There is some evidence that in prematurely greying hair, a deficiency in B vitamins, especially vitamin B12, may be speeding up the natural process of greying. So it' s certainly worth supplementing an all round multivitamin or B complex supplement. But there could be other factors involved. High levels of stress or a big shock have been known to rapidly speed up greying. What is actually happening in these unusual cases is that people lose more of the non-grey hairs, so they appear to have suddenly gone grey. In truth, it takes many months for a hair to go grey. Both stress hormones and melanin, the stuff that colours hair, are derived from the amino acid tyrosine. Theoretically, reducing stress and supplementing tyrosine (1g a day) might help, but there' s no hard evidence. So I would recommend you enjoy your natural, greying hair colour; quite a few women regard it as chic. Or use natural vegetable dyes to hide it, available from healthfood shops.