Researchers at the University of California, San Diego School of Medicine and Creighton University School of Medicine in Omaha have reported that people taking vitamin D to protect against breast cancer and other major diseases will need to take much more than healthexperts originally thought.
While these levels are higher than traditional intakes, they are largely in a range deemed safe for daily use in a December 2010 report from the National Academy of Sciences Institute of Medicine.
Cedric Garland, DrPH, professor of family and preventive medicine at UC San Diego Moores Cancer Center said scientists found it could take as much as 4000 to 8000 international units (IU) of vitamin D daily to reduce the risk of diseases like breast cancer, colon cancer, multiple sclerosis, and type 1 diabetes.
"I was surprised to find that the intakes required to maintain vitamin D status for disease prevention were so high -- much higher than the minimal intake of vitamin D of 400 IU/day that was needed to defeat rickets in the 20th century," said Garland.
No surprise
Not all researchers were surprised by these findings, however.
"I was not surprised by this. This result was what our dose-response studies predicted, but it took a study such as this, of people leading their everyday lives, to confirm it," said Robert P. Heaney, MD, of Creighton University, a biomedical scientist who has studied vitamin D need for several decades.
The UCSD study reports on a survey of several thousand volunteers who were taking vitamin D supplements in the dosage range from 1000 to 10,000 IU/day. Blood studies were conducted to determine the level of 25-vitamin D, the form in which almost all vitamin D circulates in the blood.
"Most scientists who are actively working with vitamin D now believe that 40 to 60 ng/ml is the appropriate target concentration of 25-vitamin D in the blood for preventing the major vitamin D-deficiency related diseases, and have joined in a letter on this topic," said Garland.
Unfortunately, Garland notes, according a recent National Health and Nutrition Examination Survey, only 10 percent of the US population has levels in this range -- mostly people who work outside.
Larger doses
Interest in larger doses was spurred in December of last year, when a National Academy of Sciences Institute of Medicine committee identified 4000 IU/day of vitamin D as safe for every day use by adults and children nine years and older, with intakes in the range of 1000-3000 IU/day for infants and children through age eight years old.
While the IOM committee states that 4000 IU/day is a safe dosage, the recommended minimum daily intake is only 600 IU/day.
"Now that the results of this study are in, it will become common for almost every adult to take 4000 IU/day," said Garland. "This is comfortably under the 10,000 IU/day that the IOM Committee Report considers as the lower limit of risk, and the benefits are substantial."
He added people who may not respond well to high doses of vitamin D should discuss their nutrient needs with their family doctor.
"Now is the time for virtually everyone to take more vitamin D to help prevent some major types of cancer, several other serious illnesses, and fractures," said Heaney.
The findings are published February 21 in the journal Anticancer Research.
