That's an ongoing problem with herbal supplements generally. There's no good scientific evidence, because nobody has attempted to collect such evidence. Running multiple, properly controlled, double-blind studies of effectiveness and safety, is expensive. Very expensive. And there's little profit in it. So nobody does it. I see an opportunity for universities and perhaps the FDA to do something useful ...
They have tried before to rein in the ‘food supplement’ industry but they, like their Big Pharma bros, spread their donations around to the proper places to make sure the Congress doesn’t pas any such thing.........................