Coffee Consumption: Diabetes Benefits

Each cup of coffee per day associated with reduced diabetes risk

Consuming a healthy diet was associated with reduced risk for type 2 diabetes among women in all racial and ethnic groups but conferred an even greater benefit for Asian, Hispanic, and black women, according to a new study by researchers at Harvard T.H. Chan School of Public Health and Brigham and Women's Hospital.

"This study suggests that a healthy overall diet can play a vital role in preventing type 2 diabetes, particularly in minority women who have elevated risks of the disease. As the incidence of type 2 diabetes continues to increase at an alarming rate worldwide, these findings can have global importance for what may be the largest public health threat of this century," said lead author Jinnie Rhee, who conducted the research as a doctoral student in the Departments of Epidemiology and Nutrition at Harvard Chan and is currently a postdoctoral fellow in the Division of Nephrology at Stanford University School of Medicine.

The study appears online January 15, 2015 in Diabetes Care.

It's estimated that about 29.1 million people in the U.S. and 47 million around the world have diabetes. The World Health Organization projects that diabetes will be the seventh leading cause of death in 2030. The disease, which is often related to excess body weight and physical inactivity, is more common in African Americans, Latinos, Native Americans, and Asian Americans/Pacific Islanders, and the aged. Previous studies have shown links between diet and risk of type 2 diabetes, but most have been conducted in predominately white populations.

The researchers analyzed data on diet in 156,030 non-Hispanic white women and 2,026 Asian, 2,053 Hispanic, and 2,307 black women in the Nurses' Health Study and Nurses' Health Study II. They adjusted for a variety of factors, such as age, physical activity, smoking, family history of diabetes, alcohol intake, postmenopausal status, menopausal hormone or oral contraceptive use, total caloric intake, and body mass index. The women were followed for up to 28 years and filled out diet questionnaires every four years.

The researchers created a dietary diabetes risk reduction score that included components associated with type 2 diabetes risk. A higher score indicated a healthier overall diet--one with lower intake of saturated and trans fats, sugar-sweetened beverages, and red and processed meats; lower glycemic index foods; and higher intakes of cereal fiber, polyunsaturated fats, coffee, and nuts.

Results showed a protective association of similar magnitude between a healthy overall diet and type 2 diabetes risk in all racial and ethnic groups. Comparing the highest to the lowest quartile of dietary diabetes risk reduction score, healthy diet was associated with a 48% lower risk of diabetes in white, 42% in Asian, 55% in Hispanic, and 32% in black women. When all the minority women were combined into one group, those in the highest quartile of dietary score had a 36% lower risk of diabetes compared with women in the lowest quartile. However, because minority women were initially at higher risk of diabetes than white women, in terms of the actual number of avoidable cases, a healthier diet had greater benefit for minority women. The analysis showed that 5.3 cases of diabetes can be prevented per 1,000 white women per year with a healthier overall diet compared with 8.0 cases that can be prevented per 1,000 minority women per year.

Among the findings was that in both white and minority women, higher glycemic index foods as well as each serving of sugar-sweetened beverages, and red and processed meats were associated with increased risk of diabetes. In contrast, higher intake of cereal fiber (grams/day) and each cup of coffee per day were associated with reduced diabetes risk in both groups.

"This finding confirms that we are all in the same boat when it comes to preventing type 2 diabetes by diet. Our next challenge is to put this knowledge into practice so everyone can benefit," said Walter Willett, Fredrick John Stare Professor of Epidemiology and Nutrition and chair, Department of Nutrition at Harvard Chan.

Increasing consumption of coffee is associated with reduced risk of type 2 diabetes

New research published in Diabetologia (the journal of the European Association for the Study of Diabetes) shows that increasing coffee consumption by on average one and half cups per day (approx 360ml) over a four-year period reduces the risk of type 2 diabetes by 11%. The research is led by Dr Frank Hu and Dr Shilpa Bhupathiraju, Department of Nutrition, Harvard School of Public Health, Harvard University, Boston, MA, USA, and colleagues.

Coffee and tea consumption has been associated with a lower type 2 diabetes risk but little is known about how changes in coffee and tea consumption influence subsequent type 2 diabetes risk. The authors examined the associations between 4-year changes in coffee and tea consumption and risk of type 2 diabetes in the subsequent 4 years.

The authors used observational data from three large prospective, US-based studies in their analysis: the Nurses' Health Study (NHS) (female nurses aged 30-55 years, 1986-2006), the NHS II (younger female nurses aged 25-42 years 1991-2007), and the Health Professionals Follow-up Study (HPFS) (male professionals 40-75 years, 1986-2006). Detailed information on diet, lifestyle, medical conditions, and other chronic diseases was collected every 2 to 4 years for over 20 years.

