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Review Article
Military Effectiveness of Five
Dietary Supplements Purported
to Aid Cognitive and Physical
Performance
Bradley Baker
Abstract
Background: The effectiveness of dietary supplements in sustaining physical and/or cognitive performance is
of interest to the military Rhodiola rosea, long-chain omega-3 fatty acids (LC omega-3), beetroot juice, arginine
and beta-alanine have recently been claimed to enhance cognitive and/or physical performance when taken
as supplements
Purpose: To narratively review recent research on the military effectiveness and safety of five dietary supplements
– Rhodiola rosea, long-chain omega-3 fatty acids (LC omega-3), beetroot juice, arginine and beta-alanine
Materials and Methods: The Academy of Nutrition and Dietetics Quality Criteria Checklists were used to assign
quality ratings of positive, neutral and negative to reviewed studies
Results: Of the five substances reviewed, only LC omega-3 (commonly known as ‘fish oils’) is considered safe
and applicable as a potential supplement for use during both fresh and field feeding This applies to military
members who do not consume the recommended intake of oily fish, whether by choice or because oily fish are
not available (eg when feeding is with combat rations)
Conclusions: Conclusions are drawn on the quality of evidence for beneficial effects on health and/or military
performance in the context of sustained arduous training and operations Although health benefits may result
from supplementation with LC omega-3, the available evidence suggests that such supplementation is unlikely
to enhance either cognitive or physical performance A lack of evidence for efficacy and/or possible adverse
health outcomes suggest that supplemental use of the other substances reviewed here is not appropriate for
military members
Various supplements are described by researchers
Introduction
and the supplement industry as ‘adaptogens’ for
Dietary supplements (abbreviated to ‘supplements’ their purported ability to help the body adapt to
in the remainder of this report) can be defined as stress and aid cognitive performance, or ‘ergogenic
nutrients and other substances that occur naturally aids’ for their purported ability to enhance
in foods and herbs Military members, particularly physical performance Yet others are claimed to be
soldiers, show interest in many supplements that ‘nootropics’ (boost cognitive performance) Caffeine
have been claimed to be effective in sustaining is an example of a well-understood nootropic that is
physical and/or cognitive performance However, useful to military members to help sustain alertness
such claims are not always based on sound scientific 1
during operations However, few other supplements
evidence are currently recommended for military use
Research in this area is relevant not only in guiding Due to their highly demanding roles, military
the optimal provision of foods in barracks and personnel—Infantry and Special Forces in particular—
combat feeding, but also in the potential provision are often tempted to use dietary supplements to try
of foods and/or supplements to sustain health and 2
to enhance their job performance The self-reported
military performance in the long term In addition, use of supplements of any kind by military personnel
the use of some supplements by military personnel in the United States and United Kingdom is in the
should be cautioned, due to potential risks to health, 2
range 55–61% for males and 65–71% for females
military performance and/or lack of efficacy Anecdotal evidence also indicates that dietary use is
Volume 25 Number 2; April 2017 Page 35
Review Article
highly prevalent in military personnel in Australia In process by which salidroside may act as a cognitive
2010, The Guide to Herbs and Supplements section aid has not been elucidated, however advertisements
of the (US) Warfighter Nutrition Guide cautioned for Rhodiola rosea extract have suggested the
against the use of many dietary supplements claimed supplement is useful for military personnel during
to enhance physical and cognitive performance, due operations, especially when fatigued, such as during
3
to their adverse side effects and/or lack of efficacy times of sleep deprivation Supplementation with
Rhodiola rosea extract has also been reported to have
More recently, substances that have shown potential a beneficial effect on stress related to fatigue9, 10
in the literature to increase physical and/or cognitive
performance, including in the military context, Of particular relevance to the military,
include beetroot juice, extract from the herb Rhodiola supplementation has been shown to reduce levels
rosea, long-chain omega-3 fatty acids from fish oil, of fatigue during stressors such as night duty6,
and the amino acids arginine and beta-alanine and night duty while performing military-related
Many of these substances have also been claimed to tasks8 In total, there is evidence from four studies
enhance human performance during military-specific that support these claimed benefits against fatigue
activities, thus, their effectiveness is of interest to the in healthy individuals without a diagnosed mental
military In many cases, the physiological processes 6-8, 11
illness According to the Academy of Nutrition
by which these five substances may act as either and Dietetics Quality Criteria, these findings arise
ergogenic and/or cognitive aids have not been fully 6, 8 7, 11
from studies of positive , and neutral quality
elucidated
Two recent review articles (both of positive quality)
However, as with many dietary supplements, recent assessed the bias/quality of the available research
research relating to the effectiveness is contradictory on the effects of Rhodiola rosea extract on cognitive
This paper reviews recent research (experimental and performance in healthy individuals, and concluded
evaluative) on these five supplements, and discusses 12, 13
that there is no convincing evidence of benefits
the quality of the evidence for their efficacy in the An earlier review study (of neutral quality) concluded
