Q: I was taking two melatonin gummies each night to help me sleep. They worked very well. However, within about a week, I developed diarrhea that kept getting worse.

After several weeks, I contacted my doctor. She ran a series of blood work, including ulcer tests and at-home colon cancer tests, trying to pinpoint the problem.

I happened to read the melatonin bottle one night and it said “use as needed,” not nightly. I skipped it a few nights and my intestinal issues went away. As a test, about a week later, I took them again. After two nights, the diarrhea came back. My doctor then told me that the ingredients in some gummies can cause this problem for susceptible people.

A: We agree with your physician that non-sugar sweeteners could be the culprits behind your digestive distress. Manufacturers of gummy supplements like to advertise that they are sugar-free. Many of those contain such sweeteners as maltitol, sorbitol or xylitol. These compounds can cause gas, stomach pain and diarrhea.

You may want to look for another form of melatonin supplement instead of gummies. Pills are widely available.

Q: I read somewhere, possibly your column, that it’s advisable to have Lp(a) levels analyzed along with cholesterol at your annual wellness visit. This year, my routine blood work came back with acceptable numbers for cholesterol, HDL and LDL. However, my small LDL particles were way too high.

My doctor said that most annual blood work does not include Lp(a). I wonder why not, since this lab value seems really important for predicting the risk for stroke or heart attack.

A: We don’t understand why many physicians seem reluctant to order a blood test for lipoprotein a, abbreviated Lp(a). This compound combines two troublemakers: LDL cholesterol and apolipoprotein(a). It can lead to calcification of aortic valves and clogged arteries. When there is a family history of heart disease, Lp(a) is often the culprit.

Q: After years of trying to lessen or eliminate foot odor, I have found something that works for me when nothing else did, and it is quick and easy. Because my husband cannot use regular antiperspirant, he uses milk of magnesia as a substitute. For him, it serves as a non-irritating deodorant.

I now use a thin coating of milk of magnesia on the soles of my clean feet, rubbing it between my toes, too, and letting it dry. I then powder my feet with a popular odor-prevention foot powder. I sprinkle the powder in my shoes when I remove them. After many long years, I now have very few problems with sweaty, smelly feet.

A: Milk of magnesia (magnesium hydroxide) has been used for more than 150 years for digestive discomfort. People use it primarily as a laxative, although this ingredient is also found in some antacids.

For reasons that we don’t completely understand, magnesium hydroxide also works surprisingly well to control body odor. We suspect that it does this through both its drying action and an ability to discourage bacterial growth. It may also raise the pH of the skin, making it more alkaline. Perhaps that helps explain its good antimicrobial properties (Biomaterials Advances, October 2024). This probably makes the skin less hospitable to germs that cause unpleasant odors from feet as well as armpits.

In their column, Joe and Teresa Graedon answer letters from readers. Send questions to them via www.peoplespharmacy.com.