The availability of these repeated measures and the long-duration of follow-up allowed the authors to evaluate 4 year changes in coffee and tea intake in relation to risk of type 2 diabetes in the following 4 years. They also examined whether the association with diabetes incidence differed between changes in caffeinated and decaffeinated coffee. Diet was assessed every 4 years using a validated food frequency questionnaire. Self-reported incident type 2 diabetes cases were validated by supplementary questionnaires. The final analysis included 48,464 women in NHS, 47,510 women in the NHS II, and 27,759 men in HPFS.

The authors documented 7,269 incident type 2 diabetes cases, and found that participants who increased their coffee consumption by more than 1 cup/day (median change=1.69 cups/day) over a 4-year period had a 11% lower risk of type 2 diabetes in the subsequent 4-years compared to those who made no changes in consumption. Participants who decreased their coffee intake by 1 cup a day or more (median change=-2 cups/day) had a 17% higher risk for type 2 diabetes. Changes in tea consumption were not associated with type 2 diabetes risk.

Those with highest coffee consumption and who maintained that consumption—referred to as "high-stable consumers" since they consumed 3 cups or more per day—had the lowest risk of type 2 diabetes, 37% lower than the "low-stable consumers" who consumed 1 cup or less per day.

The authors say that the higher risk of type 2 diabetes associated with decreasing coffee intake may represent a true change in risk, or may potentially be due to reverse causation whereby those with medical conditions associated with risk for type 2 diabetes (such as high blood pressure, elevated cholesterol, cardiovascular disease, cancer) may reduce their coffee consumption after diagnosis. However, even when cases of cardiovascular disease or cancer were excluded during follow-up, the results were very similar.

While baseline decaffeinated coffee consumption was associated with a lower type 2 diabetes risk, the changes in decaffeinated coffee consumption did not change this risk. Regarding tea consumption, the authors say: "we found no evidence of an association between 4-year increases in tea consumption and subsequent risk of type 2 diabetes. This finding may have potentially been due to the relatively low number of participants who made significant changes to their tea consumption over a 4-year period thereby limiting statistical power to detect true associations. The overall low levels of tea consumption in this group may also be responsible for these findings."

The authors say: "In these 3 large prospective cohorts with more than 1.6 million person-years of follow-up, we observed that increasing coffee, but not tea, intake over a 4-year period was associated with a lower type 2 diabetes risk in the next 4 years. Decreasing coffee intake was associated with a higher type 2 diabetes risk. These changes in risk were observed for caffeinated, but not decaffeinated coffee, and were independent of initial coffee consumption and 4-year changes in other dietary and lifestyle factors."

They add: "Changes in coffee consumption habits appear to affect diabetes risk in a relatively short amount of time. Our findings confirm those of prospective studies that higher coffee consumption is associated with a lower type 2 diabetes risk and provide novel evidence that changes in coffee consumption habits are related to diabetes risk."

Moderate coffee consumption may reduce risk of diabetes by up to 25 percent

Drinking three to four cups of coffee per day may help to prevent type 2 diabetes according to research highlighted in a session report published by the Institute for Scientific Information on Coffee (ISIC), a not-for-profit organisation devoted to the study and disclosure of science related to coffee and health.

Recent scientific evidence has consistently linked regular, moderate coffee consumption with a possible reduced risk of developing type 2 diabetes. An update of this research and key findings presented during a session at the 2012 World Congress on Prevention of Diabetes and Its Complications (WCPD) was summarized in the report.

The report outlines the epidemiological evidence linking coffee consumption to diabetes prevention, highlighting research that shows three to four cups of coffee per day is associated with an approximate 25 per cent lower risk of developing type 2 diabetes, compared to consuming none or less than two cups per day1. Another study also found an inverse dose dependent response effect with each additional cup of coffee reducing the relative risk by 7-8 per cent2.

Whilst these epidemiological studies suggest an association between moderate coffee consumption and reduced risk of developing diabetes, they are unable to infer a causal effect. As such, clinical intervention trails are required to study the effect in a controlled setting. One prospective randomized controlled trial3, tested glucose and insulin after an oral glucose tolerance test with 12g decaffeinated coffee, 1g chlorogenic acid, 500 mg trigonelline, or placebo. This study demonstrated that chlorogenic acid, and trigonelline reduced early glucose and insulin responses, and contribute to the putative beneficial effect of coffee.

The report notes that the association between coffee consumption a reduced risk of type 2 diabetes could be seen as counter intuitive, as drinking coffee is often linked to unhealthier habits, such as smoking and low levels of physical activity. Furthermore, studies have illustrated that moderate coffee consumption is not associated with an increased risk of hypertension, stroke or coronary heart disease4 ,5, 6. Research with patients with CVD has also shown that moderate coffee consumption is inversely associated with risk of heart failure, with a J-shaped relationship.

