Thyroid Therapy or Dysfunction in Athletes: Is it Time to Revisit the Clinical Practice Guidelines?

Recent media have highlighted the controversy surrounding treatment of elite athletes for hypothyroidism. The World Anti-Doping Agency denied a request by the United States Anti-Doping Agency to ban the use of thyroid medication. At present, there is no scientific evidence that thyroid medication has the potential to enhance performance. Clinical practice guidelines are not definitive in regard to what classifies a patient as having hypothyroidism. Thyroid-stimulating hormone and free T4 are recommended to screen for thyroid disease; however, the thyrotropin-releasing hormone stimulation test is still advocated by some for detecting the earliest stages of hypothyroidism. Hypothyroidism has been demonstrated to reduce cardiopulmonary function and result in musculoskeletal symptoms, such as fatigue and muscle stiffness. Symptoms of hypothyroidism, including depression, fatigue, and impaired sleep, are similar to those reported in overtraining. These patients may have hypothalamic-pituitary dysfunction that may complicate interpretation of basal thyroid-stimulating hormone and free T4. To date, no association has been identified between training state and hypothyroidism. Research to more clearly define hypothyroidism using provocative testing, evaluate the potential for thyroid medication to enhance performance, and examine whether training may induce hypothyroidism in athletes is desirable.

Surveillance of the armed forces as a sentinel system for detecting adverse effects of dietary supplements in the general population.

OBJECTIVE: Half the US population takes dietary supplements, but surveillance systems available to regulatory and public health authorities to determine whether specific dietary supplements present a risk are inadequate and numerous severe injuries and deaths have occurred from their consumption. Uniformed military personnel regularly use dietary supplements and are more likely to use potentially dangerous supplements than civilians. Recently, the supplement 1,3-dimethylamylamine (DMAA) was marketed for physical performance-enhancement and weight loss. However, after over 100 reports of illness attributed to DMAA, including six deaths, the Food and Drug Administration issued a warning to cease its sale. DESIGN: When DMAA was legal (2010-2011), we conducted, using convenience samples, supplement surveys of service members and determined prevalence of use and self-reported symptoms of DMAA use. SUBJECTS: We surveyed 4374 armed forces personnel using a standardized dietary supplement survey administered by local health-care professionals. RESULTS: Overall, 11 % of survey respondents used dietary supplements labelled as containing DMAA at least once/week. Regular users were over two times more likely to report tachycardia (P<0·0001), tremors (P<0·0001) and dizziness (P=0·0004), and over three times more likely to report numbness/tingling (P<0·0001) than non-users. CONCLUSIONS: Military services could readily monitor adverse events associated with dietary supplements using electronic surveys and medical records. Since armed forces personnel are much more likely than civilians to use potentially dangerous dietary supplements like DMAA, near real-time surveillance of them using electronic surveys and medical records would provide early warning to regulatory agencies and the medical and public health communities when high-risk dietary supplements are introduced.

Use of the TRH Stimulation Test to Assess Long Term Changes of Thyroid Function in an Olympic Athlete.

This case report presents the utility of the thyroid-releasing hormone (TRH) stimulation test for assessing endocrine disease in athletes. On two occasions, 4 years apart (1992 and 1996), a TRH stimulation test was performed to corroborate clinical symptoms and observation. On the first occasion, the patient's symptoms were not attributed to thyroid disease. He was treated for a sinus infection with amoxicillin/clavulanate 500 mg three times per day for 1 wk. On the second occasion, thyroid disease was confirmed and treatment with 100-µg L-thyroxine was initiated. Baseline screening and TRH stimulation testing were used at both assessment time points. Baseline screen for TSH was 2.2 and 1.2 uUI·mL and stimulated TSH was at 15.2 uUI·mL at 30 min and 30.6 uUI·mL at 45 min for the first (1992) and second (1996) assessment, respectively. Patient was positive on the second visit for antithyroglobulin antibodies at 70 IU·mL (normal, 0-59 IU·mL). Three months postdiagnosis, TSH was 0.66 uIU·mL and the patient was asymptomatic. At the most recent visit, 20 years and 4 months later, no symptomology was reported and TSH was 0.55 uIU·mL A greater understanding of the interaction between stress and end organ function is warranted in occupations undergoing unique stressors.

