Introduction

The relationship between occupation and various health-related behaviors has not been an area of extensive investigation. One common self-initiated health-related behavior is consumption of dietary supplements (DS). Dietary supplement use by the United States (U.S.) adult population has steadily risen over the past 20 years [1–2]. National surveys of civilians have shown that 48–53% of adults regularly use DS and overall approximately 64–69% of adults consume DS at least annually [1–4]. Studies of specific occupational subgroups, including military and athletic populations, suggest DS use is more prevalent among individuals who engage in greater amounts of physical activity [5–10] or believe they can gain an advantage in sport or work performance by using DS to modify their body weight and composition [5–10]. Military personnel, like athletes, report greater use of DS products that are marketed to increase fitness and performance such as protein powders and combination products which they believe will help them meet the demands of their occupation [11–13].

The U.S. Coast Guard (USCG) is a military service and is legally defined as an “Armed Force” entity of the United States. Armed Forces personnel regularly engage in physically and mentally demanding tasks [14]. The USCG is responsible for maritime safety and security. The USCG has multiple missions and is also a law enforcement agency. Its personnel can carry firearms, make arrests, and perform law enforcement duties as designated by the Secretary of Homeland Security [15]. In peacetime, the USCG is under the authority of the Department of Homeland Security; in wartime, the USCG is directed by the U.S. Navy [15]. USCG personnel are required to adhere to a variety of regulations like other military services. For example, USCG personnel are required to meet regulations for fitness and body weight standards to remain in service and be eligible for promotion [16,17].

Coast Guardsmen are engaged in a wide-variety of occupational duties. Many of these occupational specialties require substantial physical activity, and USCG personnel may use DS to help meet these demands. For example, they man ships and aircraft and serve as maritime communication and intelligence specialists and experts in weapon systems. Specialty roles include electronic and information system specialists, machinery technicians, damage controlmen and survival technicians. Personnel with administrative and scientific duties provide food and health services, conduct marine science research and provide public affairs services [14,15].

To optimize operational physiological and psychological fitness, the USCG has implemented policies that encourage service members to seek guidance from medical personnel prior to self-administration of DS [18]. Education regarding the effects of DS use and their potential impact on fitness and readiness is also provided to USCG personnel in an attempt to enhance compliance with this policy [18]. Armed Forces personnel, including the USCG, are included in defense health surveillance studies [19], but not in national health surveillance studies, such as the National Health and Nutrition and Examination Survey (NHANES), that monitor the use of DS by the U.S. civilian population [1–4,6]. Given the policies regarding DS implemented by the USCG and the considerable diversity in culture and behavior patterns of each Armed Forces subpopulation, a description of prevalence and patterns of DS use by this population may provide information on various factors that are associated with DS use [19].

This study assessed use of DS, sport nutrition products (drinks, bars and gels) and meal replacement beverages, and reasons for the use of these products by USCG personnel. Furthermore, associations with demographic and lifestyle factors, including sex, age, rank, occupational specialization, marital status, tobacco use, aerobic exercise and participation in strength training were assessed. In addition, we compared use patterns and types of DS consumed by USCG personnel to patterns of DS use by military personnel and the civilian population.

Methods

Survey

Prior to administering the anonymous survey (Dietary Supplement and Caffeine Intake Survey of U.S. Coast Guard Active Duty Personnel), participants were briefed regarding its contents and appropriate procedures for completing all questions. The survey instrument utilized in the present study was previously developed at the U.S. Army Research Institute of Environmental Medicine for studies related to supplement use by Army Soldiers and was modified in conjunction with USCG staff to reflect population differences. The survey consists of 43 items and included questions on type of DS used, frequency of use (never, 1 time/mo, 1 time/wk, >1 time/wk and daily), reasons for use (general health, enhance performance, improve endurance, increase muscular strength, weight loss, unsure or other) and money spent on DS. Ninety-two individual supplements were listed in the survey including 55 general supplements such as multivitamins, individual vitamins and minerals, combination antioxidants and 37 specific-named products. Selection of branded DS for inclusion was based on then-current patterns of DS purchases at Armed Forces exchange systems and General Nutrition Center stores on or near military installations.

