It seems that not a week goes by without scientists identifying some gene or other that is believed to play a critical role in our susceptibility to a specific illness. Now researchers in Italy have found a gene involved in the production of serotonin - a brain chemical that helps maintain a cheery disposition. It is believed that individuals afflicted with some fault in this gene will be prone to undesirable mood states such as anxiety, and that the early identification of such individuals may give them a head start in terms of finding peace of mind through appropriate psychological support.

While psychological approaches have an obvious role in calming an overanxious mind, physiological remedies may have much to offer too. One dietary factor that can heighten feelings of anxiety, or even panic, is caffeine. While some people can seemingly drink several cups of tea or coffee without any ill effect, some unfortunates can be exquisitely sensitive to caffeine. For individuals prone to anxiety, as little as one daily cup of coffee worsens their symptoms. So for those on the anxious side, I generally recommend complete elimination of caffeine from the diet.

Another nutritionally related factor that affects mood concerns blood-sugar levels. Should they fall below normal levels, the body may compensate by secreting hormones that stimulate the conversion of glycogen (a carbohydrate fuel store found in the muscles and liver) into sugar. One hormone used to stimulate this conversion is adrenaline - a stress hormone that can induce anxiety and irritability. Stability in blood-sugar levels and mood is more likely if regular meals are taken, perhaps with healthy snacks. Nuts are a good snack choice, as their high-protein and low-carbohydrate nature means they give a very sustained release of fuel into the system. Nuts are also a very rich source of magnesium, low levels of which are thought to predispose to feelings of anxiety and nervousness. Brazil nuts are a good choice for highly strung individuals, as they also offer good levels of the mineral selenium, which studies suggest can quell anxiety. Just three or four Brazil nuts a day may help stabilise mood.

In addition to eating nuts, I recommend supplementation with magnesium for those on the nervy side. Taking 400mg per day can have a calming effect, and does seem to help reduce anxiety when taken in the long term.

You ask the questions

Is there anything about nutrition you'd like to ask Dr John Briffa? Email him at john.briffa@observer.co.uk and read his answers in a special Ask the Experts edition of OM at the end of July