Here is a very recent picture of Nicole Kidman coming home from the gym. I have no advice for this woman, other than to sit down once a day an eat a protein-rich meal. Natural redheads have less hair than blondes or brunettes, and going grey hasn't helped her hair much either.
As you can see from this au naturale shot, she doesn't have much hair to work with. This is why you always see her in wigs and hair pieces. For all the people over the years who didn't believe me, this shot is for you!