GUEST BLOG by David A. Mark
The Institute of Medicine is currently reviewing the Dietary Reference Intake value for vitamin D that last changed in 1997. While a final report is not expected until May 2010, some dietary supplement companies are boosting their dosages now. The increases have implications not only for consumer health but for regulatory action.
The Tolerable Upper Intake Level for vitamin D for adults today is 2,000 International Units per day. The Daily Value is 400 units. Depending on a person’s age, the Adequate Intake is between 200 and 600 units. Those numbers could go higher once the Institute issues its report.
Most people get 100 to 200 units of vitamin D daily from their food. Most multivitamins provide a daily dosage of 400 units. Some manufacturers have begun to offer products with 1,000, 2,000 and even 5,000 units per day. The last is more than double the current upper limit.
Is there a benefit – or a danger — from getting more vitamin D? A growing scientific consensus says that a combination of food, dietary supplements and the typical exposure to sunlight is not sufficient to reach blood levels for ideal health.
While the cumulative evidence supports an increase in the figure for adult intake of vitamin D to perhaps 1,000 units per day or higher, there is not an equivalent body of new evidence sustaining an argument for a safe, higher upper limit.
The identified risk of chronic, high, vitamin D consumption is elevated serum calcium, resulting in inappropriate tissue calcification. The current Daily Recommended Intake text identifies 3,800 units per day as leading to abnormally high serum calcium. The text also says that 2,400 units per day produces an elevated serum average, but still within the normal range. This was a small, short study without evaluation of clinical consequences. Ongoing, massive, multi-year vitamin D clinical trials may detect subtle negative outcomes. Researchers will keep an eye out for harm to kidneys and arteries.
It is reasonable to assume that the Food and Drug Administration is also watching the situation. It would not surprise me if the agency issued warning letters to companies selling vitamin D products containing 2.5 times the current upper level, telling those businesses that their products are potentially unsafe.
FDA action is not the only risk. Recently, the FDA amended the qualified health claim for selenium. Shortly thereafter, the consumer advocacy group Center for Science in the Public Interest filed a complaint with the FDA against Bayer Healthcare, stating that the existing (now superseded) label claim for One A Day Men’s Health Formula overstated the putative prostate cancer health benefit. The Center also said that recent research suggested that selenium supplementation might increase risks for hypertension and diabetes.
The center and other non-government organizations might take the same action against high-dose vitamin D products, potentially creating negative publicity, especially if new research links them to negative health effects. The supplement industry would be wise to prepare for such developments.
David A. Mark, Ph.D., is president of dmark consulting LLC, a science consulting company serving the dietary supplement and functional food industry. Contact him at firstname.lastname@example.org or 978-897-0890.