Where I come from this was a widely held belief by the end of the 2000's: If you raise a child in an overly sterile environment and/or feed them a very limited diet, they are much more likely to develop a bad immune system and allergies. It was also believed that this idea came from science, but I guess not?

Here's an early preview for the next bombshell of this area. Breastfeeding is extremely beneficial. "Infant formula" should not be the main thing a baby is consuming.

To me it discredits science a lot more when things like this are treated as arcane or brand new knowledge. It's good when we can lock in reasoned beliefs as definite fact, instead of just reasoning which is often incomplete or flat out wrong. But when it's right and people act like this about it, it just makes it look like "scientists" know less about the world than my grandma, and that my grandma would make better calls on national health policy than the people currently in charge. Obviously that's not the case but I wouldn't be unjustified in thinking that during times like this.