The secret to healthier-looking hair may not be hiding in an expensive bottle. It could be a nutrient your body is simply not getting enough of. Biotin is widely promoted for hair, yet the NIH says there is little evidence that extra biotin improves hair in people who already get enough. Vitamin C has a clear role in collagen production, while zinc is essential but can become harmful when taken in excess. Omega-3 and collagen supplements are also popular, but their benefits should not be overstated. Here are five nutrients worth knowing before adding anything to your routine.