Q: I just read your column about the effects of coffee on moving one’s bowels. It may not be the caffeine doing the work.

My grandmother did not drink coffee, but every morning first thing she drank a cup of hot water “for her bowels,” she said. I think hot water would have the same effect whether it had caffeine in it or not.

A: The researchers we mentioned who tested the effects of coffee on rats’ digestive function found that decaf worked like regular coffee to enhance the power of intestinal contractions, demonstrating that caffeine is not the primary actor.

Scientists have used hot water as a control in a study of postoperative recovery of bowel function (European Journal of Obstetrics, Gynecology and Reproductive Biology, January 2018).

Among women who had undergone cesarean section deliveries, those who drank coffee were quicker to pass gas. Surgeons pay a lot of attention to flatulence because it demonstrates that the digestive tract is returning to normal.

A meta-analysis involving six clinical trials with 600 patients concluded: “Postoperative coffee consumption is effective and safe for enhancing the recovery of gastrointestinal function after abdominal surgery” (Scientific Reports, Nov. 26, 2018).

Many other readers share the conviction that hot beverages of any sort can benefit bowel function. One would need to experiment between hot and cold coffee to see if temperature is a key factor. At least one reader claims, “I find that quickly drinking a large glass of ice-cold water gets things moving.”

Q: My husband (age 70) was just diagnosed with a vitamin B12 deficiency. Why is a B12 test not a part of regular blood work after a certain age? The symptoms mimic dementia and myriad other illnesses, including depression and anxiety. He’s gradually getting better after a month on vitamin B12 supplements.

A: You are correct that vitamin B12 deficiency is common among elderly people (Journal of Nutrition, Health & Aging, February 2015). A Canadian study found that older men who get more vitamin B12 from their diets are less likely to be depressed (European Journal of Clinical Nutrition, March 2016).

Testing for vitamin B12 is not a simple blood test, though. The diagnosis may require a test for methylmalonic acid (MMA) as well as serum B12 (cobalamin). Doctors should consider such testing for people with symptoms of cognitive decline.

According to Dr. Tieraona Low Dog, people over 60 are at particular risk of vitamin B12 deficiency. She notes that the diabetes drug metformin and acid-suppressing drugs increase that risk.

To learn more about how B vitamin deficiencies can lead to depression, weakness and other problems, you may wish to consult her book “Fortify Your Life: Your Guide to Vitamins, Minerals, and More.” It is available at PeoplesPharmacy.com.

Q: I found that low-sodium soy sauce does not work for burns, but regular soy sauce does.

A: Many dermatologists would be aghast at the idea of putting soy sauce on a kitchen burn. There is no science to support this home remedy. First aid for most burns is cold tap water!

That said, we have heard from hundreds of readers that soy sauce can be helpful in easing the pain and reducing the redness. Some, like you, have found that low-sodium soy sauce is ineffective.