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Harvard University researcher Nicole Wedick, ScD., recently gave 45 overweight adults an unusual dietary order — drink 5 cups of coffee a day for two months. The order was part of Wedick’s research into the benefits of coffee for those at risk of developing type 2 diabetes. Her research is part of a growing body looking into the links between coffee and diabetes. Wedick focused her research on the metabolic effects of coffee, particularly as it affects several substances in the body that have been implicated in insulin resistance and/or diabetes mellitus.
Wedick’s research was designed to determine the effect of substances in coffee on the levels of those compounds in the body that may have an effect on the development of diabetes mellitus.
Wedick, from the Harvard School of Public Health, recruited 45 healthy but overweight 40-year-old adults to participate in the study. The volunteers were asked to drink either five cups of caffeinated coffee, 5 cups of decaffeinated coffee or five cups of water daily for eight weeks. The researchers measured tested the blood for insulin, glucose and several other substances at the start of the study, at the 4-week mark in the study and at the end of the 8-week study.
The researchers found that those who drank caffeinated coffee had signifincaly more adiponectin in their blood than either of the other groups. Those who drank decaf had slightly elevated levels of adiponectin. Tests for a second substance, fetuin-A, shows that those who drank caffeinated coffee had slightly lower levels of fetuin-A in their blood than those who drank water, while those who drank decaf had significantly decreased levels of fetuin-A. Coffee consumption didn’t seem to have any effect on blood sugar or insuline levels during the study.
Breaking It Down
Adiponectin is a hormone that is secreted by fat cells. It helps sensitize the body to insulin. Multiple studies have shown that higher levels of adiponectin in the blood are a significant predictor of lower rates of type 2 diabetes — that is, people who have higher levels of adiponectin in their blood are less likely to develop type 2 diabetes.
In Wedick’s study, participants who drank five cups of coffee a day — the study used instant Nescafe, for those who are keeping track — had significantly more adiponectin in their blood at the end of eight weeks than those who drank water. While the study doesn’t suggest a cause-and-effect relationship, there appears to be a definite correlation between the consumption of caffeinated coffee and the levels of adiponectin in the blood.
Fetuin-A is a protein in the blood that seems to increase insulin resistance in those who do not have type 2 diabetes but are at risk for develping it. Higher levels of fetuin-A have been associated with increased risk of developing type 2 diabetes. Lower levels of fetuin-A are associated with a decreased risk of developing type 2 diabetes. In the study, those who drank decaf coffee showed significantly lower concentrations of fetuin-A in their blood than those who drank water and somewhat less fetuin-A than those who drank caffeinated coffee.
Wedick suggests that components in coffee, including phytochemicals which are present in minute amounts, may help improve liver function and adipocyte funcions (fat-burning). Those improvements may be part of the reason that coffee seems to reduce the risk of develping type 2 diabetes.