Walnuts Not to be outdone by the oats, walnuts are one of the most hairfriendly nuts in the category. Not only do walnuts have more omega-6 fatty acids than any other food, but they’re also full of zinc, iron, B vitamins (B1, B6 and B9), and plenty of protein. However, a word of caution, walnuts also contain a small trace of selenium, a mineral known to cause hair loss in people who are selenium-deficient or have way too much in their system. So a handful of nuts over the week should tide you over without much trouble.