Finally, the report puts forward some of the key mechanistic theories that underlie the possible relationship between coffee consumption and the reduced risk of diabetes. These included the 'Energy Expenditure Hypothesis', which suggests that the caffeine in coffee stimulates metabolism and increases energy expenditure and the 'Carbohydrate Metabolic Hypothesis', whereby it is thought that coffee components play a key role by influencing the glucose balance within the body. There is also a subset of theories that suggest coffee contains components that may improve insulin sensitivity though mechanisms such as modulating inflammatory pathways, mediating the oxidative stress of cells, hormonal effects or by reducing iron stores.

Coffee protects against diabetes

Coffee, that morning elixir, may give us an early jump-start to the day, but numerous studies have shown that it also may be protective against type 2 diabetes. Yet no one has really understood why.

Now, researchers at UCLA have discovered a possible molecular mechanism behind coffee's protective effect. A protein called sex hormone–binding globulin (SHBG) regulates the biological activity of the body's sex hormones, testosterone and estrogen, which have long been thought to play a role in the development of type 2 diabetes. And coffee consumption, it turns out, increases plasma levels of SHBG.

Reporting with colleagues in the the journal Diabetes, first author Atsushi Goto, a UCLA doctoral student in epidemiology, and Dr. Simin Liu, a professor of epidemiology and medicine with joint appointments at the UCLA School of Public Health and the David Geffen School of Medicine at UCLA, show that women who drink at least four cups of coffee a day are less than half as likely to develop diabetes as non-coffee drinkers.

When the findings were adjusted for levels of SHBG, the researchers said, that protective effect disappeared.

The American Diabetes Association estimates that nearly 24 million children and adults in the U.S. — nearly 8 percent of the population — have diabetes. Type 2 diabetes is the most common form of the disease and accounts for about 90 to 95 percent of these cases.

Early studies have consistently shown that an "inverse association" exists between coffee consumption and risk for type 2 diabetes, Liu said. That is, the greater the consumption of coffee, the lesser the risk of diabetes. It was thought that coffee may improve the body's tolerance to glucose by increasing metabolism or improving its tolerance to insulin.

"But exactly how is elusive," said Liu, "although we now know that this protein, SHBG, is critical as an early target for assessing the risk and prevention of the onset of diabetes."

Earlier work by Liu and his colleagues published in the New England Journal of Medicine had identified two mutations in the gene coding for SHBG and their effect on the risk of developing type 2 diabetes; one increases risk while the other decreases it, depending on the levels of SHBG in the blood.

A large body of clinical studies has implicated the important role of sex hormones in the development of type 2 diabetes, and it's known that SHBG not only regulates the sex hormones that are biologically active but may also bind to receptors in a variety of cells, directly mediating the signaling of sex hormones.

"That genetic evidence significantly advanced the field," said Goto, "because it indicated that SHBG may indeed play a causal role in affecting risk for type 2 diabetes."

"It seems that SHBG in the blood does reflect a genetic susceptibility to developing type 2 diabetes," Liu said. "But we now further show that this protein can be influenced by dietary factors such as coffee intake in affecting diabetes risk — the lower the levels of SHBG, the greater the risk beyond any known diabetes risk factors."

For the study, the researchers identified 359 new diabetes cases matched by age and race with 359 apparently healthy controls selected from among nearly 40,000 women enrolled in the Women's Health Study, a large-scale cardiovascular trial originally designed to evaluate the benefits and risks of low-dose aspirin and vitamin E in the primary prevention of cardiovascular disease and cancer.

They found that women who drank four cups of caffeinated coffee each day had significantly higher levels of SHBG than did non-drinkers and were 56 percent less likely to develop diabetes than were non-drinkers. And those who also carried the protective copy of the SHBG gene appeared to benefit the most from coffee consumption.

When the investigators controlled for blood SHBG levels, the decrease in risk associated with coffee consumption was not significant. This suggests that it is SHBG that mediates the decrease in risk of developing type 2 diabetes, Liu said.

And there's bad news for decaf lovers. "Consumption of decaffeinated coffee was not significantly associated with SHBG levels, nor diabetes risk," Goto said. "So you probably have to go for the octane!"

Coffee Consumption = Reduced Risk of Diabetes

Drinking more coffee (regular or decaffeinated) or tea appears to lower the risk of developing type 2 diabetes, according to an analysis of previous studies reported in the December 14/28 2009 issue of Archives of Internal Medicine, JAMA

By the year 2025, approximately 380 million individuals worldwide will be affected by type 2 diabetes (1).

Despite considerable research attention, the role of specific dietary and lifestyle factors remains uncertain, although obesity and physical inactivity have consistently been reported to raise the risk of diabetes mellitus. A previously published meta-analysis suggested drinking more coffee may be linked with a reduced risk, but the amount of available information has more than doubled since.

Rachel Huxley, D.Phil, of The George Institute for International Health, University of Sydney, Australia, and colleagues identified 18 studies involving 457,922 participants and assessing the association between coffee consumption and diabetes risk published between 1966 and 2009.

Six studies involving 225,516 individuals also included information about decaffeinated coffee, whereas seven studies with 286,701 participants reported on tea consumption.

