Ask the nutritionist: No need to drink extra water with coffee

Q: Do I need more water when I drink coffee so I don't get dehydrated?

A: Drinking water throughout the day is an excellent habit but you don't need extra because you drink coffee. Research now shows that moderate amounts of coffee, whether regular or decaf, contribute to keeping your body hydrated. The small diuretic effect from the caffeine is more than counterbalanced by the fluid we get as we drink coffee.

In two recent studies in men, coffee did not differ from tea, a sports drink, sugary cola, diet cola, or plain water in how it affects signs of water loss over a few hours or days. Studies showing little or no dehydrating effect of coffee usually involve amounts of caffeine in two or three eight-ounce cups of coffee (250 to 300 milligrams). Given these findings, there's no reason to expect having more coffee would cause dehydration problems.

Moderate coffee consumption, three to five cups a day, is linked to lower risk of Type 2 diabetes and AICR's latest reports found that coffee links to lower risk for endometrial and liver cancers. The concern, then, is simply to avoid amounts of coffee that lead to sleep disturbance or individual health issues.

• The American Institute for Cancer Research is the cancer charity that fosters research on the relationship of nutrition, physical activity and weight management to cancer risk, interprets the scientific literature and educates the public about the results. AICR has published two landmark reports that interpret the accumulated research in the field, and is committed to a process of continuous review. AICR is a member of the World Cancer Research Fund International.