AF bt multivitamin

MILITARY MEDICINE, 180, 5:554, 2015
The Effects of Prenatal Vitamin Supplementation on Operationally
Significant Health Outcomes in Female Air Force Trainees
LCdr Kirsten R. Barnes, Canadian Armed Forces*; Juste N. Tchandja, PhD, MPH†;
Capt Bryant J. Webber, USAF MC†; Lt Col Susan P. Federinko, USAF MC†;
Col Thomas L. Cropper, USAF (Ret.)†
ABSTRACT Objectives: A prenatal vitamin supplementation program for female basic military trainees at Joint Base
San Antonio—Lackland was initiated in June 2012 with the goals of decreasing attrition and improving performance.
This project examined whether supplementation influences attrition rates, incidence of stress fractures and iron defi-
ciency anemia, and physical performance. Methods: This was a cohort-based pilot study with an historical control
group. Primary outcome measures included all-cause attrition, medical attrition, stress fractures, and iron deficiency
anemia. Results: Incidence rates of all-cause attrition, medical attrition, stress fractures, and anemia were similar in both
groups, although the lower medical attrition in the supplementation group approached statistical significance (risk ratio,
0.74; 95% confidence interval, 0.54–1.01). Conclusion: Although this study found no statistical benefit, the operation-
ally significant reduction in medical attrition of 26% suggests that providing prenatal vitamin supplementation to female
basic trainees in the Air Force may be worthwhile.
INTRODUCTION
Female military recruits—or “trainees,” as they are known
in the U.S. Air Force—face several physical, cognitive, and
environmental stressors during basic military training (BMT).
Given these known stressors and the subsequent risks for iron
deficiency and stress fractures, the Institute of Medicine
(IOM) published a report in 2006 outlining the increased
mineral requirements of female trainees. Among other things,
the IOM established a recommended dietary allowance of
22 mg iron/d for female service members and suggested
supplementation or fortification programs for those who are
unlikely to meet this requirement through diet alone, such as
for female trainees. In addition to iron, calcium and vitamin
D requirements may be higher among military trainees,1
and
deficiencies thereof have been associated with increased
stress fractures. Specifically, in a double-blind, placebo-
controlled study of female U.S. Navy recruits, daily supple-
mentation with 2000 mg of calcium and 800 IU of vitamin D
resulted in a 20% reduced incidence of stress fractures.2
In light of this evidence, the Trainee Health Surveillance
team at Joint Base San Antonio (JBSA)—Lackland initiated
a program in June 2012 to provide nutritional education to all
incoming female trainees and offer them daily supplementa-
tion with a prenatal vitamin (containing, among other things,
27 mg of iron, 200 mg of calcium, and 400 IU of vitamin D).
The prenatal vitamin was chosen for the following reasons:
(1) prenatal vitamins have an iron content that approximates
the IOM’s estimated 22 mg daily iron requirement for
females in military training; (2) prenatal vitamins are on the
organization’s formulary—whereas multivitamins are not—
and are available at a very low cost of approximately $0.03 per
day; and (3) they contain other important minerals and vita-
mins, including calcium, vitamin D, and folic acid (the U.S.
Preventive Services Task Force currently recommends that
all women planning or capable of pregnancy consume a daily
supplement containing 0.4 to 0.8 mg of folic acid3
). The
program’s ultimate goal was to improve performance and
decrease rates of attrition (i.e., noncompletion of training),
which had historically been higher among females. At the time
of program initiation, female attrition was approximately
10%, compared to about 5% for males. In particular, health
outcomes such as iron deficiency anemia, stress fractures, and
mental health issues were known to be significant contribu-
tors to attrition from BMT for females.
