in april 1998 "nature" reported alleged carcinogenic and teratogenic effects of excessive doses of vitamin c. this was given great prominence in the world's media. the effects were noted in test tube experiments and on only two of the 20 markers of free radical damage to dna. they have not been supported by further evidence from living organisms. almost all mammals manufacture their own vitamin c in amounts equivalent to human doses of thousands of milligrams per day. large amounts of the vitamin are used in orthomolecular medicine and no harmful effects have been observed even in doses of 10,000 mg per day or more.