When the authors combined and analyzed the data, they found that each additional cup of coffee consumed in a day was associated with a 7 percent reduction in the excess risk of diabetes.

Individuals who drank three to four cups per day had an approximately 25 percent lower risk than those who drank between zero and two cups per day.

In addition, in the studies that assessed decaffeinated coffee consumption, those who drank more than three to four cups per day had about a one-third lower risk of diabetes than those who drank none. Those who drank more than three to four cups of tea had a one-fifth lower risk than those who drank no tea.

That the apparent protective effect of tea and coffee consumption appears to be independent of a number of potential confounding variables raises the possibility of direct biological effects, the authors write. Because of the association between decaffeinated coffee and diabetes risk, the association is unlikely to be solely related to caffeine. Other compounds in coffee and tea including magnesium, antioxidants known as lignans or chlorogenic acids may be involved, the authors note.

If such beneficial effects were observed in interventional trials to be real, the implications for the millions of individuals who have diabetes mellitus, or who are at future risk of developing it, would be substantial, they conclude. For example, the identification of the active components of these beverages could open up therapeutic options for the primary prevention of diabetes mellitus. The findings also pose the question of whether patients most at risk for diabetes mellitus may in the future be advised to increase their consumption of tea and coffee in addition to increasing their levels of physical activity.

Spokesperson for the European Society of Cardiology, Professor Lars Rydén (Sweden), who is a diabetes specialist had the following advice: "This is a cautiously and carefully conducted meta-analysis which means authors have carefully conducted studies although each are too small to give an answer to the question although they indicate a positive correlation between the consumption of coffee and a decreasing occurrence of diabetes. So the principle is that if you drink coffee whether it is decaffeinated or not, you have less chance of developing diabetes. The data has been strengthened by bringing several studies together.

There are sometimes claims that coffee may do harm, that it may increase the propensity to Cardiovascular disease, but there is no evidence for this. The message is that people may drink coffee safely. Coffee from this point of view may actually be of benefit, as well as reducing the risk of getting diabetes – although the reduction is small (around 7%)."

However Prof Rydén warns that lifestyle changes far outweigh a regular coffee intake.

"Coffee helps, but other things are even more important. Those who are overweight should reduce their bodyweight by 5-10% - not too much - and include physical activity such as a brisk walk for 30 minutes a day. Then those people who are at risk of developing diabetes will reduce this risk by 40-50%.

It is interesting to consider why a beverage like coffee has a beneficial effect. It is obviously not the caffeine as decaffeinated coffee has the same efficiency as caffeinated coffee. Coffee may contain antioxidants but the studies have not measured the number of chemicals in the blood which is important."

Coffee Consumption: Athletic Performance/Exercise Benefits

A morning cup of coffee could help improve athletic endurance

The caffeine in a morning cup of coffee could help improve athletic endurance, according to a new University of Georgia review study.

Authored by Simon Higgins, a third-year doctoral student in kinesiology in the College of Education, the study was published in this month's issue of the International Journal of Sport Nutrition and Exercise Metabolism.

To research the issue, Higgins reviewed more than 600 scholarly articles and screened them for those that focused only on caffeinated-coffee conditions, measured the caffeine dose and measured an endurance performance. Of these, nine randomized control trials specifically used coffee to improve endurance.

"Previous research has focused on caffeine itself as an aid to improve endurance," Higgins said. "Coffee is a popular source of caffeine, so this paper looked at the research surrounding its ergogenic benefits."

Looking at the nine trials, Higgins found that between 3 and 7 milligrams per kilogram of body weight of caffeine from coffee increased endurance performance by an average of 24 percent. The amount of caffeine in a cup of coffee can vary from 75 mg to more than 150, depending on the variety and how it's roasted and brewed.

"This is helpful for athletes because coffee is a naturally occurring compound," Higgins said. "There's the potential that getting your caffeine by drinking coffee has similar endurance benefits as taking caffeine pills."

In the nine trials, participants either cycled or ran after drinking coffee. They then exercised vigorously and the results were measured. In a majority of cases, endurance was noticeably improved after the use of coffee.

When researching the effects of caffeine from coffee, Higgins found two important discoveries: that caffeine from coffee has ergogenic benefits -- that it enhances physical performance -- and that more research is needed on the use of caffeine from coffee versus pure caffeine use.

"While there is a lack of high-quality research on coffee as a source of caffeine, there is an abundance of research on pure caffeine," he said. "It's surprising how little we know about caffeine from coffee when its endurance effects could be just as beneficial as pure caffeine."

Higgins said that coffee shouldn't be dismissed as less beneficial for endurance. He found that coffee appears to be just as helpful as taking caffeine in the form of powder or tablets.

"There's a perception that coffee won't give you the same benefits as pure caffeine," he said. "New research could mean that athletes could have a cup of coffee versus taking a pill."

Higgins says that more research is needed before giving official recommendations to athletes, especially since the amount of caffeine in a cup of coffee can vary depending on how it's prepared.

