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Use of Dietary Supplements by Military Personnel
2
Recent Survey Findings and Implications for Future Surveys of Dietary Supplement Use
INTRODUCTION
Dietary supplements are widely available through a rapidly expanding market of products that are commonly advertised as being beneficial for health, performance enhancement, and disease prevention. These claims may influence the use of dietary supplements by military personnel, given the importance and frequent evaluation of physical performance and health as criteria to join and remain in the military. Given the large number and wide variety of supplements readily available, as well as a lack of scientific evidence addressing health benefits or safety, it is important to monitor the use of supplements by military personnel. One effective approach to this is the use of surveys with comprehensive data collection (e.g., well-designed questions on patterns of use). Previous reports from the Institute of Medicine (IOM) have recommended monitoring dietary intake and supplement use (IOM, 1999, 2006).
Two national surveys have recently collected data on dietary supplement use, the National Health and Nutrition Examination Survey (NHANES) and the National Health Interview Survey (NHIS), both conducted by the Centers for Disease Control and Prevention’s National Center for Health Statistics (see Gardiner et al. in Appendix B). These data, collected through in-home interviews, are representative of the U.S. population. Although to conduct military surveys might be perceived as duplicative, there is ample justification for such surveys, given the differences in population, settings, and products used.
The specific characteristics of some military subpopulations (e.g.,
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Use of Dietary Supplements by Military Personnel
Rangers, Special Forces) justify the continuation and improvement of data collection from distinct dietary supplement use surveys from military personnel for the following reasons: (1) the higher physical fitness demands of some military subpopulations (e.g., Rangers, Special Forces) compared to those of the general population, (2) the lower proportion of women in these subpopulations, (3) the differences in motivation for using dietary supplements (e.g., meeting military weight standards and improving performance), and (4) differences in military culture and behavior patterns. As an example, the military imposes serious consequences for weight gain and substandard performance, which likely lead to supplement use in the military that differs from that of the civilian population. Data from civilian populations may also not provide an accurate description of the prevalence, patterns of use, and key issues of certain military populations (e.g., Rangers, Special Forces).
In general, survey research uses questionnaires or interviews in relatively large groups of people and, if appropriately planned and conducted, gathers reliable and valid data on various characteristics of the population of interest. The use of survey methodology can be effective to investigate and monitor supplement use in the military. Since it is not feasible to survey everyone, survey data can be collected from a well-defined sample of individuals and, from this, generalized to an entire group (e.g., all military personnel or all Rangers). Challenges in performing surveys include ensuring high response rates, comprehensive data collection, and the validity of the individual responses. The validity of the data from these surveys may be compromised by several factors: incorrect sample selection, unclear terminology (common usage terms versus scientifically defined terms), or survey respondents’ lack of knowledge of and inability to determine total dose of or exposure to supplements or inability to remember their supplement use accurately. A low response rate can lead to a biased sample that does not represent the supplement use of the targeted military population.
The benefits of survey use include having data on the extent of the use of dietary supplement products, changes in patterns of use, and insights on specific health behaviors (e.g., reasons for use, degree of consultation with physician, views on dietary supplements). As also recommended in Chapter 5, an important application of survey data on changes in patterns of use is their utilization as a trigger to initiate a safety review of a specific dietary supplement when there is an initial signal for concern (e.g., because it chemically resembles a hazardous product or there are adverse events associated with its consumption). The outcome of this safety review should be the basis for policy-making decisions by military leadership. A systematic evaluation of patterns of use can therefore be used to develop effective educational messages for military personnel and to formulate health policy. If survey data are representative of the targeted military subpopulation, then
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Use of Dietary Supplements by Military Personnel
the frequency of use can also be used to calculate the reporting proportion (adverse events associated with a particular dietary supplement divided by level of use), an estimate of the occurrence of adverse events compared to the level of use.
When using surveys to track supplement use, it is important to clearly define the term dietary supplement. Published literature often includes various products in the category of dietary supplement that might not conform with the legal definition.1 These include sport drinks, bars, or gels—products not legally qualifying as dietary supplements but which include dietary supplement ingredients in their formulas. For practical purposes, however, it is justifiable to include them in the surveys as dietary supplements. In this report, the committee’s deliberations about dietary supplements also included products that meet the legal definition as well as food products that are commonly perceived as nutritionally enhanced with dietary ingredients, botanicals, or vitamins and minerals (e.g., sports drinks, sports bars). Fortified foods were not included in the report because they are not generally perceived as dietary supplements.
