Be careful what you read… and drink.
The findings were published in the Journal of Nutritional Science.
The results were widely publicized with headlines proclaiming that 100 percent fruit juice doesn’t raise blood sugar levels.
However, some experts are questioning the results of the study.
For starters, the research was funded by the Juice Products Association, a trade organization representing juice makers.
In addition, the researchers concluded that fruit juice without added sugars doesn’t affect fasting blood glucose or fasting blood insulin levels. This isn’t necessarily the same as blood sugar levels throughout the day.
The American Diabetes Association recommends only drinking juice in small portions — about 4 ounces or less a day. They also tell consumers to “be sure the label says it is 100 percent juice with no sugar added.”
Even then, the organization advises people with diabetes to avoid fruit juices.
"Dietitians and diabetes educators generally discourage the consumption of beverages that contain carbohydrates, including 100 percent fruit, for people with diabetes due to the fast rise in blood glucose that occurs in addition to the lack of satiety from consuming a drink versus eating the actual fruit," the association said in a statement to Healthline. "Consuming whole fruit with dietary fiber is recommended over juice. While fruit juice is an acceptable choice for treating hypoglycemia due to its ability to raise blood glucose quickly, it is by no means a necessary dietary component for somebody living with diabetes."
Kristin Kirkpatrick, a registered dietitian, is in agreement. She told Healthline that despite this new research, she’s still leery of fruit juice.
“All juices, even those without added sugar, have a high sugar content due to the concentrated source. An average cup of 100 percent juice has about 28 grams in an 8-ounce serving. Juice also lacks the fiber, a critical component that provides one of the many benefits of whole fruits (including their skin),” she said.
“I tell my patients to eat and chew their fruit, not drink it. It would take a lot more data for me to consider altering that message,” Kirkpatrick added.
The results of the study
Researchers in the latest study reviewed 18 randomized control trials in which participants drank either 100 percent fruit juice or a control beverage, such as water, and examined metrics related to diabetes risk.
“When we pooled all these results together, we found no significant association between 100 percent juice and any of these four markers of glycemic control,” Mary Murphy, MS, RD, a senior managing scientist at the consulting firm Exponent Inc. and the lead author of the study, told Healthline.
The study builds on another prior
However, this new research is different because it looks exclusively at 100 percent juice, rather than other substitutes.
“There is a lot of talk in the literature about whether juice is good or bad, and I think the findings from this study suggest that 100 percent juice does not have an adverse effect, or positive — it’s a neutral effect,” said Murphy.
Harvard researchers looked at the role of fruit and fruit juice in the diets of more than 180,000 British adults and concluded that whole fruit consumption led to an overall decrease in type 2 diabetes risk. Juice consumption led to an 8 percent increase.
“Fluids pass through the stomach to the intestine more rapidly than solids, even if nutritional content is similar. For example, fruit juices lead to more rapid and larger changes in serum levels of glucose and insulin than whole fruits,” said Qi Sun, one of the study’s authors.
Sysy Morales, who has lived with type 1 diabetes for 23 years, cautioned readers about the new study on her blog Diabetes Daily.
She noted the metrics were taken on participants’ blood sugar levels after they had fasted. She said the participants were healthy and should show normal blood sugar levels after fasting.
She added the study does seem legitimate, but she noted that the sugar in even “natural” fruit juice is still fructose.
The American Diabetes Association agrees with Morales.
"This meta-analysis examined 16 studies, none of which included people with diabetes, and none of which measured blood glucose levels soon after consuming juice -- only fasting blood glucose levels," the organization said in its statement.
Defending the research
Despite the criticism, Murphy defends her team’s research.
“These results are suggesting a very neutral effect in the diet, which is consistent with other research,” said Murphy.
Murphy argues that there are still plenty of individuals who would benefit from 100 percent fruit juice.
“We would never encourage individuals to get all of their fruit servings from juice, but certainly many people fall short of their fruit and vegetable servings, and 100 percent juices may be a way to help reach that 100 percent of that recommended intake,” she said.
Research that is “industry funded” has been the target of consumer groups in recent years.
A major study funded by cranberry giant Ocean Spray in 2016 about the benefits of cranberry juice consumption to treat urinary tract infections was called out by members of the media as “smoke and mirrors.”
Ocean Spray continues to fund research and, in a subsequent interview with Healthline, stood by their work, as well as pledged to continue investigating the health benefits of cranberries.
However, Murphy said not all industry research is the same.
“Funding source isn’t synonymous with quality of a study,” she said.
“Good quality studies can be funded by industry. It is correct that Juice Products Association provided funding for this research, but this research was designed and conducted and written up by myself and our colleagues, independent of input from JPA,” Murphy said.