Over the years, coffee has been much maligned as an indulgence, a trigger of blood pressure and brown teeth, a diuretic that works against good hydration. Some studies from the 1980s even suggested increased risk for heart attack. Coffee has been classified by many in the "undesirable" list, along with hydrogenated fats and too much alcohol.

But there's another part of the discussion that often gets little attention: coffee's ability to reduce the likelihood of developing diabetes and heart disease.

Initial studies suggested that coffee consumption, especially in non-coffee drinkers, increases blood sugar. Coffee consumption especially increases blood sugar after a meal, with caffeinated coffee eliciting a greater response compared to decaffeinated coffee.

However, chronic consumption may be different, i.e. habitual consumption of coffee over a long period. A recent Dutch study demonstrated that coffee reduces after-eating, or postprandial, glucose, up to 8.8% with consumption of 3 or more cups per day.

Chronic consumption of coffee appears to reduce the likelihood of developing diabetes. The 18-year long observations of the 120,000 men and women participants in the Nurses' Health Study and Health Professionals' Follow-up Studies showed up to 50% less diabetes in heavy coffee drinkers of 5 cups or more per day. A pooled analysis of 15 studies showed up to 35% less development of diabetes in people chronically drinking 3 or more cups of coffee per day. An analysis that combined data from 18 studies involving 457,922 participants conducted from 1966 to 2009 showed 7% less likelihood of developing diabetes for every additional cup of coffee consumed. The effect is only partly due to caffeine, as decaffeinated coffee exerts a similar effect; teas, including green tea, may exert a similar effect.

Large observational studies suggest fewer heart attacks with chronic coffee consumption. A series of studies from Harvard showed 20% less heart attack over 24 years in men and women who drank 4 cups of coffee per day.

Much of the disconnect between the acute adverse effects and the chronic beneficial effects of coffee may be explained by weight loss: Coffee drinkers tend to be thinner. Thinner people are at lower risk for both diabetes and heart disease.

Beyond caffeine, an astounding 600 compounds in coffee have been catalogued to date; not all beneficial components have been identified. Coffee's benefits may be due to its rich flavonoid content (the family of plant compounds found in foods like blueberries and dark chocolates), as well as compounds like chlorogenic acid and trigonelline.

If you enjoy your coffee but want to be sure you are not obtaining any adverse health effects, then:

• Use a coffee maker with a paper filter. Boiled coffee without a filter can increase LDL cholesterol; the effect (due to a component called cafestol) is eliminated with a filter.
• Drink it frequently, since many of the acute effects of coffee-increased blood pressure, artery constriction, increased blood sugar-are reduced or eliminated with daily or frequent consumption.