Demographic factors associated with dietary supplement prescriptions filled by United States Military Service Members 2005-2013.

BACKGROUND: Dietary supplements (DSs) can be purchased over-the-counter but may also be prescribed by medical personnel for specific therapeutic reasons. Few studies have examined this latter source of DSs despite the fact that 79% of physicians and 82% of nurses have recommended DSs to their patients. This investigation examined demographic factors associated with temporal trends in oral DS prescriptions filled by all United States (US) service members (SMs) from 2005 to 2013 (n = 1,427,080 ± 22,139, mean ± standard deviation per year). METHODS: The Food and Drug Administration National Drug Code database and the formularies of the US Defense Health Agency's Pharmacoeconomic Center were queried to identify DSs available to SMs. The number of these DS prescriptions filled by all SMs from 2005 through 2013 was then obtained from the US Department of Defense Pharmacy Data Transaction System. Data were grouped by American Hospital Formulary System (AHFS) pharmacologic-therapeutic classifications and examined over time. Denominators (number of SMs each year) were obtained from the Defense Health Agency. RESULTS: Major findings included 1) generally greater prevalence of prescriptions filled by women and older SMs for most AHFS categories; 2) a temporal decline in total prescriptions filled by Marine Corps personnel accounted for by a decline in the prevalence of zinc preparations filled by younger male Marines; 3) a temporal decline in the prevalence of iron preparations filled by women; 4) a temporal increase in the prevalence of prescriptions for replacement preparations filled by women accounted for largely by more prescriptions for calcium compounds; and 5) a temporal decline in the prevalence of prescriptions filled for cathartics/laxatives in older SMs accounted for largely by a decline in prescriptions for sodium/potassium compounds. CONCLUSIONS: These temporal trends may be associated with the greater health care utilization of women and older SMs as well as the perceptions of prescribers and/or patients on appropriate roles of these substances in medicine and public health.

ACTN3 R577X and ACE I/D gene variants influence performance in elite sprinters: a multi-cohort study.

BACKGROUND: To date, studies investigating the association between ACTN3 R577X and ACE I/D gene variants and elite sprint/power performance have been limited by small cohorts from mixed sport disciplines, without quantitative measures of performance. AIM: To examine the association between these variants and sprint time in elite athletes. METHODS: We collected a total of 555 best personal 100-, 200-, and 400-m times of 346 elite sprinters in a large cohort of elite Caucasian or African origin sprinters from 10 different countries. Sprinters were genotyped for ACTN3 R577X and ACE ID variants. RESULTS: On average, male Caucasian sprinters with the ACTN3 577RR or the ACE DD genotype had faster best 200-m sprint time than their 577XX (21.19 ± 0.53 s vs. 21.86 ± 0.54 s, p = 0.016) and ACE II (21.33 ± 0.56 vs. 21.93 ± 0.67 sec, p = 0.004) counterparts and only one case of ACE II, and no cases of ACTN3 577XX, had a faster 200-m time than the 2012 London Olympics qualifying (vs. 12 qualified sprinters with 577RR or 577RX genotype). Caucasian sprinters with the ACE DD genotype had faster best 400-m sprint time than their ACE II counterparts (46.94 ± 1.19 s vs. 48.50 ± 1.07 s, p = 0.003). Using genetic models we found that the ACTN3 577R allele and ACE D allele dominant model account for 0.92 % and 1.48 % of sprint time variance, respectively. CONCLUSIONS: Despite sprint performance relying on many gene variants and environment, the % sprint time variance explained by ACE and ACTN3 is substantial at the elite level and might be the difference between a world record and only making the final.