Iron deficiency—defined as “an abnormal value for at
least two of the following three indicators: serum ferritin,
transferrin saturation, or free erythrocyte protoporphyrin”—
is more prevalent among females and is particularly common
among female athletes and service members.4
For females, a
diagnosis of iron deficiency anemia requires both iron defi-
ciency and a hemoglobin level below 12 g/dL.4
Females in
the U.S. Armed Forces have 7.8 times the incidence rate of
iron deficiency anemia as compared to males.5
During BMT,
iron stores naturally deplete, resulting in reduced aerobic
performance.6
A study of U.S. Army females found a 20.9%
prevalence of iron deficiency anemia immediately following
basic training,7
and a similar study of Israeli female recruits
found a prevalence of 12.8%.8
A stress fracture (also known as a fatigue or march fracture)
is defined as “a partial or complete fracture of bone that results
*Directorate Force Health Protection, Canadian Forces Health Services
Group Headquarters, 1745 Alta Vista Road, Ottawa, ON, Canada K1A 0K6.
†Trainee Health Surveillance, 1515 Truemper Street, Bldg 6612 Rm 930,
Joint Base San Antonio—Lackland, TX 78236.
This work is the sole responsibility of the authors and does not represent
the official views of the Uniformed Services University of the Health Sci-
ences, the Department of Defense, the U.S. Air Force, or the Canadian
Armed Forces.
doi: 10.7205/MILMED-D-14-00258
MILITARY MEDICINE, Vol. 180, May 2015554
Downloaded from publications.amsus.org: AMSUS - Association of Military Surgeons of the U.S. IP: 070.160.034.193 on Aug 26, 2017.
Copyright (c) Association of Military Surgeons of the U.S. All rights reserved.

from the repeated application of a stress lower than that
required to fracture the bone in a single loading situation.”9
Stress fractures are commonly diagnosed in the military popu-
lation, especially among recruits, whose incidence exceeds
that of nonrecruits by 18 times.10
The risk of stress fracture in
female recruits ranges from 1.2 to 12 times that of male
recruits, with reported rates ranging from 1.6% to 21.0%.2,9,11–13
Sixty percent of U.S. Army female recruits who sustain a stress
fracture during BMT do not complete training.2
As a result,
stress fractures incur considerable expense for the military and
negatively affect military readiness.2
We conducted a cohort-based pilot study to analyze the
relationship between prenatal vitamin supplementation in
females during U.S. Air Force BMT and subsequent attrition
rates, iron deficiency and stress fracture rates, and physical
fitness performance. Since the Air Force is the only U.S.
service branch conducting such a program, the results
could influence health promotion programs at other mili-
tary training sites and, potentially, in other high-stress environ-
ments worldwide.
METHODS
JBSA—Lackland is located in San Antonio, Texas, and is the
sole site for U.S. Air Force enlisted BMT. At any given time,
there are approximately 1000–1200 females undergoing such
training, with each course lasting 8.5 weeks. As of August 29,
2012, all incoming female trainees were offered prescriptions
for prenatal vitamins during their first week of training and
counseled about the potential benefits and risks of taking such
supplementation. This study examined data on all female
trainees who began BMT between August 29, 2012 and
March 27, 2013, a group consisting of 4,303 females. An
historical comparison group was selected, which included all
4,051 female trainees who began BMT at Lackland between
August 31, 2011 and March 28, 2012. The use of a season-
matched comparison group was intended to control for any
environmental differences that may affect training during
different months of the year (e.g., endogenous vitamin D
production from sun exposure). The study size was based on
data availability and not on an a priori power calculation.
Given the 4,303 female trainees who were offered prenatal
vitamins during the study period and a 7.3% risk of all-cause
attrition in the comparison group, a relative risk of 0.79
would have been required to obtain 80% power.
The primary outcome of interest was the rate of attrition
because of all causes. Secondary outcomes included rates of
medical attrition, iron deficiency anemia diagnoses, stress
fracture diagnoses, and performance on the Air Force physi-
cal fitness assessment. Attrition from BMT has a number of
causes, with medical attrition accounting for about 30 to 40%
of cases (unpublished data from Lackland Trainee Health
Surveillance). Other causes of attrition include fraudulent
enlistment (e.g., lying on official documents), mental health
issues, and positive urine toxicology screening on arrival.
