Background: Dietary supplements are regularly used by at least half of the American population, yet the health benefits of these agents are unclear. Objective: A systematic review to determine the benefits and risks of dietary supplements in Westernized societies. Data Sources: MEDLINE, Embase, Cochrane Register of Controlled Trials and citation review of relevant articles. Study Selection: Randomized, placebo-controlled clinical trials in non-pregnant Westernized adults that evaluated clinical outcomes of nutritional supplements. Data Extraction: Data were abstracted on study design, study size, study setting, patient population, dietary intervention and clinical outcomes. The outcome of each study was classified as non-beneficial, beneficial or harmful according to whether theend-point(s) of interest reached statistical significance. Data Synthesis: Sixty-three studies met the criteria for our systematic review. No benefit was recorded in 45 studies, with 10 of these showing a trend towards harm and with two showing a trend towards benefit. Four studies reported harm with increased cancer deaths (n=2) and increased fractures (n=2). Two studies reported both a harmful as well as a beneficial outcome. A beneficial outcome was reported in 12 studies; 6 which studied vitamin D and three which investigated omega-3 fatty acids. While a benefit was reported in one study each which investigated Vitamin E, folic acid and Ginkgo biloba this benefit was not confirmed by larger and more adequately powered studies. Conclusions: With the possible exceptions of Vitamin D and omega-3 fatty acids there is no data to support the widespread use of dietary supplements in Westernized populations; indeed, many of these supplements may be harmful.
Online Dietary Supplement Resources
With the vast amount of information and resources on the Internet, it’s easy for individuals to look up information on dietary supplements. The difficulty for consumers and health professionals is identifying Web sites that provide reliable information. This article provides registered dietitians (RDs) and dietetic technicians, registered (DTRs) with examples of federal Web sites that contain accurate, reliable, and unbiased information on dietary supplements and examples of commercial Web sites that currently provide useful information on dietary supplements.
In 1994 the Dietary Supplement Health and Education Act (DSHEA) created a new category of foods called dietary supplements and defined them for regulatory purposes (1). DSHEA also fueled the growth of the dietary supplement industry that has increased more than five-fold since its passage; from around $4 billion in 1994 to 23.7 billion in 2008 (2). Currently, an estimated 4% of all dietary supplement sales are made through the Internet (2). Internet marketing and sales are in part responsible for the growth and development of the dietary supplement industry over the past decade. National survey data collected from 2003 to 2006 indicate that 53% of US adults report dietary supplement use (3). Consumers can easily find information about dietary supplement over the Internet and on social networking sites such as Twitter and Facebook, but its veracity is sometimes questionable. This is of concern because with the high prevalence of dietary supplement use, and easy access to information on the Internet, it is not surprising that many individuals may circumvent health professionals as a source of information and go directly to the Web for help.
GENERAL INFORMATION SITES
The Figure provides a quick reference list of US government Web sites discussed in this paper that provide free access to facts and authoritative information on dietary supplements. One of the most reliable sources is the National Institutes of Health (NIH), and, in particular, the Office of Dietary Supplements (ODS). The ODS Web site has five sections:
Health Information: Provides authoritative fact sheets on dietary supplement ingredients, nutrient recommendations, information on dietary supplement use and safety, and some database resources. These fact sheets can be used to quickly educate the reader on specific dietary supplements, vitamins, minerals, herbals, and botanicals.
News, Events & Media Resources: Provides links to conferences and workshops as well as announcements and news releases on dietary supplement related matters.
About ODS: Describes the ODS office and its staff.
Research & Training Programs: Describes the ODS programs and offers links to research resources and research sponsored by ODS.
Funding: Notes grant opportunities for those interested in conducting dietary supplement research.
The ODS “Health Information” section also contains databases where dietitians and others can search for published information on dietary supplements, research in progress, and databases on dietary supplement composition. To stay current on ODS activities, individuals can subscribe to the ODS newsletter/e-mail list either online from the ODS home page or by sending an e-mail (with a blank subject line and the following text in the message body: “subscribe NIH-ODS-L your name) to vog.hin.tsil@vrestsil. For example, John Smith would subscribe as follows: “subscribe NIH-ODS-L John Smith.”
Each of the NIH’s 26 institutes and centers has independent Web sites, which can be accessed from the NIH home page. For example, the National Center for Complementary and Alternative Medicine Web site is an excellent resource for facts on botanicals. Herbs at a Glance and Using Dietary Supplements Wisely are two free publications that can be downloaded. The National Cancer Institute Web site provides information sources on dietary supplements and cancer.
There are also non-federally operated Web sites that provide information on dietary supplements. The federal government does not endorse these Web sites, but some practitioners and researchers report that they have found them useful. These include: 1) ConsumerLab.com, which conducts independent testing of products and reports the findings (www.consumerlab.com); 2) Natural Standard Professional Database, which evaluates and reports the quality of available evidence (www.naturalstandard.com); 3) Natural Medicines Comprehensive Database (www.naturaldatabase.com); and 4) Quackwatch: Your Guide to Quackery, Health Fraud, and Intelligent Decisions (www.quackwatch.com). These Web sites charge for their services and/or ask for a donation to support their work.
