A scientific paper published in this week’s Canadian Medical Association Journal recommends adults double their intake of vitamin D, which helps the body absorb calcium. Health Canada suggested in 2002 that adequate daily vitamin D intake is 200 international units, while older adults require a minimum of 400 IUs. New guidelines published in the medical journal recommend daily supplements of 400 to 1,000 IUs for adults under age 50 without conditions affecting vitamin D absorption. Adults over 50, meanwhile, should take between 800 and 2,000 IUs a day.