Temper that Vitamin D and Calcium Intake
Not getting enough vitamin D? No time or afraid to get rays? Warning: higher dosing isn't necessary and might possibly be harmful! IOW, it's no panacea.
The IOM panel, which included Harvard Women’s Health Watch advisory board member Dr. JoAnn Manson, reviewed nearly 1,000 studies, representing more than 15 years of scientific findings. The panel decided that vitamin D’s importance for bone building and the prevention of bone disease was well substantiated, but the evidence for its role in preventing other conditions was inadequate to justify its use at much higher doses. Thus, the Recommended Dietary Allowance (RDA) for vitamin D was set on the basis of bone health alone: 600 IU a day for everyone through age 70 and 800 IU a day for those 71 and older. (In setting these standards, the panel assumed no access to vitamin D through sun exposure.)
To reach its decision, the panel evaluated data correlating bone disease with blood levels of 25-hydroxyvitamin D (25OHD), which is made from food and supplements and, in the skin, in response to sunlight. They determined that a blood level of 20 nanograms per milliliter (ng/ml) was adequate to prevent bone disease in at least 97.5% of the population. Citing a lack of standardized lab methods and reporting, the panel also cast doubt on the widespread practice of vitamin D testing. Many labs currently specify 30 to 70 ng/ml as the normal range; that would make most of the North American population vitamin D–deficient.
Finally, the panel set 4,000 IU per day as the Tolerable Upper Intake Level, or the amount above which there is risk for adverse events. The report found no evidence of toxicity at doses less than 10,000 IU, but the risk for certain chronic conditions, including heart disease and pancreatic cancer, begins to rise when daily intake passes 4,000 IU.
The panelists also reviewed the data on calcium and concluded that scientific research supported the existing recommendation of 1,000 milligrams (mg) per day for women 50 and under and 1,200 mg per day for those over 50. Surprisingly, nutritional surveys revealed that many postmenopausal women are taking too much calcium through supplements, and the incidence of kidney stones is increasing as a result.
What to do. Read your food labels before you hit the supplements. The RDAs represent a total from food and supplements. It’s all but impossible to overdose from dietary sources, and you may be surprised at how much calcium and vitamin D you can get from dairy products and fish.
For the time being, postpone vitamin D testing. The results may be misleading until standards are revised, and your insurance might not cover it.
Don’t panic if you’ve been taking 1,000 to 2,000 IU of vitamin D a day. There is no evidence of harm at those levels.
If you’re 65 or over, consider joining the VITAL study (vitamin D aand omega A-3 trial), which is testing vitamin D for the prevention of cancer, cardiovascular disease, and other conditions (www.vitalstudy.org, 800-388-3963, toll-free). The IOM didn’t shut the door on vitamin D; it just called for more conclusive evidence from randomized controlled trials — like VITAL. You could help provide it."
Harvard Women’s Health Watch Vol.18; No. 6