Several surveys (published and unpublished) have been conducted on dietary supplement use by military personnel (Tables 2-1 and 2-2). Most of these surveys have been administered in the U.S. Army, with a focus on Rangers and members of Special Forces. This chapter briefly reviews the questionnaires and findings from the latest unpublished surveys on dietary supplement use conducted among various military groups and makes recommendations to improve various aspects of survey design and administration. A summary of the survey results is shown in Table C-1 (Appendix C). Table 2-1 describes the surveys’ populations and focus. This chapter examines limitations of the data that decrease the value of the survey findings; it also provides recommendations for overcoming these limitations and improving the design of the surveys, including suggestions for the phrasing of specific questions and for collecting additional information. Published data from the civilian and military populations are also reviewed for comparison. For the purposes of this chapter, supplement use will be characterized by the available research (published and unpublished) in three separate general supplement categories: multivitamins, single vitamins/minerals, and ergogenic/health enhancement food supplements, including botanicals. Er-
1
As defined by Congress in the Dietary Supplement Health and Education Act (http://www.fda.gov/opacom/laws/dshea.html#sec3), which became law in 1994, a dietary supplement is a product (other than tobacco) that is intended to supplement the diet; contains one or more dietary ingredients (defined as vitamins, minerals, herbs or other botanicals, amino acids, or other dietary substances for use by man to supplement the diet by increasing the total dietary intake, or concentrates, constituents, metabolites, extracts, or combinations of any of the aforementioned dietary ingredients); is intended to be taken by mouth as a pill, capsule, tablet, or liquid; and is labeled on the front panel as being a dietary supplement.
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Use of Dietary Supplements by Military Personnel
TABLE 2-1 Most Recent Surveys (Unpublished Data), Presented at February 2007 Workshop “Dietary Supplement Intake by Military Personnel”
Reference (see Appendix B)
Study Population and Year of Survey
Gender, Age, and Number of Respondents
Focus and Details of Survey
Sampling Method and Response Rate
Corum
Army Fiscal years 2003 to 2005
Males, n=3,789 (77%)
Females, n=1,146 (23%)
Mean age=25.4 y
Dietary supplement use by soldiers (frequency of use, reason for use, adverse effects, information sources, and purchasing locations), with a focus on education efforts
Center for Health Promotion and Preventive Medicine–Europe health promotion teams administered the questionnaire to soldiers as part of their in-processing at the military base.
Response rate not known.
French
Military (“currently serving in the military, National Guard, or Reserve”) 2005
Adults, 18 + y
n=376
Military vs. nonmilitary supplement use Profile and motivations of military supplement users
Online survey.
Response rate not known.
Jaghab
Army physicians and ancillary care providers
Physicians, n=573
Ancillary, n=614
Survey of Army health care providers on dietary supplement usage, supplement types, usage concerns, educational interventions for soldiers; goal was to develop educational tools for health care providers from these data sets
Electronic survey on Army Medical Department Knowledge Management website. Participants were e-mailed a link to the survey.
Response rate: 15%.
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Reference (see Appendix B)
Study Population and Year of Survey
Gender, Age, and Number of Respondents
Focus and Details of Survey
Sampling Method and Response Rate
Lieberman
General Army Ongoing
Males, n=444
Females, n=40
Average age=Males, 29.5±10.1 y
Females, 28.8±8.2 y
Use of dietary supplements in U.S. Army populations (type and frequency of use, reasons for use, user demographics, supplement knowledge, amount spent on supplements)
A 43-question survey was used for this Army-wide assessment. At each study site, a health care professional administered the questionnaire.
Response rate: 80%.
Rangers 1999
Males, n=768
Average age=23.6 ± 4.3 y
Same as above for general Army
Response rate not known.
Special Forces 2000
Males, n=152
Average age=31.3 ± 6.1 y
Same as above
The surveys were administered in aclassroom setting by U.S. Army Research Institute of Environmental Medicine staff.
Response rate not known.
Army War College (senior-level officers) 1999–2001
Males, n=284
Females, n=31
Average age=Males, 44.0 ± 3.7 y
Females, 44.7 ± 5.1 y
Same as above
This 13-question survey was one of many administered as part of a Health and Fitness Assessment at the Army War College.