INFORMATION ON BRANDED AND GENERIC PRODUCTS
MedlinePlus: Drugs, Supplements, and Herbal Information, a service of the National Library of Medicine and NIH, is a comprehensive and free government-funded source for facts on generic and brand name drugs; including special precautions about their use. The site also provides links to related sites for herbs and dietary supplements.
Other sites that provide this information on brand and generic products are commercial and fee-based. Although the federal government does not endorse these, they may be helpful. They include the Facts & Comparisons Web site from Wolters Kluwer Health Clinical Solutions (www.factsandcomparisons.com); Medscape from WebMD (http://search.medscape.com/drug-reference-search); and Drugs & Supplements from the Physicians’ Desk Reference (www.pdrhealth.com/drugs/drugs-index.aspx).
INFORMATION ON THE COMPOSITION OF DIETARY SUPPLEMENTS
Access to all searchable databases on dietary supplements that are government funded and maintained can be found under “Health Information” on the ODS Web site. They are briefly described as follows:
The Dietary Supplement Ingredient Database (DSID)
The USDA/NIH’s DSID contains research-based information on the composition of dietary supplements. DSID provides statistical estimates of selected ingredients, based on chemical analysis, for dietary supplement products collected from various US market channels, compared with label-reported ingredient levels. The first release of the DSID data (DSID-1, April 2009) provides access to predicted nutrient amounts and variability parameters based on regression analysis estimates of 18 nutrients for a range of labeled levels. The estimates are derived from the analysis of representative adult multivitamin/mineral supplements (MVM) consumed in the United States. These estimates will improve assessment of total nutrient intakes from foods and dietary supplements and will enhance researchers’ abilities to investigate relationships between dietary supplement intakes and health indicators. DSID-1 features include data files, a research summary, and an MVM calculator. The MVM calculator is an interactive Web-based research tool that can be used along with DSID-1 files to obtain analytically-derived data estimates for nutrients in generic forms of adult MVMs in order to create and store electronic files for the purpose of combining this information with food data for total nutrient intake estimates.
In contrast to the DSID, other databases provide the composition of dietary supplements as declared by the dietary supplement manufacturer on product labels. Examples of such databases hosted on government Web sites include:
National Library of Medicine Dietary Supplements Labels Database includes information from the labels of over 4,000 dietary supplement products in the marketplace.
National Health and Nutrition Examination Survey (NHANES) Dietary Supplements Label Database from the National Center for Health Statistics (NCHS) of the Centers for Disease Control and Prevention. NCHS collects data on a representative sample of the US population in order to monitor and assess the health and nutritional status of adults and children. One component of NHANES collects information from participants on their use of dietary supplements. Dietary supplement names are recorded during the interview and then product labels are obtained by NCHS nutritionists and the information from those product labels such as serving size, amount, ingredients, and ingredient amounts are then recorded in an internal database. This database, along with information on reported participants’ usage patterns of all dietary supplements have been publicly released in 2-year cycles since 1999 and are available on the NHANES Web site. Currently, NCHS is updating and creating a comprehensive dietary supplement label database to encompass all dietary supplements and non-prescription antacids containing calcium and/or magnesium reported by survey participants from 1999-2008. This database is anticipated to be publicly released in the summer of 2010 and will include more than 7,000 dietary supplements and non-prescription antacids that have been reported by NHANES participants.
The Interactive DRI for Healthcare Professionals tool launched in November 2009, can be used to calculate daily nutrient recommendations for dietary planning based on the Dietary Reference Intakes (DRIs). When an individual’s age, sex, height, weight, and physical activity levels are entered, the appropriate nutrient recommendations are provided. The DRIs represent the most current scientific knowledge on nutrient needs and are developed by the Food and Nutrition Board of the Institute of Medicine. This DRI tool can help an RD evaluate how actual nutrient intakes compare with recommendations, using estimates from the US Department of Agriculture food composition database and the NHANES dietary supplement database. Universities and independent, for-profit groups maintain Web-accessible databases on food and dietary supplements. While some, such as the University of Hawaii, maintain these databases solely to support epidemiological research, others, like the University of Minnesota, have commercialized their product. Both of these products have been developed under grants or contracts from the federal government. The Dietary Supplement Assessment Module from the University of Minnesota allows for the automated collection and coding of dietary supplement use in conjunction with its larger dietary assessment program. Information on this system and costs is available from the vendor (www.ncc.umn.edu/news/20070816DSAM.html).
INFORMATION ON DIETARY SUPPLEMENT RESEARCH PROJECTS
Through the ODS Web site, RDs and DTRs can access the Computer Access to Research on Dietary Supplements and the International Bibliographic Information on Dietary Supplements. The Computer Access to Research on Dietary Supplements provides access to information about federally-funded research specific to dietary supplements, compiled from information available from other government sites. The International Bibliographic Information on Dietary Supplements provides access to citations and abstracts from published, international, and scientific literature on dietary supplements.
