DEAR DR. ROACH: I am a man in my late 50s. I now am told to sleep on my right side and not my left side, because it's better for the heart. However, my sinuses seem to open up and it's easier to breathe lying on my left side. What, if anything, will happen if I sleep on my left side? Can it damage the heart permanently or lead to an early death? — M.N.
ANSWER: Most people can sleep in whatever position they find comfortable without any problem. However, there are a few instances in which sleeping on the left side may potentially cause problems. One is in people with untreated obstructive sleep apnea, in which several studies have shown that sleeping on the left side leads to slightly more breathing problems than sleeping on the right. However, in people who are treated, that should not be a problem.
Pregnant women should sleep on the side. Although women have often been recommended to sleep on their left side, either side is fine for the baby. Left-sided sleeping may reduce swelling in the feet.
People with known severe congestive heart failure or coronary artery disease and who habitually sleep on the left side have a small increase in death compared with back or right-side sleepers. However, my opinion is that the benefit is so small that comfort and quality of sleep is more important.
DEAR DR. ROACH: I have read that many runners drink too much water and that this can be dangerous. What are the signs of drinking too much? — H.C.
ANSWER: Exercise-associated hyponatremia ("hypo" means "too little," and "natremia" means "sodium in the blood") is common for endurance athletes, such as long-distance triathletes and marathoners. It is caused by losing salt and water, mostly through sweat, and replacing it with only water. Most cases are mild and have few symptoms, but if there are symptoms, they are most commonly weakness, headache and dizziness. Severe cases cause disorientation and can lead to seizures and death. In a study of the Boston Marathon in 2002, 13% of finishers had hyponatremia, but only 1% had critical levels.
To avoid hyponatremia, you need to ignore the advice to "drink as much as possible" during exercise. Further, most sports drinks do not have enough sodium to protect against hyponatremia. As simple as the advice is, drinking when you are thirsty when you exercise is the best way of preventing hyponatremia while still preventing volume depletion or dehydration.
DEAR DR. ROACH: You wrote last year about cod liver oil as a source of vitamin D and omega-3. Can you recommend a brand? — M.E.T.
ANSWER: I don't like to recommend specific brands unless there are scientific studies showing a difference between brands, which I can't find with cod liver oil. However, I would look for a brand that is labeled "certified USP," meaning it is tested for contaminants, and one that has a low vitamin A level (below 10,000 IU daily). You also might want one with high (450 mg or greater) EPA plus DPA (the most commonly recommended omega-3 fats).