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Reply to BN Ames et al

Institute of Medicine
The National Academies
500 Fifth Street, NW
Washington, DC 20001
E-mail: mcginnis{at}nas.edu

Diane F Birt

Iowa State University
Ames, IA

Patsy M Brannon

Cornell University
Ithaca, NY

Raymond J Carroll

Texas A & M University
College Station, TX

Robert D Gibbons

University of Illinois at Chicago
Chicago, IL

William R Hazzard

VA Puget Sound Health Care System
Seattle, WA

Douglas B Kamerow

Georgetown University and RTI International
Washington, DC

Bernard Levin

University of Texas MD Anderson Cancer Center
Houston, TX

James Ntambi

University of Wisconsin–Madison
Madison, WI

Nigel Paneth

Michigan State University
East Lansing, MI

Douglas Rogers

The Cleveland Clinic
Cleveland, OH

Audrey F Saftlas

The University of Iowa College of Public Health
Iowa City, IA

William Vaughan

Consumer's Union
Washington, DC

Dear Sir:

The above letter from Ames et al provides the opportunity for some useful clarification about National Institutes of Health (NIH) State-of-the-Science conferences and about the particular conference in which we participated as panel members. The NIH State-of-the-Science Conference on Multivitamin/Mineral Supplements and Chronic Disease Prevention was convened primarily to reflect on the strength of the available evidence, to identify gaps in the evidence, and to offer recommendations to address those gaps. Ames et al are correct that the planning committee for the conference—as distinct from the panel that authored the conference statement—did restrict the formal evidence review (1) to randomized controlled trials (RCTs). That review, prepared by an Evidence-based Practice Center under contract to the Agency for Healthcare Research and Quality, was a resource used by the panel in its preparations for the conference and in its deliberations. However, at the conference itself, several speakers—including Ames and Stampfer—presented results from important observational studies. These studies were considered in, and also were helpful to, the panel's deliberations.

We agree that there are practical challenges to the conduct of RCTs in any arena, in particular an arena as complex as diet, and we made reference to such limitations in the conference statement. Similarly, we noted both the usefulness and the limitations of observational studies (2). The panel's recommendations focused on measures that would enhance the ability to answer the key conference questions by improving the quality and the quantity of the evidence available, including observational studies, and on measures that would improve the safety and reliability of the products marketed to the American public.

It is important to note that our panel was not charged with asking whether vitamins and minerals play a role in human disease—a topic that occupies much of the letter by Ames et al, and for which observational evidence is indeed central—but, as a State-of-the Science Panel, was charged to reflect on the state of the available evidence for a treatment recommendation on the use of vitamins and minerals in the general population. For treatment decisions, the RCT is the established standard. No better proof of this principle can be found than in the RCTs reviewed in our report, which showed serious harm from vitamin ingestion in certain circumstances.

Hence, on the basis of the evidence and its charge, the panel made no recommendation regarding the use of multivitamin/mineral supplements to prevent chronic disease; it only observed that study results were insufficient to compel a recommendation either for or against their use. We were not charged with, and did not consider, other factors that may prompt such recommendations by other groups or persons.

ACKNOWLEDGMENTS

None of the authors had a personal or financial conflict of interest.

REFERENCES

1. Huang HY, Caballero B, Chang S, et al. Multivitamin/mineral supplements and prevention of chronic disease. Evidence Report/Technology Assessment no. 139 (prepared by The Johns-Hopkins University Evidence-based Practice Center under contract no. 290-02-0018). Rockville, MD: Agency for Healthcare Research and Quality, 2006. (AHRQ Publication no. 06-E012.)
2. National Institutes of Health State-of-the-Science Panel. National Institutes of Health State-of-the-Science Conference Statement: multivitamin/mineral supplements and chronic disease prevention. Am J Clin Nutr 2007;85(suppl):257S–64S.[Free Full Text]

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