What Are the Effects of Grapefruit on Diabetes?

Grapefruit provides significant amounts of vitamins A and C, and it’s relatively low-calorie and low on the glycemic index (GI), according to Cleveland Clinic. That can make it a nutritious fruit choice for people with diabetes.

Eating grapefruit may also support more–stable blood sugar levels. But if you take certain medications, you may be better off choosing other fruits due to potential medication interactions.

The glycemic index estimates the effect of a food that contains carbohydrates on your blood sugar levels. Not every food that has carbohydrates will act on your blood sugar the same way, and the GI reflects this, according to Cleveland Clinic.

Foods with a low glycemic index (55 or lower) aren't likely to cause significant increases in blood sugar levels. But those with a high glycemic index of 76 or more may cause rapid spikes in your blood sugar levels after you eat them.

Raw grapefruit has a low GI of 26, according to The University of Sydney. So, it isn’t likely to have a significant effect on your blood sugar as long as you watch your portion size.

Not many studies have examined the direct effect of grapefruit on people with diabetes. However, older research found that fresh grapefruit helped improve insulin resistance as well as insulin levels two hours after eating.

A group eating fresh grapefruit also showed signs of significant weight loss, which can play an important role in diabetes management for some people. However, the reason for the weight loss was unclear. More studies are needed to confirm the benefits of grapefruit in diabetes management.

A more-recent study concluded that eating fresh fruit can help to reduce the risk of death from cardiovascular disease, stroke, and all causes in people with diabetes when included as part of a physically active lifestyle. Eating grapefruit in moderation, along with other fruits, may contribute to a heart-healthy lifestyle that reduces the risk of complications.

According to the U.S. Department of Agriculture’s FoodData Central, half of a large grapefruit weighing 154 grams (g) has 64.7 calories and 16.4 g of carbohydrates, including 2.46 g of fiber.

If you control your blood sugar by counting carbohydrates, this counts as just over one carbohydrate serving — that’s usually around 15 g of carbs, according to the Centers for Disease Control and Prevention (CDC). Eating the same amount of carbs at every meal can help keep your blood sugar levels regular.

There’s no set amount of carbs you need per meal, as the amount you can eat while avoiding blood sugar spikes depends on your age, activity level, body weight, and other factors. Speak to a diabetes self–management education and support (DSMES) practitioner for tailored advice on carb intake.

However, grapefruit can still provide nutritional benefits when you eat it as part of a diet that accounts for overall carb intake.

Stick with fresh grapefruit instead of grapefruit juice, which is higher in both calories and carbohydrates. Each 8-oz glass has 96.8 calories and 22.8 g of carbohydrates, according to FoodData Central. It’s also very low in fiber, providing only 0.25 g in an 8-oz serving.

Check with your doctor before increasing your grapefruit intake, because this fruit can interact with many medications, according to Harvard Medical School. While the exact cause is unclear, the main culprit might be a compound in grapefruit called furanocoumarin.

This doesn’t interact with the chemicals in medications directly, but with an enzyme in the gut, CYP3A4, that reduces how much of certain medications your body can absorb. This may mean you absorb dangerously high levels of certain medications after eating grapefruit while you take some medicines.