Glycemic Index and Summer Fruits: What Applies to People with Diabetes

Summer Fruits in our Diet

Summer brings with it high temperatures, increased hydration needs, and a plethora of fresh, delicious fruits. Peaches, watermelon, grapes, and many other seasonal fruits are prominent in both the diet and the cravings of most people during this period.

They are light, refreshing, full of vitamins and antioxidants, and are an integral part of a healthy, Mediterranean lifestyle.

For people with diabetes, however, enjoying these fruits is often accompanied by concern. How much do they affect blood sugar and how can they be consumed daily?

But which fruits are considered safer and which require more attention?

The answer to the above questions is not always simple. The way fruits affect glycemia depends on many factors:

• the variety
• the degree of ripeness
• the quantity, the overall composition of the meal
• their glycemic index.

What is the Glycemic Index (GI) and how Does it Affect Us?

The glycemic index (GI) is one of the basic tools that can help people with diabetes choose foods that do not cause sharp increases in blood glucose.

It is a method used to classify carbohydrate-containing foods according to how quickly and intensely they raise blood glucose levels after consumption, compared to pure glucose (which has a GI = 100).

• GI is measured on a scale from 0 to 100.
• This value is derived from experiments on humans, where the increase in blood glucose after consuming a specific food is compared to the corresponding increase caused by pure glucose or white bread.

Glycemic Index (GI) Categories
GI Range	Category
0 – 55	Low
56 – 69	Medium
≥ 70	High

 

The glycemic index matters because it affects:

1. Blood glucose levels: Foods with a high GI cause a rapid and sharp increase in glucose, while foods with a low GI raise blood sugar more gradually.
2. Satiety: Foods with a low GI cause more prolonged satiety.
3. Energy stability: More gradual absorption leads to more stable energy levels and avoidance of hypoglycemic episodes.
4. Glycemic control in people with diabetes: A diet based on low or medium GI can help in better blood sugar regulation, reduction of post-meal peaks, and improvement of glycated hemoglobin.

GI alone doesn’t tell the whole story. Glycemic load (GL) is also very important, which takes into account the amount of carbohydrates per serving of food.

Thus, even foods with a high GI, if they contain a small amount of carbohydrates, can have a low glycemic impact.

A balanced diet with knowledge and moderation does not exclude fruits but incorporates them correctly, enjoying every season wisely.

Summer Fruits and Glycemic Index

If you have diabetes, fruits are not forbidden. On the contrary, they can offer valuable health benefits, as long as they are consumed in moderation and in the right combination.

Fruits are rich in fiber, vitamins, antioxidants, and water. All these elements contribute to reducing the risk of cardiovascular disease – something particularly important, as diabetes increases the likelihood of cardiovascular events. The natural components of fruits help regulate cholesterol, blood pressure, and overall vascular protection.

Furthermore, the fiber in fruits plays an important role in regulating blood glucose. They slow down the digestion and absorption of carbohydrates, preventing sharp increases in glucose and simultaneously helping to control hunger and weight. They also contribute to proper bowel function and, combined with their high water content, support body hydration.

The glycemic index (GI) of each fruit indicates how quickly blood glucose increases. However, it is not the only thing that matters – the portion you consume is also a decisive factor. For example, watermelon has a high GI, but because it consists mainly of water, the amount of carbohydrates per serving is low (about 11 grams per cup). Thus, even fruits with a high GI can be included in the diet when consumed in small quantities.

The method of consumption also plays a role. Consuming a fruit alone can raise blood glucose levels faster than when it is accompanied by protein or good fats – such as yogurt, nuts, or tahini. These combinations slow down glucose absorption and contribute to better glycemic balance.

Finally, prefer fruits in their natural form. Even if they have a low GI, when they are juiced or pureed, they raise blood sugar levels faster due to the loss of fiber.

Fruit (1 equivalent)	GI (approximate)	Category
Cherry	29	Low
Peach	28	Low
Apricot	34	Low
Fig	35	Low
Grape	43-54 (depends on variety)	Low
Melon	60	Medium
Watermelon	72	High
Plum	24	Low
Apple	44	Low

 

For example:

• 1 apple (whole): low GI.
• 1 glass of apple juice: significantly higher impact.