The Air Force physical fitness assessment consists of four
components: waist circumference (scored out of 20 points),
1 minute of push-ups (10 points), 1 minute of sit-ups
(10 points), and a 1.5 mile timed run (60 points). Pull-ups
are also performed as part of the assessment during BMT,
although they do not factor into the final score. A body mass
index (BMI; calculated as weight in kilograms divided by
height in meters squared) is also obtained for basic trainees.
During the 8.5 weeks of BMT, trainees complete the assess-
ment at multiple times, with the initial assessment performed
within a week of arrival and the final assessment performed
within a week of graduation. For this study, initial BMI and
component scores were used to compare the two groups at
baseline, and final BMI and component scores were used to
compare intervention effectiveness. Fitness data were only
available for those who completed BMT.
As part of their routine operations, the Trainee Health
Surveillance team at JBSA—Lackland collects data on demo-
graphics, trainee attrition, and medical encounter information.
Medical encounter information is based on International Clas-
sification of Diseases, 9th Revision, Clinical Modification
(ICD-9) codes logged in the Armed Forces Health Longitudi-
nal Technology Application, whereas demographic and attri-
tion information is derived from the Basic Military Training
System database. This study was reviewed and approved by
the Office of Research at the Uniformed Services University,
Bethesda, Maryland.
Incidence rates were compared for all-cause attrition,
medical attrition, stress fracture diagnoses, and anemia diag-
noses in female trainees who either were or were not offered
prenatal vitamin supplementation. Using the chi-square test,
these rates were compared to determine relative risks (RR)
and 95% confidence intervals (CI). The number needed to
treat (NNT; defined as the inverse of the absolute risk reduc-
tion) for each of these outcomes was also calculated. Mean
fitness measures were compared using independent-samples
t-tests, with a 2-sided p-value established at 0.05. All analy-
ses were performed with SPSS version 20.
RESULTS
At baseline, mean BMI (23.44 vs. 23.41; p = 0.546) and run
time (15.81 minutes vs. 15.79 minutes; p = 0.719) were
similar in the supplementation and comparison groups, respec-
tively (Table I). The supplementation group had a smaller
mean waist circumference (29.10 vs. 29.57; p < 0.001) and
completed more push-ups (28.70 vs. 27.63; p < 0.001) and
sit-ups (15.36 vs. 14.70; p = 0.001) at baseline.
The risk of all-cause attrition in the prenatal vitamin sup-
plementation group was nonsignificantly reduced by 8%
(RR 0.92; 95% CI, 0.78–1.07), with an NNT of 163 to pre-
vent one trainee attrition. Likewise, the risk of medical attri-
tion in the supplementation group was nonsignificantly
reduced by 26% (RR 0.74; 95% CI, 0.54–1.01), with an
NNT of 176. For stress fractures there was a nonsignificant
reduction of 3% (RR 0.97; 95% CI, 0.68–1.39), and for iron
MILITARY MEDICINE, Vol. 180, May 2015 555
Effects of Prenatal Vitamin Supplementation in Female Air Force Trainees

deficiency anemia there was a nonsignificant increase of 8%
(RR 1.08; 95% CI, 0.83–1.40) (Table II).
The mean final run time was 0.080 minutes (4.8 seconds)
longer in the prenatal vitamin supplementation group than
in the comparison group (p = 0.014). The mean number of
push-ups was 0.38 greater in the supplementation group
(p = 0.045). There were no differences found between the
mean number of sit-ups and pull-ups completed between the
two groups (Table III).
DISCUSSION
This analysis of an existing health promotion program found
a statistically nonsignificant effect of prenatal vitamin sup-
plementation on attrition from training and on development
of stress fractures and iron deficiency anemia among females
undergoing U.S. Air Force BMT.
