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Coffee for Type 2 Diabetes Prevention?

Discussion in 'Endocrinology' started by Dr.Scorpiowoman, Jan 4, 2019.

  1. Dr.Scorpiowoman

    Dr.Scorpiowoman Golden Member

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    Researchers aim to associate drinking the caffeinated beverage with reduced risk; experts say 'not so fast'

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    A number of observational studies have suggested that coffee could prevent type 2 diabetes in a dose-dependent manner. An influence possibly related to antioxidants, which decrease glucose and insulin levels, as well as the effect of oxidative stress on cells. However, the evidence for this association is mixed.

    A recent study showed that coffee drinking was inversely related to insulin levels and insulin resistance, with participants taking <65 mg of caffeine/day having a 55% lower risk for prediabetes versus those taking >152 mg of caffeine/day. In this study, tea was the main source of dietary caffeine (>90%). In another U.S.-based, and nationally representative study, caffeine consumption is associated with lower mortality among diabetic women, but not men. Compared with women who did not consume caffeine, women who consumed caffeine had lower risk of death - 43% lower risk of death for consuming<100 mg of caffeine per day, 50% for 100 to <200 mg of caffeine per day, and 61% for ?200 mg of caffeine per day. Furthermore, those with coffee as the main source of caffeine had a lower mortality rate than those with alternative sources of caffeine. This suggests that the benefits of coffee might also be related to components other than caffeine, including antioxidants. The antioxidant effect may explain the beneficial effect described with decaffeinated coffee consumption.

    However, studies are not consistent. A Mexican-based study found no evidence for an association between coffee consumption and self-reported type 2 diabetes. In addition, there is only one other study showing a lack of association. The putative reasons for the lack of association have included the geographic localization of the sample studied, tribal customs related to coffee consumption, low coffee consumption, sample size, average age of the population, and methodological differences with other studies.

    There is limited evidence to recommend coffee consumption for prevention of type 2 diabetes in clinical practice. Indeed, extant studies were not designed to specifically answer the question, and did not have enough power to do so. The ideal study population would include a large number of prediabetes patients with various levels of steady coffee intake, followed for up to 5 years.

    In brief, evidence-based lifestyle changes (healthy diet and exercise) remain the best approach to type 2 diabetes prevention. Pharmacotherapy may also be used when needed, such as among prediabetes patients with a high family risk of diabetes.

    Full Critique

    A cup of coffee a day can keep type 2 diabetes away?

    "Several observational studies have shown that coffee can prevent (type 2) diabetes in a dose-dependent manner. This effect appears to be due to antioxidants in coffee which decrease glucose and insulin levels and decrease oxidative stress on the cells," M. Tufail Ijaz, MD, FACE, FRCP of Genesis Endocrinology in Zanesveille, Ohio told MedPage Today in an email.

    As noted, the topic of caffeine as a preventive method for type 2 diabetes has been explored in several studies, including one as recent as December 2018, published in Nutrition, Metabolism & Cardiovascular Diseases.

    The study evaluated more than 4,000 adults, monitoring their intake of coffee and caffeine based on the results of a questionnaire.

    "Coffee drinking was inversely related to insulin levels and insulin resistance index. Compared with participants in the lowest tertile of total caffeine intake (<65 mg/d), those in the highest tertile (>152 mg/d) had a 55% lower risk for pre-diabetes," Mirmiran, et al. wrote.

    The intake of coffee for this study was low, at only one cup per week. The authors went on to note that it might be caffeine consumption in general that lowers type 2 diabetes risk.

    "Because drinking of tea was the main source of dietary caffeine (more than 90%) in our population, the beneficial effect of caffeine on the risk of pre-diabetes must be related to the high intake of tea rather than low intake of coffee," they wrote.

    There may be a connection, according to a September 2018 study, an analysis of the National Health and Nutrition Examination Survey (NHANES) 1999 - 2010 that suggested caffeine consumption can be an indication of a reduction of mortality in diabetic patients -- particularly diabetic women, but not men.