Response rate not known.
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Marriott
Active duty military (Army, Navy, Marine Corps, Air Force) 2005
n=16,146 (Army: 3,636; Navy: 4,626; Marine Corps: 3,356; Air Force: 4,627)
Dietary supplement use by active duty military personnel (type of use, frequency of use, reasons for use, information sources); data collected as part of the 2005 DoD Survey of Health Related Behaviors Among Active Duty Military Personnel
Questions were included in the 2005 Department of Defense (DoD) Survey of Health Related Behaviors Among Active Duty Military Personnel. Military liaison officers at each installation coordinated the survey, a 50-minute questionnaire either completed in group sessions or returned by mail.
Response rate: 51.8%.
Thomasos
Air Force 2006
n=11,000
Dietary supplement use by Air Force personnel (frequency of use, amount spent on supplements, where supplements were purchased, reasons for use, adverse effects, information sources)
An electronic link to the survey was sent in an e-mail invitation signed by the U.S. Air Force Surgeon General.
Response rate: 24%.
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Use of Dietary Supplements by Military Personnel
TABLE 2-2 Published Surveys Used to Collect Data on Supplement Use by Military Personnel
Reference
Study Population
Age of Respondents
Focus of Survey
Sampling Method and Response Rate
Arsenault and Kennedy, 1999
U.S. Army Special Forces and Ranger training schools
n=2,215 men
Average age=25 y (18–47 y)
Use of vitamins, minerals, performance or other supplements
Voluntary respondents among trainees entering the Special Forces Assessment and Selection School at Fort Bragg and the Ranger Course at Fort Benning.
Response rate: 99%.
Sheppard et al., 2000
U.S. civilian and military health club users
n=229 (133 military)
Average age=Civilian 33 y
Military 30 y
Use of supplements
A two-page survey was placed in 12 health clubs in eastern Virginia for one month.
Response rate: 40%.
McPherson and Schwenka, 2004
U.S. Army soldiers, retirees, spouses in military hospitals
n=291
Average age=39 y (18–83 y)
Use of complementary and alternative medicine (CAM)
A random, anonymous, self-administered survey on the frequency of use of 18 different CAM therapies.
Response rate: 73%.
McGraw et al., 2000
U.S. Army Rangers
n=367
Average age=22 y
Use of supplements andassociated factors
Response rate not known.
Bovill et al., 2000
U.S. Army Special Forces
n=152 men
Average age=31 y
Use of supplements andnutrition knowledge
Response rate not known.
Bovill et al., 2003
U.S. Army Special Forces (SF) and support soldiers (non-SF)
n=157 males (119 SF, 38 non-SF)
Average age=31 y
Use of supplements andnutrition knowledge
A questionnaire containing 54 items was administered to volunteers.
Response rate: 89%.
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Use of Dietary Supplements by Military Personnel
Deuster et al., 2003
U.S. Army Rangers
n=38
Average age=25 y (18–40 y)
Use of alcohol, tobacco, and supplements; diet and physical activity patterns
This survey was part of another study that examined the effects of creatine on military performance. It included measures of body weight and height, a food frequency questionnaire, a health assessment questionnaire, and a symptoms checklist questionnaire designed to assess side effects that might be associated with supplement use.
Response rate: 100%.
Brasfield, 2004
U.S. Army enlisted active duty
n=874 (750 males, 124 females)
Average age=24.9 y (17–49 y)
Use of supplements and motivation for use; sources of information; adverse events
The 15-question survey on dietary supplement use and demographic information was administered at 16 Army posts in the United States.
Response rate: 64%.
Johnson et al., In press
U.S. Army Rangers
n=294
Average age=23 y
Use of supplements, factors potentially associated: age, participation in competitive or recreational athletics, weight training; sources of information
Members of the 1st Ranger Battalion completed an anonymous, self-reported survey administered by the battalion surgeon.
Response rate: 40%.
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Use of Dietary Supplements by Military Personnel
gogenic dietary supplements are those that may improve performance, remove psychological constraints that affect performance, and increase the speed of recovery from training and competition. The committee did not attempt to analyze the data collected but relied on analyses provided to them; in some instances, the committee requested that further analyses be conducted, and results were provided by military researchers. Likewise, this chapter does not provide an account of the statistical methods used; the reader is referred to excellent publications in this matter (Aday, 1996; Bernard, 1999; Converse and Presser, 1986).