context of sustained military training and operations that ‘a single dose of Rhodiola rosea extract prior
The potential harmful effects of each supplement are to acute stress produces favourable results’14
also discussed However, two of the three authors of this review were
employees of a company which sells Rhodiola rosea
Quality Assessment extract, indicating a conflict of interest and hence
The quality of studies reviewed was assessed using the the potential for bias Until the reported benefits
Academy of Nutrition and Dietetics Quality Criteria of Rhodiola rosea extract supplementation are
Checklists (Primary Research and Review Article)4, replicated by independent researchers, the body of
12, 13
5 Each of these checklists contains four relevance evidence remains unconvicing
questions and ten validity questions that assess In summary, it is concluded that supplementation
scientific rigor They were used to assign a quality with Rhodiola rosea extract is unlikely to be of
rating of negative (ie mostly weak methodological value as a cognitive aid in the military context,
design), neutral (ie some strengths and weaknesses and its use should be cautioned due to lack of
in the methodological design) or positive (ie mostly efficacy There is no evidence that substantiates a
strengths in the methodological design) to the mode of action of the purportedly active substance,
research used to assess the effectiveness of each salidroside
supplement The strongest quality evidence identified
in this review is summarised for each supplement in Rhodiola rosea Extract and Exercise Performance
Table 1
Evidence on the effects of Rhodiola rosea extract on
Rhodiola rosea exercise performance is limited, and findings vary
Is Rhodiola rosea Extract a Cognitive Aid? among studies One recent study (neutral quality)
found no benefits to delayed onset of muscle soreness
15
Rhodiola rosea is a plant that grows in cold and (DOMS) or vertical jump performance Another
high-altitude regions of the Arctic An extract recent study (also neutral quality) demonstrated a
of Rhodiola rosea, which contains a substance benefit to performance in a time trial (TT, a measure
7
known as salidroside, has gained the attention of of endurance performance) Benefits to time-to-
the military due to its claimed ability to enhance exhaustion (TTE, a measure of endurance capacity)
were reported in 200416
cognitive performance by reducing the effects of , but to our knowledge, have
6-8 not been replicated
fatigue in stressful situations The physiological
Page 36 Journal of Military and Veterans’ Health
Review Article
Overall, there is some convincing evidence from cognitive performance/functioning or prevent a
a small number of neutral quality studies that decline in cognitive functioning in cognitively healthy
20, 21
Rhodiola rosea is effective in sustaining exercise older adults However, some researchers have
performance Further research, conducted in a acknowledged that longer term studies are required
19, 22
manner that reduces potential for bias, is required in this area
A small number of studies have investigated the
Long Chain Omega-3 Fatty Acids effects of LC omega-3 on cognitive function and mood
What are LC Omega-3 Fatty Acids? in younger populations These studies are of greater
relevance to the military population than those
All dietary fats contain a mixture of three types of discussed above involving older adult populations
‘fatty acids’—polyunsaturated (abbreviated to PUFA), A recent review article (neutral quality) found that
monounsaturated and saturated Omega-3 fatty the available data from randomised controlled trials
acids are one form of PUFA, and they are essential (RCTs) revealed ‘neither robust benefits nor a clear
in the diet (together with the other major form of lack of efficacy’ and described the evidence as weak
PUFA, omega-6 fatty acids) Of special importance and preliminary23 Further investigation is warranted
and indeed is continuing23
to health are the long-chain (LC) omega-3 fatty acids
docosahexaenoic acid (DHA) and eicosapentaenoic Effects of LC Omega-3 on Cognitive Function and
acid (EPA) These are derived mainly from marine Brain Health
food sources, particularly dark-fleshed fish, so are
commonly known as ‘fish oils’ Recent research has placed an emphasis on dietary
How much LC omega-3 do humans need? or supplementary intake of LC omega-3 throughout
life for general health and to sustain normal
In Australia, the Suggested Dietary Target (SDT)—ie cognitive function and brain health in ageing
the daily intake recommended for the prevention of Researchers Luchtman & Song reviewed studies
chronic disease based on the available evidence—for involving both animals and humans and found that
LC omega-3 fatty acids is 610 mg for men and 430 mg supplementation with LC omega-3 is consistently
for women17 shown to have protective effects throughout life on
The mean intake of LC omega-3 in the
general Australian population has been estimated neurodegeneration, cognitive impairment and long-
at only 189 mg per day18 term potentiation (the strength of signals in the
Although military fresh
feeding combat rations contain some fish meals, brain) Thus, further research is required in this area
LC omega-3 intakes in military populations have to explain the way in which LC omega-3 exerts these
22
not been estimated Military members who do not protective effects Reviews of human studies have
consume the recommended serves of oily fish or emphasised the importance of an adequate dietary
intake of LC omega-320, 24, 25
an LC omega-3 supplement may therefore have
intakes even less than the general population Low The effects of LC omega-3 intake—from both
LC omega-3 levels may have deleterious effects, supplementation and diet—on various other aspects
particularly on mood, as discussed in the next sub- of cognition have been widely investigated26-29
section There is strong evidence of a benefit of LC omega-3
LC Omega-3 and Enhancement of Cognitive supplementation on symptoms of depression in
Performance people without a diagnosis of major depressive
disorder27
Mental health-related benefits of LC