    "Hazard ratios (HR) for death among women who consumed caffeine, as compared with women who did not consume caffeine, were as follows: 0.57 (95% confidence interval [CI], 0.40-0.82) for less than 100 mg of caffeine per day, 0.50 (95 % CI, 0.32-0.78) for 100 to less than 200 mg of caffeine, and 0.39 (95 % CI, 0.23-0.64) for 200 mg or more of caffeine per day. In contrast, this association was not observed among men," Neves, et al. wrote.

    They further found that those who drank coffee as their caffeine source had a lower mortality rate than those who got their caffeine elsewhere.

    "The benefits of coffee may be directly related to caffeine or to other components present in coffee, including minerals, phytochemicals, and antioxidants. The antioxidant capacity of these drinks may contribute to the health-protective effect described with decaffeinated coffee consumption," the authors noted.

    But not all research has positive results toward coffee and diabetes. An August 2018 study from Mexico failed to find the connection.


    "We did not encounter evidence for an association between coffee consumption and self-reported type 2 diabetes. There is only one other study that has reported this lack of association. It is likely that the geographic localization of the sample where the study was performed, and the tribal customs related to coffee consumption may have contributed to this lack of association," Madrigal, et al. wrote.

    They went on to say that there were several limitations to their study that could have made their results different from others.

    "Low coffee consumption in our population, sample size, average age, and methodological differences with other studies contributed to the lack of association, and future studies that overcome these limitations should be carried out," they wrote.

    In practice

    Still, physicians are hesitant to recommend coffee as a prevention method for type 2 diabetes.

    Gabriel I. Uwaifo, MD, FACP, FACE, senior clinical research scientist and endocrinologist at Ochsner Diabetes and Weight Management Clinical Research Institute in New Orleans, La., told MedPage Today in an email that the question about coffee and diabetes will continue to rage on because studies like this one out of Mexico were not designed to answer the question.

    "This study simply explores association between coffee intake and presence of diabetes in a retrospective cohort analysis. It is not surprising that the study shows no significant finding as the sample size (1277) is rather small to explore this effect," he said.

    Uwaifo went on to say that it may be possible that coffee has a preventive role in type 2 diabetes, but it is unlikely to be a strong effect.

    "And so, to demonstrate it the population to study would be patients with prediabetes and it would require a large population of such patients followed prospectively for a period of time of ~ 5 years and with different levels of consistent coffee intake," he said.

    Preeti Kishore, MD, department of Medicine Endocrinology, New York Health and Hospitals, told MedPage Today in an email that the studies that have shown the association between coffee drinking and lowering diabetes are cross-sectional and do not factor in other factors that could influence the outcome.

    "Cross-sectional studies are meant to generate a hypothesis and then need to be confirmed in the gold standard randomized controlled trial in order to make a confident determination of the benefit. While the data are tantalizing, we do not have such trials for coffee consumption and diabetes," she said. "And therefore, I do not believe we have good evidence to support recommending coffee consumption for preventing type 2 diabetes to the general public."

    Tom A. Elasy, MD, MPH, professor of medicine and director of the Center for Diabetes Translational Research at Vanderbilt University, Nashville, Tenn. had similar sentiments. He explained in an email correspondence with MedPage Today that there are not long-term, large experimental studies to support the connection between coffee and diabetes prevention.

    "In fact, some smaller studies specifically examining caffeine have found a negative effect on glucose and insulin levels. If there is a positive effect of coffee, it may be due to something other than the caffeine in coffee," Elasy said.

    Ijaz notes that other studies have shown that other substances such as cinnamon and chromium have also been shown to prevent type 2 diabetes, but the best advice for patients in prevention is the one most commonly given.

    "Eating a healthy diet and exercise are the best ways to prevent type 2 diabetes and have been proven scientifically," Ijaz said.

    Uwaifo added that beyond these lifestyle interventions, medication interventions may also be important when needed.

    "Patients with prediabetes and high family risk of diabetes should meet with their healthcare providers to discuss potential medications that could assist with prevention of transition to diabetes as well as possible substitutions and/or discontinuations of medications that they presently are taking that could be aggravating their blood sugar and weight struggles," he said.

    Elasy added that coffee and diabetes research should not influence drinking habits.

    "If you enjoy coffee, keep drinking, if not, don't start for the purpose of impacting your diabetes risk. If you are at risk for developing diabetes, you are far more likely to prevent diabetes through weight loss, however achieved, and through certain medications," he said.

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