Multivitamin and protein supplement use is associated with positive mood states and health behaviors in US Military and Coast Guard personnel.

Approximately 60% of Armed Forces personnel regularly consume dietary supplements (DSs). We investigated the association of mood and health behaviors with multiple classes of DSs in military and Coast Guard personnel (N = 5536). Participants completed a survey of DS use and the Quick Mood Scale to assess mood domains of wakeful-drowsiness, relaxed-anxious, cheerful-depressed, friendly-aggression, clearheaded-confused, and well coordinated-clumsy. Supplements were categorized as multivitamin/minerals (MVM), individual vitamin/minerals, protein/amino acid supplements (PS), combination products (C), herbals (H), purported steroid analogs, (S) and other (O). One-way analyses of covariance assessed associations of DSs and perceived health behavior with mood controlling for age. Logistic regression determined associations between DS use and health behavior. Users of MVM and PS reported feeling significantly (P < 0.05) more awake, relaxed, cheerful, clearheaded, and coordinated. Participants using PS and S reported feeling less friendly (more aggressive, P < 0.02). Users of MVM and PS were more likely to report their general health, eating habits, and fitness level as excellent/good (P < 0.05). Participants reporting health behaviors as excellent/good were more (P < 0.01) awake, relaxed, cheerful, friendly, clearheaded, and coordinated. As no known biological mechanisms can explain such diverse effects of MVM and PS use on multiple mood states, health, eating habits, and fitness, we hypothesize these associations are not causal, and DS intake does not alter these parameters per se. Preexisting differences in mood and other health-related behaviors and outcomes between users versus nonusers of DSs could be a confounding factor in studies of DSs.

A systematic review and meta-analysis on the prevalence of dietary supplement use by military personnel.

BACKGROUND: Although a number of studies have been conducted on the prevalence of dietary supplement (DS) use in military personnel, these investigations have not been previously summarized. This article provides a systematic literature review of this topic. METHODS: Literature databases, reference lists, and other sources were searched to find studies that quantitatively examined the prevalence of DS use in uniformed military groups. Prevalence data were summarized by gender and military service. Where there were at least two investigations, meta-analysis was performed using a random model and homogeneity of the prevalence values was assessed. RESULTS: The prevalence of any DS use for Army, Navy, Air Force, and Marine Corps men was 55%, 60%, 60%, and 61%, respectively; for women corresponding values were 65%, 71%, 76%, and 71%, respectively. Prevalence of multivitamin and/or multimineral (MVM) use for Army, Navy, Air Force, and Marine Corps men was 32%, 46%, 47%, and 41%, respectively; for women corresponding values were 40%, 55%, 63%, and 53%, respectively. Use prevalence of any individual vitamin or mineral supplement for Army, Navy, Air Force, and Marine Corps men was 18%, 27%, 25%, and 24%, respectively; for women corresponding values were 29%, 36%, 40%, and 33%, respectively. Men in elite military groups (Navy Special Operations, Army Rangers, and Army Special Forces) had a use prevalence of 76% for any DS and 37% for MVM, although individual studies were not homogenous. Among Army men, Army women, and elite military men, use prevalence of Vitamin C was 15% for all three groups; for Vitamin E, use prevalence was 8%, 7%, and 9%, respectively; for sport drinks, use prevalence was 22%, 25% and 39%, respectively. Use prevalence of herbal supplements was generally low compared to vitamins, minerals, and sport drinks, ≤5% in most investigations. CONCLUSIONS: Compared to men, military women had a higher use prevalence of any DS and MVM. Army men and women tended to use DSs and MVM less than other service members. Elite military men appeared to use DSs and sport drinks more than other service members.

Efficacy and safety of protein supplements for U.S. Armed Forces personnel: consensus statement.

