Doc: In hydration game, coffee counts

Keith Roach
To Your Health

Dear Dr. Roach: I drink a lot of coffee, about 80 ounces per day. I feel no ill effects and have no stomach discomfort, but my wife says water is better. A kidney specialist basically said, “fluid is fluid.” With studies showing that coffee has antioxidants and reduces certain cancers, what should I do?


Dear M.K.: People with long memories may recall that in the early 1980s, coffee was linked to an increased risk of pancreatic cancer. However, the study has become a textbook example of poor design, and further studies have suggested that coffee drinking may be associated with lower risk of breast, prostate and oral cancers. I wouldn’t recommend drinking coffee just for this reason, as the effect size, if it really exists, is pretty small.

As far as hydration goes, your kidney specialist is completely right. The caffeine in regular coffee is perceived as a diuretic (a substance that makes you urinate excessively), but that turns out to be myth, as well, at least in regular coffee drinkers.

One potential ill effect of caffeine is that it minimally cuts calcium absorption. However, this amounts to the equivalent of calcium in a tablespoon or two of milk, so it is unlikely to affect overall calcium balance.

Eighty ounces of coffee is a lot of caffeine, and some people will get jittery or have sleep disturbances. It also can have effects on gut motility (it commonly causes diarrhea, but it also can cause constipation). All that said, if you aren’t having ill effects from drinking so much coffee, it is fine — though I still think that, as your wife says, water is better for many people.

Dear Dr. Roach: I’d like your opinion. I’m 80 years old, in good health with no cancer in the family. I have always had regular Pap smears and mammograms. Now I’m aware there are different thoughts as to whether those tests are needed at my age. What is your advice?


Dear J.G.: For Pap smears, there is very good evidence that women who have never had any problems with their Pap smears by age 65 are very unlikely to ever develop any, and I agree with the recommendation by the U.S. Preventive Services Task Force to stop them at age 65.

Mammograms are more controversial, but my practice is to continue to recommend them for most women until about age 75. I stop recommending them to women when they have an underlying medical condition that makes it unlikely that they will get benefit from continued screening. Deciding when that is takes some experience and a lot of talk with the patient and sometimes her family. There is no absolute age cutoff for mammograms, and getting a mammogram on a healthy 80-year-old might make sense. Getting one on a woman with incurable lung cancer, for example, does not.

Email questions to