PREVALENCE OF USE OF DIETARY SUPPLEMENTS BY MILITARY PERSONNEL
Overall Use and Behavioral Patterns
This section summarizes the results from surveys (published and unpublished) conducted on dietary supplement use by military personnel (Tables 2-1 and 2-2). Most of these surveys have been administered in the U.S. Army, with a focus on Rangers and members of the Special Forces. The reliability of the survey results depends strongly on the response rate. Therefore, the committee emphasizes the importance of obtaining response rates on the surveys. As Table 2-1 shows, the committee did not obtain the response rate for all surveys. The conclusions from those surveys for which response rate is not available should be drawn with this limitation in mind.
Surveys performed in the general population might not be directly applicable to military surveys because of variation in respondent demographics or differences in the questionnaires themselves. Comparison of the results can nonetheless suggest some differences in the rate of use. Gardiner et al. (2007) (see Appendix B) provides a summary of the NHANES III (1999–2002) and NHIS (2002) data on dietary supplement use for a cohort close in age to military personnel. The NHANES data from 1971–1974, 1976–1980, and 1999–2002 in response to the question, “Have you used or taken any vitamins or other dietary supplements in the last month?” indicate that the rate of dietary supplement use has increased from 23 percent to 37 percent of the U.S. population (see Gardiner et al. in Appendix B; Radimer et al., 2004). Results from NHANES I (1971–1974) showed that the prevalence rate for dietary supplement use in adults was 23 percent; NHANES II (1976–1980), 35 percent; and NHANES III (1999–2002), 37 percent (see Gardiner et al. in Appendix B; Radimer et al., 2004).
In contrast, the 2005 DoD Survey of Health Related Behaviors found that 60 percent of active duty personnel reported using a dietary supplement at least once a week over the previous 12 months (Marriott, 2007).
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In the 2006 survey of active duty Air Force personnel, only 31 percent of respondents had never used a dietary supplement (Thomasos, 2007), and data published by Arsenault and Kennedy (1999) show that 85 percent of those entering Special Forces and Ranger training reported current or previous use of dietary supplements, and 64 percent reported current usage.
The patterns of dietary supplement use among athletes might be expected to be similar to those of military populations. A review of 51 studies found that among athletes participating in various sports, the overall mean prevalence of supplement use was 46 percent, and most studies reported over half the athletes used vitamins and minerals (ranging from 6 to 100 percent). Larger studies, however, found lower prevalence levels. They also found that patterns of supplement use varied by sport, with weight lifters and bodybuilders consuming the most supplements. Elite athletes were also found to use supplements more than high school and college athletes, and women used them more often than men. Only 32 of the 51 studies provided information about the types of supplements used. The most frequently used supplements, in descending order, were multivitamins/multiminerals, vitamin C, iron, B-complex vitamins, vitamin E, calcium, and vitamin A (Sobal and Marquart, 1994).
Lieberman and colleagues (2007) reported the Army-wide usage in ranges of number of supplements used per week (one or two; three or four; and five or more). Those figures showed that 30–36 percent reported using one to two different supplements per week. Among males, 12–14 percent reported using five or more supplements per week compared to 18–23 percent of females; among elite units, 41–45 percent of Special Forces and Rangers reported using one to two different supplements per week and 7–15 percent reported using more than five supplements (Lieberman et al., 2007).
Multivitamin/Multimineral Supplement Use
Vitamin and mineral supplements are often used in combination by athletes as ergogenic aids. The composition of products with vitamin and mineral combinations varies; this chapter refers to this range of supplement products as multivitamins/multiminerals (MV/MMs). National surveys report that 18–26 percent of Americans routinely take MV/MMs (see Gardiner et al. in Appendix B; French, 2007; Kaufman, 2007). The usage of MV/MM supplements by military personnel varies from 23 to 45 percent (Lieberman et al., 2007; Marriott, 2007). In a 2005 survey conducted by French (2007), 18 percent of civilians reported using MV/MMs as the only supplement versus 23 percent of those serving on active duty, in the National Guard, or in the Reserves. This contrasts with the 45 percent of active duty service members reporting such use in the 2005 DoD Survey of
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Health Related Behaviors (Marriott, 2007), a difference perhaps reflecting a higher use of dietary supplements among active duty personnel compared to those in the National Guard or Reserves, although they might also be on active duty. Various smaller surveys suggest a similar level of usage among active duty military personnel. In the ongoing Army-wide survey, 30 percent of male respondents reported using MV/MM supplements (Lieberman et al., 2007). Among active duty Army personnel assigned to Europe from 2003 to 2005, 33.8 percent reported using them (Corum, 2007). Another survey found that 39 percent of active duty senior Army officers attending the U.S. Army War College in 1999–2001 used MV/MMs (Lieberman et al., 2007). Within the subpopulations of special interest—active duty Rangers and Special Forces—23 and 32 percent, respectively, were routinely taking MV/MMs (Lieberman et al., 2007).