To provide evidence-based guidance regarding the efficacy and safety of dietary protein supplement (PS) use by members of the U.S. Armed Forces, a panel of internationally recognized experts in the fields of protein metabolism and dietary supplement research was convened by the Department of Defense Center Alliance for Dietary Supplement Research and the U.S. Army Medical Research and Material Command. To develop a consensus statement, potential benefits, risks, and strategies to optimize military performance through PS use were considered in the context of specific warfighter populations and occupational demands. To maintain muscle mass, strength, and performance during periods of substantial metabolic demand and concomitant negative energy balance the panel recommended that warfighters consume 1.5-2.0 g · kg(-1) · d(-1) of protein. However, if metabolic demand is low, such as in garrison, protein intake should equal the current Military Dietary Reference Intake (0.8-1.5 g · kg(-1) · d(-1)). Although PS use generally appears to be safe for healthy adults, warfighters should be educated on PS quality, given quality-control and contamination concerns with commercial dietary supplements. To achieve recommended protein intakes, the panel strongly urges consumption of high-quality protein-containing whole foods. However, when impractical, the use of PSs (20-25 g per serving or 0.25-0.3 g · kg(-1) per meal), particularly after periods of strenuous physical activity (e.g., military training, combat patrols, and exercise), is acceptable. The committee acknowledges the need for further study of protein requirements for extreme, military-specific environmental conditions and whether unique metabolic stressors associated with military service alter protein requirements for aging warfighters.

Predictors of the relationships between nutritional supplement use and weight-modification goals of U.S. Army soldiers.

BACKGROUND: U.S. Army Soldiers must meet body weight and composition standards and consequently may use nutritional supplements (NS) purported to assist in weight modification (WM). Nutritional supplements are dietary supplements (DS) and foods intended to supplement the diet. PURPOSE: This study assessed relationships between NS use, demographic characteristics, health-related behaviors, and WM goals among U.S. Army personnel. METHODS: Participants (N = 990) self-reported NS use, categorized as energy drinks, sport nutrition products, or DS, and WM goal (lose, gain, or maintain) was ascertained by survey. DS were subcategorized as health, weight-loss, weight-gain, or other DS. Chi-square and logistic regression were used to assess relationships between predictors, NS use, and WM goal. Most respondents (70.3% ± 1.7%) consumed some NS; however, overall NS use was not related to WM goal. Significant relationships were observed between predictors (tobacco use, age, body-mass index, fitness score, general health, and eating habits) and both WM goal and NS use. Respondents attempting to lose or maintain weight were less likely to consume energy drinks and weight-gain DS. CONCLUSION: WM goal is related to multiple health behaviors including tobacco use, physical fitness score, and self-perception of health and eating behavior. NS are consumed in this population regardless of WM goal.

Dietary Supplement Use in a Large, Representative Sample of the US Armed Forces.

BACKGROUND: Dietary supplement (DS) use is prevalent among the US Armed Forces personnel, but representative cross-service comparisons and characteristics of personnel using DSs are limited. OBJECTIVE: Examine DS use and characteristics associated with use in a representative sample of US Armed Forces personnel (Army, Navy, Air Force, Marine Corps, and Coast Guard) using data from the 2011 Department of Defense Survey of Health-Related Behaviors. DESIGN AND PARTICIPANTS: A stratified random sample of service members (SMs) was contacted and asked to complete a questionnaire assessing personal characteristics and DS use. RESULTS: Overall, 69% of the 39,877 SMs reported using DSs ≥1 time per week. The most commonly used DSs were multivitamin or multiminerals (50%), antioxidants (34%), individual vitamins or minerals (33%), bodybuilding supplements (27%), fish oils (26%), herbals (16%), and weight-loss supplements (16%). Multiple logistic regression indicated overall DS use was higher among women, those with higher educational levels, Marine Corps SMs, officers, those with higher body mass index, those engaged in greater physical activity and weight training, and people in weight control programs. DS use was lower when peer groups or leadership discouraged substance abuse. CONCLUSIONS: DS use was considerably higher in the US Armed Forces compared with civilian populations, although many demographic and lifestyle factors associated with use were similar. Some categories of DSs extensively used by SMs such as bodybuilding supplements have been associated with adverse events. Discouraging substance abuse through peer groups and leadership actions may reduce use of unnecessary or dangerous DSs.

