Coffee and green tea linked with lower mortality in people with Type 2 diabetes, reveals study

26 Oct 2020 --- Two separate studies have hinted that consuming plenty of green tea and coffee, as well as some potatoes, may benefit people with Type 2 diabetes (T2D).

Drinking plenty of both green tea and coffee is linked to a lower risk of dying from any cause among people with T2D. This is according to new research published in BMJ Open Diabetes Research and Care.

Drinking four or more daily cups of green tea plus two or more of coffee was associated with a 63 percent lower risk of death over a period of around five years, the findings show.

“This prospective cohort study demonstrated that greater consumption of green tea and coffee was significantly associated with reduced all-cause mortality. The effects may be additive,” the researchers write. 

Drinking four or more daily cups of green tea plus two or more of coffee was associated with a 63 percent lower risk of death over a period of around five years.Previously published research suggests that regularly drinking green tea and coffee may be beneficial for health because of the various bioactive compounds these beverages contain. 

Researchers were unable to explain the mechanism of action in this observational study. However bioactives, such as antioxidants, phenols and caffeine, are thought to play a role. 

Lowering all-cause mortality risk
Higher quantities of both green tea and coffee lowered risk of all-cause death. The main causes of death among the participants in the study period were cancer and cardiovascular disease. 

Drinking up to one cup of green tea every day was associated with 15 percent lower odds of death, while drinking two to three cups was associated with 27 percent lower odds. Getting through 4 or more daily cups was associated with 40 percent lower odds.

Among coffee drinkers, up to one daily cup was associated with 12 percent lower odds, while one cup a day was associated with 19 percent lower odds. Two or more cups were associated with 41 percent lower odds.

The risk of death was even lower for those who drank both green tea and coffee every day: 51 percent lower for two to three cups of green tea plus two or more of coffee; 58 percent lower for four or more cups of green tea plus one cup of coffee every day; and 63 percent lower for a combination of four or more cups of green tea and two or more cups of coffee every day.

Potatoes were found to have a more positive effect on overnight glycemic response than basmati rice when eaten in an evening meal. 

Meanwhile, increased consumption of green tea and coffee was associated with reduced all-cause mortality in an observational study of nearly 3,000 Japanese people with T2D. 

Glycemic index in a whole-meal context
People with T2D are often told to avoid high glycemic index (GI) foods, such as potatoes, to mitigate blood glucose levels. 

This is because spikes in blood sugar, particularly at night, are associated with cardiovascular disease (CVD) and endothelial dysfunction in those with T2D. New research suggests that some high glycemic foods can be part of a balanced dinner for those with Type 2 diabetes.

Contrary to prevalent dietary guidance, a recent clinical trial of 24 individuals with T2D suggests that GI is not an accurate surrogate for an individual’s glycemic response (GR) to a food consumed.

“Despite its frequent use among nutrition researchers, GI is not an appropriate tool for understanding how a meal impacts glycemic control,” says Dr. Brooke Devlin, the primary investigator at Australian Catholic University in Melbourne. 

It is a very specific measurement for foods consumed in isolation, typically conducted under controlled laboratory conditions, she adds. 

“It’s rare that people eat foods in isolation, and findings from this study demonstrate how other factors, such as the time of day or food pairings, need to be considered when investigating the GR of mixed meals in individuals with T2D.”

Putting potatoes to the test
Participants were provided the same breakfast and lunch, but they were randomly assigned to one of four dinners, each including either skinless white potatoes (test meal) prepared in three different ways (boiled, roasted, boiled then cooled then reheated) or basmati rice (control meal). 

Participants repeated the experiment, with a 9-day break in between each trial, to cycle through all test meals and the control. In addition to having blood samples collected regularly (both immediately after the meal and again every 30 minutes, for 2 hours), participants also wore a continuous glucose monitor overnight to track changes in blood sugar levels while sleeping.

There were no differences between meals in glucose response following the dinner that contained any of the potato dishes or basmati rice. 

Moreover, participants’ overnight GR was more favorable after eating the evening meal that included any of the high GI potato side dishes compared to low GI basmati rice.

High GI foods may fit in a balanced diet
The study, which was funded by the Alliance for Potato Research and Education, concluded that “high GI foods, like potatoes, can be consumed as part of a healthy evening meal without negatively affecting GR.” 

The study’s authors note, however, that long-term glycemic control was not assessed.

By Missy Green