Prior to data analyses, individual supplement and supplement types were grouped into the following categories: multivitamin and multimineral, individual vitamins and minerals, protein/amino acid supplements, combination products, herbal supplements, purported steroid analogs and other based on the definitions provided in Table 1. This is a standardized taxonomy similar to that used in national surveys such as NHANES [12]. Participants were also asked about the use of sports drinks, bars or gels, and meal replacement beverages based on previous reports indicating they are frequently used by military personnel [12]. These nutritional products were categorized separately as they are not regulated as DS as specified by the Dietary Supplement Health and Education Act (DSHEA) of 1994. The survey also collected information on demographic and lifestyle factors including age, sex, body mass index (BMI), education, occupation, marital status, tobacco use and participation in aerobic and strength training exercise. An individual’s occupational specialization was categorized as: 1) operational, which includes jobs such as fireman, damage controlman, maritime law enforcement specialist; 2) support, which includes jobs such as health service technician, food service specialist, electronics technician; and 3) officer, which is a supervisory position.

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Table 1. Dietary supplement categories as defined in Dietary Supplement and Caffeine Intake Survey of U.S. Coast Guard Active Duty Personnel.

https://doi.org/10.1371/journal.pone.0133006.t001

Data Analyses

Completed surveys were scanned using ScanTools Plus with ScanFlex (version 6.301; Scantron Corporation, Eagan, MN) and data imported into Statistical Package for the Social Sciences (SPSS) (version 20.0; SPSS Inc, Chicago, IL) for conversion to a Statistical Analysis System (SAS) (version 9.2; SAS Institute, Cary, NC) data file for all statistical analyses. Data were weighted prior to analysis to obtain a sample representative of the overall Coast Guard composition as of November 2011 (Table 2). Weights were based on demographic data, including sex, age and rank, obtained from the Defense Manpower Data Center (www.dmdc.osd.mil/) and the characteristics of survey respondents. Survey weightings were calculated by dividing the number of Coast Guard personnel in each cell who were eligible to take the survey by the number in the cell that completed the survey.

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Table 2. Prevalence (% ± SE) of reported use of any dietary supplement (DS), sports drink, sports bar/gel, and meal replacement beverage among U.S. Coast Guard Active Duty Personnel.

https://doi.org/10.1371/journal.pone.0133006.t002

Wald chi-square tests were used to test for significant differences in percentages among multiple characteristic levels using the “surveyfreq” procedures (Table 3). Analysis of variance (ANOVA) using the “surveymeans” procedure was used to test mean values across multiple characteristic levels. A p-value of <0.05 was considered statistically significant. Statistical comparisons conducted were pre-planned and restricted to comparisons conducted in a previous study of DS use by other military personnel [12].

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Table 3. Prevalence (% ± SE) of reported use of number and type dietary supplements (DS) at least once per week or more often over the six months prior to the survey by demographic and lifestyle characteristics among Active Duty U.S. Coast Guard Personnel¹.

https://doi.org/10.1371/journal.pone.0133006.t003

Analyses are presented as frequency (or mean) ± standard error. Standard errors were estimated using a Taylor series linearization method that incorporated sampling weights. Logistic regression models using the “surveylogistic” procedure examined relationships between measures of DS use and demographic characteristics of Coast Guard personnel including age, sex, education, marital status, BMI, tobacco use, as well as aerobic exercise duration and strength training (Table 4). Models were adjusted for sex, age and rank. Categorical levels of rank and education variables were highly related, therefore, analyses were performed on models adjusted only for age, sex, and rank. Results of multivariate logistic regression are presented as odds ratios (OR) and 95% confidence intervals (CIs). The use of the survey procedures allowed for sample weights to be applied to all analyses.

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Table 4. Association of number and type of dietary supplement (DS) use at least once per week over the previous six months by supplement ingredients and amount spent per month on DS with selected demographic and lifestyle characteristics.

https://doi.org/10.1371/journal.pone.0133006.t004

Results

Reasons for DS Use

Reasons for the use of DS are reported in Table 5. Among supplement users, the most common reason cited for DS use was to promote general health (55%), followed by increasing muscle strength (24%), providing more energy (20%), enhancing performance (18%) or ‘other’ (16%). Users of multivitamins and minerals, individual vitamins and minerals, herbals and ‘other’ primarily reported using these DS classes to promote general health. However, users of protein and amino acid DS primarily used this class of DS to increase muscular strength (21%). Participants reporting the use of combination products stated they did so to enhance performance (10%).

