I have always had little to no grey hairs and am into my sixties. I eat a lot of shellfish. I read that zinc intake is related to hair colour and lack of zinc can lead to grey hair, and even more interestingly taking zinc can restore hair colour.
Zinc
In laboratory tests animals fed with a zinc supplement showed signs of more hair growth, as opposed to loss of hair in animals that were deprived of zinc in their feed. It was discovered that there was a change in the hair protein structure when zinc was deficient in the diet.
Severe zinc deficiency in humans has been shown to produce baldness and scalp problems that were reversed when zinc was returned to the diet.
Zinc has also been shown to stop hair turning grey. One doctor taking zinc for a year reversed the grey hairs which returned to their original colour.
Zinc can be depleted by high stress levels. For a good source of zinc, wheat germ is the best, other sources are brewer's yeast, pumpkin seeds, oysters and mussels, shrimps and egg yolks.