Caffeine consumption among active duty United States Air Force personnel.

Data from the National Health and Nutrition Examination Survey (NHANES) indicated that 89% of Americans regularly consumed caffeinated products, but these data did not include military personnel. This cross-sectional study examined caffeine consumption prevalence, amount of daily consumption, and factors associated with caffeine intake in active duty United States (US) Air Force personnel. Service members (N = 1787) stationed in the US and overseas completed a detailed questionnaire describing their intake of caffeine-containing products in addition to their demographic, lifestyle, and military characteristics. Overall, 84% reported consuming caffeinated products ≥1 time/week with caffeine consumers ingesting a mean ± standard error of 212 ± 9 mg/day (224 ± 11 mg/day for men, 180 ± 12 mg/day for women). The most commonly consumed caffeinated products (% users) were sodas (56%), coffee (45%), teas (36%), and energy drinks (27%). Multivariate logistic regression modeling indicated that characteristics independently associated with caffeine consumption (≥1 time/week) included older age, ethnicity other than black, tobacco use, less aerobic training, and less sleep; energy drink use was associated with male gender, younger age, tobacco use, and less sleep. Compared to NHANES data, the prevalence of caffeine consumption in Air Force personnel was similar but daily consumption (mg/day) was higher.

Large-scale GWAS identifies multiple loci for hand grip strength providing biological insights into muscular fitness.

Hand grip strength is a widely used proxy of muscular fitness, a marker of frailty, and predictor of a range of morbidities and all-cause mortality. To investigate the genetic determinants of variation in grip strength, we perform a large-scale genetic discovery analysis in a combined sample of 195,180 individuals and identify 16 loci associated with grip strength (P<5 × 10-8) in combined analyses. A number of these loci contain genes implicated in structure and function of skeletal muscle fibres (ACTG1), neuronal maintenance and signal transduction (PEX14, TGFA, SYT1), or monogenic syndromes with involvement of psychomotor impairment (PEX14, LRPPRC and KANSL1). Mendelian randomization analyses are consistent with a causal effect of higher genetically predicted grip strength on lower fracture risk. In conclusion, our findings provide new biological insight into the mechanistic underpinnings of grip strength and the causal role of muscular strength in age-related morbidities and mortality.

Self-reported side-effects associated with use of dietary supplements in an armed forces population.

Approximately 60-70% of Armed Forces personnel consume a dietary supplement (DS) at least once a week and there have been numerous reports of severe adverse events among DS users. This study assessed patterns of DS use and self-reported side-effects among 4400 Armed Forces personnel using a paper-and-pencil survey. Multivariable logistic regression was used to examine associations between patterns of DS use and self-reported side-effects. Sixty-nine percent of personnel surveyed reported using a DS. Seven percent of DS users reported experiencing abnormal heart beats, 6% tremors, 5% stomach pain, 3% dizziness, and 3% numbness/tingling and they believed these symptoms were associated with the use of DS. After adjustment for use of other DS classes, total supplement use, and demographic characteristics, protein supplement users were more likely than non-users to report numbness/tingling; combination product users were more likely to report experiencing abnormal heart beats, stomach pain, dizziness, tremors, and numbness/tingling; and users of purported steroid analogues were more likely to report dizziness. Use of more than one DS per week was associated with an increased likelihood of reporting side-effects. Respondents with a higher body mass index were more likely to report side-effects. Further research is necessary to determine whether self-reported side-effects associated with multiple DS use and some DS classes impact the long-term health or performance of service members. Surveillance of military populations using surveys like this one may provide a method for detecting adverse health events of DS before they are apparent in the civilian population. Copyright © 2015 John Wiley & Sons, Ltd.

Longitudinal trends in use of dietary supplements by U.S. Army personnel differ from those of civilians.

