The figures for lactose intolerance, say some researchers, are grossly exaggerated. The difference between the two conditions, we're told, is that maldigesters can still digest some milk products.

In addition, if there is an ample supply of Lactobacilli in the gut, some milk sugar will be broken down even if the lactase enzyme isn't there. But as disturbed gut flora is common in those with digestive difficulties, this doesn't always happen.

!AKathryn Marsden

Adapted from Hotline to Health by Kathryn Marsden (Pan, 1988, £5.99).