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Grapefruit Juice May Affect Insulin Resistance

Drinking grapefruit juice daily can lead to weight loss and help control blood glucose…

Grapefruit juice is considered to be high in nutrients while remaining relatively low in calories when compared to other fruit juices. These diets often rely on daily low calorie commitment, which calls into question the true weight loss effect of grapefruit juice. Also, previous studies have shown mixed results.

The purpose of this study was to determine the impact of using grapefruit juice while maintaining a diet that was high in fat which is typical of many Americans. These results would be compared to those given a low fat diet. The study was performed on mice. The mice were randomized into groups that were given a diluted grapefruit juice or water sweetened with glucose and saccharin. Grapefruit juice use was also compared to water sweetened with glucose and saccharin that contained metformin. Weight and blood glucose samples were collected three times per week. An insulin ELISA was used to monitor insulin concentrations.

Results showed that mice fed the high fat diet receiving grapefruit juice weighed 18.4% less than the controls after 100 days (31.4+0.7g vs 38.5+2.8g, P<0.05). This group also saw fasting blood glucose that was 13% lower compared to controls (P<0.05). Fasting serum insulin levels were 72% lower compared to controls (P<0.05). Finally, triglycerides in the liver were reduced by 38% in this group compared to the control group. Those mice on the low fat diet saw a decrease in fasting insulin, but none of the other effects as seen in the high fat diet group.

Grapefruit juice use compared favorably to those receiving metformin. Weight loss was seen in both groups with no statistically significant difference noted. Both groups also saw lowered fasting blood glucose and serum insulin levels (P

The use of grapefruit juice in reducing weight and improving blood glucose was seen in this study using mice even when consuming a high fat diet. Based on these results, a 70kg human would need to consume about 3.5-4 cups of grapefruit juice per day to compare to the amount given to mice. Trials are needed to determine if grapefruit juice can produce similar results in humans. In human trials, attention should be placed on the impact grapefruit juice can have on inhibiting cytochrome P450 enzymes which are responsible for the metabolism of medications.

Practice Pearls:

  • Grapefruit juice has been an important part of many weight loss plans and trendy diet plans.
  • In this study performed on mice, grapefruit juice showed weight loss, improved fasting blood glucose, lowered fasting serum insulin levels and reduced triglycerides when compared to controls.
  • Grapefruit juice also compared favorably to metformin in reducing weight, fasting blood glucose and serum insulin levels.

Chudnovskiy R, Thompson A, Tharp K, Hellerstein M, Napoli JL, et al. Consumption of Clarified Grapefruit Juice Ameliorates High-Fat Diet Induced Insulin Resistance and Weight Gain in Mice. PLoS ONE. 2014.