Although perhaps a less definitive source because it requires users to have reported to a physician, 13 percent of 573 Army physicians surveyed indicated that their patients reported using MV/MM supplements and 20 percent of 614 ancillary health care personnel surveyed indicated that their patients reported using MV/MM supplements (Jaghab, 2007).
The available survey data also report usage of individual vitamin and mineral supplements (see Table 2-3); however, only one set of survey data (personal communication, Sonya Corum, U.S. Army Training and Doctrine Command, April 10, 2007) was analyzed for use of MV/MM supplements concurrent with the use of single-nutrient supplements. The single nutrients
TABLE 2-3 Percentage Ranges of Respondents Using Individual Nutrient Supplements (from military and civilian surveys)
Type of Supplement
Military Population (%)
Civilian Population (%)
Unspecified Gender
Male
Female
Unspecified Gender
Antioxidants (unspecified)
21
6–14
23
Vitamin E
6–9
6–22
8–32
2–20
Vitamin C
24
11–17
13–29
7
Vitamin A/Beta-carotene
13
5
16
Calcium
6–19
5–6
15–32
3–26
Vitamin B Complex
8
6
13
1–14
Vitamin D
3–5
5
8
3–8
Vitamin B6
12
10
Iron
14
10
2
Folate
13
Magnesium
13
Potassium
12
SOURCE: Data extracted from Table C-1, Appendix C.
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Provide response options to determine reasons for use of dietary supplements
Select the reasons that you use supplements:
promote general health
reduce fatigue
lose weight
prevent illness
Select the reasons that you use supplements:
promote general health (health is defined as …)
reduce fatigue
lose weight
prevent illness
other: _______ (please explain)
Include appropriate options that are consistent with respondents’ actual experiences. May be necessary to add a response such as “Other: ____ (please explain).” Response options may be obtained from open questions in preliminary interviews or pretests of the survey.
Determine whether supplement users experience adverse events when using a specific dietary supplement
Current surveys do not ask for this information.
During the time that you were using (insert supplement name here), did you experience any of the following symptoms:
shortness of breath
sleeplessness
heart palpitations
seizures
other: _________
Response options may be composed of symptoms that are reported in civilian populations, reported through surveillance methods such as MedWatch, or obtained from open questions in preliminary interviews or pretests of the survey.
Determine whether supplement users perceive benefits when using a specific dietary supplement
Current surveys do not ask for this information.
During the time that you were using (insert supplement name here), did you experience any of the following:
better job performance
increased alertness
delayed fatigue
diminished fatigue
weight loss
other: __________
Response options may be obtained from product labels (i.e., health claims made by manufacturer), open questions in preliminary interviews, or pretests of the survey.
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Objective of Question/Response
Original Question
Improved Question
Considerations
Determine circumstances of supplement use
Current surveys do not ask for this information.
Under what circumstances do you take dietary supplements (circle all that apply)?
all the time
only during deployments
only when not deployed
when need to do my job better
before performance evaluations
other: __________
Why do you take dietary supplements?
improve job performance
increase alertness
delay fatigue
diminish fatigue
weight loss
other: ___________
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Use of Dietary Supplements by Military Personnel
provided to respondents, simple words can be misinterpreted, which may compromise the validity of a survey. The committee reviewed some questionnaires that used ambiguous terms such as energy and health, which consumers might define differently. If left undefined, interpretation of results by analysts might be difficult. Other examples include terms such as antioxidants, multivitamins/multiminerals, or anabolic supplements. Antioxidants might be understood as referring to vitamins and minerals, botanicals, or some combination of both. Sports drinks, sports bars, and protein powders are highly variable in their composition and may contain any combination of vitamins, minerals, caffeine, botanicals, or other ingredients.
