John A Milner, PhD, Chief of the Nutritional Science Research Group, Division of Cancer Prevention at the National Cancer Institute presented a talk on vitamin D supplementation at the recent meeting of the American Society of Clinical Oncology (ASCO) in Chicago. He stated that current guidelines suggest 400 IU of vitamin D, possibly more for the elderly, up to 600. He also noted that too much vitamin D can be toxic, e.g. 50,000 IU daily for a long time, but that there is probably a safe range between those.
He cited the 2007 data from a Creighton University four-year study of 1179 healthy women aged 59-73, all from rural Nebraska. Subjects took 1400-1500 mg calcium and 1100 IU vitamin D daily, and the study was designed to assess the effect on bone health. In a secondary analysis of the results, researchers found that subjects taking the supplements had almost a 75% reduction in the risk of cancer, all cancers.
Dr Milner noted that the study did not have a "vitamin D only" arm, so there was no way to assess the value of taking vitamin D supplements alone. The NIH is funding further research. Further, he cautioned that other studies have shown that too much vitamin D actually increases the risk of some specific cancers. He also believes that this is a very individual issue, and that additional research will help doctors understand just who might benefit from supplementation and who might not.
I have been taking 1200 mg calcium and 2000 - 5000 IU vitamin D3 (cholecalciferol) daily for several years now. I don't plan to change, but I may have my vitamin D level measured and then see. From his talk, it appeared that the risk of breast cancer and other diseases started to increase as the blood serum concentation of vitamin D reached 60 to 100 nanomoles/L (24 to 40 ng/mL).
This may be the last ASCO post. I'm out of subjects. Back to regular stuff.
Dinner aboard the Amtrak Empire Builder, Chicago to the Twin Cities, slightly blurred by the motion of the train: