Researchers have long reported that at least half of American adults are suffering from the deficiency of Vitamin D and speculation has indicated that this deficiency can lead to illnesses from osteoporosis to cancer of the colon and breast. Recently new research has asked whether Vitamin D can avert breast cancer. Earlier studies carried out between the years 1986 and 2000 have highlighted that Vitamin D could protect against cancer. Cedric Garland DrPH of the University of California San Diego in an earlier paper showed that increasing intake of vitamin D can reduce the chance of developing breast cancer by 10% to 50%. He suggested taking at least 1 000 international units (IU) of vitamin D daily to diminish the risk of breast colon and other cancers. In 2008 a Canadian study also showed that vitamin D deficiency often accompanies breast cancer. While some other studies have associated higher vitamin D intake to less likelihood of breast cancer those studies didn't directly test whether vitamin D was helpful in breast cancer prevention. However recently one such trial was prospectively carried out by the Women’s Health Initiative (WHI) on 36 000 women. The study concluded that vitamin D supplements do not affect breast cancer risk. The outcome of the study has been published last month in the Journal of the National Cancer Institute. During the study period half of the women were given 1 000 mg of calcium and 400s IU of vitamin D daily and the rest were given placebo pills. After seven years 528 women who took supplement and 546 women who were on placebo pills developed breast cancer results indicating a lack of efficacy of Vitamin D in cancer prevention. Thus earlier observations from animal and retrospective studies had suggested that the vitamin might prevent the disease were discredited. There is criticism of the dose of the vitamin D supplement used in the trial as Dr. Larry Norton a breast-cancer specialist at Memorial Sloan-Kettering Cancer Center points out that 400 IUs was too low to make a definitive difference. Many nutritionists recommend intake of up to 2 000 IUs daily for adults so the 400 IU dose may have been inadequate for an effect to become evident. Future studies Powel pointed out might compare standard doses of vitamin D with higher doses to establish whether the supplements have any effect on the cancer incidence. On the efficacy of the Vitamin D Dr. Larry Norton concluded by saying although this is a vital study the question of vitamin D's efficacy in breast cancer prevention remains unanswered. These results therefore keep the door open on vitamin D research on breast cancer in future.