Prefer whole fruits, with the skin where possible. For many summer fruits, the following amount contains approximately 15g of carbohydrates:

• 1 medium peach (150g).
• 1 1/3 cup chopped watermelon.
• 15–17 grapes.
• 3 fresh medium apricots.
• 2 small figs.

Some of the most popular summer fruits may have a medium or high GI, but this does not necessarily mean they should be avoided. Let’s look at three characteristic examples in more detail:

Peach

• GI: 28 (low).
• Content: 1 medium peach (150g) contains 15g carbohydrates.
• Nutritional benefits: Rich in vitamin C, antioxidants, and fiber.
• Suitable for people with diabetes, especially when consumed in moderation and combined with protein (e.g., a little yellow cheese).

Watermelon

• GI: 72 (high).
• GL: Low, due to high water content → 1 cup watermelon ≈ 11–12g carbohydrates.
• Nutritional benefits: Extremely hydrating, rich in lycopene (antioxidant).
• Although it has a high GI, the portion plays a decisive role; in small quantities, it can be safely included in the diet plan.

Grapes

• GI: 43-54 (low).
• Content: 15–17 grapes ≈ 15g carbohydrates.
• Nutritional benefits: Rich in resveratrol (a powerful antioxidant) and vitamin K.
• Grapes have a high sugar content, so portion control and combination with other foods are recommended.[1]

If you are counting carbohydrates or following a specific dietary plan, these amounts can guide you.

Fruits are part of a balanced diet. You don’t need to exclude them, but rather incorporate them wisely and strategically.

The right choice, the appropriate quantity, and a good combination are the “key”.

What to do	What to avoid
Whole fruits in small portions	Juices and smoothies
Combination with protein or fats	Large quantities of fruits alone
Monitoring glucose after consumption	Overconsumption of “low GI” fruits
Prefer low or medium GI fruits	Dried or sweetened fruits

Practical Tips for People with Diabetes

Practical tips help in the daily application of theory, making diabetes management more simple, safe, and sustainable in practice.

Let’s look at some of the things you need to know.

1. The combination of GI and quantity (glycemic load) is more important than GI alone.
2. Portion size makes a difference: A small amount of watermelon or grapes can be safely included in the plan. Even fruits with a low GI can raise blood sugar if eaten in large quantities.
3. Combinations with good fats or protein (e.g., fruit + nuts or yogurt) reduce the glycemic response.
4. Choose whole fruits and avoid juices and large amounts of dried fruits.
5. Monitor glucose readings after fruit consumption. Especially if you are introducing new fruits into your plan.
6. Distribute fruit portions throughout the day (e.g., 1 fruit for morning snack and 1 for afternoon snack).
7. Avoid dried fruits with added sugar, as they have a very high sugar content per small amount.
8. Pay attention to ripeness. The riper the fruit, the higher its glycemic index.
9. Don’t rely solely on “fruit salads”. Although they seem healthy, they can contain a large amount of carbohydrates if you don’t control the portions.
10. Seasonality is an ally. Prefer fresh, seasonal fruits as they have better nutritional value and a lower chance of added sugars.

Conclusion

Summer fruits are not the “enemy” of people with diabetes, as long as they are consumed in moderation, with knowledge, and in the right combination.

The glycemic index is a useful tool for assessing the effect of fruits on blood sugar, but it is not the only one. Quantity, combination with other macronutrients, and individual responses are equally important factors.

Peaches, watermelon, and grapes, as well as any seasonal fruit, can be safely included in the diet of people with diabetes, provided they are consumed in the correct portion and as part of a balanced meal or snack.

Personalized dietary guidance from your clinical dietitian can offer valuable advice and practical strategies, allowing each person to enjoy summer fruits without worry and with stable glucose control.

A balanced diet, even with diabetes, should be a pleasure and not a restriction.

Bibliography

[1] THE UNIVERSITY OF SYDNEY | Glycemic Index Research and GI News. Available at: https://glycemicindex.com/gi-search. Accessed July 2025