DEAR DR. ROACH: I am a 64-year-old woman with a thin frame who was recently diagnosed with osteoporosis. In the past 10 years, my bone density has declined despite regular exercise, a diet high in dairy products and taking calcium carbonate supplements. My doctor prescribed Forteo injections for one year to hopefully improve my bone density, and then transitioned me to Prolia.

From what I’ve read, calcium carbonate supplements are not easily absorbed and did little to preserve my bone density. I now take a plant-sourced calcium supplement (from algae lithothamnion calcareous and corallioides) that claims to be more “bioavailable” than calcium carbonate. Is algae-sourced calcium better than more-traditional calcium supplements? I have found no studies that address this, and I want to take the calcium supplement most likely to improve bone density. — C.H.

ANSWER: Although calcium supplements by themselves do little to prevent osteoporosis, for men and women taking medication for osteoporosis, the body needs calcium to put into the bones. The ideal source is from the diet (supplements increase kidney stone risk and may increase calcium in arteries), but it can be difficult to get enough calcium from diet, especially if you don’t like or don’t want to ingest dairy products. Hence, many people rely on supplements.

Calcium carbonate is the cheapest and most frequently taken supplement, but it is not particularly well-absorbed. It needs to be taken with food to be absorbed well at all. Calcium citrate is better absorbed and better tolerated than calcium carbonate. It is what I usually recommend for people who take supplements and who don’t tolerate calcium carbonate.

Algal calcium has a different crystal structure from calcium carbonate. A 2010 study from Japan did show a 57 percent increase in absorption of elemental calcium compared with calcium carbonate. However, it is significantly more expensive, and requires many pills a day.

Calcium is absorbed better when it’s taken in smaller amounts, so I would say it is important to space out supplement use. It is hard to absorb more than 600 mg at a time. I still recommend calcium carbonate taken with food as the first choice, but calcium citrate or algal calcium are reasonable alternatives if the calcium carbonate isn’t well-tolerated. People with osteoporosis should aim for a total of 1,200 mg elemental calcium from a combination of diet and supplements.

DEAR DR. ROACH: During an annual physical, my primary physician discovered a soft lump on the top center of my head. He was not concerned other than to say that I will need to have that removed someday. That was 10 years ago. It has never bothered me or given me any pain. It feels perfectly round on top and I would estimate its size to be 1/2 inch diameter at the base and 3/8 inch high.

I am an active 75-year-old male and in good health. Is this a cyst? What does that mean, and what, if anything, should I do? — S.H.

ANSWER: It does sound like a cyst, most commonly an epidermoid (sometimes called sebaceous) cyst, but it could be a pilar cyst as well. Both of these are benign cysts of the hair follicle complex. Although they sometimes can spontaneously rupture or become infected, after 10 years of being stable, I would say the risk of yours causing problems is small, and you don’t need to do anything about it.

There are other possibilities, such as a lipoma (a benign fatty tumor). Still, if it is unchanging, it doesn’t need treatment unless it bothers you. A general doctor, dermatologist or surgeon can help.

Dr. Roach regrets that he is unable to answer individual letters, but will incorporate them in the column whenever possible. Readers may email questions to ToYourGoodHealth@med.cornell.edu or request an order form of available health newsletters at 628 Virginia Dr., Orlando, FL 32803. Health newsletters may be ordered from www.rbmamall.com.