Why Oh-So-Healthful Walnuts Sometimes Get a Bath

Q. I know YOU Docs are big fans of nuts, especially walnuts (I think you rate them the best nuts), but I've just heard that walnut shells are bleached before they’re sent to market. Is this true? If so, is it dangerous? Does it damage the healthy nuts inside?
-- Lavece, Turkey

A. Great "who knew" question! Now we all do, after some digging. In, uh, a nutshell, you heard right. For more than 50 years, walnuts that are sold to you still tucked inside their rock-hard shells are first given a bath in a dilute bleaching solution before they're sent to market. It cleans and disinfects the outer shells.

The active ingredient is sodium hypochlorite, a salt that, when dissolved in water, turns into chlorine bleach, a disinfectant. Yep, it's the same stuff used in laundry bleach, just in a different concentration. Large quantities of this sodium-based bleach are also used in processing fruits, vegetables, mushrooms, beef, pork, maple syrup, and fish.

For walnuts, the cleaning process is simple and quick: The outside of the shells is washed with a dilute solution of bleach and water, then rinsed several times, dried, and packaged. That's it. The process doesn't affect the nuts at all. We're about to munch a few -- 13, to be exact. Here's why.

Although all nuts are good for you, walnuts have this secret weapon.