Take a closer look at how various factors can increase risk for vitamin D deficiency, which can subsequently lead to a deficiency disease. Watch the animation to see how the body makes vitamin D by converting the cholesterol in your skin to the active form of vitamin D. Use this animation to answer the questions that follow regarding the mechanisms underlying vitamin D deficiency.

Life expectancy in the united states is (76.4 for men and 81.1 for women). life expectancy is not the same as healthy life expectancy. healthy life expectancy is the number of years a person is expected to live in this number is obtained by subtracting years spent in poor health from overall life expectancy. the world health organization (who) calculates healthy life expectancy in 194 countries. the united states ranks twenty-ninth in the world using this measurement, with an average of of healthy life expectancy. singapore ranks number one (76 years), and japan is number two (75 years).