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Table 5. Reported reasons for using any dietary supplement (DS) and specific dietary supplement types at least once per week over the six months prior to the survey (prevalence % ± SE).

https://doi.org/10.1371/journal.pone.0133006.t005

Discussion

The present study is the first to report prevalence of DS use of the USCG. Self-reported use of DS was greater among USCG personnel (70%) than has previously been cited for Army, Air Force, Navy and Marine (55%-60%) personnel [21]. Regular use by USCG was higher than reported for adult civilians (54%); however, annual use (64–69%) was similar [1–4]. Prevalence of using 1–2 DS per week was 32% among USCG personnel which is similar to earlier reports of active duty Soldiers and civilians [2–4, 12]. However, 18% of respondents used of 5 or more DS per week which is greater than previously reported for active duty Soldiers (12%) [12]. Patterns of DS use among USCG were comparable to previous reports of active duty Soldiers with multivitamins and minerals and protein and amino acid supplement use being the most common forms of DS consumed; however, overall use prevalence by USCG personnel was higher than Soldiers, especially of protein and amino acid DS. Dietary supplement use was associated with occupational specialization requiring increased levels of energy expenditure and participation in aerobic exercise and strength training but was not associated with age, education, BMI or tobacco use as previously reported for other military and civilian populations [6,12]. This study indicates that individuals engaged in an occupation requiring physical fitness and regular assessment of physical fitness will consume greater amounts of DS than the general population. Other populations, such as police, firefighters, construction and mining trades may also have unique patterns of DS consumption and their use of DS should be investigated.

The greater use of DS by USCG personnel when compared to active duty Soldiers is attributable to a higher use prevalence of multivitamin and minerals, protein and amino acids, individual vitamins and minerals and combination products. The prevalence of purported steroid analogs and herbal use was similar when USCG personnel are compared to Army personnel [12]. Longitudinal data from the general civilian population has identified an increased use of specific DS classes over time, including protein and amino acid supplements, fish oils and herbals [2,6], and recent studies of recreational athletes and regular gym users also report an increased use of protein and amino acids supplements and combination products [22, 23]. Use of protein supplements is much higher in both the USCG (33%) and Army population (19%) than the general civilian population (1%) [2,12]. Differences between USCG and Army personnel in use of certain categories of DS may be a function of their overall increasing popularity within the American culture and the influence of our respondent’s work environment (e.g. high levels of physical activity, body weight and composition requirements). Reported use of herbals by USCG personnel was similar to the civilian population (9% vs. 8%); however reasons for herbal use were not similar between populations [2]. Approximately 27% of civilians report the use of herbals to improve health [2], whereas only 5% of USCG respondents reported use of herbal DS for health purposes. In addition, herbal supplement use is associated in the civilian population with being uninsured, using more medications and specific health-related concerns (e.g. heart health or lowering cholesterol) [2]. Thus, use of herbal DS for health purposes may be less prevalent within the USCG population as a result of overall better health, participating in more physical labor, being insured and being a younger, healthier population given the age, weight and fitness requirements necessary for active duty.

In addition to assessing DS use, we also assessed use of sport nutrition products by USCG personnel. Almost twenty-five percent of respondents reported the use of sports drinks which is similar to the findings of Lieberman et al. [12] for the Soldier population (23%). Use of sports bars or gels and meal replacement beverages was substantially higher by USCG respondents, 12% vs. 6% and 10% vs. 3%, respectively. Similar to Soldiers [6], use of these products increased when greater amounts of aerobic exercise were performed each week and use was also associated with participation in strength training. Therefore, greater use of sports nutrition products by USCG personnel is associated with an increased number participating in high levels of physical activity. This relationship is also relevant to DS use, as the increased prevalence of multivitamin and mineral, protein and amino acid and combination DS use was higher in those reporting greater participation in aerobic and strength training exercise; thus, increased use may be a direct function of the active lifestyles lead by USCG personnel. Our findings are further supported by the civilian literature which reports a greater use of specific DS classes and sport nutrition products among more health-oriented and physically active individuals [4, 22–23].

