Metabolic Health

Note: The information on this site is not intended or implied to be a substitute for medical advice. If you have elevated blood glucose or have been diagnosed with pre-diabetes, Metabolic Syndrome or diabetes, please consult your doctor or a registered dietitian for advice and recommendations concerning your diet.

Detailed Nutritional Information

Blood Glucose and Insulin Sensitivity

Glucose is a sugar carried by the blood that provides energy to all cells in the body. Insulin is a hormone produced by the pancreas that helps lower blood glucose because it assists with transporting glucose inside cells to be converted to energy. In a healthy individual, cells are “sensitive” to insulin, which means that cells respond easily to small amounts of insulin for effective glucose removal from the blood. When cells become less sensitive to insulin, blood glucose levels rise which may result in a diagnosis of pre-diabetes or diabetes and its resulting complications.

Clinical studies evaluating the impacts of fresh grapefruit or 100% grapefruit juice on fasting blood glucose or insulin levels reveals no significant or adverse effects.^1-3,5 In an observational analysis of NHANES 2003-2008 participants, fasting glucose or fasting insulin levels were not significantly different between grapefruit consumers (any form of grapefruit) and non-consumers.⁴

In a study of 85 obese adults, fasting glucose, fasting insulin, and HOMA-IR (a measure of insulin sensitivity) were not affected when grapefruit or grapefruit juice was consumed before meals for 12 weeks.³

Metabolic Syndrome

In a longitudinal analysis of 2,774 adults who were part of the Coronary Artery Risk Development in Young Adults (CARDIA) cohort, consumption of 100% fruit juices, like 100% grapefruit juice, was not associated with an increased risk for metabolic syndrome.⁹

Consumption of ½ fresh grapefruit or grapefruit juice 3 times/daily for 12 weeks did not affect fasting glucose or insulin in adults.² However, in an analysis of a subset of study participants who were obese and had metabolic syndrome, there was a larger drop in 2-hour insulin levels in the grapefruit intervention groups compared to the placebo group, suggesting that grapefruit may be a beneficial dietary addition for individuals with metabolic disease.

Diabetes

Several studies have shown no association between grapefruit juice, citrus juice or 100% fruit juice intake and diabetes-related outcomes:

• No association between 100% grapefruit juice or orange juice intake and diabetes incidence in African American women living in the United States, a group at higher risk for type 2 diabetes.⁶
• Combining 12 randomized controlled trials in adults with various health conditions such as overweight/obesity, metabolic syndrome, or hypertension, a meta-analysis concluded that fruit juice intake had no significant effect on fasting glucose and insulin.¹⁰
• A meta-analysis of four prospective cohort studies concluded that the intake of 100 percent fruit juice was not associated with the risk of developing type 2 diabetes in adults.¹¹
• No association was found between consumption of fruit juice and diabetes risk in U.S. women¹², French women¹³, U.S. men¹⁴, Finnish men¹⁵, Japanese adults¹⁶, U.K. adults¹⁷, and European adults.¹⁸
• A large study in post-menopausal women (WHI) found no association between 100 percent citrus juice intake and diabetes risk, even at high levels of consumption; also,100 percent fruit juice intake was not related to diabetes risk.⁷
• Higher fruit juice intake by women prior to pregnancy was not related to increased risk of gestational diabetes.¹⁹
• Higher fruit juice consumption was not associated with increased risk of developing auto-antibodies to insulin or type 1 diabetes in children.²⁰
• Fruit juice consumption was not associated with fasting glucose or insulin, and/or HOMA-IR in two separate studies in healthy adults.^9,21
• A systematic review of randomized controlled trials found that 100% fruit juice has no effect on fasting blood glucose or insulin, insulin sensitivity (HOMA-IR), or hemoglobin A1C.²²
• A meta-analysis found there is no evidence that 100% fruit juice has adverse effects on fasting glucose or insulin and is no different than water on these variables; consumption of 100% juice did not increase the risk of diabetes.²³