Prevalence and patterns of dietary supplement (DS) use by U.S. Army soldiers differ from the civilian population. Longitudinal trends in use of DSs by civilians have been examined, but are unavailable in subpopulations such as military service members. The present study examined longitudinal changes in DS use by soldiers. A standardized questionnaire on DS use was administered in 2006-2007 (N = 989) and 2010-2011 (N = 1196) to convenience samples of active duty soldiers. Data were weighted for total population demographics of age, sex, and rank. Regular use of DSs by soldiers increased significantly (56% ± 1.6% vs. 64% ± 1.7%; p ≤ 0.001) over the 4 years primarily because of an increase of DS use among the youngest 18- to 24-year-old soldiers (43.0% ± 2.5% vs 62.3% ± 2.4%; p ≤ 0.01). Protein (22% ± 1.4% vs. 26% ± 1.5%; p ≤ 0.001) and combination (10.0% ± 1.0% vs. 24% ± 1.4%; p ≤ 0.001) product consumption also increased over the 4 years. Individual vitamin and mineral use - including iron, magnesium, selenium, and vitamins A, B6, B12, and D - significantly increased as well (p ≤ 0.05). In addition, expenditures on DSs by soldiers increased over time (p < 0.01). Reasons reported by soldiers for DS use suggest use increased to meet the occupational demands of military service. Educational interventions to minimize inappropriate use of DSs by soldiers are necessary to reduce adverse events resulting from unnecessary use of DSs and the financial burden associated with their use.

Caffeine Use among Active Duty Navy and Marine Corps Personnel.

Data from the National Health and Nutrition Examination Survey (NHANES) indicate 89% of Americans regularly consume caffeine, but these data do not include military personnel. This cross-sectional study examined caffeine use in Navy and Marine Corps personnel, including prevalence, amount of daily consumption, and factors associated with use. A random sample of Navy and Marine Corps personnel was contacted and asked to complete a detailed questionnaire describing their use of caffeine-containing substances, in addition to their demographic, military, and lifestyle characteristics. A total of 1708 service members (SMs) completed the questionnaire. Overall, 87% reported using caffeinated beverages ≥1 time/week, with caffeine users consuming a mean ± standard error of 226 ± 5 mg/day (242 ± 7 mg/day for men, 183 ± 8 mg/day for women). The most commonly consumed caffeinated beverages (% users) were coffee (65%), colas (54%), teas (40%), and energy drinks (28%). Multivariable logistic regression modeling indicated that characteristics independently associated with caffeine use (≥1 time/week) included older age, white race/ethnicity, higher alcohol consumption, and participating in less resistance training. Prevalence of caffeine use in these SMs was similar to that reported in civilian investigations, but daily consumption (mg/day) was higher.

Soldier use of dietary supplements, including protein and body building supplements, in a combat zone is different than use in garrison.

United States Army personnel in garrison who are not deployed to combat theater report using dietary supplements (DSs) to promote health, increase physical and mental strength, and improve energy levels. Given the substantial physical and cognitive demands of combat, DS use may increase during deployment. This study compared DS use by garrison soldiers with DS use by personnel deployed to a combat theater in Afghanistan. Prevalence and patterns of DS use, demographic factors, and health behaviors were assessed by survey (deployed n = 221; garrison n = 1001). Eighty-two percent of deployed and 74% of garrison soldiers used DSs ≥ 1 time·week(-1). Logistic regression analyses, adjusted for significant demographic and health predictors of DS use, showed deployed personnel were more likely than garrison soldiers to use protein, amino acids, and combination products. Deployed females were more likely to use protein supplements and deployed males were more likely to use multivitamins, combination products, protein, and body building supplements than garrison respondents. Significantly more deployed (17%) than garrison (10%) personnel spent more than $50∙month(-1) on DSs. Higher protein supplement use among deployed personnel was associated with higher frequency of strength training and lower amounts of aerobic exercise for males but similar amounts of strength training and aerobic exercise for females. Protein supplements and combination products are used more frequently by deployed than garrison soldiers with the intent of enhancing strength and energy.

