Keeping blood sugar in check is important for everyone, but especially for those with diabetes or prediabetes. Having uncontrolled blood sugar can lead to serious health problems including heart disease, vision loss, kidney disease, and nerve damage. Blood sugar surges can occur for many reasons, including stress and sickness, but one of the main occurrences is due to diet. Keeping blood sugar steady and avoiding insulin spikes can also help with weight loss.

Carbohydrate-rich foods are the ones that impact our blood sugar. They are an important source of energy for our cells, so they do not need to be avoided but rather eaten in certain quantities so that you stay within your target blood sugar range.

Although all carbohydrates affect blood sugar, some may cause a higher spike than others. New research has linked four categories of plant-based foods that have a lower effect on blood sugar in diabetic individuals.

Getty Images

What is the glycemic index?

A tool that has been helpful in managing blood sugar levels is called the glycemic index (GI). Where a food falls within the GI depends on its nutrient composition, how it’s cooked, ripeness, and any processing it’s gone through.

Foods that are higher in refined carbs and sugar quickly digest and, therefore, reach our bloodstream quicker than carbohydrate foods that contain higher amounts of protein or fiber. Carbohydrate foods are the only ones that are assigned a GI since foods without carbs like nuts, seeds, meats, spices, and oils do not raise blood sugar levels.

According to Harvard Health, foods are ranked on a scale from 0 to 100 with pure sugar being 100. The lower the number on the GI scale, the slower blood sugar rises after consuming that food. Carbohydrate-containing foods fall under the following classifications when it comes to GI foods:

  • High: ≥70
  • Moderate: 56-69
  • Low: ≤55

While the GI compares foods that contain the same amount of carbohydrates to how they raise blood sugar levels, the glycemic load (GL) of foods was also developed since some foods have higher quality and quantity of carbohydrates per serving. The GL can be calculated using the following formula:

  • GL food = (GI Food x amount (g) of available carbohydrate food per serving)/100

Take watermelon for example. When it comes to GI, watermelon falls at a 76 which is comparable to a donut. When you take into consideration the number of carbohydrates, watermelon contains 11 grams which would bring its GL to an 8 while donuts have a GL of 17.

The GL classifications include:

  • High: ≥20
  • Moderate: 11-19
  • Low: ≤10

What new research has found

A new study published in BMJ in August of 2021 found that following a low glycemic diet when you are diabetic can show improvements in blood sugar levels, cholesterol, weight, and other risk factors.

The study included 1,617 participants who either have type 1 or type 2 diabetes, are middle-aged, overweight or obese, and have moderately controlled diabetes from drugs or insulin. The results took place from 27 different randomized controlled trials that were published up until May of 2021.

The results from these studies showed that when low-GI/GL dietary habits were followed, participants had small but meaningful reductions in blood sugar (HbA1c) compared to those that followed higher GI/GL diets. The low-GI/GL diets also improved fasting glucose (blood sugar after a period of not eating), low-density lipoprotein cholesterol (LDL aka “bad” cholesterol), body weight, and C-reactive protein (a chemical that can trigger inflammation).

Following a low-GI/GL eating pattern is a great treatment addition along with drug and insulin therapy to treat diabetes and achieve target glucose levels.

Like all studies, the researchers state that there may be some limitations that affected their results. However, the findings show “low GI/GL dietary patterns are considered an acceptable and safe dietary strategy that can produce small meaningful reductions in the primary target for glycemic control in diabetes, HbA1c, fasting glucose, and other established cardiometabolic risk factors.” They also conclude that, “our synthesis supports existing recommendations for the use of low GI/GL dietary patterns in the management of diabetes.”

Low-GI Food Examples

That latest research classified low-GI foods into 4 different categories. Here are some specific examples of foods that fall in these categories and have lower GI levels.


  • Broccoli: 10 - 15
  • Cabbage: 0 - 10
  • Lettuce: 10 - 15
  • Onions: 10 - 15


  • Apples: 34 - 38
  • Oranges: 40 - 46
  • Dates: 38 - 46
  • Bananas: 48 - 54


  • Chickpeas: 19 - 37
  • Kidney beans: 20 - 28
  • Lentils: 27 - 37
  • Soya beans: 15 - 17

Whole grains

  • Sweet corn: 47 - 57
  • Whole wheat spaghetti: 47 - 51
  • Barley: 26 - 30
  • Multigrain bread: 51 - 55

The health benefits of a low-GI diet

Beyond its ability to improve blood sugar levels, following a low-GI diet can come with other health benefits.

One 2014 study published in the American Journal of Clinical Nutrition found that participants who followed a low-GI an energy-restricted diet with moderate carb intake had more weight loss than those that followed a high-GI and low-fat diet. Weight loss with diabetes can help to improve insulin resistance and even glycemic outcomes.

Following a low-GI diet could improve cholesterol levels as well. A 2013 study published in Family Practice found that individuals following a low-GI diet had improved total cholesterol and LDL cholesterol levels. This result even occurred over a short time frame of 5 to 12 weeks.

Bottom Line: The glycemic index and glycemic load are two measures that can benefit those with diabetes to keep blood sugar levels regulated. Other research also shows following a low-GI could benefit weight loss and cholesterol levels.