Most of us have a pretty good idea of what constitutes a healthy diet and will be only too aware that sugary stuff such as sweets, chocolate and coffee-bar patisseries is unlikely to do much for our waistline or wellbeing. As an occasional treat, it's fine. But despite the best of intentions, some of us can find ourselves cracking into the chocolate Hobnobs with disconcerting regularity.

The traditional view is that such dietary indiscretions are the result of a lack of self-control. Yet while a sweet tooth may seem to be rooted in some psychological feebleness, my experience tells me otherwise. Mostly, I have found that serious sugar cravings are the result of an imbalance in body, not mind. A few dietary modifications can often undo an unhealthy fondness for the sweet stuff, and take the angst out of doing the right thing nutritionally.

The body depends on a ready supply of sugar in the bloodstream to keep it functioning normally and it generally likes to keep the level of this most essential of fuels within relatively narrow parameters. However, not everyone is adept at keeping sugar on an even keel. For some, blood-sugar levels roller coaster their way through the day. But because it is so fundamental, alarm bells ring if blood-sugar levels drop to subnormal levels. If the body senses it's running low on sugar, it generally stimulates the urge to eat. Not that a salad niçoise will do, mind. When blood-sugar levels plummet, it's sugar the body needs - and cravings for sweet snacks is the almost inevitable result.

So stabilising blood-sugar levels is a top priority for those who crave sugar and the right diet is key to taking control. It is vital to avoid foods that release sugar very quickly into the bloodstream. The peaks of blood sugar these foodstuffs induce can overstimulate the body's regulatory mechanisms, leading to crashes of blood sugar (and more cravings) some time later. Obviously, foods packed with refined sugar are likely to give trouble. But many starchy foods, notably white bread, white rice, pasta and potatoes, destabilise blood-sugar levels, too, and are best given a wide berth.

Basing the diet on foods that give a long, slow release of sugar into the bloodstream is a key to ensuring good blood-sugar stability. Suitable candidates include whole rye bread, brown rice, wholewheat pasta, beans, pulses and most fresh fruits and vegetables. Another important element is protein - including some with each meal seems to help blood-sugar stability. For treats, dark chocolate is relatively low in sugar and makes a pretty decent alternative to common-or-garden sweet-shop fare.

What we eat helps keep blood-sugar levels stable, but when we eat is critical, too. Skipping breakfast, grabbing an excuse of a lunch and eating for Britain in the evening is unlikely to help our cause. Eating three square meals a day is the order of the day for blood-sugar stability. Healthy snacks such as fresh fruit and nuts keep blood-sugar levels from dropping into the danger zone. Keeping the body regularly stoked with slow-burn fuel puts pay to an unhealthy attachment to sugar, and helps keep us on the nutritional straight and narrow without the need for a cast-iron resolve.

Nutrition news

About 50 per cent of the British population takes supplements at least some of the time, often in the form of a multivitamin and mineral.

Recently, a group of middle-aged men and women were dosed up with a multivitamin and mineral for a year to see what, if any, benefits were to be had - 43 per cent of subjects were found to have a nutritional deficiency at the start of the trial. One year of supplementation corrected any deficiency in the vast majority of these.

But that's not all. The supplement takers had, over the course of the year, about half as many ill days compared to those taking placebo (inactive) medication.

This study appears to provide good evidence that taking a daily multivitamin and mineral supplement does indeed have very real benefits for health and wellbeing.

Dear John

My husband and I are planning a cruise in the Mediterranean this summer. I am prone to travel sickness from time to time and was wondering whether there are any natural remedies for this.
Alice Burke, New Malden, Surrey

Balance in the body is governed by delicate organs in the inner ear. Travel sickness is thought to be related to the effect of movement and vibration here, though why some individuals are prone to this remains a bit of a mystery. Fortunately, natural approaches to this problem are often effective.

One substance that can be very useful is ginger. It is said that the ancient Chinese mariners would ward off seasickness by keeping a slice of fresh root ginger between their cheek and gum.

You can try this if you like, but you may prefer to take ginger in capsule or tablet form. The normal recommended dose is 500mg, three times a day.

Another natural remedy you might like to try is the elasticated wristbands designed for this purpose. Each of these contains a plastic bead that stimulates the acupressure point in the wrist responsible for controlling nausea and sickness. Such bands are available from all good pharmacies, and can be worn for the duration of your trip.

·If you have any issues you would like Dr John Briffa to address in this column, please contact him by email on john.briffa@observer.co.uk . Please note that Dr Briffa cannot enter into any personal correspondence