Ask the Doctors: Not all hydration comes from drinking

The importance of staying hydrated comes up in a lot of columns. This may be a challenge for older adults, who can experience a decrease in the signals that indicate thirst. A reader with a tip to share also had a question.

“I fill a pitcher with five glasses of water, which makes it easy to remember to drink enough each day,” she wrote. “I figure that’s plenty because I’m getting water in my food, and also in my daily cups of coffee. Is that right?”

Yes, both the food we eat and the coffee, tea and other beverages we drink contribute to daily water intake. Food typically delivers about 20 percent of the water we get. This is particularly true of fruits and vegetables, yet another reason to include plenty of produce in the diet.

A recent column discussed the challenges some people face in keeping their skin moisturized. Dry skin can be caused by a dry environment, sensitivity to chemicals in soaps and cleaning products, frequent hand-washing, inadequate hydration and as an effect of aging. We heard from a reader with concerns about their solution to dealing with dry skin.

“I like to use Vaseline to help me deal with dry skin. It is amazing how well it works, and how quickly it disappears into my skin,” he wrote. “But I also have a problem with weight control. Is it possible that this is contributing to my weight?”

Vaseline, also known as petroleum jelly, is safe for most people to use on their skin. Regarding your question about Vaseline being absorbed by the body and contributing to weight gain, the answer is no. Our skin can absorb oils and fatty acids, but it does not metabolize them.

A column about resistant starch, a carbohydrate that resists digestion and thus reaches and helps feed the gut microbiota in the large intestine intact, continues to generate letters. Cooking and then cooling foods like potatoes, pasta, legumes and beans creates resistant starch. A reader wondered how much is lost as carbohydrates are frozen and then reheated.

The good news is researchers have found that although further manipulation of food, such as freezing or reheating, does diminish the total amount of resistant starch, that decrease is negligible.