Donald Hensrud, M.D.
Recent studies have generally found no connection between coffee and an increased risk of cancer or heart disease. Earlier studies didn't always take into account that known high-risk behaviors, such as smoking and physical inactivity, tended to be more common among heavy coffee drinkers at that time.
High consumption of unfiltered coffee is associated with mild elevations in cholesterol levels. And another study found that two or more cups of coffee a day can increase the risk of heart disease in people with a specific — and fairly common — genetic mutation that slows the breakdown of caffeine in the body. So, how quickly you metabolize coffee may affect your health risk.
Newer studies have also shown that coffee may have benefits, such as protecting against Parkinson's disease, type 2 diabetes and liver cancer. And it has a high content of antioxidants. But this doesn't mean you should disregard the old maxim "Everything in moderation." Although coffee may not be very harmful, other beverages such as milk and juice contain nutrients that coffee does not. Also, keep in mind that coffee accompaniments such as cream and sugar add fat and calories to your diet. Finally, heavy caffeine use — on the order of four to seven cups of coffee a day — can cause problems such as restlessness, anxiety, irritability and sleeplessness, particularly in susceptible individuals.
Source : http://www.mayoclinic.com/