Health Benefits of Coffee: The Healthiest Beverage on Earth?
Coffee contains caffeine, which is most widely consumed stimulant on the planet, yet many individuals (including myself) find the ritual of slowly sipping coffee to be relaxing and calming.
Related - Pocket Guide to Caffeine Benefits and Uses
This article examines why coffee, the second most widely consumed beverage in the United States, second only to water, is one of the healthiest beverages you can put in your body. Specifically, coffee increases your metabolism, burns fat, suppresses hunger, fights disease, increases exercise performance, and controls blood sugar.
5 Health Benefits of Coffee
Reason #1: Coffee Increases Metabolism and Energy LevelsNon-decaffeinated coffee contains the stimulant caffeine, making it one of the most popular all-natural go-to beverages for increasing the body's metabolism and energy levels.
The caffeine molecule is the most commonly consumed central-nervous-system stimulant in the world and works by increasing the metabolism and mitochondrial content in the brain and skeletal muscle.  This increased metabolism and production of mitochondria is responsible for the feelings of increased energy.
A study on healthy individuals examining the effects of 8 milligrams of caffeine per kilogram found that metabolic rate significantly increases up to 180 minutes after caffeine consumption.  For a 180-pound individual this equates to approximately 654 milligrams of caffeine.
While this amount is relatively high, two additional studies found that even just 4 milligrams of caffeine per kilogram of body weight significantly increases metabolism and with few side effects.  For reference, one eight-ounce cup of coffee contains approximately 85 milligrams of caffeine.  Caffeine is a vasoconstrictor so those with blood pressure or blood flow concerns should consult a physician before ingesting large quantities of non-decaffeinated coffee.
Reason #2: Coffee Burns Fat and Suppresses HungerIf you?re struggling to lose fat and control your appetite, then consider incorporating the moderate consumption of coffee into your daily diet. While numerous trials confirm coffee's ability to burn fat, one study found that 8 milligrams per kilogram of body weight increased the levels of plasma free fatty acid in the blood by almost 200% for multiple hours. 
Increased free fatty acid levels in the blood indicate an increased rate of fat-burning (lipolysis) and fat oxidation.
While it's conventional wisdom to attribute coffee's fat-burning and hunger suppressing effect to the caffeine content, the polyphenols, a class of phytochemicals found in coffee also assist with weight control. A study on mice found that combining coffee polyphenols with a high-fat diet significantly decreased body weight gain, as well as fat accumulation in the abdominal region and liver compared to a high-fat diet alone.
The energy expenditure from the mice consuming coffee polyphenols was also significantly higher compared to the high-fat diet-only group.  These findings suggest that the fat-burning benefits of coffee extend beyond the beverage's caffeine content.
From the hunger suppression standpoint, coffee is more effective than placebo and caffeine in water. Eleven healthy male volunteers consumed either caffeine in water, caffeinated coffee, or decaffeinated coffee.
60 minutes later they consumed the simple carbohydrate glucose. Interestingly, those consuming the decaffeinated coffee experienced the most significant decreases in hunger while those individuals consuming caffeine in water expressed no changes in hunger levels. The effects of caffeinated coffee on hunger fell in between those two beverages. 
These findings suggest that the hunger-suppression effects of coffee go beyond the caffeine content which is great for those sensitive to caffeine but looking to control their weight.
Reason #3: Coffee Fights Oxidative Stress and DiseaseLifestyle, environment, diet, stress levels, and genetics all influence the amount of oxidative stress your body undergoes and your likelihood of developing serious illnesses and diseases.
While coffee is by no means a magic elixir, a growing body of evidence suggests it protects your body against oxidative stress as well as delays the development of cancer and neurodegenerative diseases.
A study of 38 male and female volunteers involved consuming either 800 milliliters of coffee or water every day for five consecutive days. At the end of the experiment, researchers measured the amount of DNA damage in peripheral lymphocytes and found that the coffee drinkers decreased oxidative DNA damage by 12.3%.  Lymphocytes are a type of white blood cell responsible for ensuring optimal immune system function.
