Whether decaffeinated coffee can be considered healthier than regular coffee really depends on which health benefits and risks are being studied; for example, "decaf" coffee is less likely to cause birth complications like premature delivery and low birth weight, it is also more likely to increase blood lipids and the risk of heart disease. Furthermore, while both caffeinated and decaffeinated coffee have been linked to a protective effect against diabetes, this effect is more pronounced in regular coffee than it is in decaffeinated coffee.
Both beverages resist diabetes by decreasing levels of C-peptide, an indicator in the blood of insulin resistance. Decaffeinated coffee has also been linked to increased cholesterol. This may be due to the specific type of bean used in its manufacture.
The majority of decaffeinated coffees are not actually caffeine-free. Most simply have significantly lower levels of caffeine. Five cups of decaffeinated coffee could easily be the equivalent of one cup of regular coffee in caffeine content. Risks like high blood pressure and arrhythmia remain present, especially when people are unaware of the facts.
Decaffeinated coffee has been linked to cancer in the past, due to the use of the processing chemical, methylene chloride. However, this was proven to be unfounded.