"There is a caveat to athletes using coffee: Be careful because you don't know how much caffeine is in some coffee, especially when it's prepared by someone else," he said. "Athletes should run their caffeine use through their sports dietician as the NCAA lists it as a banned substance."



Coffee consumed one hour prior to exercise can improve endurance exercise performance

There is consistent evidence supporting the ergogenic effects of caffeine for endurance based exercise. However, whether caffeine ingested through coffee has the same effects is still subject to debate. The primary aim of the study, The metabolic and performance effects of caffeine compared to coffee during endurance exercise, published in PLoS One Apr. 3, 2013, was to investigate the performance enhancing effects of caffeine and coffee using a time trial performance test, while also investigating the metabolic effects of caffeine and coffee. In a single-blind, crossover, randomised counter-balanced study design, eight trained male cyclists/triathletes completed 30 min of steady-state (SS) cycling at approximately 55% VO2max followed by a 45 min energy based target time trial (TT).

One hour prior to exercise each athlete consumed drinks consisting of caffeine (5 mg CAF/kg BW), instant coffee (5 mg CAF/kg BW), instant decaffeinated coffee or placebo. The set workloads produced similar relative exercise intensities during the SS for all drinks, with no observed difference in carbohydrate or fat oxidation. Performance times during the TT were significantly faster (~5.0%) for both caffeine and coffee when compared to placebo and decaf were significantly faster performance times were similar for both caffeine and coffee. Average power for caffeine and coffee during the TT was significantly greater when compared to placebo and decaf.

The present study illustrates that both caffeine (5 mg/kg/BW) and coffee (5 mg/kg/BW) consumed 1 h prior to exercise can improve endurance exercise performance.

Study finds that caffeine cuts post-workout pain by nearly 50 percent

Although it’s too soon to recommend dropping by Starbucks before hitting the gym, a study suggests that caffeine can help reduce the post-workout soreness that discourages some people from exercising.

In a study published in the February 2007 issue of The Journal of Pain, a team of University of Georgia researchers finds that moderate doses of caffeine, roughly equivalent to two cups of coffee, cut post-workout muscle pain by up to 48 percent in a small sample of volunteers.

Lead author Victor Maridakis, a researcher in the department of kinesiology at the UGA College of Education, said the findings may be particularly relevant to people to exercise, since they tend to experience the most soreness.

“If you can use caffeine to reduce the pain, it may make it easier to transition from that first week into a much longer exercise program,” he said.

Maridakis and his colleagues studied nine female college students who were not regular caffeine users and did not engage in regular resistance training. One and two days after an exercise session that caused moderate muscle soreness, the volunteers took either caffeine or a placebo and performed two different quadriceps (thigh) exercises, one designed to produce a maximal force, the other designed to generate a sub-maximal force. Those that consumed caffeine one-hour before the maximum force test had a 48 percent reduction in pain compared to the placebo group, while those that took caffeine before the sub-maximal test reported a 26 percent reduction in pain.

Caffeine has long been known to increase alertness and endurance, and a 2003 study led by UGA professor Patrick O’Connor found that caffeine reduces thigh pain during moderate-intensity cycling. O’Connor, who along with professors Kevin McCully and the late Gary Dudley co-authored the current study, explained that caffeine likely works by blocking the body’s receptors for adenosine, a chemical released in response to inflammation.

Despite the positive findings in the study, the researchers say there are some caveats. First, the results may not be applicable to regular caffeine users, since they may be less sensitive to caffeine’s effect. The researchers chose to study women to get a definitive answer in at least one sex, but men may respond differently to caffeine. And the small sample size of nine volunteers means that the study will have to be replicated with a larger study.

O’Connor said that despite these limitations, caffeine appears to be more effective in relieving post-workout muscle pain than several commonly used drugs. Previous studies have found that the pain reliever naproxen (the active ingredient in Aleve) produced a 30 percent reduction in soreness. Aspirin produced a 25 percent reduction, and ibuprofen has produced inconsistent results.

“A lot of times what people use for muscle pain is aspirin or ibuprofen, but caffeine seems to work better than those drugs, at least among women whose daily caffeine consumption is low,” O’Connor said.

Still, the researchers recommend that people use caution when using caffeine before a workout. For some people, too much caffeine can produce side effects such as jitteriness, heart palpitations and sleep disturbances.

“It can reduce pain,” Maridakis said, “but you have to apply some common sense and not go overboard.”

Caffeine reduces pain during exercise

Stopping to smell the coffee – and enjoy a cup of it – before your morning workout might do more than just get your juices flowing. It might keep you going for reasons you haven't even considered.

As a former competitive cyclist, University of Illinois kinesiology and community health professor Robert Motl routinely met his teammates at a coffee shop to fuel up on caffeine prior to hitting the pavement on long-distance training rides.

"The notion was that caffeine was helping us train harder … to push ourselves a little harder," he said.

