DEAR DR. DONOHUE: Please explain the curse of senior men called nocturia. I must get up from three to nine times a night to urinate. I do not have this urgency during the day. I have tried Flomax at different times without any difference. – J.P.

ANSWER: It’s not a curse only of senior men. It happens to senior women too. However, since an enlarged prostate gland is a male-only problem, let’s start with that.

The prostate gland, located just below the bladder and wrapped around the urethra (the tube that empties the bladder) enlarges with age. The enlarged gland makes it impossible for men to completely empty their bladder. It fills rapidly, and men have to empty it repeatedly and urgently. Medicines like the one you took often can help. Perhaps you didn’t stay on it long enough. There are others. A host of surgical procedures, some that can be done in the doctor’s office, also can free the urethra from the grip of an enlarged prostate.

Age leads to nocturia in both women and men. In younger years, the daytime production of urine is three times the nighttime production. At older ages, urine production becomes a night-shift thing. Partly, that’s due to a diminished nocturnal output of antidiuretic hormone, a hormone that slows down the kidneys’ urine making. On top of that, the bladder shrinks. Holding less urine makes it necessary to empty it more often. To minimize nighttime urine production, cut down on evening fluid intake. Don’t drink any alcohol after dinner. Stop all caffeine from noon on. If you take a water pill, ask the doctor if you can take it first thing in the morning.

It’s been drilled into people to drink eight glasses of water a day. That much water isn’t necessary. Devotion to drinking water is another reason for nighttime trips to the bathroom.

DEAR DR. DONOHUE: I read that 10 minutes of sunlight for at least three days a week is beneficial for the production of vitamin D. Is being in the sun at 5 p.m. as good as being in the sun between 10 a.m. and 2 p.m.? – Concerned

ANSWER: The sun’s ultraviolet B rays, the ones that stimulate the skin’s production of vitamin D, are at their maximum between 10 a.m. and 3 p.m. From November through March, because of Earth’s position relative to the sun, people in northern climates get very little ultraviolet B rays. These people need to eat foods enriched with vitamin D or take a vitamin D supplement.

Dr. Donohue regrets that he is unable to answer individual letters, but he will incorporate them in his column whenever possible. Readers may write him or request an order form of available health newsletters at P.O. Box 536475, Orlando, FL 32853-6475. Readers may also order health newsletters from www.rbmamall.com.