The committee recommends that decisions be made early in the planning stage about the appropriateness, wording, and order of questions. Ambiguous terms such as health and antioxidants should be clearly defined. To the extent possible, if ambiguous terms are necessary, they should be used in a consistent manner. To help ensure the use of accurate, clear dietary supplement terminology as well as with interpretation of data, a pharmacognosist or similar expert with in-depth knowledge of botanical and bioactive substance sources and nomenclature should be included as a member of the survey design team or as a consultant.
Ingredient Identification and Total Dosage
Questions pertaining to product dosage, composition, and frequency of use are difficult for respondents to answer. This information, however, is critical to identify signals of harm or benefit. Unfortunately, dietary supplement surveys rarely capture dosage or intake details, as questionnaires do not include entries for the number of capsules taken, weight of the product consumed, or the concentration of the active ingredients. Survey questions to establish use and determine frequency vary, as shown in Table 2-7. More attention is needed to improve accuracy in data on supplements used and quantities taken.
To complicate the exposure question, many foods and medications can contribute significantly to the total consumption of a particular substance, a factor that has not been adressed in the military dietary supplement questionnaires reviewed. This might be the case for vitamins and minerals, for example, as well as other bioactive substances such as caffeine, for which the dietary intake from several sources must be included in order to determine potential impact on military personnel. Given the broad range in caffeine content in products in the market, this is a challenging task, as shown by a recent publication that analyzed products sold in various delivery forms and found that taking the amount of product recommended on the label resulted in intake of amounts of caffeine ranging from 1 to 820 mg/day (Andrews et al., 2007). One survey (see Lieberman et al. in Appendix B)
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TABLE 2-7 Examples of Questions Used in Military Surveys to Characterize Frequency of Use of Dietary Supplements
Corum (2007)
Thomasos (2007)
Marriott (2007)
Estimate how often you use each of the following vitamin and mineral supplements:
Rarely/never
1–2 times per week
3–4 times per week
5 times per week or more
Do you use or have you used any type of dietary supplements?
I have never used dietary supplements.
I have in the past, but I’m not currently using dietary supplements.
I am currently using dietary supplements.
In the past 12 months, how often did you take any of the following supplements? (Note: only a few examples of each category are listed.)
Two or more times a day
Once a day
Every other day
Once a week
Once a month
Never in the past 12 months
Estimate how often you use(d) each of the following individual vitamin supplements (pills, tablets, gel caps, etc.):
Never
Rarely
1–2 times a week
3–4 times a week
5 times a week or more
In the past 12 months, what were your reasons for taking the following supplements?
During the past 12 months, did you let any of the following conventional medical professionals know about your use of dietary supplements?
reviewed included an assessment of caffeine intake from dietary sources as well as from supplements, but the results were not available at the time of this publication. In summary, acquiring data on prevalence of use is a first step in determining the extent of dietary supplement use by military personnel; however, total dose/exposure data (e.g., from dietary supplements, food, and medication sources) is necessary to determine whether military personnel are exposed to hazardous levels of a particular dietary supplement.
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Lieberman et al. (2007) (Army War College)
Lieberman et al. (2007) (Rangers)
Lieberman et al. (2007) (Special Forces)
Have you taken dietary supplements over the past year?
Yes
No
Have you used creatine during the past 3 months?
Yes
No
Based on the past 6 months, use the table to estimate your use of each of the following supplements. Please fill in one circle for each item, then record the reason for the use and side effects.
Do you fairly regularly (once a week or more often) take any nutritional supplements?
Yes
No
Use the table to estimate your use of each of the following vitamin and mineral supplements during the past year. Please fill in one circle for each item for estimated use and then record the reason(s) for using the supplement. Do not fill out multivitamin/multimineral information under the single-item section.
How frequently did you use creatine?
Seldom (less that once per week)
Occasionally (1–3 times per week)
Frequently (3–6 times per week)
Daily
How much creatine do you consume during the loading phase?
How much creatine do you consume during the maintenance phase?
What was your reason for using creatine?
