Diabetes: Do low glycemic index diets work?

 

• People with type 1 or type 2 diabetes often use several different methods to keep blood sugar levels in a healthy range and prevent long-term complications.

• The glycemic load (GL) and glycemic index (GI) are different ways of indicating how much any given food will raise blood sugar levels.

• A new review of research suggests that a low GI diet may help people with diabetes, particularly type 2 diabetes, keep their blood sugar levels in an appropriate range.

Type 1 and type 2 diabetes affect more than 34 million people in the United States alone — 10.5% of the population. And people with type 2 diabetes make up 90–95% of that total. Both types are chronic diseases that people can manage to various extents through lifestyle modifications and medications.

People with diabetes work alongside their doctors to develop individualized treatment plans.

Nutrition and education play key roles in the management of diabetes. Specifically, people with diabetes need to be aware of how certain foods affect their blood sugar levels.

Some helpful measurements are GI and GL, which can help determine how much a particular food will make a person’s blood sugar levels rise.

In general, foods with a low GI raise blood sugar less, and foods with a high GI raise blood sugar more.

A recent analysis, which appears in BMJ, suggests that eating a diet of low GI foods may help people with diabetes, particularly type 2, maintain better average blood sugar levels and improve other health parameters.

Diabetes and GI

As the Centers for Disease Control and Prevention (CDC) explain, diabetes is a chronic disease that involves the hormone insulin. Insulin acts as a key, helping the sugar from food enter the body’s cells, which use the sugar for energy.

In people with diabetes, sugar from food remains in the bloodstream instead of entering cells. Consistently high levels of sugar in the blood can damage blood vessels and organs.

Diabetes increases a person’s risk of long-term health conditions, including nerve damage, kidney disease, and cardiovascular disease.

People can take steps to manage their diabetes, including taking medications, having an active lifestyle, and eating a healthy diet.

Monitoring blood sugar levels is also critical in diabetes management. A hemoglobin A1C (HbA1C) test measures blood sugar levels over a period of 2–3 months, and this is the main way to get an average reading of a person’s blood sugar levels.

Some foods raise blood sugar levels higher than others, and certain foods cause the levels to rise and fall rapidly. Understanding which foods do this can help people with diabetes plan their meals in a way that is optimal for their health.

Both GI and GL help people understand how much specific foods affect their blood sugar levels.

As Oregon State University notes, GI indicates the potential for the carbohydrates in a type of food to raise blood sugar levels, compared with a reference food, which is usually pure glucose.

GL is similar a tool. Measuring it involves starting with the food’s GI, multiplying it by the number of carbohydrates in a serving of that food, and dividing this by 100.

In general, foods with a higher GI cause blood sugar to rise and fall rapidly, while foods with a lower GI cause blood sugar to rise less and decline more gradually.

Benefits of low GI foods

The new investigation is a systematic review and meta-analysis of 29 randomized controlled trials.

According to the authors, the objective of the analysis was “to inform the update of the European Association for the Study of Diabetes’ clinical practice guidelines for nutrition therapy.”

To be included in the analysis, the trials must have investigated the impact of low GI/GL diets in people with diabetes for at least 3 weeks. The analysis looked at data from a total of 1,617 participants who had type 1 or type 2 diabetes.

The trials included in the analysis had taken place predominately in Canada, Australia, France, the U.S., Israel, and Mexico, with the rest taking place elsewhere in Europe or in Asia.

The researchers report that most of the participants:

• were middle-aged

• had moderately controlled type 2 diabetes

• managed their diabetes using medications, insulin, or a combination

However, some participants in some of the trials controlled their diabetes using dietary measures alone.

Based on the pooled data, the team found that people who had a low GI diet had a small but clinically meaningful reduction in blood sugar levels, compared with people who had a higher GI diet.

The data further indicate that participants with a low GI diet had small overall improvements in levels of body fat, blood lipid levels, and inflammation, compared with participants with a higher GI diet.

A co-author of the analysis, Laura Chiavaroli, who is a postdoctoral fellow at the University of Toronto, told Medical News Today:

“The available evidence provides a good indication that low GI/GL dietary patterns result in small, clinically significant reductions in the primary target of glycemic control — HbA1c.”

She also explained that there were “small, clinically meaningful improvements in other established cardiometabolic risk factors,” such as blood lipids, body weight, and levels of inflammation.

Limitations and moving forward

The review did have limitations. For instance, the authors observe, the analysis did not include many trials with children or people with type 1 diabetes. Also, trials involving pregnant or breastfeeding participants were also excluded from the analysis.

In addition, the included trials mostly compared low GI diets with moderate GI diets. This did not provide a full range of possible comparisons.

The results of the investigation are most applicable to people with type 2 diabetes. Taking into account the imprecision and limitation of the data in some areas, the authors conclude:

• There is high evidence that a low GI/GL diet helps improve HbA1C and high-density lipoprotein (HDL) cholesterol levels.

• There is moderate evidence that a low GI/GL diet helps improve inflammation, body weight, BMI, non-HDL cholesterol levels, and triglyceride levels.

• There is low evidence that a low GI/GL diet helps improve blood pressure, fasting insulin levels, low density lipoprotein cholesterol levels, and waist circumference.

Overall, the researchers observe that a low GI diet, alongside other treatments, could be benefit people with diabetes. Dr. Chiavaroli told MNT:

“The significance of these findings is that they demonstrate evidence to support existing recommendations for the use of low GI/GL dietary patterns in glycemic control for diabetes management, as well as providing data to support reduced risk of cardiovascular disease, which is the leading cause of death in those with diabetes.”

She continued, “The implication is that a low GI/GL diet is one more evidence-based option for helping patients achieve diabetes management goals with benefits that are additive with background drugs and insulin therapy.”

Written by Jessica Norris on August 10, 2021 — Fact checked by Hannah Flynn, MS

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