Vitamin D2 and vitamin D3 are the forms of vitamin D most important to human health, according to the Mayo Clinic. Vitamin D2 is manufactured by plants, while vitamin D3 is manufactured in the skin when it's exposed to the sun.
Population in families living in Washtenaw County ; Total Population: 238,069; Population Under 18 years: 70,878; Population 18 years and over: 167,191
Calhoun County is a county in the U.S. state of Michigan. As of the 2010 census, the population was 136,146. The county seat is Marshall. The county was established on October 19, 1829 and named after John C. Calhoun, who was at the time Vice President under Andrew Jackson, making it one of Michigan's Cabinet counties.