Since hair is a nonessential tissue, that means it's the last to have access to any of the nutrients you ingest. The system will take care of what's a priority first, which is cardio and lung function, not the hair. Hair is always at the bottom of the list, so that's why what and how much you eat are so important. Maintaining a well-balanced diet full of protein, iron, zinc, and antioxidant-rich foods, such as berries and leafy green vegetables, and eating regularly will have an effect on hair. Also, there are a host of helpful supplements : Vitamin K and cysteine aid in the production of keratin and melanin (to delay the appearance of grays), while iron, zinc, biotin, and silica supplements can combat thinning.