I believe these are man-made Diseases(at least contributed heavily). As the Environment gets unnatural or should I say polluted, garbage, plastic, everything you know created in last 100 year by the man.
All this must have some consequences on the Human Body as a whole. Now the Science cannot answer the Question why the body fight with itself.
For instance, I believe there was not so much a Sugar consumption 100 years ago as today....We have today more Health issues related to Sugar consumption.
I'm sure there are issues related to junk food or processed food with all the chemicals you never know inside.
It's a kind of Interaction between man and Environment(Nature). We do harm(knowingly or not) and we get something back and have to find a solution for it.
It's like a kind of Race and it will never end I think....there will be always some health related trouble We & Science have to deal with.
What you think?