The null findings may be explained by a number of rea-
sons. First, the low baseline rates of these outcomes among
female trainees at JBSA—Lackland, rates which are lower
than those reported in other military training popula-
tions,2,9,11–13
suggest that preexisting preventive measures
had been optimized in this population. Second, it is possible
that 8.5 weeks of supplementation did not allow adequate
time to demonstrate a statistically significant impact and that
the prenatal vitamin may be more efficacious if it were initi-
ated before starting BMT. Third, given the daily doses of
calcium and vitamin D that were protective against stress
fractures in a U.S. Navy recruit population—2000 mg and
800 IU, respectively2
—it may be reasonable to conclude that
the 200 mg calcium and 400 IU vitamin D in the prenatal
vitamin are insufficient to prevent stress fractures in female
military recruits. Fourth, increased clinical suspicion for iron
deficiency anemia during the intervention period, leading to
increased screening and diagnoses, may have resulted in a
cointervention bias, whereby the supplementation group
falsely appeared to have an increased risk of anemia (RR
1.08). This was a limitation of both the observational nature
of the study design and the fact that medical outcomes were
based only on diagnoses entered into the electronic medical
record, rather than on complete capture of all outcomes in the
study population.
The 26% reduction in medical attrition in the prenatal
supplementation group, though not statistically significant at
a = 0.05 (95% CI, 0.54–1.01), is operationally adequate to
justify continuation of a program that is inexpensive and has
few if any associated harms. Clearly, further research is
justified to delineate the potential impact of prenatal vitamin
TABLE I. Comparison of Initial Fitness-Related Characteristics Between Study Groupsa
Supplementation Group Comparison Group
Mean Difference p-ValueN Mean SD N Mean SD
BMI 3,940 23.44 2.73 3,755 23.41 2.56 0.03 0.546
Waist Circumference (Inches) 3,942 29.10 2.80 3,756 29.57 2.85 0.47 <0.001
Initial Run Time (Minutes) 3,942 15.81 2.16 3,756 15.79 2.16 0.02 0.719
Initial Push-Ups 3,942 28.70 10.96 3,756 27.63 10.88 1.07 <0.001
Initial Sit-Ups 3,942 15.36 8.82 3,756 14.70 8.61 0.66 0.001
a
Fitness data were only available for those females who completed basic training. SD, standard deviation.
TABLE II. Comparison of Attrition and Health-Related Outcomes Between Study Groups
Supplementation Group Comparison Group Total
RR 95% CI NNTn % n % N
All-cause Attrition 287 6.7% 295 7.3% 582 0.92 0.78–1.07 163
Medical Attrition 68 1.6% 87 2.1% 155 0.74 0.54–1.01 176
Stress Fractures 61 1.4% 59 1.5% 120 0.97 0.68–1.39 2,576
Iron Deficiency Anemia 119 2.8% 104 2.6% 223 1.08 0.83–1.40 —
CI, confidence interval; NNT, number needed to treat; RR, relative risk.
TABLE III. Comparison of Final Fitness Measures Between Study Groups
Supplementation Group Comparison Group
Mean Difference p-ValueN Mean SD N Mean SD
Final Run Time (Minutes) 3534 13.04 1.35 3754 12.96 1.30 0.080 0.014
Final Push-Ups 3546 47.16 8.37 3756 46.78 8.06 0.38 0.045
Final Sit-Ups 3545 32.16 9.62 3756 32.46 9.53 0.30 0.192
Final Pull-Ups 3536 0.72 1.71 3755 0.72 1.55 <0.01 0.964
SD, standard deviation.

supplementation on the health and performance of female
military trainees. A randomized control trial that could
account for the confounders and biases described below
would provide a more robust evidence base for this interven-
tion. With respect to overall fitness as a measure of perfor-
mance in female recruits, although some differences were
found between the two groups on their final fitness tests,
prenatal vitamin supplementation did not appear to produce
any significant effects.
The strengths of this study included its relatively large
sample size with enough power to detect an operationally
significant reduction of 21% in all-cause attrition, control for
seasonal variation by using a time-matched historical com-
parison group, complete capture of female trainees under-
going U.S. Air Force BMT during the surveillance period, and
its potential generalizability to other female military recruits,
especially in the Air Force.
