As far as the sun did that improve your walking distance significantly or decrease post exertional malaise?
Again, I consider a really laid-back tropical beach only one of many - though certainly just as well as important - synergistic factors for my recovery. After years of 'practicing' it, both my walking-disabilty and PEM went into complete remission.
The only more direct and immetiate effect was the remission from a year-long chronic bronchitis. Afterwards diagnosed as COPD stage 1, and asymptomatic since.
PS: actually I really got sick for a whole month the first year, and after 1 1/2 months on the beach. Diarhea, vomiting, chills and fevers for a whole months. Unable to eat anythings than curd. Probably thyphoid fever (stuhl testing), the first fevers in many years.