The cyclists didn't know why it helped, they just knew it was effective.

"I think intuitively a lot of people are taking caffeine before a workout and they don't realize the actual benefit they're experiencing. That is, they're experiencing less pain during the workout," Motl said.

He said it's becoming increasingly common for athletes – before competing – to consume a variety of substances that include caffeine, motivated by "the notion that it will help you metabolize fat more readily."

"That research isn't actually very compelling," Motl said. "What's going on in my mind is … people are doing it for that reason, but they actually take that substance that has caffeine and they can push themselves harder. It doesn't hurt as much."

The U. of I. professor has been investigating the relationship between caffeine and physical activity since taking a slight detour during his doctoral-student days, when his work initially was focused on exploring possible links between caffeine intake, spinal reflexes and physical activity.

Seven years later, with several studies considering the relationship between physical activity and caffeine behind him, Motl has a much better understanding of why that cuppa Joe he used to consume before distance training and competing enhanced his cycling ability.

Early in his research, he became aware that "caffeine works on the adenosine neuromodulatory system in the brain and spinal cord, and this system is heavily involved in nociception and pain processing." Since Motl knew caffeine blocks adenosine from working, he speculated that it could reduce pain.

A number of studies by the U. of I. professor support that conclusion, including investigations considering such variables as exercise intensity, dose of caffeine, anxiety sensitivity and gender.

Motl's latest published study on the effects of caffeine on pain during exercise appears in the April edition of the International Journal of Sport Nutrition and Exercise Metabolism.

"This study looks at the effects of caffeine on muscle pain during high-intensity exercise as a function of habitual caffeine use," he said. "No one has examined that before.

"What we saw is something we didn't expect: caffeine-naïve individuals and habitual users have the same amount of reduction in pain during exercise after caffeine (consumption)."

The study's 25 participants were fit, college-aged males divided into two distinct groups: subjects whose everyday caffeine consumption was extremely low to non-existent, and those with an average caffeine intake of about 400 milligrams a day, the equivalent of three to four cups of coffee.

After completing an initial exercise test in the lab on an ergometer, or stationary cycle, for determination of maximal oxygen consumption or aerobic power, subjects returned for two monitored high-intensity, 30-minute exercise sessions.

An hour prior to each session, cyclists – who had been instructed not to consume caffeine during the prior 24-hour period – were given a pill. On one occasion, it contained a dose of caffeine measuring 5 milligrams per kilogram of body weight (equivalent to two to three cups of coffee); the other time, they received a placebo.

During both exercise periods, subjects' perceptions of quadriceps muscle pain was recorded at regular intervals, along with data on oxygen consumption, heart rate and work rate.

"What's interesting," Motl said, "is that when we found that caffeine tolerance doesn't matter, we were perplexed at first. Then we looked at reviews of the literature relative to caffeine and tolerance effects across a variety of other stimuli. Sometimes you see them, sometimes you don't. That is, sometimes regular caffeine use is associated with a smaller response, whereas, other times, it's not."

No one's been able to figure out the reason for the inconsistency, Motl said.

"Clearly, if you regularly consume caffeine, you have to have more to have that bigger, mental-energy effect. But the tolerance effect is not ubiquitous across all stimuli. Even brain metabolism doesn't show this tolerance-type effect. That is, with individuals who are habitual users versus non-habitual users, if you give them caffeine and do brain imaging, the activation is identical. It's really interesting why some processes show tolerance and others don't."

Regarding the outcome of the current research, he said, "it may just be that pain during exercise doesn't show tolerance effects to caffeine."

Motl said one of the next logical steps for his research team would be to conduct studies with rodents in order to better understand the biological mechanism for caffeine in reducing pain.

"If we can get at the biological mechanism, we can begin to understand why there may or may not be this kind of tolerance."

Motl said another research direction might be to determine caffeine's effect on sport performance.

"We've shown that caffeine reduces pain reliably, consistently during cycling, across different intensities, across different people, different characteristics. But does that reduction in pain translate into an improvement in sport performance?"

Meanwhile, the current research could prove encouraging for a range of people, including the average person who wants to become more physically active to realize the health benefits.

"One of the things that may be a practical application, is if you go to the gym and you exercise and it hurts, you may be prone to stop doing that because pain is an aversive stimulus that tells you to withdraw. So if we could give people a little caffeine and reduce the amount of pain they're experiencing, maybe that would help them stick with that exercise.

"Maybe then they'll push a little harder as well … maybe get even better adaptations to the exercise."

Moderate coffee consumption does not lead to dehydration

New research published in the PLOS ONE, has found no evidence for a link between moderate coffee consumption and dehydration. The research, conducted by researchers at the University of Birmingham School of Sport and Exercise Sciences, UK, found that drinking moderate amounts of coffee does not result in dehydration and contributes to daily fluid requirements in regular coffee drinkers just as other fluids do.

