Q I spent a weekend by the sea, running each day on the beach. Now I have severe back pain. What have I done and can I cure it? NR from Woodbridge, Suffolk

A Running on hard sand without well-cushioned running shoes has probably triggered spasm of your lower back muscles. Rest, gentle stretching and anti-inflammatory painkillers should improve things.

Q A friend says sea salt is much better for your health than the low-sodium salt that I use. Who’s right? MR from Southampton

A Low sodium “salt” – to avoid confusion it is better to call it low-sodium food flavouring – is generally better, although people with kidney problems should check with their GP. The quantity of true salt in a product is directly related to its sodium content. To calculate the amount of salt, multiply the sodium content by 2½ times. As a rough guide, adults should eat no more than 6g of salt a day.

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

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