“These are diseases and ailments that we get because our lifestyle and/or environment are unhealthy.”

as it might imply that all those diseases are always caused by lifestyle or environment.

I don’t think she meant it to come off like that, but it seems obvious that some of those diseases at least some of the time (perhaps most of the time!) are not completely avoidable with a healthy lifestyle and environment. My take, though, is that she meant that they are influenced by lifestyle and environment and, therefore, we have some control.

For example, while sunlight doesn’t “cure” depression, getting out in the daylight or using a light therapy box can make a big difference for some people. And while alcohol doesn’t make alcoholics, per se, and abstinence doesn’t cure an alcoholic, taking away temptation will certainly help, especially when you’re talking about preventing things like liver damage.