The truth is stranger than fiction

I've heard rumors that diet, promoted by:
Heart Association - conveniently increases the number of heart patients,
Cancer Association - conveniently increases the number of cancer patients,
Diabetes Association - conveniently increases the number of diabetes patients.

And if one follows all three? Are effects caused by diets
a) overlap,
b) add,
c) multiply,
d) increase exponentially?
(Cancel each other - не предлагать!)