Q: As a nurse, I was appalled by your answer to the woman who wanted to have sex more than once every three months. You implied that she had an “overactive libido,” and that the problem was all hers.

Perhaps her husband should get some testing to rule out low testosterone. Maybe he is gay but in the closet. Who knows?

A: Although we were answering the reader’s question, a number of people disagreed with our response. Another reader wrote that only wanting to make love every three months is a problem, and that the husband should seek medical treatment.

A gynecologist scolded: “Do you really think that the best answer is to tamp down her libido? She’s not the one with the problem.” Like you, he suggested that the husband might have low testosterone, or he might be struggling with his sexuality or having an affair.

The woman in question is 34. We agree that desiring sex two or three times a week does not represent an overactive libido. Her husband may indeed have a hormonal imbalance or some other problem that needs to be addressed in counseling.

Some people truly wish to suppress their sex drive, but there are no Food and Drug Administration-approved treatments for this purpose. Many medications, including antidepressants and progesterone, can cause sexual dysfunction or lowered libido as a side effect. We don’t think that is an appropriate solution, however. Some readers report that spearmint tea may calm an overactive libido.

Q: I have lived in Seattle for 35 years, but this past winter I spent three months in Arizona. I have noticed a definite, dramatic improvement in my memory, and I am thinking more clearly. Could this be due to the vitamin D I have gotten from sun exposure in Arizona?

I am 59 and do not take vitamins. I eat well, ride a bike about 50 miles a week and lift weights. Is it possible that the sun exposure has really made a difference in my mental ability?

A: There’s no way to know if living in the Northwest led to a vitamin D deficiency. A research review concluded, “Recent studies have confirmed an association between cognitive impairment, dementia, and vitamin D deficiency” (Clinical Interventions in Aging, April 2, 2014).

To learn more about vitamin D and how to make sure you are getting enough, you may want to read our Guide to Vitamin D Deficiency. Anyone who would like a copy, please send $3 in check or money order with a long (No. 10), stamped (70 cents), self-addressed envelope to: Graedons’ People’s Pharmacy, No. D-23, P.O. Box 52027, Durham, NC 27717-2027. It also can be downloaded for $2 from our website: www.peoplespharmacy.com.

Q: Prebiotics? Probiotics? What is the difference? And what are the most important ingredients? There are so many companies making them that it is hard to know which one to take.

A: Prebiotics are complex carbohydrates that are consumed to provide nutritional support to intestinal microbes. Probiotics are beneficial bacteria that are sometimes used to treat gastrointestinal problems such as colic in infants or irritable bowel syndrome in adults.

The proliferation of products can indeed be confusing, particularly since they contain different strains and amounts of bacteria. ConsumerLab.com recently analyzed 41 probiotic supplements for both humans and their pets. There is a charge for the information, which you will find at www.ConsumerLab.com.

Joe and Teresa Graedon answer letters from readers via their website at www.PeoplesPharmacy.com. Their newest book is “Top Screwups Doctors Make and How to Avoid Them.”