Natural Remedies for Gray Hair

I was astonished to find my 16 year old son had not 1 but over 23 grey hairs . On speaking to my Asian neighbour , she advised me to massage him daily before bed generously with mustard oil (available very cheaply from asian shops ).Then wash his hair in he morning . After two weeks not a single grey hair ! I tried the same on my self over 40 and over half of my head is grey .So far in one week there' is a marked decrease in the number of grey hairs.