Due to early research showing the acute effects of caffeine as a mild diuretic, there appears to be a common assumption that caffeinated beverages, such as coffee also have this effect. However, the effect of coffee consumption on fluid balance cannot be directly compared with that of pure caffeine. Interestingly, prior to publication of this new study only two studies had specifically investigated the effects of caffeine in the form of coffee on hydration status(3,4) with mixed and inconclusive results.

This is the first study to directly assess the effects of a moderate consumption of coffee compared to equal volumes of water. Sophie Killer a Doctoral researcher and lead author of the study commented: "Despite a lack of scientific evidence, it is a common belief that coffee consumption can lead to dehydration and should be avoided, or reduced, in order to maintain a healthy fluid balance. Our research aimed to establish if regular coffee consumption, under normal living conditions, is detrimental to the drinker's hydration status."

In a sample of regular coffee drinkers, Killer and colleagues measured the effects of moderate consumption of black coffee compared to the consumption of equal volumes of water on fluid balance and hydration status. Fifty male participants were tested in two phases, where they were required to drink four mugs (200ml) of either black coffee or water per day for three days. In the second phase, those who had initially drunk coffee switched to water and vice versa. The two phases were separated by a ten day 'wash out' period. Females were excluded from the trial to control against possible fluctuations in fluid balance resulting from menstrual cycles.

To assess hydration status, the researchers used a variety of well-established hydration measures including body mass and total body water, as well as blood and urine analyses. The researchers found no significant differences in total body water or any of the blood measures of hydration status between those who drank coffee and those who drank water. Furthermore, no differences in 24-hour urine volume or urine concentration were observed between the two groups.

"We found that consumption of a moderate intake of coffee, four cups per day, in regular coffee drinking males, caused no significant differences across a wide range of hydration indicators compared to the consumption of equal amounts of water," said Sophie Killer. "We conclude that advice provided in the public health domain, regarding coffee and dehydration, should be updated to reflect these findings."

Liver Disease: Benefits of Coffee Consumption

Coffee consumption reduces mortality risk from liver cirrhosis

New research reveals that consuming two or more cups of coffee each day reduces the risk of death from liver cirrhosis by 66%, specifically cirrhosis caused by non-viral hepatitis. Findings in Hepatology, a journal published by Wiley on behalf of the American Association for the Study of Liver Diseases, show that tea, fruit juice, and soft drink consumption are not linked to cirrhosis mortality risk. As with previous studies heavy alcohol use was found to increase risk of death from cirrhosis.

A 2004 report from The World Health Organization (WHO) estimates that each year 1.3% of total death worldwide is caused by liver cirrhosis. Previous research shows that 29 million Europeans have chronic liver disease, with 17,000 deaths annually attributed to cirrhosis. Further WHO reports state that liver cirrhosis is the 11th leading cause of death in the U.S.

"Prior evidence suggests that coffee may reduce liver damage in patients with chronic liver disease," said lead researcher, Dr. Woon-Puay Koh with Duke-NUS Graduate Medical School Singapore and the National University of Singapore. "Our study examined the effects of consuming coffee, alcohol, black tea, green tea, and soft drinks on risk of mortality from cirrhosis."

This prospective population-based study, known as The Singapore Chinese Health Study, recruited 63,275 Chinese subjects between the ages of 45 and 74 living in Singapore. Participants provided information on diet, lifestyle choices, and medical history during in-person interviews conducted between 1993 and 1998. Patients were followed for an average of nearly 15 years, during which time there were 14,928 deaths (24%); 114 of them died from liver cirrhosis. The mean age of death was 67 years.

Findings indicate that those who drank at least 20 g of ethanol daily had a greater risk of cirrhosis mortality compared to non-drinker. In contrast, coffee intake was associated with a lower risk of death from cirrhosis, specifically for non-viral hepatitis related cirrhosis. Non-alcoholic fatty liver disease (NAFLD), a chronic liver disease related to the metabolic syndrome and more sedentary affluent lifestyle, likely predominates among the non-viral hepatitis related cirrhosis group. In fact, subjects who drank two or more cups per day had a 66% reduction in mortality risk, compared to non-daily coffee drinkers. However, coffee intake was not associated with viral hepatitis B related cirrhosis mortality.

"Our study is the first to demonstrate a difference between the effects of coffee on non-viral and viral hepatitis related cirrhosis mortality," concludes Dr. Koh. "This finding resolves the seemingly conflicting results on the effect of coffee in Western and Asian-based studies of death from liver cirrhosis. Our finding suggests that while the benefit of coffee may be less apparent in the Asian population where chronic viral hepatitis B predominates currently, this is expected to change as the incidence of non-viral hepatitis related cirrhosis is expected to increase in these regions, accompanying the increasing affluence and westernizing lifestyles amongst their younger populations."

Coffee and Tea May Contribute to a Healthy Liver

An international team of researchers led by Duke-NUS Graduate Medical School (Duke-NUS) and the Duke University School of Medicine suggest that increased caffeine intake may reduce fatty liver in people with non-alcoholic fatty liver disease (NAFLD).

