"Astronaut Koichi Wakata didn't change underwear for a month."

"Wakata’s special clothing range was designed ... by the Japanese space agency, JAXA, and is known as J-Wear. Made of cotton and polyester with a silver coating that gives it its special properties, it also includes socks, T-shirts, trousers and leggings."

I don't know what your days-old underpants are coated with, but Wakata's are coated with silver!