To Your Good Health
DEAR DR. ROACH: Naps are a big part of the day for most of my adult friends. Please comment on their significance and any techniques that increase their value. What are good times of day to nap? What about length of naps? — N.M.G.
ANSWER: Some people do very well with naps; others do not. In general, I don’t advise people for or against naps unless they are having sleep problems. But, being an evidence-driven physician, I would note that there is evidence that short naps — situated not too close to a person’s regular bedtime — have been shown to reduce fatigue and help improve concentration. The optimal length of a nap seems to be about 20 minutes; longer than that and there is a higher risk of a condition called “sleep inertia,” which is the period of sleepiness and poor brain performance when you first wake up. This can be quite long for some people after a prolonged nap.
Naps also can help regulate a person’s sleepwake cycle, especially for night-shift workers, either right before or during the shift, if possible. Businesses might do better to allow a break for a 20-minute nap, as there is evidence it can improve productivity among night-shift workers.
DEAR DR. ROACH: Approximately three years ago, I developed a calcium oxalate kidney stone, which was removed by surgery. What can I do to prevent the calcium oxalate kidney stone from forming again? — V.V.
ANSWER: Calcium oxalate stones, the most common kind of kidney stone, develop when the concentrations of calcium and oxalate in the urine reach a particular level favorable to formation. Preventing them is primarily aimed at reducing concentration of these chemical ions in the urine.
Reducing oxalate in the diet is one step. The foods highest in oxalate include spinach, rhubarb, potatoes, some legumes and nuts (peanuts, cashews and almonds). I recommend the list at https://tinyurl.com/383tn3r4 for more detailed information. It’s not necessary to reduce all oxalate. Just avoid those few foods with lots of oxalate.
Increasing your intake of water reduces the concentration of calcium and oxalate, so more fluid is important for virtually all people with kidney stones.
Paradoxically, a low calcium diet is NOT recommended. Calcium in the diet reduces stone formations, mostly by preventing oxalate from being absorbed. Dietary calcium is helpful for bone strength as well. On the other hand, calcium supplements have so much calcium, absorbed so quickly, that they DO increase stone risk and should be avoided in people with a history of calcium stones.
Animal protein, excess salt and excess added sugar — specifically table sugar (sucrose) and fructose — all promote stone formation and should be limited. Fruits and vegetables, partly due to their high potassium content, help protect against stones.
People who still have very high urinary calcium despite lifestyle changes will need medication therapy. Some diuretics reduce urinary calcium, as does potassium citrate, which is also found in citrus fruits. Kidney specialists are the experts in management of kidney stones.