Glycaemic load, simplified

To study dietary carbohydrates and inflammation, researchers invited 41 normal weight and 41 overweight and obese, 18- to 25-year-old adults to participate in a study. Participants were randomly selected to follow one of two diets for 28 days. The groups then switched diets, so that everyone followed both diets, for 28 days each. Blood measures of inflammation were collected throughout the study.

The diets were identical in terms of calories and amounts of protein, fat, and carbohydrates, but the carbohydrate type was different. One diet contained predominantly high-glycaemic load (GL) carbohydrates, while the other contained low-GL carbohydrates. Glycaemic load is a measure of how quickly carbohydrate is turned into blood sugar in the body.

Generally, slower digesting, complex carbohydrates are considered healthier, leading to sustained energy and blood sugar levels. Eating simple carbohydrates, on the other hand, such as those found in regular fizzy drink, desserts, cakes, pies, and refined grains, can raise blood sugar, and insulin levels, quickly. Fluctuating blood sugar and insulin may increase a person’s likelihood of developing diabetes, heart disease, cancer, and other chronic health conditions over the long term.

Inflammation by the numbers

Compared with the high-GL diet, C-reactive protein (CRP) levels went down and levels of a different blood marker (adiponectin) increased during the low-GL diet. Decreased CRP may signal improved health, because high CRP levels mean more inflammation, and are linked with higher disease risk. Increased levels also are a positive, because this substance improves the body’s insulin regulation, and has anti-inflammatory effects on cells lining blood vessels. Higher levels are linked with lower heart attack risk, and being overweight seems to suppress the body’s adiponectin production.

Use our tips on how to include more healthy, low-GL foods in your diet:

• Go natural. The closer a food is to when it came out of the ground, or off the vine or tree, the better. Stick with foods such as beans, chickpeas, lentils, nuts and seeds, whole grains, and vegetables to craft a naturally low-GL dietary plan.
• Pass on processed food. Foods that come in a package with a label tend to be more processed, and often have a higher glycaemic load. You don’t need a label to tell you that steel cut oats, sweet potatoes, almonds, walnuts, fish, and black beans are healthy. If you spend a lot of time reading labels, consider shifting away from these packaged products.
• Pick protein, healthy fat, and fibre. Eating more protein, fat, and fibre will slow carbohydrate digestion, and lower the overall GL of any meal or snack. Try Greek yoghurt, hard-boiled eggs, or tuna for protein; nuts, nut butters, and olive oil for healthy fat; and whole grains and non-starchy vegetables for fibre.

(J Nutr 2012;142:369–74)