Despite what mainstream media might be telling you, regular coffee drinkers are not a higher risk for developing heart disease and irregular heartbeats. In fact, regular coffee drinkers tend to have lower rates of diabetes, liver disease, Parkinson's disease, and overall mortality. 
I don't know about you, but a calorie-free beverage with moderate amounts of caffeine and high levels of antioxidants sounds like the perfect trifecta to me. Those looking to optimize the disease and oxidative stress-fighting benefits of coffee should consume an average of two to three cups per day. 
A cup of coffee is not equivalent to a cup of water. Each cup is approximately six ounces rather than the eight ounces per cup used for other beverages.
Reason #4: Coffee Increases Exercise PerformanceMany fitness enthusiasts use coffee and other caffeinated products like energy drinks and pre-workout powders to increase power output and fight fatigue. Unlike the other two products, coffee is all-natural and packed with antioxidants as well as reasonable amounts of caffeine.
The prevailing research indicates that moderate caffeine consumption significantly improves aerobic output for bouts lasting longer than 60 seconds as well as endurance, speed, and power in activities requiring explosive movement.  Nine competitive male and female cyclists consumed either decaffeinated coffee or coffee containing 330 milligrams of caffeine 60 minutes prior to exercising.
The athletes then exercised until exhaustion on a bicycle ergometer at a pace equivalent to 80% of their Vo2 maximum. Individuals consuming caffeinated coffee exercised for nearly 20% longer, burned more fat, and felt less tired than individuals consuming decaffeinated coffee.  You can obtain 330 milligrams of caffeine from approximately four cups of coffee.
Scientists interested in the performance-enhancing effects of coffee as related to weightlifting asked nine resistance-trained males to perform as many repetitions as possible, to muscular failure, on the squat and bench press using 60% of their one-repetition maximum.
Prior to performing the movements and on different occasions, the individuals consumed 0.15 grams of caffeinated coffee, 0.15 grams of decaffeinated coffee, 0.15 grams of decaffeinated coffee plus 5 milligrams of anhydrous caffeine, or only 5 milligrams of anhydrous caffeine per kilogram of bodyweight.
The consumption of either caffeinated coffee and a combination of decaffeinated coffee plus caffeine anhydrous led to significant increases in total weight lifted.  These findings suggest that the non-caffeine compounds in coffee improve exercise performance beyond simply consuming caffeine anhydrous by itself.
Those worried about dehydration can rest-assured that while caffeine has a slight diuretic effect, the magnitude of the effect is almost identical to that caused by plain water. Coffee may cause a brief fluid-electrolyte imbalance but the current researcher maintains that such an imbalance is not dangerous or harmful to exercise performance.
Increasing your tolerance to caffeine may decrease the resulting fluid-electrolyte imbalance.  As a precaution you may consider consuming a high-quality electrolyte beverage intra-workout.
Reason #5: Coffee Controls Blood SugarCoffee's ability to control blood sugar generally receives little praise and attention, but this benefit is huge for those struggling to keep their blood sugar within a normal range.
A study of ten healthy males consumed either caffeinated coffee, decaffeinated coffee, or water while simultaneously consuming a cereal with a high glycemic index.
180 minutes after consuming this cereal, to test insulin sensitivity, these individuals then consumed 75 grams of pure glucose. While those drinking both the caffeinated and decaffeinated coffee experienced slightly larger spikes in insulin immediately after consuming the cereal, only individuals consuming caffeinated coffee experienced a significant decrease in the insulin sensitivity index. 
If you plan to eat a meal high in carbohydrates then consider having coffee a few hours beforehand to decrease the insulin response.
A meta-analysis of over 7,000 subjects between 32 and 88 years old found that individuals consuming ground caffeinated coffee were significantly less likely to develop diabetes compared to those that did not report drinking coffee throughout the study.  While coffee may not be able to reverse diabetes, it could help to prevent or manage the disease.
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