Q: "I have recently discovered xylitol and stevia. Can you tell me a bit about them and how they rate nutritionally?"
Cathy Levan, via email
A: Both xylitol and stevia are sweeteners used as a replacement for sugar in diet products. Xylitol, a sugar alcohol found in fruits and vegetables, is often used to make sugar-free chewing gum and sweets, and may be listed under its additive code, 967. It is absorbed slowly, so doesn't have much effect on blood sugar, making it useful for people with diabetes or hypoglycaemia. Its other advantage is that it doesn't cause dental decay. It seems safe: the only side effect occurs if you overdo it, when it may cause wind or diarrhoea.
Stevia is a sweetener with a slight licorice taste. The stevia leaf is 30 times sweeter than cane sugar but supplies no kilojoules. You'll see it sold as a white powder, a liquid extract, or as tablets for tea and coffee. It works well in beverages or yoghurt, but not in baked goods as it can't duplicate sugar's ability to add bulk or contribute to a golden-brown colour. At this point, stevia appears safe but is still under assessment in the US, Canada and Europe. It has, however, been used in Japan and Korea since the 1970s to sweeten beverages and confectionery, and there have been no adverse reports.