Your hair is made up of protein—about 95% of it, in fact, comprises the protein keratin. It's quite literally what gives hair its structure; just as protein is critical for building muscle mass, it also strengthens hair and gives it a healthy bounce. That's why experts are quick to recommend a nutritious, balanced diet for healthy, thriving strands, especially one filled with amino acids to provide the building blocks of keratin.
And as you browse the hair care aisle, you may come across products with keratin or bond-building slapped on the label—these protein-infused formulas promise to rebuild broken hair bonds, but (sigh) you can get too much of a good thing.
Here's how to tell if your hair actually has too much protein, a concept known as "protein overload."