Page 71 - Journal of Special Operations Medicine - Spring 2014

anxiety, and sleep impairment. Vitamin D levels have at optimizing human performance in SOF. Prospective
not been assessed in PTSD patients, but testosterone lev- unitwide screening of vitamin D status and randomized
els are altered in veterans with PTSD. 57,58 As discussed, placebo-controlled supplementation trials will elucidate
testosterone levels have been positively correlated with the benefits of optimizing vitamin D status in deficient
vitamin D levels, and vitamin D supplementation in- Servicemembers. Most notably, vitamin D status may
42
creased testosterone levels in vitamin D–deficient men. 43 affect recovery from mTBI due to its role in regulating
This suggests that hypogonadism is influenced by vita- inflammatory cytokines. To date, human studies have
min D status. Furthermore, low vitamin D levels have not evaluated vitamin D status in mTBI, although vi-
been linked to increased risk of suicide in active duty tamin D has shown potential as treatment following
Servicemembers, reinforcing that vitamin D has an im- TBI.
49
portant role in mental health. 13
Conclusion
Recommendations
Implementing an aggressive clinical intervention to reduce
The IOM set the vitamin D Recommended Dietary vitamin D deficiency is paramount in addressing related
Allowance at 600IU/day and a tolerable upper intake cognitive and physical performance deficits. Vitamin
level of 4000IU/day. However, many experts suggest D supplementation presents a safe, non-invasive, man-
10
that most adults require 1500–2000/per day to main- ageable, and low-cost intervention for maintaining
tain blood levels above 30ng/mL. Treatment of vita- health within the force. Evidence suggests that opti-
11
min D deficiency generally requires supplementation of mal vitamin D levels may provide resilience to mTBI
50,000IU/week for 8 weeks or until serum 25(OH)D by modifying the inflammatory response. Many of the
exceeds 30ng/mL, followed by a maintenance dose of chronic symptoms associated with mTBI such as de-
1500–2000IU/day. While dietary supplements are avail- pression, balance problems, and cognitive decline are
able as vitamin D or D , research suggests that vitamin also associated with vitamin D deficiency. Furthermore,
3
2
D is more effective at increasing serum 25(OH)D due these symptoms are associated with endocrine dysfunc-
3
to its more efficient hydroxylation and greater affinity tion and deficiencies in testosterone and growth hor-
for VDR. 59 mone, which may be regulated by vitamin D.
Vitamin D is toxic at high doses, manifesting initially There is additional evidence to support that vitamin D
as elevated calcium and phosphate and then as calcifi- deficiency may have a role in PTSD related to its as-
cation of soft tissue. However, vitamin D intoxication sociation with testosterone production and relationship
is rare. Healthy men have supplemented with 10,000IU with other mental health disorders. Furthermore, vita-
vitamin D /day for 5 months without adverse effects. min D deficiency has the potential to limit physical per-
8
3
Further evidence shows that subjects supplemented formance via reduced muscle strength and poor balance.
with 50,000IU vitamin D/week for 8 weeks followed by Unidentified vitamin D deficiencies are likely contrib-
50,000IU vitamin D every other week for 6 years expe- uting to loss of combat power and effectiveness. With
rienced no toxicity, changes in calcium status, or kidney deficiency potentially widespread, vitamin D status has
stones. Vitamin D endogenous synthesis is regulated implications in physical training as well as cognitive
60
tightly. Therefore, if Operators are exposed to UV ra- functioning related to the treatment and prevention of
diation with high vitamin D levels, endogenous vitamin mTBI and PTSD. While vitamin D is one component
D synthesis will be limited, thereby avoiding toxicity. of multifactorial conditions, correcting vitamin D defi-
An important distinction in clinical recommendation is ciency will eliminate a treatable etiology that inhibits
to treat vitamin D deficiency rather than indiscriminate progression of treatment for cognitive and/or perfor-
pharmacological supplementation. Most research indi- mance impairments.
cates that no further benefits ensue with serum 25(OH)
D levels exceeding 40 to 50ng/mL.
References
1. Wentz LM, Eldred JD, Chambers PC, et al. Correlation of
Limitations and Future Directions vitamin D with testosterone levels in Special Operations
Preliminary data show that vitamin D deficiency is Personnel. Poster session presented at: Special Operations
widespread across SOF personnel. However, these Medical Association Scientific Assembly; 14–17 December
2013; Tampa, FL.
data are retrospective and do not provide accurate 2. Fairbrother B, Shippee R, Kramer T, et al. Nutritional and
prevalence of vitamin D deficiency in Servicemembers. immunological assessment of Soldiers during the Special
Nevertheless, further analysis may identify significant Forces Assessment and Selection Course. 1995 Technical
relationships between vitamin D status and other lab- Report. Natick, MA: U.S. Army Research Institute of Envi-
oratory measurements to design future studies aimed ronmental Medicine.

Vitamin D Status in Soldiers and Physical and Cognitive Performance 63