Nails that chip and crack—every woman has been there. The truth is, no matter how fabulous that pricey manicure might be, malnourished nails still need more serious TLC from the inside out. The reason? Nails are made of keratin, which means they need protein so they don’t become thin and brittle (which is why crash diets wreak havoc on your manicure).

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Luckily you can easily strengthen your nail health with biotin, a B vitamin used for decades to strengthen horse hooves. In one small study, women with brittle nails who took a daily biotin supplement saw a 25 percent increase in nail thickness—now that’s something you won’t find on the salon menu! Just remember, your body doesn’t store biotin naturally. Think: eggs, pork, liver, salmon…your sources for your new beauty vice are endless!

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