| albeit at a lower rate than mice fed a sugary drink. Their blood sugar levels and insulin sensitivity were also better regulated than mice that did not drink grapefruit juice.
The mice were given either a high-fat diet or a low-fat diet in a range of experiments.
Mice fed a high-fat diet and grapefruit juice had an 18% reduced rate of weight gain compared with mice given sugary water with the same number of calories as the grapefruit juice. They also had 13% lower fasting blood sugar levels. There was no effect on weight gain in mice fed a low-fat diet.
Drinking grapefruit juice improved insulin sensitivity in mice, regardless of their diet (in people, reduced insulin sensitivity can be a sign of impending diabetes).
Grapefruit juice lowered blood sugar as effectively as metformin, a drug widely used to treat people with type 2 diabetes. However, none of the mice actually had diabetes, so this research has little immediate relevance to humans with the condition.
For the time being, people with diabetes should not swap their metformin for grapefruit juice on the basis of this study.
The study was carried out by researchers from the University of California and was funded by the California Grapefruit Growers Cooperative, although it had no role in the study design, data collection, analysis or decision to publish.
Both the Mail Online and The Daily Telegraph’s headlines incorrectly state that grapefruit juice can help people lose weight. Leaving aside the fact that this study involved mice, rather than humans, none of the mice actually lost any weight –
they just differed in the rate they put on weight.
The Daily Express’ headline was also irresponsible, as it suggests that grapefruits “tackle diabetes as well as a leading drug”, with an accompanying picture of a smiling woman (not a mouse) tucking into a grapefruit. None of the reports seemed to mention that the work was funded by the California Grapefruit Growers Cooperative. This doesn’t mean that the study results aren’t correct, but it’s worth mentioning so people can make their own conclusions.
The Mail Online does, however, include a balancing comment from the British Dietetic Association, which said that until further trials are carried out in humans, it’s too early for people to try grapefruit diets.
Links To The Headlines
Grapefruit juice ‘could be the key to weight loss’. The Daily Telegraph, October 8 2014
Study shows grapefruits tackle diabetes as well as leading drug. Daily Express, October 9 2014
Links To Science
Chudnovskiy R, Thompson A, Tharp K, et al. Consumption of Clarified Grapefruit Juice Ameliorates High-Fat Diet Induced Insulin Resistance and Weight Gain in Mice. PLOS One. Published online October 8 2014