The Council for Responsible Nutrition, one of the dietary supplement industry's leading trade associations, in consultation with independent osteoporosis and vitamin A experts, responded to the results of a new study on hip fractures from the Nurses' Health Study (NHS) data by reaffirming that the current Upper Limits (UL) for vitamin A set by the Institute of Medicine (IOM) provide an appropriate safeguard for the general population.
John Cordaro, president and chief executive officer, Council for Responsible Nutrition, concluded, ``The findings of the Nurses' Health Study on hip fractures must be evaluated within the context of the totality of credible science on vitamin A safety.
Vitamin A has long been established as a vitally important human nutrient, essential for growth, immune function, reproduction, and vision, and it may also help reduce the risk of some cancers.
This recent study does not change these facts and does not warrant policy changes.''
CRN's conclusions were grounded in comments from a number of highly respected, independent scientists including Robert P. Heaney, M.D., professor of medicine, Creighton University School of Medicine and renowned osteoporosis expert.
Dr. Heaney referred specifically to a recent study based upon the National Health and Nutrition Examination Survey (NHANES III) data conducted by investigators at the Centers for Disease Control and Prevention (CDC) which found no association between retinyl esters, a marker of high vitamin A intake, and bone density problems.
He asserted, ``I find the vitamin A and bone analyses of NHANES III to be more convincing than the Nurses' Health Study in terms of what can be applied to the population at large.
The Nurses' Health Study is termed an observational study.
An observational study, by its very nature, never provides proof, but, at best, can suggest other studies to see if the association can be found in an independent database.
In this case, the association was not confirmed in the NHANES III data.
Thus, there is not the slightest reason to change existing policy.''
The Nurses' Health Study is an epidemiological (observational) study in which a cohort of nurses is followed over a long period of time, to relate diet and other lifestyle habits to eventual health outcomes.
Of the many studies that have been published on findings from the Nurses' Health Study, the most recent examined vitamin A intake in postmenopausal women.
A statistical relationship between vitamin A and apparent risk of hip fracture was found only in the women not using hormone replacement therapy.
The population observed in this study was not representative of the general population or of postmenopausal women and, therefore, the results cannot be extrapolated to the general population.
``This study cannot serve as the basis for policy on a vitamin A limit because it is contradicted by other powerful studies,'' said John Hathcock, Ph.D., vice president, nutritional and regulatory science, Council for Responsible Nutrition.
``The IOM should continue to evaluate all the scientific evidence and not change its UL of 3,000 mcg, equivalent to 10,000 IU, unless there is a sufficient scientific reason to do so.''
The Council for Responsible Nutrition (CRN), founded in 1973, is a science-based trade association representing more than 100 companies in the dietary supplement industry, including ingredient suppliers and manufacturers.
CRN members adhere to a strong code of ethics, comply with dosage limits and manufacture dietary supplements to high quality standards under good manufacturing practices.