Unpack the world of carbohydrates, glycaemic index, and how it affects your metabolic health with our comprehensive guide. Understand the different types of carbs, discover a list of low to high GI foods, and learn how carbs impact your blood sugars.

Key takeaways

• Carbohydrates, available in simple and complex forms, can affect your blood glucose levels in different ways depending upon their glycaemic index.
• The glycaemic index is a rating system for foods containing carbohydrates. It indicates how quickly each food affects your blood sugar level.
• Glycaemic load is a measurement that considers the quantity of carbohydrates consumed alongside the GI of the food.
• The method of food processing, physical form, fibre content, ripeness, and fat/acid content can impact the GI of the food.

Carbohydrates are a macronutrient available in various forms. We've all heard of them, but why do they get so much air time? Let's dive into our carbohydrates guide.

The types of carbs

Carbohydrates are generally broken down into two broad categories: simple and complex.

• Simple carbohydrates have only a few molecular bonds and are easily and quickly broken down. Examples include sucrose, fructose and glucose. Sucrose, or table sugar, is a combination of a fructose and glucose molecule.
• Complex carbohydrates are long chains of sugars that take longer to be digested. These are also known as starches. They generally have higher amounts of protein and fibre which slows the breakdown into glucose.

Understanding the different types of carbohydrates and their glycaemic index is crucial for managing your metabolic health.

The basics of carbohydrate metabolism

The process of carbohydrate metabolism involves several steps, primarily digestion, absorption, and glucose metabolism.

• Digestion: when you consume carbohydrate food sources, enzymes in your mouth start to break down these large molecules into smaller ones. This process continues in the stomach and small intestine, where the process continues, breaking the carbohydrates down into glucose.
• Absorption: once broken down, glucose is absorbed in the small intestine and transported into the bloodstream. This causes a rise in blood sugar levels. This rise in blood glucose signals the pancreas to release the hormone insulin.
• Glucose metabolism: insulin tells the cells to take up glucose to be used for energy. The glucose can either be used immediately for energy or is stored. The liver and muscles store glucose as glycogen. When these stores are full, the excess glucose is converted into fat and stored in adipose tissue.

The glycaemic index (GI) explained

The glycaemic index definition refers to how rapidly a food is digested and absorbed into the bloodstream. This influences blood glucose levels. The GI scale ranges from 0 to 100, with values categorised as low (0-55), medium (56-69), and high (70-100).

Foods with a high GI tend to move quickly into the bloodstream and are more likely to cause a glucose spike. These foods usually contain simple sugars or highly processed carbohydrates with low fibre content. Conversely, low GI foods, often whole foods high in fibre, fat, or protein, have a minimal impact on blood glucose levels.

For example, the glycaemic index of brown rice is approximately 52, whereas the white basmati rice glycaemic index is 84. This means that cooked brown rice may have less of an impact on your blood sugar levels.

Carbohydrate food lists with GI

Low GI carbohydrate examples include:

• Bran cereals
• Apples, oranges and other citrus fruits
• Kidney, adzuki beans, lentils, and black beans
• Skim milk
• Cashews, peanuts, and walnuts
• Carrots

Medium GI foods include:

• Brown rice: 3/4 cup cooked
• Oatmeal: 1 cup cooked
• Bulgur: 3/4 cup cooked
• Rice cakes: 3 cakes
• Whole grain bread: 1 slice
• Whole grain pasta: 1 1/4 cup cooked

High GI foods include:

• Baked potato and french fries
• Refined breakfast cereal: 28 grams
• Sugar-sweetened beverages and chocolate bars
• Couscous: 1 cup cooked
• White rice: 1 cup cooked
• White pasta: 1 1/4 cup cooked

Understanding glycaemic load

Glycaemic load is used to determine the impact of a portion of carbohydrates on blood glucose response.

Glycaemic load formula: glycaemic load = glycaemic index x carbohydrate content / 100

Even if you were to only consume low GI foods, the portion of this food will impact your glucose responses. For example, there will be a difference in glucose response if you were to consume 1 apple versus 3 apples in one sitting.

Modifying glycaemic index

While the glycaemic index is valuable, it's essential to understand that various factors can affect your glucose response:

• Processing: Refined grains have a higher GI than minimally-processed whole grains due to the removal of bran and germ.
• Physical form: finely-ground grain is digested faster than coarsely ground grain. Therefore, consuming grains in their whole form like brown rice or quinoa can be healthier than processed whole grain bread.
• Fibre content: high-fibre foods slow digestion and the rise of blood sugar levels, reducing the glycaemic impact.
• Ripeness: ripe fruits tend to have a higher GI than unripened fruits as more of the starches have been converted into sugars.
• Fat/acid content: meals with fat (e.g. avocado) or acid (e.g. lemon juice) are converted to sugar more slowly, reducing the glycaemic response.
• The order you eat your foods: consuming protein before carbohydrates slows the absorption and changes the insulin response, thereby managing the glycaemic impact.

The importance of fruits and vegetables

A diet rich in fruits and vegetables can help reduce your risk of diabetes, heart disease, stroke, some cancers, and digestive problems.

Fruits and vegetables are generally rich in complex carbohydrates and are an excellent source of fibre. It's recommended to consume at least 2 serves of fruit and 7 serves of vegetables per day. Opt for a rainbow of vegetables each week, including green and purple vegetables such as spinach, purple cabbage, purple carrots, kale, or bok choy.

Interestingly, the order in which you consume your foods can affect your glucose response. Eating vegetables first can lower your glucose spikes. Ways to incorporate a vegetable starter include:

• Having a green salad before a meal
• Snacking on veggie sticks while preparing dinner
• Eating your vegetables before your proteins/fat and other carbohydrates

It's always advisable to consult an accredited practising dietitian for personalised advice on your diet. They can help you understand your unique metabolic needs and guide you on the best ways to maintain balanced glucose levels.

To keep track of your metabolic health and improve your diet, consider Vively. Vively is a metabolic health platform that uses continuous glucose monitors (CGMs) to help you understand how different food types affect your body. This data can be used to optimise your lifestyle in small, manageable ways, enhancing your glucose control. By providing insights into the impact of your dietary choices, Vively is an invaluable tool for managing your metabolic health effectively.