Worldwide, 70 percent of people diagnosed with diabetes and obesity have NAFLD, the major cause of fatty liver not due to excessive alcohol consumption. It is estimated that 30 percent of adults in the United States have this condition, and its prevalence is rising in Singapore. There are no effective treatments for NAFLD except diet and exercise.

Using cell culture and mouse models, the study authors - led by Paul Yen, M.D., associate professor and research fellow, and Rohit Sinha, Ph.D of the Duke-NUS Graduate Medical School’s Cardiovascular and Metabolic Disorders Program in Singapore - observed that caffeine stimulates the metabolization of lipids stored in liver cells and decreased the fatty liver of mice that were fed a high-fat diet. These findings suggest that consuming the equivalent caffeine intake of four cups of coffee or tea a day may be beneficial in preventing and protecting against the progression of NAFLD in humans.

The findings were published in the September, 2013 issue of the journal Hepatology.

The team said this research could lead to the development of caffeine-like drugs that do not have the usual side effects related to caffeine, but retain its therapeutic effects on the liver. It could serve as a starting point for studies on the full benefits of caffeine and related therapeutics in humans.

Consuming Coffee = Lower Risk of Liver Disease

Regular consumption of coffee is associated with a reduced risk of primary sclerosing cholangitis (PSC), an autoimmune liver disease, Mayo Clinic research shows. The findings were being presented at the Digestive Disease Week 2013 conference in Orlando, Fla.

PSC is an inflammatory disease of the bile ducts that results in inflammation and subsequent fibrosis that can lead to cirrhosis of the liver, liver failure and biliary cancer.

"While rare, PSC has extremely detrimental effects," says study author Craig Lammert, M.D., a Mayo Clinic gastroenterologist. "We're always looking for ways to mitigate risk, and our first-time finding points to a novel environmental factor that also might help us to determine the cause of this and other devastating autoimmune diseases."

The study examined a large group of U.S. patients with PSC and primary biliary cirrhosis (PBC) and a group of healthy patients. Data showed that coffee consumption was associated with reduced risk of PSC, but not PBC. PSC patients were much likelier not to consume coffee than healthy patients were. The PSC patients also spent nearly 20 percent less of their time regularly drinking coffee than the control.

Caffeine consumption = decreased risk of liver disease

Caffeine consumption has long been associated with decreased risk of liver disease and reduced fibrosis in patients with chronic liver disease. Now, newly published research confirms that coffee caffeine consumption reduces the risk of advanced fibrosis in those with nonalcoholic fatty liver disease (NAFLD). Findings published in the February, 2012 issue of Hepatology, a journal of the American Association for the Study of Liver Diseases, show that increased coffee intake, specifically among patients with nonalcoholic steatohepatitis (NASH), decreases risk of hepatic fibrosis.

The steady increase in rates of diabetes, obesity, and metabolic syndrome over the past 20 years has given rise to greater prevalence of NAFLD. In fact, experts now believe NAFLD is the leading cause of chronic liver disease in the U.S., surpassing both hepatitis B and C. The majority of patients will have isolated fatty liver which has a very low likelihood of developing progressive liver disease. However, a subset of patients will have NASH, which is characterized by inflammation of the liver, destruction of liver cells, and possibly scarring of the liver. Progression to cirrhosis (advanced scarring of the liver) may occur in about 10-11% of NASH patients over a 15 year period, although this is highly variable.

To enhance understanding of the correlation between coffee consumption and the prevalence and severity of NAFLD, a team led by Dr. Stephen Harrison, Lieutenant Colonel, U.S. Army at Brooke Army Medical Center in Fort Sam Houston, Texas surveyed participants from a previous NAFLD study as well as NASH patients treated at the center's hepatology clinic. The 306 participants were asked about caffeine coffee consumption and categorized into four groups: patients with no sign of fibrosis on ultrasound (control), steatosis, NASH stage 0-1, and NASH stage 2-4.

Researchers found that the average milligrams in total caffeine consumption per day in the control, steatosis, Nash 0-1, and Nash 2-4 groups was 307, 229, 351 and 252; average milligrams of coffee intake per day was 228, 160, 255, and 152, respectively. There was a significant difference in caffeine consumption between patients in the steatosis group compared to those with NASH stage 0-1. Coffee consumption was significantly greater for patients with NASH stage 0-1, with 58% of caffeine intake from regular coffee, than with NASH stage 2-4 patients at only 36% of caffeine consumption from regular coffee.

Multiple analyses showed a negative correlation between coffee consumption and risk of hepatic fibrosis. "Our study is the first to demonstrate a histopatholgic relationship between fatty liver disease and estimated coffee intake," concludes Dr. Harrison. "Patients with NASH may benefit from moderate coffee consumption that decreases risk of advanced fibrosis. Further prospective research should examine the amount of coffee intake on clinical outcomes."