Danish research has identified substances in coffee that may explain why Denmark’s favourite hot beverage can counteract several major noncommunicable diseases. Coffee contains 1500 identified substances, but Danish researchers have discovered one that is especially promising for reducing the risk of obesity, cardiovascular diseases and type 2 diabetes.
Coffee has previously been associated with several positive health effects. According to a population studies, coffee can reduce the risk of cardiovascular diseases, obesity and type 2 diabetes. The inky brew can do this because it reduces the risk of metabolic syndrome, the precursor of type 2 diabetes.
Since coffee affects health so positively, an obvious idea would be to extract one or several of the beneficial substances from coffee and to market them as dietary supplements or medicine. This might help to reduce the accelerating global obesity epidemic.
The problem is that coffee contains 1500 identified substances, and determining which ones are really beneficial has been impossible.
Danish researchers have focused on one that appears promising. In a series of experiments, the researchers examined the effects of various substances in coffee. Although they often left the laboratory with no positive results, they now appear to have hit the jackpot.
“We have discovered a substance in coffee that looks especially promising as a dietary supplement. In a broader perspective, a supplement like this may help to minimize the global burden of obesity and type 2 diabetes,” explains a researcher behind the new study, Søren Gregersen, Senior Physician, Department of Clinical Medicine, Aarhus University.
Søren Gregersen’s research on the various substances in coffee has been published in such journals as Journal of Natural Products and Nutrients.
Coffee makes rats lose 10% of their body weight
Søren Gregersen and colleagues selected various substances from coffee and examined them for slimming and blood glucose–lowering effects.
They fed 24 rats a special diet designed to induce metabolic syndrome. They then divided the rats into three groups and administered 1) coffee, equivalent to 4 cups daily for a person; 2) water; or 3) a sample of the target substances extracted from coffee. This method enabled the researchers to examine the effects of the compounds cafestol, caffeic acid, trigonelline and 5-O-caffeoylquinic acid.
“This was like a fishing expedition aiming to find some of the promising substances in coffee grounds,” explains Søren Gregersen.
The researchers obtained their results during a 14-week trial in which the rats consumed coffee, water or the various target substances. First, the study confirmed that coffee slims and lowers blood glucose in rats and thus confirmed population studies in humans. During the 14 weeks, the liver fat content was reduced by half, the fatty acids circulating in the blood declined and body weight fell by 8–10% in the rats consuming coffee. These rats were also more sensitive to insulin, consumed less food and had lower blood glucose levels.
“This confirms earlier studies indicating that coffee possesses these effects. Our trial shows that coffee contains several substances that improve the metabolism of fat and sugar,” says Søren Gregersen.
Promising substance for a dietary supplement
The researchers did not find the promising effects for caffeic acid, trigonelline and 5-O-caffeoylquinic acid. The rats consuming these substances metabolized sugar and fat similarly to the rats that only consumed water.
But cafestol seemed promising based on several experiments, because the rats consuming cafestol had almost exactly the same effects on weight loss and fat and glucose metabolism as the control rats consuming coffee.
Cafestol comprises 0.4–0.7% by weight of Arabic coffee (60–70% of the global coffee bean production), and brewed French press coffee has the greatest amounts. Filtering the coffee traps the cafestol in the filter, with little ending up in the brewed coffee.
“Cafestol seemed potent and effective in reducing fat in the liver and blood and controlled blood glucose better. However, we do not yet know whether this is the only substance that has these effects or whether combining several substances produces the beneficial effects of coffee,” explains Søren Gregersen.
Trials on people with prediabetes
Søren Gregersen and colleagues have decided to study cafestol further. Their goal is to examine whether cafestol is suitable as a dietary supplement or possibly as medicine that can be deployed in battling obesity and type 2 diabetes. However, this means trials involving people.
The researchers are currently developing a protocol for a clinical trial involving people with prediabetes. If the research on cafestol has discovered something that can mitigate metabolic syndrome, then hopefully this will also influence the development of type 2 diabetes.
At least this is what they hope.
“We need to find money to carry out such a trial, and we also need to investigate how we can sustainably extract cafestol from coffee grounds, for example. The further research has many exciting perspectives, and we are well on the way,” concludes Søren Gregersen.
“Effects of Unfiltered Coffee and Bioactive Coffee Compounds on the Development of Metabolic Syndrome Components in a High-Fat-/High-Fructose-Fed Rat Model” has been published in Nutrients. The Danish Diabetes Academy, supported by the Novo Nordisk Foundation, provided funding for this project in the form of a doctoral fellowships to Ph.D. Pedram Shokouh from Department of Clinical Medicine at University of Aarhus.