Study: High Doses of Vitamin D May Prevent Cancer

Researchers now say higher levels of vitamin D may be necessary to reduce one's risk of cancer. Scientists at the University of California, San Diego School of Medicine and Creighton University School of Medicine in Omaha just published a new study in the journal Anticancer Research, noting that traditional intakes of the essential vitamin just aren't enough to reach blood levels that can prevent or significantly decrease the risk of breast cancer and several other major diseases.

"We found that daily intakes of vitamin D by adults in the range of 4,000 to 8,000 IU [international units] are needed to maintain blood levels of vitamin D metabolites in the range needed to reduce by about half the risk of several diseases -- breast cancer, colon cancer, multiple sclerosis and type 1 diabetes," said Dr. Cedric Garland, professor of family and preventive medicine at the UC San Diego Moores Cancer Center, in a press release. "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 per day that was needed to defeat rickets in the 20th century."

During the study, researchers surveyed several thousand volunteers who were taking vitamin D supplements with a dosage ranging from 1,000 to 10,000 IU per day. They found those taking the highest amounts of vitamin D were less likely to contract major diseases such as cancer.

Despite these findings, some doctors say just boosting your vitamin D levels aren't enough for disease prevention and in some cases may be dangerous.

Dr. James Spencer, a dermatologist and American Academy of Dermatology board member, says the levels of vitamin D suggested in the study are way too high and that reducing the risk of cancer is not as easy as eating more oranges or taking more vitamin supplements. "Generally, when things are too good to be true, they usually are," Spencer told AOL Health.

Dr. Sophie Balk, attending pediatrician at the Children's Hospital at Montefiore in New York City agrees. "We know that vitamin D is good for muscle health and osteoporosis -- the research shows that," Balk explained to AOL Health. "But the research isn't conclusive about its effects on cancers. We really need more research about these other possible effects because we really can't say for sure."

Both doctors agree the dosage of 4,000 to 8,000 IU could be dangerous. "If you take that amount, over time it could be toxic," warns Balk.

"Very high levels of vitamin D, usually above 10,000 [IUs] per day, are known to cause kidney and tissue damage," adds Spencer.

To get sufficient amounts, but not too much vitamin D, Spencer recommends including salmon, milk, oranges or orange juice, egg yolk and mushrooms in your diet.

Although the sun and its UV rays are the best source of vitamin D, Spencer says there are other harmful results that can stem from too much sunshine, like skin cancer, and doesn't recommend people seek vitamin D through sunbathing.

Balk recommends 400 IU per day of vitamin D for children and adolescents, while Spencer says the recommended dosage for adults is 600 IU per day and 800 IU per day for adults over 70 years old.