The answer depends on who you ask. The National Institutes of Health (NIH) suggests a daily dose of 200 international units (IU) for people age 50 and under, 400 IU for those 51 to 70 and 600 IU for anyone over 70.

Some organizations put those numbers even higher for certain age groups. The American Academy of Pediatrics recommends 400 IU a day for breastfed babies and other children who may not get enough D through their diets. The Canadian Paediatric Society advises that pregnant and breastfeeding women consider taking 2,000 IU daily.

The Canadian Cancer Society suggests that adults get 1,000 IU of vitamin D during the autumn and winter months of low sunlight exposure. The American Cancer Society has no similar recommendation. In general, most experts agree that it's safe for adults to take in up to 2,000 IU a day from a combination of food and supplements and the limit for infants is 1,000 IU.

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