Coffee consumption and diabetes: the positive link

Scientific research has found another reason why consumers should indulge in additional cups of coffee. In January, the Insti undefined

tute for Scientific Information on Coffee (ISIC), an industry funded organisation, released a session report highlighting the links between coffee consumption and the development of Type 2 diabetes.

“Recent scientific evidence has consistently linked regular, moderate coffee consumption with a possible reduced risk of developing Type 2 diabetes,” Roger Cook, Science Manager at the ISIC, tells Global Coffee Review.

According to the ISIC session report, overall findings from studies published in the past five years point to epidemiological evidence that drinking three to four cups of coffee per day may help prevent Type 2 diabetes by up to 25 per cent, compared to consuming none or less than two cups per day.

In order to further understand the latest findings, the ISIC sponsored a session at the seventh World Congress on Prevention of Diabetes and Its Complications (WCPD) on 12 December 2012. The session brought together a panel of experts in this field to further explore and understand key findings.

The session was titled ‘Good things in life: Can coffee help in diabetes prevention?’. According to Professor Edith Feskens, Professor of Nutrition and the Metabolic Syndrome at the Wageningen University in The Netherlands, the answer to that question in yes.

“Yes, our work definitely confirms this,” Feskens said at the WCPD congress. “Our previous research showed that people who drink coffee have a reduced risk of Type 2 diabetes, and lately we saw that also.”

Feskens said the reduced risk has been confirmed despite the fact that the standard amount of caffeine in a cup is unknown.
“I think it’s an important issue, but also a difficult issue,” Feskens said. “In the United States you have coffee in a mug, [in Spain] the cups are small, some places serve less strong coffee, but absolutely with every cup the risk reduces.”

According to The World Health Organisation (WHO), Type 2 diabetes, formerly called non-insulin dependent diabetes, is caused by the body’s ineffective use of insulin that results in high blood glucose and insulin resistance. Type 2 diabetes is the most common form, affecting 85 to 90 per cent of all people with diabetes. It is primarily influenced by lifestyle factors such as diet, physical activity, alcohol consumption and smoking.

More than 220 million people worldwide were diagnosed with diabetes in 2011, according to the WHO. The organisation estimates that by 2025 that number will increase by 65 per cent, affecting an estimated 380 million individuals worldwide.

Professor Jaakko Tuomilehto, Professor of Public Health at the University of Helsinki, Finland, presented his research findings from coffee intervention trials at the 2012 WCPD. Tuomiletho’s study selected diabetic patients and followed their coffee intake for 10 years.

Follow-up results showed that mortality risk and cardiovascular risk were lower in individuals drinking more than five cups of coffee a day.

“In our population studies we [had] people drinking up to 10 cups of coffee a day,” Tuomiletho told the delegates at the congress.

“Especially in women, it seems the diabetes risk goes down by 80 per cent if you drink over 10 cups of coffee.”

Tuomiletho said his research clearly shows that those individuals who were drinking more than five  cups of coffee a day had reduced risk of liver cancer. Individuals who had an increased marker of liver damage were also found to benefit more from coffee drinking, in the context of diabetes incidence.

To discover the different effects coffee has on bodily functions and biochemical measurements, Tuomiletho said a clinical trial with people drinking different amounts of coffee would be beneficial. However, his initial findings put coffee consumption in a positive light.

“It’s very clear that people should not avoid coffee drinking. It seems to be a healthy habit. And like many other plants, the juices and extracts [of coffee] seem to be one of the healthy drinks,” he said.

Tuomiletho’s findings are not the only ones pointing in this direction. Several population studies have suggested a consistent dose response – meaning that the higher the consumption level, the lower the risk of developing Type 2 diabetes.

In 2002, a Dutch study of 17,111 adults aged between 30 and 60 years were investigated on the association between coffee consumption and risk of clinical Type 2 diabetes. After a follow-up period, 360 new cases of Type 2 diabetes were identified. Subjects drinking at least seven cups of coffee per day were found half as likely to develop Type 2 diabetes. Since then, the ISIC report says that more than a dozen other studies have confirmed this same finding in other populations.

