I grilled Dr. Gross on vitamins for hair. While he's skeptical about the clinical data that's out there, he does have a favorite supplement. "There's one thing I love to recommend for hair, especially in the wintertime," says Gross. "It's called Super GLA, and it promotes better overall hair and skin health." He's seen it help everything from brittle hair to eczema — and he takes it himself, which is always a good sign. The supplement is packed with linoleic acid, as well as other essential fatty acids that your body cannot make.

Celebrity hairstylist Danilo says that many of his clients have had success with Viviscal. When I told him I was nervous about it, he said, "It's basically seaweed! What's there to worry about?" And he's right; the primary ingredient is AminoMar, a marine protein complex. It also contains Biotin, Iron, Zinc, and other vitamins that are beneficial to hair. I have a bunch of beauty editor friends who've tried it and all of them thought their hair grew faster — but a few did complain about oily scalp. Also, it can take up to six months for Viviscal to work, so patience is necessary.

Biotin is a water-soluble version of Vitamin B, and it's one of the most popular hair growth vitamins out there — although the research isn't solid. People who experience hair loss (alopecia) are often deficient in biotin, and it's also necessary for cell growth throughout the body. However, a study conducted by the University of Maryland Medical Center found that a surplus of Biotin may not do much your hair and nails. So Biotin supplements may only make a difference if you're deficient. In addition to supplement form, biotin can be found in nuts, eggs, and leafy greens — and that's how I plan to up my intake.

Nutrafol for Women, $88, is specifically aimed at fighting hair loss. It helps balance stress hormones (you can end up with excessive shedding when they're out of wack), and it has ingredients like hyaluronic acid and marine collagen to nurture each hair follicle. Add to that the fact that it has 15 patented ingredients and seriously impressive clinical results, and you've got one home run of a hair vitamin.

Keranique recently did a survey that found the number of women struggling with hair loss is up 50 percent in the last 10 years. The Keranique Daily Essentials, $49, has biotin, beta-carotine and a procollagen blend to encourage hair to grow thicker and fuller.