What Hair Says

Millimeter by millimeter, your hair is building a record of your diet. As hair strands are built from amino acids that come from your food, they preserve the chemical traces of the protein in that food. It’s a strong enough record to show whether you prefer veggie burgers or double bacon cheeseburgers.

A study led by U researchers finds that this record reveals a divergence in diet according to socioeconomic status (SES). Lower-SES areas display higher proportions of protein coming from cornfed animals. It’s a way, the authors write, to assess a community’s diet and their health risks. The study is published in Proceedings of the National Academy of Sciences.

“This information can be used to quantify dietary trends in ways that surveys cannot capture,” says Distinguished Professor Jim Ehleringer, of the U’s School of Biological Sciences. To collect samples, the researchers went—where else?—to barbershops and hair salons in 65 cities across the United States and 29 ZIP codes in the Salt Lake Valley. Barbers and salon owners were supportive, Ehleringer says. “They would let us go to the trash bin and pull out a handful or two of hair, which we then sorted into identifiable clusters representing individuals.” All together, they collected samples representing nearly 700 people.

Surprisingly, carbon isotopes in hair correlated with the price of the haircut at the sampling location. And researchers went a step further. Using driver’s license data to calculate trends in body mass index for particular ZIP codes, the authors found that the isotope ratios also correlated with obesity rates. This, they write, draws potential connections between diet, SES, and health.