Demographic, Lifestyle Factors, and Reasons for Use of Dietary Supplements by Air Force Personnel.

BACKGROUND: Dietary supplement (DS) use is common among U.S. Army personnel to purportedly improve health, provide energy, and increase strength. However, a comprehensive analysis of DS use among U.S. Air Force (USAF) personnel has not been conducted using the same survey instrument, which would permit direct comparisons to DS use by Army personnel. METHODS: A standardized questionnaire was used to assess DS use, demographic factors, and reasons for use of DS by USAF personnel (N = 1750). Logistic regression models adjusted for age, sex, and rank were used to determine relationships among categories of DS (multivitamin and multimineral, individual vitamins and minerals, protein/amino acid supplements, combination products, herbal supplements, purported steroid analogs, and other) and demographic factors. Findings were compared to reports from other military services and civilian populations. RESULTS: DS were used by 68% of USAF personnel: 35% used 1-2 DS ≥ 1 time/wk, 13% 3-4 DS ≥ 1 time/wk, and 20% ≥ 5 DS ≥ 1 time/wk. There were 45% of personnel who used a multivitamin and mineral, 33% protein supplements, 22% individual vitamins/minerals, 22% combination products, and 7% herbals. Logistic regression demonstrated aerobic exercise duration and strength training were associated with increased DS use. Individuals who previously deployed were more likely to use DS. CONCLUSIONS: Like Army personnel, college students and athletes, USAF personnel use more DS than the general population and are more likely to use purported performance enhancing DS, such as protein supplements, and concurrently consume multiple DS. Austin KG, Price LL, McGraw SM, Leahy G, Lieberman HR. Demographic, lifestyle factors, and reasons for use of dietary supplements by Air Force personnel. Aerosp Med Hum Perform. 2016; 87(7):628-637.

Interstitial glucose concentrations and hypoglycemia during 2 days of caloric deficit and sustained exercise: a double-blind, placebo-controlled trial.

Military personnel and some athlete populations endure short-term energy deficits from reduced energy intake and/or increased energy expenditure (EE) that may degrade physical and cognitive performance due to severe hypoglycemia (<3.1 mmol/l). The extent to which energy deficits alter normoglycemia (3.9-7.8 mmol/l) in healthy individuals is not known, since prior studies measured glucose infrequently, not continuously. The purpose of this study was to characterize the glycemic response to acute, severe energy deficit compared with fully fed control condition, using continuous glucose monitoring (CGM). For 2 days during a double-blind, placebo-controlled, crossover study, 23 volunteers (17 men/6 women; age: 21.3 ± 3.0 yr; body mass index: 25 ± 3 kg/m) increased habitual daily EE [2,300 ± 450 kcal/day [means ± SD)] by 1,647 ± 345 kcal/day through prescribed exercise (~3 h/day; 40-65% peak O2 consumption), and consumed diets designed to maintain energy balance (FED) or induce 93% energy deficit (DEF). Interstitial glucose concentrations were measured continuously by CGM (Medtronic Minimed). Interstitial glucose concentrations were 1.0 ± 0.9 mmol/l lower during DEF vs. FED (P < 0.0001). The percentage of time spent in mild (3.1-3.8 mmol/l) hypoglycemia was higher during DEF compared with FED [mean difference = 20.5%; 95% confidence interval (CI): 13.1%, 27.9%; P = 0.04], while time spent in severe (<3.1 mmol/l) hypoglycemia was not different between interventions (mean difference = 4.6%; 95% CI: -0.6%, 9.8%; P = 0.10). Three of 23 participants spontaneously reported symptoms (e.g., nausea) potentially related to hypoglycemia during DEF, and an additional participant reported symptoms during both interventions. These findings suggest that severe hypoglycemia rarely occurs in healthy individuals enduring severe, short-term energy deficit secondary to heavy exercise and inadequate energy intake.

Prevalence, Adverse Events, and Factors Associated with Dietary Supplement and Nutritional Supplement Use by US Navy and Marine Corps Personnel.