The study should be interpreted cautiously, however,
given its limitations. Because of the use of an historical
comparison group and the absence of randomization, this
study is best viewed as an investigational pilot study based
on cohort study principles. Its findings may be influenced by
potential confounders that were not measured—such as
macro- and micronutrient intake during meals and menstrual
abnormalities—and by various biases, such as contamination
bias (e.g., if trainees in the comparison group had been taking
prenatal vitamins in the months leading up to training or had
been prescribed prenatal vitamins during their time in BMT).
Cointervention bias is also possible, but the authors are
unaware of any other significant interventions, such as pro-
grammatic changes in nutritional education or meal plans that
occurred during the surveillance period.
Since it is unknown which trainees actually received and
took the prenatal vitamin, the findings should also be
interpreted as reflecting the effectiveness, rather than the
efficacy, of the prenatal vitamin. It is reasonable to assume
that many trainees in the intervention arm, though offered the
supplement, did not consume the supplements. Among those
who did consume them, moreover, it is unknown how many
doses were missed during the 8.5 weeks of training. In a
survey of 161 females conducted in early 2014, 99% reported
accepting the prescription, 65% taking the supplement on
most days, and 47% taking the supplement daily throughout
the entirety of training (Lt Col Stacey Van Orden, Perfor-
mance Nutrition, personal communication). These data are
consistent with pharmacy review, which found a supplement
prescription distribution rate approaching 99%. In light of
this high rate of acceptance, it was deemed unnecessary to
exclude trainees who were not prescribed the supplement
from the analysis.
This study was further limited by lack of standardized case
definitions of outcome measures and lack of other pertinent
data. For the purposes of this study, ICD-9 codes were used
to determine incident diagnoses of stress fractures and iron
deficiency anemia. Given interprovider variability in diag-
nosing and coding these conditions, however, there may have
been some variability in outcome data. Furthermore, it was
impossible to exclude prevalent (i.e., preexisting) cases of
iron deficiency anemia. Demographic data such as age, date
of birth, and race/ethnicity were unavailable in the database,
and fitness assessment data (i.e., height, weight, initial run
time, initial push-ups, and initial sit-ups) were not obtainable
for individuals who failed to complete training. Adjustment
for potential confounders for the outcomes of interest was
therefore limited. Finally, since the dates of training initiation
and attrition were unknown, medical outcomes were assigned
as binary variables and not based on person-time.
CONCLUSIONS
Beginning in June 2012, a daily prenatal vitamin supplement
was offered to all females entering U.S. Air Force BMT.
Among the 4,303 females who enlisted between August 29,
2012 and March 27, 2013—and who were thus offered the
supplement—rates of all-cause attrition, medical attrition,
stress fracture, and iron deficiency anemia were statistically
equivalent to the 4,051 females who entered training during
the same period of time the previous year. Nonetheless, given
(1) the operationally significant reduction in medical attrition
of 26%, (2) the low rates of stress fracture and anemia in this
population at the outset of the study, (3) the IOM recommen-
dations for iron requirements during military training, (4) the
low cost and absence of associated harms, and (5) the poten-
tial for other benefits not analyzed in the present study, the
findings of this report do not justify discontinuation of the
prenatal vitamin supplementation program. Further research
should be considered to delineate the impact of prenatal vita-
min supplementation on other medical outcomes in U.S. Air
Force BMT, as well as the impact of other vitamin and min-
eral formulations on health and performance in warrior and
athlete populations.
ACKNOWLEDGMENTS
The authors acknowledge Robert DeFraites, MD, MPH; Tomoko Hooper,
MD, MPH; and Roger Gibson, DVM, MPH, PhD, of the Uniformed Services
University of the Health Sciences (USUHS) for their assistance in the design
and development of this project and also Cara Olsen, MS, DrPH, of USUHS
for statistical consultation.
REFERENCES
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