Your good health: short naps can reduce fatigue and improve concentration

The optimal length of a nap seems to be around 20 minutes; longer than that and there is a higher risk of “sleep inertia”

Dear Dr. Roach: Naps are a big part of the day for most of my adult friends. Please comment on their importance and any techniques that increase their value. What are the best times of the day to take a nap? What about nap times?


Some people do very well with naps; Others don’t. In general, I don’t advise people against napping unless they have trouble sleeping. But, being an evidence-based doctor, I would note that there is evidence that short naps – located not too close to a person’s usual bedtime – have been shown to be effective in reducing fatigue and helping to improve concentration. The optimal length of a nap seems to be around 20 minutes; longer than that and there’s a higher risk of a condition called ‘sleep inertia’, which is the period of drowsiness and poor brain performance when you first wake up. This can be quite long for some people after an extended nap.

Naps can also help regulate a person’s sleep-wake cycle, especially for night workers, just before or during the shift, if possible. Companies might be better off allowing a break for a 20-minute nap, as it’s been proven to improve the productivity of night shift workers.

Dear Dr. Roach: About three years ago I developed a calcium oxalate kidney stone, which was surgically removed. What can I do to prevent calcium oxalate kidney stones from forming?


Calcium oxalate stones, the most common type of kidney stone, develop when the concentrations of calcium and oxalate in the urine reach a particular level favorable for formation. Their prevention is primarily aimed at reducing the concentration of these chemical ions in the urine.

Reducing oxalate in the diet is one step. Foods highest in oxalate include spinach, rhubarb, potatoes, some legumes, and nuts (peanuts, cashews, and almonds). I recommend the listing at for more detailed information. It is not necessary to reduce all the oxalate. Just avoid these few oxalate-rich foods.

Increasing your water intake reduces calcium and oxalate levels, so more fluid is important for virtually everyone with kidney stones.

Paradoxically, a diet low in calcium is NOT recommended. Calcium in the diet reduces stone formation, primarily by preventing the absorption of oxalate. Dietary calcium is also helpful for bone strength. On the other hand, calcium supplements contain so much calcium, absorbed so quickly, that they increase the risk of stones and should be avoided in people with a history of calcium stones.

Animal protein, excess salt, and excess added sugar — especially table sugar (sucrose) and fructose — all promote stone formation and should be limited. Fruits and vegetables, thanks in part to their high potassium content, help protect against stones.

People who still have very high urinary calcium levels despite lifestyle changes will need drug treatment. Some diuretics reduce urinary calcium, as does potassium citrate, which is also found in citrus fruits. Kidney specialists are the experts in managing kidney stones.

Dr Roach regrets that he cannot respond to individual letters, but will incorporate them into the column whenever possible. Readers can email questions to [email protected]

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