Increase muscle mass, strength, and/or power
As an energy source
Promote general health
Physician directed
Other
The committee recommends that dietary supplement surveys be complemented with questions about intake from dietary sources (foods and beverages) as well as from pills or powders. This was also supported by the IOM Committee on Mineral Requirements for Military Personnel (IOM, 2006). Special attention needs to be paid to the changing ingredients and amounts in military rations, and future determinations of total dosage and exposure should also incorporate emerging vehicles of dietary supplement ingredient delivery, such as lotions, patches, swabs, and intradermal routes.
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If it is not feasible to collect data on total dose, it is important to collect descriptive data on the supplements being taken and the frequency and timing of their use.
The validity of survey responses is also compromised when the respondents are not fully aware of the ingredients of the dietary supplement product they are consuming. This lack of knowledge was evident in one ongoing Army-wide survey in which only 16.7 percent of respondents reported knowing all the ingredients in their supplements, and 9.3 percent of those taking supplements were unable to identify any of their ingredients (see Lieberman et al. in Appendix B). The majority reported knowledge of some or most of the ingredients. Some questionnaires to the general population (see Gardiner et al. in Appendix B; Kaufman, 2007) expanded this question to request that the subjects bring in containers to have the product ingredients verified, but the majority of the surveys were based on self-reporting, when verification of ingredients was unlikely. These figures demonstrate that the difficulty in acquiring dosage data on specific ingredients originates not only from the questionnaire design but also from poor consumer knowledge and lack of label accuracy. One feasible approach to address the challenge of obtaining accurate ingredient information from survey respondents would be to record detailed information about the product name and usage. The emphasis in product information collection should be on obtaining a comprehensive list and quantities of the products used so that the ingredients can be identified later. As Kaufman (2007) observes (Appendix B), when questionnaires are self-administered, as was the case with the ones reviewed, there is no control over the quality of the information received. Data quality is also easily compromised when obtaining information about dosage. Because there are many approaches to obtaining dosage information, such as open-ended questions or collection of product containers from users, it is important to establish an unbiased, practical approach to gather this information. One approach is to provide instructions on how to record product names, ingredients, and quantities.
Frequency of Use
Although none of the surveys of military populations was designed to obtain dose information, some surveys ask questions regarding frequency of use (e.g., “Are you taking it five or more times per week?”). However, the number of pills or doses per day or the amount of active component per dose was not requested. With the amount of active substance in products varying substantially, it is critical that survey respondents note the amount from the product label (though it should be noted that product labels can also be inaccurate [Andrews et al., 2007]).
In an effort to define a true “user” of supplements, the committee rec-
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ommends that future surveys assess the time period of use more accurately. This would allow for consistency and clarification of prevalence of use of dietary supplements. For example, supplement use might be characterized as episodic (e.g., for short-term weight management), long-term (e.g., most of adult life), short-term (e.g., before a physical assessment), current (recently began regular use), past, or never (Table 2-6). When respondents are properly characterized by usage categories, analyses can be conducted by subgroups of users of interest (e.g., those who use only sports bars or gels) who are subsequently classified by types of dietary supplements and doses.
As mentioned above, questions on frequency should be expanded to specify the period of time and circumstances surrounding the use of a product (e.g., respondent reports used creatine once a day from December to March while deployed).
Association Between Adverse Effects and Dietary Supplement Consumed
The committee recommends enhancement of questions intended to assess associations between consumption of dietary supplements and adverse events. For example, given the common use of caffeinated products in the military and their potential synergistic effects with other stimulants, there is a need to better characterize total intake of caffeine. Several surveys included self-reported (with no adjudication) adverse effects perceived to be attributable to dietary supplements. In-depth probing about adverse events or outcomes (heart palpitations, headaches, etc.) thought to be associated with supplements should be added to the surveys. These questions are especially relevant when conducting surveys in special subpopulations, such as Rangers and Special Forces, with heightened risks and higher dietary supplement usage.
As with the data on frequency of use, questions on adverse events should be linked to information about the environment and conditions in which respondents consume the specific dietary supplement (e.g., soldiers might be taking creatine only before deployment or in between sustained missions). Questions on adverse events and beneficial outcomes should be posed prior to questions on dietary supplement use to minimize the potential for biases in responses.
Demographic Factors
Differences between U.S. military personnel and the general population (e.g., service members have higher socioeconomic status and education, different age distribution, a higher minority representation, and different levels of stress) are substantial enough to require specific military surveillance.