In 2010, D.S Sartorelli et al. published a study that analysed the long-term effects of coffee, decaffeinated coffee and tea consumption on Type 2 diabetes. This meta-analysis covered 457,922 individuals and 21,897 newly diagnosed cases of Type 2 diabetes from eight different countries. The combined data showed that up to six to eight cups of coffee per day was associated with a 5 – 10 per cent lower risk of developing Type 2 diabetes.

The study also suggested that the time of coffee drinking plays a distinct role in glucose metabolism. Results concluded that drinking coffee, particularly at lunchtime, reduced the risk of developing diabetes, compared with those who didn’t drink coffee at lunchtime.

Since the 2010 study, five more epidemiological studies have been published on the subject, including that of American Indian men and women, and population studies in The Netherlands, France, Japan and the United States – each confirming a strong association between consumption of coffee and a lower incidence of Type 2 diabetes.

Despite the encouraging results, Cook says no “recognised mechanism of action” has been established to explain the link. Further research is needed to confirm what exactly is responsible for the association.

Dr. Nathan Matusheski, Associate Principal Scientist at Mondelez International, discussed the potential mechanisms driving the strong association between coffee and the risk reduction of Type 2 diabetes at the 2012 WCPD, including caffeine as a possible source.

“Caffeine’s a tricky one,” Matusheski said. “Some short term studies have shown caffeine acutely disrupts glucose tolerance, which has got a little bit of press. But really that’s only happened with really large doses of caffeine. There’s limited data on longer-term exposure to caffeine over time of what those effects might entail.”

The ISIC report says that because coffee and tea are the main sources of caffeine in diets in most countries, it is difficult to separate the effects of caffeine from either coffee or tea. However, since decaffeinated coffee is reported to have a similar level of association as regular coffee, it is unlikely that caffeine plays a role in the negative association for development of Type 2 diabetes.

Matusheski said that “possibly” in some cases, antioxidant compounds found in coffee (such as chlorogenic acid and trigonelline) or compounds that have antioxidant activity, could interact with some cellular pathways that affect glucose and acutely reduce sensitivity to insulin.

At the WCPD, Matusheski discussed a number of possible key mechanistic theories that could underlie the relationship between coffee consumption and the reduced risk of diabetes. These included the Energy Expenditure Hypothesis, which suggests that caffeine in coffee stimulates metabolism and increases energy expenditure; and the Carbohydrate Metabolic Hypothesis, where it is thought that coffee components influence the glucose balance within the body.

Subset theories also suggest other components of coffee could change the way the body handles carbohydrates or sugars during digestion, or that coffee components may improve insulin sensitivity in the body. However, Matuskeski speculates that the compound causing the effect could be a number of things not yet determined.

“The bottom line is that we see a strong association between coffee consumption and the reduction of risk for Type 2 diabetes, but that’s what it is right now, it’s not a cause and effect relationship,” Matusheski said. “Future and further research into the possible implications, especially in a clinical context, will help better understand this.”

The good news for individuals already diagnosed with Type 2 diabetes is that coffee consumption can do no harm, said Riobó, Associate Chief of Endocrinology and Nutrition at the Jiménez Díaz Hospital of Madrid.

“Coffee doesn’t result in the worsening of diabetic complications and it does not result in worse metabolic control,” Riobó told WCPD delegates. “There is no need for diabetic or obese patients to refrain from drinking coffee. It is very useful in clinical practice.”

Riobó’s research found that coffee consumption is associated with lower C-peptide, a byproduct created when insulin is produced, especially in overweight or obese people. Her studies were also associated with higher levels of hormone adiponectin, a protein involved in regulating glucose levels as well as fatty acid breakdown.

In the ISIC report, Riobó clarified that coffee consumption is not responsible for the increased risk of cardiovascular disease, hypertension, stroke or any chronic disease, even if it has been associated with lower mortality in the general popular and also in diabetics.

“The association between coffee consumption and the risk of Type 2 diabetes is of considerable relevance because coffee is a widely consumed beverage worldwide and any effect on health that it may cause will have public health consequences,” Riobó said.

“Although more research is needed to make firm conclusions, the findings suggest that coffee can be safely enjoyed by the health and as well as by the diabetic population and might even be helpful in diabetes prevention.” 

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