Reports of vitamin C raising blood uric-acid levels - or ‘rebound scurvy’ - have proved to be unfounded, as is the supposed increased risk of kidney stones - which, although postulated in theory, have never been found in practice. As a recent review of all the evidence puts it: “Numerous studies of vitamin C supplementation have provided no pattern of evidence to support concerns about safety other than occasional gastrointestinal upset” (Am J Clin Nutr, 2005; 81: 736-45). Neither has anyone yet found a dose above which the vitamin becomes unsafe (Nutr Rev, 1999; 57: 71-7).

Vitamin C boosts iron uptake, so individuals with the genetic iron-overload problem called ‘haemochromatosis’ should take extra vitamin E to counteract the effects of vitamin C.