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Available survey data on supplement use by military personnel give important clues about such use; however, they are limited in their ability to allow assessment of prevalence of use and differences in use by demographic factors across multiple studies. Surveys conducted to date do not collect this information consistently; even demographic data (e.g., age, rank, geographic area, organizational unit) collected varies among surveys. A consistent method of collecting and analyzing data by demographic characteristics would allow for a comprehensive, comparable description of dietary supplement use in various populations and across time.
Additional Questions
Questions on health and performance The committee recommends the collection of data on the association of dietary supplement use with health and performance outcomes. Data should be linked to information about the environment and conditions in which respondents consume the specific dietary supplement.
Such data would provide evidence of whether the expectations of benefit are being met under the real-life circumstances of the U.S. military. In addition, these questions help determine whether there are differences in outcomes for individuals with healthy lifestyle patterns versus those who use supplements to counter unhealthy behaviors such as smoking, drinking alcohol to excess, and eating a poor-quality diet. Such analyses may be possible if the DoD links dietary intake to dietary supplement intake. Although one survey collected self-reported Army Physical Fitness Test (APFT) results and would therefore allow correlation between dietary supplement use and APFT scores, the data to evaluate the impact of confounding factors (e.g., training regimen) are not available. Data on possible confounders are needed in the analyses of relationships between health outcomes and dietary supplement intake. Potential confounders (i.e., variables that are related to both supplement use and the health outcome of interest but are not in the causal pathway between these two variables) should be considered prior to creating surveys so that they are included in the questionnaire; it may be helpful to consult with an epidemiologist for assistance with determining confounders a priori.
Questions on effectiveness of communication The committee recommends that questions about sources of information on dietary supplements that military personnel consult be added to questionnaires as these would help determine the most effective methods to disseminate accurate information. Once strategies to disseminate information are implemented, survey questions to measure the level of outreach and effectiveness of the information strategy will also be needed.
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Administration Stage: Recommendations for Data Collection
In the survey administration stage, respondents are recruited, survey data are collected by interviewers or self-report, and nonrespondents are followed up. Each survey should be pretested. Follow-up efforts may be necessary to ensure an adequate response rate. During this stage, data should also be inspected for systematic biases in response patterns and efforts made to adjust the participant demographics or account for bias in the data analysis stage.
Presurvey a Few Individuals
To validate the survey, the committee recommends that it be pretested on a small number of persons with characteristics similar to the target group of respondents. These data should also be inspected for systematic biases in response patterns. Statistical expertise should be sought prior to survey administration to prevent biases in the questions or the demographics of participants.
Verify Self-Reported Data in a Subpopulation
A choice must be made between a self-reported or personal interview survey, and the questionnaire should be designed accordingly. When validated, self-reported questionnaires provide higher quality data if designed as highly structured surveys because they minimize biases caused by misinterpretation of questions. Unstructured surveys (using open-ended questions) work better when interviews are conducted; however, they require administration by trained personnel and entail complex data analysis, resulting in higher expenses than structured surveys. Although a personal interview may be more informative than self-reported surveys, responses can be influenced by the manner, tone, and opinion of the interviewer. Thus, while personal interviews offer better survey compliance and in-depth information, interviewer training and quality control are key elements to minimize potential sources of data bias.
Surveys will likely be administered more often with self-reported questionnaires than with personal interviews due to cost considerations. Self-reported surveys present the following limitations: (1) lower response rates; (2) a higher rate of incomplete or inaccurate responses; and (3) a need for simpler, structured designs to elicit reliable responses. The committee recommends the application of strategies to overcome these limitations, which will assist with interpreting self-reported data and revising the questionnaires and, ultimately, help improve self-reported data. One strategy consists of conducting personal interviews with a smaller group of individu-
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als, and correlating these results with self-reported data. These personal interviews allow for more controlled resposes and ensure higher accuracy and data quality. For example, to verify responses related to ingredient accuracy, this subgroup could be asked to bring in the bottles/containers of the products consumed. Lack of statistical power limits comparisons, so statistical power calculations should be conducted to ensure sufficient ability to relate findings from this group to those of the targeted military population. Another strategy to verify responses on use patterns is to compare survey results to sales data from military bases, considering both the types of products that are being purchased and the ingredients in those products.
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