Hard to tell exactly on this map, but in Japan, most people will want to supplement with Vitamin D during the darker months, such as December and January. It costs almost nothing, and it has no side effects except a balanced immune system and better overall health. Almost all humans nowadays are deficient and many of the top killers can be prevented with Vitamin D.

Cancer sucks but there are cures, especially for skin cancers. You could even treat your skin prophylactically with a cannabis topical (cream or oil). No psychological effects that way, but it would treat/prevent any cancers thinking of starting. I use it for joint pain. Gets in there within seconds, and relieves at least 50% of my pain, letting me get back to life, kids, etc. Don't worry too much about cancer, we can fix that! : p