higher GI
• Processing: Fresh fruits and vegetables release their carbs more slowly than juiced, mashed, or pureed vegetables
• Cooking: Different methods of cooking can alter the GI of vegetables. For example, the ADA states that boiled white potatoes have a GI of 74–82, instant mashed potatoes have a GI of 84–90, and French fries have a GI between 58–68

Legumes and pulses

Pulses are the harvested beans, peas, or lentils that derive from plants belonging to the Leguminosae or pea family. Most legumes have a GI of 50 or below. Examples include:

Legume (per 150 g) GI score

• Kidney beans 19
• Red lentils 21
• Pinto beans 33
• Chickpeas 36
• Butter beans 36
• Green lentils 37

Legumes also have a high fiber and protein content, both of which help people to feel fuller for longer. They may, therefore, be beneficial in aiding weight loss, when eaten as part of a healthful, balanced, Mediterranean-style diet.

Legumes also provide a range of important micronutrients, including B vitamins, iron, copper, magnesium, phosphorous, manganese, and zinc.

Nuts and nut butters

Nuts and no-added-sugar nut butters are low in carbohydrates. They are also high in fiber and protein, which increases the amount of time the body takes to digest them. As a result, nuts release their energy slowly without spiking blood glucose levels.

Nuts may be a particularly healthful snack for people with type 2 diabetes. Not only do they have a low GI, but they also contain a high amount of healthful, monounsaturated fats (MUFAs), which may aid blood glucose control and improve cardiovascular health.

A 2013 study found that women with type 2 diabetes who consumed peanuts or peanut butter each day had reduced appetite and improved blood glucose control compared with people who did not consume these foods. For a filling, low-GI snack, try spreading almond or peanut butter on low-GI fruits, such as sliced apple.

Fresh fruits

Fresh fruits tend to have a low GI, which raises blood sugar levels at a fairly slow and steady rate. However, tropical fruits tend to have a higher GI. Examples of low-GI fruits include:

Fruit (per 120 g) GI score

• Plum 24
• Grapefruit 25
• Peach 28
• Apricot 34
• Apple 40
• Orange 40
• Strawberry 40
• Pear 42
• Grapes 43

Examples of fruits with a higher GI include:

Fruit (per 120 g unless otherwise stated) GI score

• Lychee (100g) 57
• Mango 60
• Papaya 60
• Pineapple 66
• Watermelon 80

People who are looking to stabilize their blood sugar levels should opt for low-GI fruits wherever possible. When buying canned fruits, avoid those canned in sweetened fruit juices or those containing added sugars. This type of fruit will have a higher GI. Dried fruits also tend to be higher in calories and higher on the GI scale.

Dairy

Many dairy products, such as milk and yogurt, are low on the GI scale. For example, according to the ADA, whole milk has a GI of 36–42, and a fruit flavored yogurt has a GI of 39–43. Both have a minimal effect on blood glucose levels.

Dairy products are also a good source of protein and calcium. For a low-GI breakfast, combine yogurt with low-GI fruits and nuts or blend the ingredients with vegetables for a healthful breakfast smoothie. For vegans and people allergic or sensitive to dairy, soy milk has a GI of 30–38. This makes it a good, low-GI alternative.

White bread alternatives

The ADA lists white bread as having a GI of 73–77. White bread releases its carbs very quickly, causing a significant peak and subsequent crash in blood glucose levels. To help maintain a healthy blood glucose level, try swapping white bread for one of the following low-GI breads:

Bread (per 30g) GI score

• Mixed grain 34
• Pumpernickel 41
• Sourdough rye 48
• Rye 50
• Soy and linseed 50
• Sourdough wheat bread 54

Other important considerations

The following factors are also important when attempting to follow a healthful low-GI diet.

Portion size: Smaller meals have less effect on blood glucose levels than larger meals.

Food combinations: The GI of a food describes how it affects blood glucose when eaten alone. However, combining high and low-GI foods in the same meal increases the digestion time of high-GI foods. This means they will release glucose into the bloodstream at a steadier rate.

Nutritional content: Many high-GI foods have a higher nutrient content than low-GI foods. People who follow a low-GI diet should ideally avoid the low-GI foods that offer little nutritional value. Examples of such foods include:

• Chocolate bars
• Cakes
• Jams
• Corn chips
• Rice noodles

Summary

Following a diet that consists mainly of low-GI foods can have a range of health benefits. There are many low-GI options to suit a variety of diets and nutritional needs. When creating a low-GI meal plan, consider other factors that can affect blood glucose levels, such as cooking methods, portion sizes, and the ripeness of fresh produce.

It is also important to consider that the GI of a food does not reflect its overall nutritional content. People should aim to eat a variety of foods, especially of nutrient-dense fruits and vegetables, to fulfill their dietary requirements.