Q Does having white spots under the fingernails indicate a calcium deficiency?

ES from Cambridge

A No. White nail-spots – punctate leuconychia – are probably the result of a minor knock that temporarily disrupts the developing nail. The spots “grow out” because the nail grows from base to tip. As calcium constitutes only 0.03% of the fingernail, taking calcium supplements has never been known to improve nail quality. Better signs of calcium deficiency are muscle twitching and cramps.

Q I am a fit 45-year-old man who cycles and runs. In bed after exercising I get such hot feet and legs that I can’t bear to have the duvet on me, and I wake up sweating. How can I alleviate this problem?

HW via e-mail

A Burning feet, known as Grierson-Gopalan syndrome, is common from middle age, and usually worst at night. The feet can also be painful to the touch. Possible causes include excessive exercise, diabetes, anaemia, vitamin B12 deficiency and trapped nerves in the feet.

Once a GP has excluded these, make sure you wear well-fitted training shoes, avoid synthetic-fibre socks, use cold-water foot baths for 10 minutes after exercising, and try shock-absorbing sorbothane insoles to reduce foot impact.

Q I’m in my thirties and in recent months my saliva has occasionally slipped down my windpipe, making me choke. It doesn’t happen when I eat or drink, and neither activity is affected. Is there such a thing as a lazy epiglottis?

TC from Hull

AIf this occurs infrequently, it’s probably nothing. The epiglottis, a flap of cartilage behind the tongue and before the larynx, stops food and liquid going down the windpipe by folding backwards to cover the entrance of the larynx when we swallow. Afterwards it returns to its original position.

Saliva, and sometimes food, can go down “the wrong way”, causing the harmless symptom you describe. If the frequency increases, though, you should be assessed for the possibility of a neurological condition.

All questions are answered by a practising doctor. To consult Dr Know, e-mail drknow@sunday-times.co.uk. E-mails cannot be answered individually

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