A report about cockroach milk being considered a superfood prompted Elon Musk to express his disgust. Elon Musk's one-word reaction to a report on cockroach milk has sparked conversations online. The unusual substance, produced by Pacific beetle cockroaches, has attracted scientific interest. Elon Musk reacted with a one-word comment, "Gross", after the New York Post reported on cockroach milk and its potential as a future superfood.