Every once in a while, there is a lot of hype about the so-called grapefruit diet. While scientific studies haven’t always confirmed any correlation between consuming grapefruit juice and weight loss per se, many of the early studies had issues with controls, or the fact that the sample size was quite small. There is some encouraging research from 2014 that indicates grapefruit juice – especially red fleshed grapefruits – may have a beneficial effect on blood glucose levels, insulin, and triacylglycerol, a type of fat.
Researchers at UC Berkeley designed a controlled study that would put the thesis of how grapefruit juice affects the blood to a more definitive test than in the past. The study used mice who were fed a high fat diet, and divided into two groups. They compared the results from one group that drank grapefruit juice that had been clarified, with the pulp removed, and another group that drank only water.
While the study was funded by the California Grapefruit Growers Cooperative, the researchers maintained that this did not influence either the results, or the study’s design. In fact, the UC Berkeley faculty members who conducted the study said they were initially quite skeptical of the premise.
Andreas Stahl, associate professor of nutritional sciences and toxicology, is quoted in a university publication. “I was surprised by the findings. We even re-checked the calibration of our glucose sensors, and we got the same results over and over again.”
The results surprised the researchers, and were very encouraging.
• The important point about the study was that, no matter how much fat the mice ate in their diet, drinking grapefruit juice lowered the fasting insulin levels in the blood.
• The anti-glycemic effect, the researchers observed, was about the same as that achieved by using metformin, a common drug prescribed for Type II Diabetes.
• Drinking the grapefruit juice was also associated with lower blood glucose and triacylglycerol levels.
• The mice who drank grapefruit juice gained 18 percent less weight than the water drinking group, despite consuming the same high fat diet.
Researchers were unable to identify the mechanism, or the way that grapefruit juice affects these issues., but speculated about the possibility that anti-inflammatory properties or other cumulative effects were at work.
The researchers say the results indicate that more study on the effects of grapefruit juice on health is called for.