It’s the dose that makes the poison. The idea behind this phrase is that a substance only becomes toxic when you ingest enough of it. Therefore, anything less than this toxic dose threshold is considered safe to consume.
Swiss born physician and alchemist Paracelsus made this observation in the 1500s, and the idea has more or less persisted up through today. Chinese medicine used low doses of poisonous substances as medicine for millennia, knowing that what might kill in excess could be therapeutic in lower doses. Regulators use the dose threshold concept to identify the relative toxicity of industrial chemicals, naturally occurring poisons, and pharmaceutical drugs
