Coffee Reduce Risk of Type 2 Diabetes, But Bad For Diabetics
If you web search "coffee diabetes", you find conflicting information. You find that coffee may be protective against developing Type 2 diabetes. You also find that coffee may worsen diabetes. Keep in mind that not all studies indicate a conclusive result. There often may very well be conflicting studies that reach different conclusions.
In this example, which is correct? They both are to a certain degree. Note that the first says that coffee my be protective against developing Type 2 diabetes. The key word being "developing". But if you already have Type 2 diabetes, then the caffeine in the coffee is bad because it makes it difficult for your cells to regular blood sugar.
Whereas caffeine is bad for blood sugar, it is the other ingredients in coffee such as magnesium, chlorogenic acid, and quinides that are beneficial in improving blood glucose control. So switching to de-caffeinated or eliminating coffee may be beneficial if you are diabetic.
But does the positive ingredients in coffee offset the detriments of caffeine? In term of glucose control, Duke University researcher James D. Lane says not -- as reported on CBSNews.com article "Diabetes Sufferers: Beware of Caffeine". 
Coffee May Reduce Risk of Developing Type 2 Diabetes
Harvard researcher Rob van Dam says ...
"This is quite a consistent observation, that coffee has a positive effect on diabetes. But it is becoming increasingly clear it is not the caffeine that is beneficial. The picture is now evolving where we see that some other components of coffee besides caffeine may be beneficial in long-term in reduction of diabetes risk."
Chapter 1 of the book "Doctor Chorpa Says" is titled "Is Coffee Truly A Life Saver?" Dr. Chorpa writes...
"We know that coffee is insulin sensitizing; there are people whose pancreas produces sufficient insulin but for some reason it does not have its desired target effect. Coffee sensitizes cells to insulin so that it does have the necessary effect."
WebMD reports ...
"Every Cup of Coffee Per Day Lowers Risk of Type 2 Diabetes by 7% ... drinking regular or decaffeinated coffee and tea all lower the risk of type 2 diabetes."
ScienceDaily reported recently in January 2011 that a UCLA Study showed 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."
There are many factors that affect the risk of diabetes. De-caffeinated coffee may have be just one minor factor when it comes to diabetes. If you want to avoid diabetes, diet and exercise will have a much bigger effect. That is to increase physical exercise, maintain normal weight, and avoid sugar.
Caffiene Bad for Diabetics
Small studies have indicated that caffeine in coffee may elevate blood sugar levels for those already with type 2 diabetes. Caffeine increases adrenaline and stress hormones which raise blood sugar. Other studies show that caffeine makes diabetes worse.
MayoClinic reports Dr. Maria Collazo-Clavell as saying ...
"Caffeine impairs insulin action but not glucose levels in young, healthy adults, but people with type 2 diabetes may experience a small rise particularly after meals,"
Coffee May Protect Against Alzheimer's
To make things more confusing... If you web search "coffee Alzheimer's", you find that coffee may be protective against developing Alzheimer's. However, in this case it is the caffeine that is the ingredient protecting against Alzheimer's.
Neuro-scientist Gary Arendash drinks 5 to 6 cups a day because he is convinced from mice studies that it helps prevents Alzheimer's. [source: NPR Radio]
Coffee and Heart Disease
What about Coffee and Heart Disease?
Article in PubMed reports suggests that ...
"caffeine-containing coffee increases the risk of myocardial infarction and that men who drink at least five cups daily may increase their risk by about twofold or more."
New England Journal of Medicine reports ...
"A positive association between coffee consumption and acute myocardial infarction was confirmed by analyses of data from a multipurpose survey of 12,759 hospitalized patients, including 440 with a diagnosis of acute myocardial infarction"
But then other studies shows ...
"These data do not provide any evidence that coffee consumption increases the risk of CHD." where CHD stands for Coronary Heart Disease.
This goes to show that knowing whether a food or drink is good for you is not that simple. One can not just do one web search, read one article, and then come to a conclusion. Because one article may focus on the positives while another article may focus on the negatives. One also has to look at the size and method of the individual studies.
Coffee a Double-Edge Sword
So coffee appears to be a double-edge sword. It may be good in some instances and it may be bad in others. And certainly it depends on the individual. That is why one should always consult a physician for one's particular situation.
That is why references to sources are provided so that you can investigate in greater details the findings by the scientists and weigh the pros and cons.
We have only touched the surface of coffee and its effect on the human body. There are many other studies looking at coffee and prostate cancer, heart disease, liver disease, suicide, and so on. (Some of which suggests that coffee may be protective against those). If you are interested in these effects, a good place to start is Wikipedia's article Health Effects of Coffee which explains the benefits and risk along with references to detailed studies.
Also, don't drink coffee if you are pregnant, have sleeping problems, or if you are just not able tolerate it (such as upset stomach, etc).
In the book The Blood Sugar Solution 10-Day Detox Diet by Mark Hyman writes ...
"The research is a bit mixed on coffee because in some population studies, coffee seems to be associated with a decreased risk of diabetes. But in experimental studies, caffeine and coffee have been shown to impair insulin sensitivity in healthy individuals as well as obese individuals and type 2 diabetics."
Article written in February 2011. Author is not a medical profession. This is opinion and is not medical advice.
-  Diabetes Sufferers: Beware Of Caffeine - CBS News
Study Shows Caffeine Elevates Blood Glucose Levels in People With Diabetes
-  Why coffee protects against diabetes
Researchers have discovered a possible molecular mechanism behind coffee's protective effect against type 2 diabetes.
-  Coffee, Tea May Stall Diabetes - WebMD
Every cup of coffee a person drinks per day may lower the risk of diabetes by 7%.
-  Caffeine And Diabetes
-  Caffeine and blood sugar: What's the connection? - MayoClinic.com
Caffeine may have some impact on those with type 2 diabetes.