The most common reason cited for overall DS use by the USCG population was to improve general health. This finding is consistent with reasons for DS use cited by civilian and military populations [2, 12]. Multivitamins and minerals and individual vitamin and mineral DS are the two primary DS classes that USCG, military and civilian populations report they use to improve overall health [2, 12]. Similar to other studies of uniformed personnel, protein supplements and combination products were reported to be used by USCG personnel to promote gains in muscle strength, increase endurance, provide more energy and facilitate weight loss. Reasons for the use of protein supplements and combination products by USCG personnel were similar to those reported by athletes [24] but differed from civilians who cite the primary reason for use of PS as improving overall health [2]. Civilians do not generally report the use of DS for reasons related to physical performance or weight modification [2]. Such differences between the general civilian population and USCG personnel are most likely a function of physical activity levels and occupational requirements, such as the mandatory weight and fitness standards of the USCG.

Unlike other studies of uniformed personnel, we observed greater use of DS by certain occupational subgroups, specifically heavy use of protein and amino acid supplements and combination products by operational personnel. Operational personnel of the USCG are responsible for performing high tempo operations on a daily basis such as security boarding of suspicious vessels, search and rescue missions, military tactical operations, and drug interdiction. These tasks can result in a high level of energy expenditure and thus may promote increased use of DS by occupations which believe DS sustain physical and mental energy levels, an observation that is consistent with the reasons USCG personnel cite for use of protein and amino acid DS and combination products.

On average, USCG personnel spent $40 every 3 months on DS, and almost 29% spent $50 or more per month which is similar to expenditures reported by active duty Soldiers (12). Females, older respondents, married personnel and officers in the USCG were less likely to spend $50 or more per month. Similar to the Army population, sex, age, rank, participation in aerobic exercise of long durations and strength training influenced the level of financial expenditure by USCG personnel on DS and the number of supplements taken each week.

Education efforts by the USCG include course instruction on the use of dietary supplements and the unknown health effects of some DS classes [16]; however, since many USCG service members use substantial quantities of DS, especially combination products, further efforts to educate personnel are warranted. While scientific evidence for the use of vitamin and mineral DS to address nutritional deficiencies is readily available [25, 26], there is limited evidence regarding the safety and efficacy of many ingredients contained in combination product and herbal DS [27–28]. As such, increased awareness of ingredients in DS that may be harmful is necessary to protect the health and well-being of service members. Educational tools, such as the Operation Supplement Safety website, provided by the DoD Human Performance Resource Center [29], could provide USCG personnel guidance regarding potentially harmful DS. Since many service members wish to improve their performance and obtain health benefits associated with increased physical fitness, further efforts are necessary to provide personnel with information on how to obtain such benefits using performance training and nutrition.

Limitations & Strengths

While the present descriptive analyses provide insight into patterns and prevalence of DS use by a unique arm of the Armed Forces, limitations of this cross-sectional study design must be acknowledged. First, the prevalence and patterns of DS use by this group was determined in a convenience sample that was not random or stratified potentially leading to bias because participants willing to complete surveys or have a strong belief regarding DS use or health could be more likely to participate. In addition, as with all surveys involving self-report, the present study may also reflect recall bias since the participants were requested to recall DS used over the prior 6 months. Despite these limitations, the present study has multiple strengths including the use of a large sample, application of survey weights, and use of multivariate analyses to arrive at conclusions.

Conclusion

In summary, seventy percent of USCG personnel reported regular use of DS which is greater than previously reported for military services and US civilians. The greater prevalence of DS use is attributable to increased use of multivitamins and minerals, protein and amino acid supplements, individual vitamins and minerals and combination products, and is associated with participation in high volumes of aerobic exercise and strength training. These findings highlight the need for randomized clinical trials to evaluate the efficacy and safety of many currently available DS on the market. Given limited FDA regulation of DS and the unknown health effects of consuming ergogenic and botanical ingredients contained in some DS, USCG personnel should be advised to seek guidance from healthcare personnel before initiating DS use. All Armed Forces personnel would benefit from further guidance on the risks and benefits of DS use.

Acknowledgments

The authors would like to thank the United States Coast Guard personnel who participated in this study and the health performance staff for assisting with data collection. The views, opinions, and findings in this report are those of the authors and should not be construed as an official Department of Defense or Army position, policy, or decision, unless so designated by other official documentation. Citations of commercial organizations and trade names in this report do not constitute an official Department of the Army endorsement or approval of the products or services of these organizations. The investigators have adhered to the policies for protection of human subjects as prescribed in DOD Instruction 3216.02 and the research was conducted in adherence with the provisions of 32 CFR Part 219.