To dramatically cut the risk of breast cancer and multiple sclerosis, people need to consume far more vitamin D than researchers expected, according to a new study.

A daily vitamin D intake of 4,000 to 8,000 international units (IU) is needed for adults to maintain blood levels high enough to halve their risks of breast and colon cancers, multiple sclerosis and Type 1 diabetes, said study researcher Cedric Garland, professor of family and preventive medicine at University of California, San Diego.

However, only about 10 percent of the U.S. population has vitamin D levels in this range, according to the National Health and Nutrition Examination Survey.

The minimum daily amount of vitamin D recommended for adults is 600 IU, according to the Institute of Medicine.

"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 [a] day that was needed to defeat rickets in the 20th century," Garland said in a statement.

The study was published Feb. 21 in the journal Anticancer Research.

Decrease in disease risk

The researchers surveyed several thousand volunteers taking vitamin D supplements ranging from 1,000 to 10,000 IU a day. They also measured the participants' levels of the compound 25-vitamin D, which is the form of almost all vitamin D found in the blood, the study said.

People who took 4,000 to 8,000 IU of vitamin D a day were about half as likely to have vitamin D deficiency-related diseases as those whose intake was less than 4,000 IU, the study said.

To help prevent breast and colon cancers, Type 1 diabetes and multiple sclerosis, people should have 40 to 60 nanograms of 25-vitamin D per milliliter of blood, the study said.

However, most people's levels are far below that range. The average level in a U.S. adult's blood was 24 nanograms per milliliter, said a 2009 study in the journal Archives of Internal Medicine.

Vitamin D intake

A vitamin D intake of 4,000 IU a day is safe for adults and children 9 years and older, according to the Institute of Medicine. A vitamin D intake of 1,000 to 3,000 IU a day is safe for infants and kids ages 8 and younger.

"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," study researcher Dr. Robert Heaney, of the Creighton University School of Medicine in Omaha, said in a statement.

Vitamin D can be attained through natural sunlight , dairy products, fish and vitamin-fortified foods, according to the University of Washington.

Pass it on: A daily intake of 4,000 to 8,000 international units of vitamin D can halve the risk of developing certain cancers, multiple sclerosis and Type 1 diabetes.

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