You often advise people to keep low on carbohydrates. Are rye crispbreads any better than bread in terms of carbs?
Betty Harris, London N1

Grain-based carbohydrates tend to give a relatively brisk and considerable release of sugar into the bloodstream, which in turn can cause surges in insulin (excesses of which increase the risk of several health issues, including weight gain, type 2 diabetes and heart disease).

The extent of blood-sugar release from a food can be measured and is expressed as its glycaemic index. In the glycaemic index scale, glucose is assigned an arbitrary value of 100. Bread, including wholemeal, generally has glycaemic indices of about 70 and above (high). Rye crispbreads have glycaemic indices around the mid-60s, which means they are perhaps slightly better than bread, but far from ideal, with regard to their effect on blood sugar and insulin levels. However, it is not just a food's glycaemic index, but also how much of it is eaten. One or two crispbreads here and there are unlikely to pose a problem, but don't fill up on this sort of food.

· If you have any issues you would like Dr Briffa to address in his column, please email him on john.briffa@observer.co.uk. Please note that Dr Briffa cannot enter into any correspondence. You can also visit www.drbriffa.com. Before following any recommendations in this column, you should consult your own medical adviser about any medical problems or special health conditions