What to Eat, and Avoid, for Amazing Hair and Nails

2. Not all fish are fantastic

While salmon, halibut, and other fatty fish are tasty additions to your diet, other fish can create problems. Fish with high levels of mercury can cause brittle nails and thinning hair. While true mercury poisoning is not common, elevated levels of mercury in the body can create health issues. Eating fish that are prone to collecting mercury multiple times each week may be enough to allow mercury to build up in the body. Fish prone to high mercury levels include fresh tuna, mackerel, and swordfish.