BACKGROUND: About 50% of Americans and 60% to 70% of US military personnel use dietary supplements, some of which have been associated with adverse events (AEs). Nutritional supplements like sport drinks and sport bars/gels are also commonly used by athletes and service members. Previous dietary supplement and nutritional supplement surveys were conducted on Army, Air Force, and Coast Guard personnel. OBJECTIVE: The aim of this cross-sectional study was to investigate dietary and nutritional supplement use in Navy and Marine Corps personnel, including the prevalence, types, factors associated with use, and AEs. DESIGN: A random sample of 10,000 Navy and Marine Corps personnel were contacted. Service members were asked to complete a detailed questionnaire describing their personal characteristics, supplement use, and AEs experienced. RESULTS: In total, 1,708 service members completed the questionnaire during August through December 2014, with 1,683 used for analysis. Overall, 73% reported using dietary supplements one or more times per week. The most commonly used dietary supplements (used one or more times per week) were multivitamins/multiminerals (48%), protein/amino acids (34%), combination products (33%), and individual vitamins and minerals (29%). About 31% of service members reported using five or more dietary supplements. Sport drinks and sport bars/gels were used by 45% and 23% of service members, respectively. Monthly expenditures on dietary supplements averaged $39; 31% of service members spent ≥$50/mo. Multivariate logistic regression modeling indicated that female sex (women/men; odds ratio [OR]=1.76, 95% CI 1.32 to 2.36), higher educational level (college degree/no college degree; OR=2.23, 95% CI 1.62 to 3.30), higher body mass index (calculated as kg/m(2)) (≥30/<25; OR=1.67, 95% CI 1.06 to 2.63), and a greater amount of resistance training (≥271/0 to 45 min/week; OR=2.85, 95% CI 1.94 to 4.17) were associated with dietary supplement use. Twenty-two percent of dietary supplement users and 6% of nutritional supplement users reported one or more AEs. For combination products alone, 29% of users reported one or more AEs. CONCLUSIONS: The prevalence of dietary supplement use in Navy and Marine Corps personnel was considerably higher than reported in civilian investigations for almost all types of dietary supplements, although similar to most other military services. Factors associated with dietary supplement use were similar to those reported in previous military and civilian investigations. Prevalence of self-reported AEs was very high, especially for combination products.

Temporal trends in dietary supplement prescriptions of United States military service members suggest a decrease in pyridoxine and increase in vitamin D supplements from 2005 to 2013.

Dietary supplements (DSs) can be obtained over-the-counter but can also be prescribed by health-care providers for therapeutic reasons. Few studies have documented this later source despite the fact that 79% of physicians and 82% of nurses have recommended DSs to patients. This investigation assessed prevalence and temporal trends in oral DS prescriptions filled by all United States service members (SMs) from 2005 to 2013 (n = 1 427 080 ± 22 139, mean ± standard deviation (SD)/y). We hypothesize that there would be temporal variations in specific types of DSs. Data obtained from Department of Defense Pharmacy Data Transaction System were grouped by American Hospital Formulary System pharmacologic-therapeutic classifications and prevalence examined over time. About 11% of SMs filled one or more DS prescriptions of 235 180 ± 4926 (mean ± SD) prescriptions/y over the 9-year period. Curve-fitting techniques indicated significant linear declines over time for multivitamins (P = .004), iron preparations (P < .001), antacids (P < .001), and vitamin B and B complex vitamins (P < .001). There were significant quadratic trends indicating a rise in early years followed by a leveling off in later years for replacement preparations (P < .001) and vitamin C (P < .001). There were significant quadratic trends (P < .001) for vitamin E indicating a decline in early years and leveling off in later years, and vitamin D indicating little change in early years followed by a large rise subsequently (P < .001). This study identified temporal trends in specific DS categories that may be associated with changing perceptions of prescribers and/or patients of the appropriate roles of DSs in medicine and public health.