Research from the Queensland Institute of Medical Research, in Australia, has found supplemental vitamin D3 reduces the incidence of infection among seniors. More than 600 subjects, ages 60 to 84, were divided into three groups and for one year took either 1,000 international units (IU) a day of vitamin D3, 2,000 IU a day of vitamin D3, or a placebo.

Those given the 2,000 IU of vitamin D3 per day were 28 percent less likely to require antibiotics prescriptions than those taking the placebo. Those older than 70 years were 47 percent less likely to be prescribed antibiotics than the placebo group.