Assertion? That’s who Rabbeinu Bachya quotes. That is the only source earlier than the Beis Yoseph. It is not from Chazal. That’s all.
The fact that it is not on any list of unhealthy foods should be enough to tell you what modern doctors think of it. If you so please, ask your nutritionist, unless you think he’ll laugh at you.
I have nothing against keeping it. I keep it, too. But I don’t worry about it as if it is an actual Sakana. Had it been from the Gemara, or had it originated from our Chachamim I wouldn’t say this. But, once you know where it comes from it doesn’t matter how many times it’ll be quoted or mentioned.
The fact that Rabbeinu Bachya lends Divrei Torah to it and suggests a reason Al Pi Sohd is more of a reason to keep it, but that still does not render it a Sakana.
And if my attitude is to be Mashlich Acharei Gavi opinions of the 14th century doctors, well, I’m sure you know that modern doctors agree with that. They were not known to be very scientific about their assumptions. You know that the Beis Yoseph didn’t make it up, nor did he or any Posek review the data to check the assertion. They merely relayed what was told or written. That doesn’t make it more of a Sakana. Do you really wonder what modern doctors say about it? Now, that’s a bit dishonest.
Here’s another question. Does it cause heart attacks, insomnia, ADHD, hiccups, lyme disease, housemade’s knee, floaters, schizophrenia? The biggest reason to keep it is to listen to the Poskim. Perhaps it’s a Sakana not to listen, but I’m talking about it being Batul Beshishim.