By Kay Quinn, Healthbeat Reporter
St. Louis, MO (KSDK) - Vitamin D has become a popular supplement because of its ability to strengthen bones and the immune system.
On our 8 Ways to Prevent Cancer segment this week, a viewer wants to know if taking 2,000 international units (IU) a day of a version of Vitamin D called "D-3" can prevent breast or other cancers.
"That is a very difficult question first of all," says Dr. Antonella Rastelli, a specialist in breast disease and bone disease at Siteman Cancer Center.
Difficult because while some studies show Vitamin D can lower your risk of certain cancers, other studies show the opposite.
"There is a lot of literature out there showing that lower levels of Vitamin D are associated with higher mortality and possibly cancer," says Dr. Rastelli.
Dr. Rastelli says the body's metabolism of Vitamin D supplements is a complicated process, so she recommends moderation if you're taking it daily.
"We don't know what is the safer upper limit of Vitamin D," says Dr. Rastelli, "so we cannot say 'oh, just take it and go high, high, high.' We just don't have that knowledge yet. For sure there is an epidemic of Vitamin D deficiency and sufficiency. We just have to be moderate in our approach to supplementing it."
If you're taking Vitamin D supplements of any kind, be sure to tell your doctor.
And consider a test to check your levels.
Supplements of Vitamin D-3 tend to accumulate faster in the body than D-2.
Here's how many IU Dr. Rastelli recommends every day.
"One thousand," says Dr. Rastelli. "If you're a little overweight, 2,000 is fine, but always in conjunction with a doctor."