I'll mention, regarding metformin, that although it's useful for longevity (my father is on it for diabetes and seems well), it can create some significant GI i

I'll mention, regarding metformin, that although it's useful for longevity (my father is on it for diabetes and seems well), it can create some significant GI issues. If your parents are not firmly convinced of the benefits of what you're suggesting, you may encounter resistance because of those issues.