There is also a link to the Clinical Trials Database, which is a registry of federally and privately supported clinical trials conducted in the United States and worldwide. ClinicalTrials.gov currently contains 82,706 trials sponsored by the NIH, other federal agencies, and private industry. The site provides information about a trial’s purpose, who may participate, locations, and contact phone numbers to obtain more details.
INFORMATION ON REGULATIONS PERTAINING TO DIETARY SUPPLEMENTS
The Food and Drug Administration is responsible for regulating dietary supplement label declarations, while the Federal Trade Commission (FTC) oversees the advertising of dietary supplements. Through the Food and Drug Administration Web site, RDs and DTRs can access product alerts and recalls, regulations governing labeling and claims, and other useful information for consumers and health practitioners. The FTC Web site has several useful downloadable offerings, including Dietary Supplements: An Advertising Guide for Industry and the FTC Enforcement Policy Statement on Food Advertising.
CREDIBILITY OF WEB SITES
Given the growing popularity of the Internet, it is important for health professionals to consider carefully the source of the information presented on the site. Many commercial Web sites containing food and supplement composition data link to a common source and do not contain original information themselves, so there is no guarantee the information they provide is valid.
Many sites are available that provide direction for evaluating the credibility of Web sites. For example, the ODS Web site contains questions and answers on how to evaluate information on the Internet. The Stanford Persuasive Technology Lab at Stanford University (http://credibility.stanford.edu/guidelines/index.html) and The University of California, Berkley (www.lib.berkeley.edu/TeachingLib/Guides/Internet/Evaluate.html) are other sites hosted through universities that provide guidelines for evaluation.
RDs and DTRs will find the federal Web sites listed in the Figure to contain valid and reliable information on dietary supplements. These sites should be used as primary resources and monitored periodically for new launches and updates. RDs and DTRS over the coming years can expect to find expansions to the dietary supplement composition databases and tools to derive intakes from dietary supplements, and how to combine nutrient estimates from foods with dietary supplement to derive estimated total nutrient intakes. These sites also provide information on upcoming conferences and workshops, and access to educational materials that can count toward meeting continuing education requirements. Finally, RDs and DTRs should sign-on to the federal e-mail lists to receive timely updates on these projects and learn about other federal developments in dietary supplements.
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Leila G Saldanha, Office of Dietary Supplements, National Institutes of Health, 5904 Sandbrook Ct, Alexandria, VA 22307.
Johanna T Dwyer, Office of Dietary Supplements, National Institutes of Health, 6100 Executive Blvd MSC 7517, Room 3B01, Bethesda, MD 20892, Phone: 301-496-0048, Fax: 301-480-1845, vog.hin.do@1JreywD..
Karen W Andrews, US Department of Agriculture, Agricultural Research Service, Nutrient Data Laboratory, 10300 Baltimore Avenue, Building 005, Beltsville, MD 20705, Phone: 301-504-0710, Fax: 301-504-0713, email@example.com.
Regan L Bailey, Office of Dietary Supplements, National Institutes of Health, 6100 Executive Blvd MSC 7517, Room 3B01, Bethesda, MD 20892, Phone: 301-496-0187, Fax: 301-480-1845, vog.hin.liam@ryeliab..
Jaime J. Gahche, National Health and Nutrition Examination Survey/Planning Branch, National Center for Health Statistics/CDC, 3311 Toledo Road, Room 4332, Hyattsville, MD 20782, Phone: 301-458-4767, Fax: 301-458-4028, vog.cdc@ehchaGJ..
Constance J Hardy, Center for Food Safety and Applied Nutrition Food and Drug Administration, College Park MD 20740, Phone: 301-436-2375, Fax: 301-436-2636, vog.shh.adf@ydraH.ecnatsnoC.
Joanne M Holden, US Department of Agriculture, Agricultural Research Service, Nutrient Data Laboratory, 10300 Baltimore Avenue, Building 005, Beltsville, MD 20705; Phone: 301-504-0630, Fax: 301-504-0713, firstname.lastname@example.org.
Mary Frances Picciano, Office of Dietary Supplements, National Institutes of Health, 6100 Executive Blvd MSC 7517, Room 3B01, Bethesda, MD 20892-7517, Phone: 301-435-3608, Fax: 301-480-1845, vog.hin.do@FMonaicciP.
Janet M Roseland, US Department of Agriculture, Agricultural Research Service, Nutrient Data Laboratory, 10300 Baltimore Avenue, Building 005, Beltsville, MD 20705, Phone: 301-504-0715, Fax: 301-504-0713, email@example.com.
Paul R. Thomas, Office of Dietary Supplements, National Institutes of Health, 6100 Executive Blvd MSC 7517, Room 3B01, Bethesda, MD 20892, Phone: 301.435.2920, Fax: 301 443-0503, vog.hin.do@luaPsamohT.
Wayne R. Wolf, Food Composition and Methods Development Lab, Room 203C, 10300 Baltimore Avenue, Bldg 161 BARC-East, Beltsville, MD, 20705-2350, Phone: 301-504-8927 ext. 227, Fax: 301-504-8314, vog.adsu.sra@floW.enyaW.
1. Dietary Supplement Health and Education Act of 1994. Oct 25, 1994. Pub L 103-417, 108 STAT. 4235.
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