Eating fruit is part of a healthy diet, but some people with diabetes or prediabetes worry that the natural sugars in fruit can cause blood sugar spikes. This is a valid concern since all carbohydrates, including the carbs in fruit, get broken down into sugar in the body. However, not all fruits impact blood sugar equally. The glycemic index (GI) measures how quickly foods cause blood sugar to rise. Low GI foods cause a gradual rise, while high GI foods lead to rapid spikes.
The glycemic index of fruits
The glycemic index ranks foods from 0 to 100. The higher the number, the bigger the blood sugar spike. Here’s a look at where some common fruits fall on the GI scale:
| Low GI fruits (55 or less) | Medium GI fruits (56-69) | High GI fruits (70 or more) |
|---|---|---|
| Cherries | Bananas | Watermelon |
| Strawberries | Pineapple | Dates |
| Peaches | Grapes | Raisins |
| Plums | Oranges | Mango |
As you can see, most fruits fall into the low or medium GI categories. Berries, stone fruits, and citrus fruits tend to be lower on the scale, while tropical fruits and dried fruits are higher.
Why does blending fruit matter?
Blending, juicing, and pureeing fruits affects their glycemic index. These processes break down the cell walls in the fruit, allowing sugars to be absorbed faster during digestion. For example, a whole apple may have a GI of 38, whereas apple juice has a GI of 58. The juicing process eliminates the fiber and makes the sugars much more accessible.
The same goes for blending fruit to make smoothies. The mechanical force breaks down the fruit and can lead to a quicker rise in blood sugar compared to eating the whole fruit. Exactly how much the GI increases depends on the specific fruit and the blending method.
Glycemic impact of blended fruits
Here’s how blending affects the glycemic index of some popular fruits:
| Fruit | Whole | Blended |
|---|---|---|
| Bananas | 51 | 59 |
| Strawberries | 32 | 51 |
| Blueberries | 53 | 64 |
| Mangos | 51 | 66 |
As shown, blending causes a moderate increase in GI for most fruits. The degree depends on the structure of the fruit. Berries have seeds and skins that stay somewhat intact when blended, slowing sugar absorption. Meanwhile, mangos transform into a uniform puree, allowing for rapid digestion.
Tips for managing blood sugar with smoothies
Enjoying fruit smoothies in moderation is unlikely to cause big blood sugar spikes for most people. Those with diabetes or prediabetes can take extra steps to prevent increases when blending fruits:
- Use low GI fruits like berries as the base
- Add healthy fats from nuts, seeds, or avocado
- Include protein powder or yogurt
- Blend with high-fiber vegetables like spinach
- Avoid adding sugary ingredients like fruit juices or syrups
- Stick to 1/2 – 1 cup portion sizes
- Consume with other solid foods
Pairing blended fruits with protein, fat, and fiber slows down digestion and prevents a rapid influx of sugar into the bloodstream. Portion control is also key – smoothies can pack a lot of concentrated carbs and calories in one serving.
The bottom line
Blending does increase the glycemic index of fruits by breaking down their fiber. However, when consumed in normal amounts as part of a balanced diet, smoothies should not cause major blood sugar concerns for most people. Those with diabetes should take care to choose low GI fruits, add protein and fat, and drink smoothies as part of meals.
Enjoying a variety of whole fruits is ideal for managing blood sugar. But blending occasionally can fit into a healthy type 2 diabetes diet when done mindfully. Speak to a registered dietitian for personalized guidance on incorporating smoothies into your meal plan.
