Determining how much fruit to consume is complicated for many people with diabetes. Because fruit is a source of naturally occurring glucose, some people with diabetes believe — either from their own experiences or from sources of dietary advice — that it can raise their blood glucose levels. Fruit is, of course, also a source of fructose, which has been associated with negative health effects even though it tends not to raise blood glucose levels very much. Until recently, though, there was very little reliable data on the effects of fruit in people with diabetes.
Earlier this month, a study on fruit consumption in people with diabetes was published by Nutrition Journal. The study was small, involving only 63 participants with newly diagnosed Type 2 diabetes. It was, however, randomized, meaning that some participants were randomly selected to be told to eat at least two pieces of fruit daily. The other participants were told to reduce their fruit consumption. As noted in a post on the study at the New York Times blog Well, all participants in the study were given individually appropriate medical care and counseled on other aspects of their diet and lifestyle, which included advice to limit their calorie intake. The high-fruit group ended up increasing its daily fruit consumption by an average of 125 grams, while the low-fruit group reduced its average consumption by 51 grams, compared with just before the study. The result was a daily average fruit consumption of 319 grams for the high-fruit group but only 135 grams for the low-fruit group, which is about the equivalent of a single orange or banana.
Perhaps surprisingly, this stark difference in the amount of fruit consumed had no measurable impact on blood glucose control, nor on body weight or waist circumference. Both groups saw improvements in each of these areas, most likely the result of both lifestyle changes and the medical care they received. While the high-fruit group saw a greater drop in HbA1c — 0.48%, versus 0.29% for the low-fruit group — the end result was nearly identical, with an average HbA1c level of 6.26% in the high-fruit group and 6.24% in the low-fruit group. The researchers concluded, based on this evidence, that advising people with newly diagnosed diabetes to reduce their fruit consumption would be misguided.
Like any study, though, this one has its limitations. In addition to its small size and likely lack of ethnic and racial diversity (it was conducted in Denmark), the study did not examine the effects of moderate versus very high levels of fruit consumption. This leaves open the possibility that there is an upper limit for safe fruit consumption for people with diabetes. The study also did not examine the health effects of different fruits, which vary widely in levels of sugar, fiber, and other nutrients. Eating half a pound of apples each day (high in fiber) may not yield the same results as eating half a pound of watermelon (low in fiber, high in sugar).
What do you think — is eating fruit a good idea for people with diabetes? Have you experienced better or worse blood glucose control as a result of changes in the amount of fruit you eat? Are some fruits fine, while others lead to blood glucose spikes? Have you noticed a difference between whole fruits and fruit juices? Leave a comment below!