@feasting – I believe that walnut oil has helped my hair grow faster and thicker. I bought a shampoo containing walnut oil that was supposed to help it grow, and I have noticed a dramatic difference.
Before I started using the shampoo, my hair grew maybe half an inch a month or less. Now, it seems to be growing at twice that rate. I have gone from having shoulder-length hair to having nearly waist-length hair in under a year.
I think that the walnut oil is somehow making my hair stronger, so it breaks less. The fact that it helps get rid of junk on my scalp means that nothing is clogging the follicles, so the hair can grow out more easily.