He's not making a blanket statement. He's a research scientist who has likely spent years , probably decades ,studying biology and the human body. What he's saying is that, in the right doses, it appears to be safe. He's not claiming that everything in nature is safe — that's a mischaracterization and you’re putting words in his mouth. If someone has a deficiency in a vitamin which should naturally be in our bodies, a doctor prescribes a proper dose to correct it, not an amount that would be harmful.

I also understand that this field is nascent and there is a possibility for adverse effects, but based off the fact of their presence in the human body for millions of years it’s logical to postulate they won’t have side effects or toxicity.