DEAR DR. ROACH: Please explain the difference between probiotics and prebiotics? I know they are both helpful for the digestive system, but I’m not sure why. — A.B.

ANSWER: Prebiotics are nondigestible food ingredients, such as fiber, that promote the growth of beneficial microorganisms in the intestines. Probiotics are the healthy organisms themselves, such as Lactobacillus and others. The proposed benefits include treatment and prevention of allergic disease, treatment of several intestinal diseases, such as inflammatory bowel disease and infectious diarrhea, and alleviating symptoms of depression. However, the purported benefits of prebiotics and probiotics have not been proven to the point of consensus among experts.

Our understanding of the microflora of the gut is really in its infancy. While I believe there are potential benefits in people with particular medical conditions, it is not yet clear which conditions they should be used for nor which specific products to use. More importantly, many people use both prebiotics and probiotics in absence of any disease or symptoms. I do not recommend this, as there is no convincing evidence that they are effective at preventing disease.

Dr. Keith Roach

A healthy diet contains foods that contain prebiotics, and may contain probiotics as well, in the case of yogurt and other foods with active healthy bacteria.

DEAR DR. ROACH: I am a 75-year-old male in decent health. I have osteoporosis of the spine and three fractured vertebrae. I have on and off back pain but consider myself fortunate to be able to walk and move as much as I do. Exercise is a regular daily thing in my life. One year ago, I was unable to walk at all because my pain was unceasing.

I have studied all the types of osteoporosis treatments. There is quite a range but no cure for the problem. The side effects of treatment force a huge number of people to stop taking them. No one will recommend a particular treatment for me. I take the recommended dose of vitamin D and calcium supplement, but I am reluctant to start any chemical treatment. Am I being foolish to wait? — G.W.

ANSWER: With a history of three fractures, it’s not wise to refuse therapy beyond vitamin D and calcium. The next fracture could be even worse than the three you have had before. Vertebral fractures are usually painful and can lead to compression of the nerves to the body, with complications of worse pain, weakness and numbness. Worse yet, a hip fracture is a devastating injury, usually necessitating major surgery and always with significant risks.

I don’t have enough information about you to recommend a particular therapy. I will say that men with osteoporosis should always have a check of the testosterone level, since low testosterone frequently is associated with osteoporosis, and testosterone treatment increases bone density (although it is unproven to reduce fracture risk). Most men with osteoporosis are treated with anti-resorptive therapy, such as alendronate or risendronate.

You are right that many people stop treatment. In randomized trials, about 30% of people will stop their treatment, although that number was about the same in those assigned to placebo. Most people can tolerate the side effects well with the help of a provider who has experience managing this condition.

Especially in someone like you, with a history of multiple fractures, the benefits of treatment greatly outweigh the potential harms.

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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 send mail to 628 Virginia Dr., Orlando, FL 32803.