Background
Compared to eating whole fruit, drinking fruit juice seems to increase glucose levels to a greater extent, perhaps because fruit juice lacks the fiber found in whole fruit, which can slow absorption of the sugars.
A common way of consuming fruits is by blending them into smoothies. In blended form, the fiber is retained, but the fruit’s cellular structure is broken, which may increase the speed at which the sugars are absorbed. Do blended fruits increase glucose levels more than whole fruits?
The study
This acute (short-term) randomized controlled trial assigned 20 healthy college students (average age of 20) to consume apple (190 grams; central core and seeds removed) and blackberries (148 grams), either whole or blended with water and ice. To control for water intake, the whole-fruit group also drank the amount of water provided by the blended smoothie. The participants consumed the fruit 3–4 hours after eating lunch.
Glucose levels, including maximum glucose level, glucose area under the curve (AUC; the total rise in glucose during the time), and glucose incremental area under the curve (iAUC; AUC adjusted for baseline glucose levels), were assessed in the 60-minute period after consuming the fruit.
The results
Compared to whole fruit, blended fruit resulted in a lower maximum glucose level and lower glucose AUC. The blended fruit also resulted in a lower iAUC, but this finding was not statistically significant (p=0.057).
Note
The authors speculated that the blended fruit reduced glucose levels compared to whole fruit because the blending process causes a greater release and dispersion of compounds like fiber and polyphenols from the fruit matrix compared to chewing. Because these compounds may inhibit glucose absorption, this could have attenuated the glucose response.
Every month we summarize over 150 of the most noteworthy health and nutrition studies. Other health categories related to this summary include:
to view the latest research in 25 health categories and the entire Study Summaries archive, access our
Supplement Guides, and unlock the Examine Database. Plus, earn continuing education credits!
This Study Summary was published on January 5, 2023.