Omega-3 PUFAs are abundant in the brain, and omega-3 are of interest in the context of sustained
their concentration in brain cells wholly depends on cognitive performance, because negative thoughts
how much is consumed in the diet19 may be linked to increased cognitive load and errors
LC omega-3 in
in judgement30
the brain is an important factor in facilitating many There is also convincing evidence
brain processes, including neurotransmission19 that a higher intake of LC omega-3 in the diet (and
possibly supplementary LC omega-3) are effective in
LC omega-3 supplementation, with the aim to the prevention and treatment of depression28, 29
increase the level of LC omega-3 in the brain,
has been investigated for its effects on cognitive LC Omega-3 and Military Mental Health
performance However, based on the findings of
20 The military’s interest in the optimal intake of LC
two recent articles, including one of positive , and
one of neutral quality21 omega-3 by military personnel has increased in
, daily supplementation for
between 12 weeks and 3 years does not enhance recent years Researchers in the US found that
male US military personnel on active duty with the
Volume 25 Number 2; April 2017 Page 37
Review Article
lowest levels of DHA (docosahexaenoic acid) were presents various potential cognition-related benefits
at a 62% greater risk of suicide than counterparts of an optimal intake of LC omega-3 by military
with higher levels31 This and other similar findings members, particularly during times of deployment
led to a recommendation to the US Department of (eg cognition related to mental health) While it
Defense for ‘a comprehensive, coordinated research may be premature to recommend supplementation
program to evaluate the multiple uses of omega-3 for cognitive enhancement, it is clear that optimal
32 dietary intake of LC omega-3 is important for brain
fatty acids’ However, subsequent research
involving military service members found no effect structure and function throughout life
of relatively short term (60 days) supplementation
on psychological health or cognitive function33, and Current review evidence indicates that there is
another study found no association between blood insufficient consistent and high-quality evidence
34 to recommend supplementation to reduce physical
LC omega-3 level and levels of depression
activity-induced inflammation and soreness in the
LC Omega-3, Inflammation and Physical military context
Performance
It is concluded that all military members who
The effect of LC omega-3 supplementation on do not eat oily fish may obtain health benefits,
inflammation has been widely investigated However, but probably not performance benefits, from
a recent review article (positive quality) found supplementing with LC omega-3 in the range of
there is a ‘lack of evidence’ to support the ‘use of the NHMRC SDTs (610 mg for men and 430 mg
omega-3 supplementation to reduce inflammatory for women) to 3000 mg per day This applies to
biomarkers’ in healthy individuals35
This finding is military personnel when they are relying on either
consistent with a previous a previous review of the fresh foods or combat rations
evidence36
The effect of LC omega-3 supplementation on Beetroot Juice (Inorganic Nitrate)
physical performance and recovery in the military Inorganic nitrate, the substance of interest in beetroot
37
context was recently reviewed (neutral quality) juice, is abundant in a healthy diet Various leafy
It was found that studies reporting positive results green and root vegetables are good sources Beetroot
for reduced muscle damage and inflammation juice has been widely investigated for its ability to
after physical activity outnumbered those finding increase plasma levels of nitrate (NO -), nitrite (NO -
no effect However, it was concluded that there is 3 2
38, 39
currently insufficient human data to support the ), and nitric oxide (NO) These compounds are
involved in activating vasodilation40 Thus, increased
use of LC omega-3 to mitigate the inflammatory and plasma levels as a result of drinking beetroot juice
immunologic response to exercise and thus possibly may beneficially augment blood flow, oxygen uptake
enhance subsequent performance This is attributed and muscle oxygenation during exercise, leading to
partly to the limited ability to compare findings performance enhancement39, 40
due to the differing methodologies and dosage
protocols used The use of a single exercise bout The use of beetroot juice as an ergogenic supplement
to investigate the effect of LC omega-3 on physical has recently been reviewed numerous times (in
performance and recovery has been described as studies of neutral quality)39, 41-43 However, further
a major limitation in the relevance of the current research was considered necessary in all of these
evidence to the military Troops are likely to engage reviews, and one researcher concluded that there are
in multiple bouts of exercise per day, so the effect promising findings for ‘… enhancing aspects of the
may not be strong enough to confer benefits in the physiological response to exercise, such as muscle
military context37
Future research involving military efficiency and oxygenation, which might augment
personnel should be designed to produce findings performance’39
which are more applicable to the military Such
experimental designs might include, for example, Beetroot Juice Supplementation, Endurance
military personnel engaged in sustained operations Performance and the Military
in the field, with repeated TTE performance tests Military personnel often undertake prolonged physical
throughout activity during both training and operations, so
LC Omega-3 Summary substances which are claimed to enhance endurance
performance are of military interest Time-trial (TT)
The effects of LC omega-3 intake on sustained performance—a measure of endurance performance
brain and cognitive health are continually being in well-trained individuals—has been used to study
investigated Currently, the body of research the effectiveness of beetroot juice In a recent review
Page 38 Journal of Military and Veterans’ Health
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