New study reveals that 12-week supplementation with the coffee compound cafestol significantly reduces body weight and visceral fat in individuals at risk for type 2 diabetes.
Study: Effects of 12-Week Supplementation with Coffee Diterpene Cafestol in Healthy Subjects with Increased Waist Circumference: A Randomized, Placebo-Controlled Trial. Image Credit: PeopleImages.com - Yuri A/Shutterstock.com
Researchers conducted a randomized, controlled trial (RCT) in a recent Nutrients study to assess the effects of pure cafestol on insulin sensitivity and glucose tolerance in healthy individuals with an elevated waist circumference at risk of developing insulin-independent diabetes.
Background
Diabetes is a rising metabolic disorder that affects millions of individuals throughout the world. It is critical to discover safe and cost-effective approaches to prevent and manage diabetes. Studies demonstrate an inverse relationship between coffee consumption and insulin-independent diabetes, although causative evidence is lacking.
Most coffee intervention studies employ instant coffee, which has a low quantity of diterpenes like kahweol and cafestol. Cafestol, a bioactive molecule found in coffee, has been demonstrated to reduce blood glucose levels and increase insulin secretion.
However, its long-term effects on fat mass, glucose metabolism, and potential as a type 2 or insulin-independent diabetes prevention strategy remain unknown.
About the study
In the present double-blinded RCT, researchers investigated whether administering cafestol to healthy individuals with large waist circumferences could enhance mixed-meal reactions, insulin sensitivity, and body fat proportions.
The researchers conducted the trial at the Steno Center in Aarhus, Denmark, including 40 adults aged up to 80 years with waist circumferences exceeding 102 cm for males and 88 cm for females.
None were pregnant or breastfeeding, had type 2 diabetes or other significant comorbidities, glycated hemoglobin (HbA1c) exceeding 6.5%, or consumed antidiabetic medications.
Participants were randomized in a 1:1 ratio to receive 6.0 mg capsules of cafestol (intervention) or a placebo twice daily over 12 weeks. They visited the center six times for the study. At the initial visit, researchers inserted continuous glucose monitoring (CGM) sensors on one arm of the participants to measure glucose levels.
They placed ambulatory blood pressure monitors (ABPM) on the alternate arm to record blood pressure over 24 hours. At the subsequent visit, individuals underwent mixed-meal testing (MMT) and magnetic resonance imaging (MRI) and provided blood samples.
At the third study visit, individuals completed insulin suppression tests (IST), following which the researchers initiated the intervention. Six weeks post-intervention, they assessed kidney and liver function using participant blood samples.
The fourth (10 to 11 weeks post-third visit), fifth, and sixth visits were similar to the first, second, and third visits, respectively. Participants filled out questionnaires to indicate intervention adherence at six weeks.
The primary outcomes included steady-state plasma glucose (SSPG) levels during IST and four-hour total area under the curve (tAUC) values for glucose during MMT. Secondary outcomes included tAUC values for triglycerides (TG), glucagon, and insulin during magnetic resonance spectroscopy, HbA1c, and MMT.
Other outcomes included subcutaneous and visceral fat volumes measured by MRI, blood pressure while awake and asleep, mean blood glucose, glucose variability, and time within the normal range measured by CGM.
Study recruitment began on April 23, 2022. The intervention commenced on June 22, 2022, and the final participant visit occurred on December 22, 2022.
Participants were allowed to drink drip coffee and instant coffee with low diterpene levels in unrestricted amounts but only one cup of unfiltered coffee beverage (French press coffee, expresso, or boiling coffee) per day.
Results
Participant ages ranged between 25 and 78 years. Among the participants, 6.0 mg of cafestol consumed two times per day did not improve glucose tolerance or insulin sensitivity but significantly reduced body weight, visceral fat volumes, and gamma-glutamyl transferase levels by 2.0%, 5.0%, and 15%, respectively, compared to the placebo.
Mean visceral fat volumes were significantly decreased by 400 mL among cafestol recipients. In addition, the team observed a statistically significant inter-group difference in weight/body mass index change.
Cafestol users lost 880 g of weight, whereas placebo users gained 920 g. Further, the intervention group showed significantly higher free-fatty acid (FFA) levels in the initial (hypoinsulinemic) than in the subsequent (hyperinsulinemic) stage of IST compared to the placebo group. The initial FFA levels could indicate increased insulin resistance in the adipose tissues of cafestol consumers.
No participant showed abnormal liver or renal function changes. Cafestol modestly increased alanine aminotransferase levels in one individual with infectious mononucleosis. Side effects included increased flatulence, nausea, loose stools, and mild headaches.
Six mg of cafestol did not alter low-density lipoprotein (LDL), total cholesterol, or blood pressure. The findings indicate that the dosage used in the present study is unlikely to pose a cardiovascular risk.
Conclusion
The study found that cafestol could lower body weight, visceral fat, and gamma-glutamyl transferase levels. Cafestol did not affect glucose tolerance or insulin sensitivity, but it may contribute to the observed inverse correlations between coffee consumption and insulin-independent diabetes.
Future studies must determine the effects of higher doses provided over prolonged periods, especially among individuals with impaired glucose metabolism and insulin-independent diabetes.
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