Positive beta decay can and does happen, so while this assertion is correct for all intents and purposes, it is not strictly accurate. One of the potassium-40

Positive beta decay can and does happen, so while this assertion is correct for all intents and purposes, it is not strictly accurate. One of the potassium-40 decay paths is the emission of a positron, and this does happen in the human body. Stars with potassium-40 metalicity would see this beta decay as well. "Very rarely (0.001% of events), it decays to 40Ar by emitting a positron (β+) and a neutrino." https://en.wikipedia.org/wiki/Potassium-40 https://en.wikipedia.org/wiki/Potassium-40