Dr. Keith Roach

DEAR DR. ROACH: Please write about the correct amount of water that people should drink. There’s so much misinformation! — E.N., MD

ANSWER: There is so much misinformation since a simple answer, like “more is always better,” is easier than a nuanced answer. It depends on your age, activity level, the temperature and humidity, any medications you might be taking, and whether your kidneys have any issues. However, the simplest answer, which is true for most people, is that your body has a built-in system, called the thirst reflex, to make sure that you are getting enough fluid. There are only a few times when you should override this system.

The most important exception is in older people, who sometimes have a decreased thirst mechanism. This is particularly the case in people who live in long-term care facilities or those who have physical or cognitive disabilities. As such, reminders to drink a reasonable amount (1.6 liters or about seven 8-ounce glasses for women; 2 liters or eight 8-ounce glasses for men) of all liquids during the day can be helpful. (Alcohol, of course, isn’t helpful and can be harmful to a person’s fluid status.)

People who are taking diuretics do not need more water. In fact, excess water drinking while on most diuretics can lead to abnormally low sodium levels. Another way to tell if you are getting enough water is the volume and concentration of your urine. People should generally void every few hours, and the color of the urine shouldn’t be dark. Needing to urinate less frequently or having concentrated urine should be an indication for a person to drink a few glasses of water.

DEAR DR. ROACH: What’s a good general wellness supplement to take? I’m a 47-year-old female, and I have always taken a multivitamin, collagen with biotin, probiotics, decaffeinated green tea pills, and my usual prescriptions (losartan, levothyroxine and metformin). I’m looking for more natural ways to lower my weight and cholesterol. Sometimes I take oregano oil and apple cider vinegar. Any good suggestions? — C.A.

ANSWER: I don’t know of any over-the-counter supplements to lower weight or cholesterol that are both effective and safe, so I don’t recommend any supplements specifically for these purposes. You might be taking decaffeinated green tea extract for this, but a clinical trial showed no significant changes in weight or waist size (although green tea extract with caffeine did show a small benefit).

Metformin, which is normally used for diabetes, has much larger effects in promoting weight loss, but it does have a higher potential for side effects, particularly gastrointestinal ones.

I am concerned about the combination of biotin and levothyroxine. My concern isn’t an interaction between them, it’s that the blood tests to check thyroid levels can be misleading in people who take biotin. I hope your doctor has advised you to stop taking biotin at least a couple of days before receiving your blood tests.

A recent study on multivitamins did show an improvement in “global cognition,” but there was no reduction in the incidence of mild cognitive impairment or dementia during the time period of the study. Previous trials haven’t shown an improvement in cognition.

A mostly plant-based diet and moderate exercise has larger effects on the body than any supplement, and most people would benefit more from a diet change over a supplement.

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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.