I've made this schematic chart for Book 2 to depict my broad understanding of the relative contribution of different factors in improving human life expectancy. 

There is now comprehensive proof that WEALTH --> HEALTH. The rich live longer because they have: 

a) more - and more nutritious - food
b) cleaner, bigger and better housing
c) access to clean water and removal of human waste
d) access to clean food and high levels of protection from germs (hygiene)
e) access to the best medicines and medical advances
f) vaccines

STEP 1: BECOME RICH (this applies also to nations)

STEP 2: FOLLOW THE SCIENCE (real science, not the quackery of "public health")