Many people wonder if grapes raise blood sugar or not and if they should eat them with diabetes. The truth is all fruits raise blood sugar because they contain digestible carbohydrates. Digestible carbohydrates are broken down into sugar which is their simplest form, then absorbed into the bloodstream, raising levels there. But how fast the carbohydrates in a fruit like grapes or some other food raise blood sugar levels determines if said fruit or food is okay to eat with diabetes or not.
Grapes being low-glycemic, they have overall limited effects on blood sugar and should not produce spikes unless eaten in excessive amounts. Having small servings at once ensures you get a limited number of carbohydrates and experience lesser effects on blood sugar. Because the fruit is an important source of digestible carbohydrates, most of which are sugars and very little dietary fiber to limit glycemic effects. As such, keeping to a moderate intake becomes a prerequisite for achieving blood sugar control, even when eating foods that are low-glycemic like grapes.
The glycemic index for grapes is low and ranges between 45 and 53. Despite the fruit being a significant source of digestible carbohydrates (on average, between 14-18 g of carbs per 100 g), most of which are sugars and very little dietary fiber to slow down the rate of sugar absorption into the bloodstream. The glycemic index (GI) measures how fast the carbohydrates in a food raise blood sugar levels. Below 55 is a low GI. Between 56-69 is a moderate GI. Between 70-100 is a high GI. If you have diabetes or pre-diabetes, then it is advisable to choose foods with as low a GI as possible, as often as possible and avoid high GI foods to the best of your efforts.
The glycemic load for grapes is also low, but varies according to serving size. Typically, the smaller the portion of grapes you eat, the fewer carbohydrates you get from it and the lesser the effects on blood sugar. The glycemic load (GL) measures how fast the carbohydrates in a serving of a food raise blood sugar. Between 0-10 is a low GL. Between 11-19 is a moderate GL. Over 20 is a high GL. Anyone with diabetes or pre-diabetes benefits most from choosing foods with low GI as well as low GL values.
The glycemic load varies according to serving size and variety of food – different serving sizes provide different amounts of carbohydrates while different varieties of the same food are often nutritionally dissimilar and thus have slightly varying carbohydrate contents. The glycemic load is also reliant on the glycemic index of a food. The GL is determined by multiplying the glycemic index by the number of carbohydrates in a serving of a food, then diving by 100. The following formula is used:
GL = GI X no. of carbs expressed in grams/100.
What is the glycemic load of grapes considering their varying glycemic index and difference in carbohydrate content per variety? An exact GL score can only be given if we know the precise amount of carbohydrates in a serving of grapes and the precise GI score of the variety considered. But since the GI score would have to be studied in a laboratory setting for every variety of the fruit at different stages of ripening (to account for changes in carbohydrate profiles), that would be a rather exhaustive approach.
Fortunately, we can get a pretty good idea of the effects of grapes on blood sugar from less precise determinations. Below are the glycemic load scores for 3 different grape varieties determined based on serving size and average number of carbohydrates per serving for each variety, first for the lowest GI and second for the higher GI.
Glycemic load of grapes determined for lowest GI (45):
– 100 g of the muscadine variety: 45 X 13.93/100 = 6.2, estimated at 6 (low GL)
– 10 muscadine grapes (60 g): 45 X 8.4/100 = 3.78, estimated at 4 (low)
– 100 g of American slip-skin variety: 45 X 17.15/100 = 7.7, estimated at 8 (low)
– 10 grapes, American variety (24 g): 45 X 4.1/100 = 1.8, estimated at 2 (low)
– 1 cup American variety (92 g): 45 X 15.78/100 = 7.1, estimated at 7 (low)
– 100 g of Red/Green European variety: 45 X 18.1/100 = 8.1, estimated at 8 (low)
– 10 European variety grapes (49 g): 45 X 8.87/100 = 3.99, estimated at 4 (low)
– 1 cup European variety (151 g): 45 X 27.33/100 = 12.2, estimated at 12 (moderate GL)
Glycemic load of grapes determined for highest GI (53):
– 100 g of the muscadine variety: 53 X 13.93/100 = 7.3, estimated at 7 (low GL)
– 10 muscadine grapes (60 g): 53 X 8.4/100 = 4.45, estimated at 4.5 (low)
– 100 g of American slip-skin variety: 53 X 17.15/100 = 9 (low)
– 10 grapes, American variety (24 g): 53 X 4.1/100 = 2.1, estimated at 2 (low)
– 1 cup American variety (92 g): 53 X 15.78/100 = 8.36, estimated at 8 (low)
– 100 g of Red/Green European variety: 53 X 18.1/100 = 9.59, estimated at 10 (low)
– 10 European variety grapes (49 g): 53 X 8.87/100 = 4.7, estimated at 5 (low)
– 1 cup European variety (151 g): 53 X 27.33/100 = 14.4, estimated at 14 (moderate GL)
So are grapes low or high glycemic? Grapes are generally low glycemic index foods, but below 150 g per serving, they are also pretty much low glycemic load and can be eaten safely with diabetes. A serving size of over 150 g may produce more visible effect on blood sugar and not all diabetics may tolerate higher amounts very well. About 10 grapes of most varieties have a glycemic load score between 2-5, which is low and perfectly adaptable to a diabetic diet.
Overall, grapes and diabetes are good together only in the context of a limited intake: small servings that provide few carbohydrates and produce minimal glycemic effects. Bigger servings provide too many carbs and can fuel a substantial rise in blood sugar levels. To further reduce their blood sugar effects, remember to eat your grapes with skin and after a meal providing lean protein or some fat.