Effects of vitamin D supplementation on salivary immune responses during Marine Corps basic training

A comprehensive review of dietary supplements mission-specific health and performance enhancement in military soldiers

Soldiers undergo intensive physical training, maintain high levels of concentration, and require rapid recovery from various traumas, making them highly specialized individuals. Under high physical and mental stress conditions, soldiers experience health issues related to decreased muscle function, impaired immunity, depression, and cognitive decline. A growing need exists for dietary supplements to mitigate these issues, and the usage patterns of such supplements are continuously increasing. Therefore, as dietary supplement consumption rises within the military, a sophisticated approach to addressing nutritional supplement requirements is essential. We discuss health problems that may arise under stressful conditions in soldiers, suggesting various nutritional supplements that are essential to address these issues. In conclusion, these nutritional supplements can be used as promising interventions for numerous health problems, including enhanced muscle function, improved immunity, mental stress alleviation, and cognitive enhancement. This ultimately suggests a contribution to military personnel health and the strengthening of national defense capabilities.

The Variability of the Salivary Antimicrobial Peptide Profile: Impact of Lifestyle

Saliva is crucial in maintaining oral health; its composition reflects the body's physiological and diseased state. Among salivary components, antimicrobial peptides (AMPs) stand out for their broad antimicrobial activities and role in modulating the oral microbiota and innate immune response. Local and systemic diseases can affect the levels of AMPs in saliva, making them attractive biomarkers. However, the large variability in their concentrations hampers their use in diagnostics. Knowledge of the various factors influencing the profile of salivary AMPs is essential for their use as biomarkers. Here, we examine how lifestyle factors such as physical activity, dietary supplementation, tobacco smoking, and psychological stress impact salivary AMP levels. By understanding these sources of variability, we can take a step forward in using AMPs for diagnostics and prognostics and develop new tailored and preventative approaches.

Intensive, Real-Time Data Collection of Psychological and Physiological Stress During a 96-Hour Field Training Exercise at a Senior Military College: Feasibility and Acceptability Cohort Study

BACKGROUND

Poor physical fitness, stress, and fatigue are factors impacting military readiness, national security, and economic burden for the United States Department of Defense. Improved accuracy of wearable biosensors and remote field biologic sample collection strategies could make critical contributions to understanding how physical readiness and occupational stressors result in on-the-job and environment-related injury, sleep impairments, diagnosis of mental health disorders, and reductions in performance in war-fighters.

OBJECTIVE

This study aimed to evaluate the feasibility and acceptability of intensive biomarker and biometric data collection to understand physiological and psychological stress in Army Reserved Officer Training Corps cadets before, during, and after a 96-hour field training exercise (FTX).

METHODS

A prospective pilot study evaluated the feasibility and acceptability of multimodal field data collection using passive drool saliva sampling, sweat sensors, accelerometry, actigraphy, and photoplethysmography. In addition, physical fitness (Army Combat Fitness Test), self-reported injury, and psychological resilience (Brief Resilience Scale) were measured.

RESULTS

A total of 22 cadets were included. Two were lost to follow-up due to injury during FTX, for a retention rate of 91%. Assessments of performance and psychological resilience were completed for all remaining participants, resulting in 100% testing adherence. All participants provided saliva samples before the FTX, with 98% adherence at the second time point and 91% at the third. For sweat, data collection was not possible. Average daily wear time for photoplethysmography devices was good to excellent, meeting a 70% threshold with data collected for ≥80% of person-days at all time points. Of the participants who completed the FTX and 12 completed a post-FTX acceptability survey for a response rate of 60%. Overall, participant acceptance was high (≥80%) for all metrics and devices.

CONCLUSIONS

This study demonstrates that wearable biosensors and remote field biologic sample collection strategies during a military FTX have the potential to be used in higher stakes tactical environments in the future for some, but not all, of the strategies. Overall, real-time biometric and biomarker sampling is feasible and acceptable during field-based training and provides insights and strategies for future interventions on military cadet and active-duty readiness, environmental stress, and recovery.

Effects of Vitamin D Supplementation and Baseline Vitamin D Status on Acute Respiratory Infections and Cathelicidin: A Randomized Controlled Trial

Background

Vitamin D supplementation may lower the risk of acute respiratory infection (ARI), and the effects may be mediated through the induction of cathelicidin production.

Objective

To study the effect of vitamin D supplementation on ARI and cathelicidin concentration in a randomized controlled trial (RCT) and to study the associations between baseline serum 25 hydroxyvitamin D (25(OH)D) and ARIs and cathelicidin concentrations in a 14-week follow-up study.

Methods

In the RCT study, the participants were randomized into 2 groups to receive either 20 µg of vitamin D3 or an identical placebo daily. Blood samples were obtained 3 times, at the beginning (study week 0), mid-term (study week 6), and at the end of the study period (study week 14). The follow-up study had 412 voluntary young men from 2 different locations and seasons (January and July). The primary outcomes were the number of ARIs diagnosed and the number of days off because of ARI.

Results

In the RCT, vitamin D supplementation had no effect on ARI or days off because of ARI. However, regardless of the group, vitamin D insufficiency (<50 nmol/L) was associated with increased ARI. In the 14-week follow-up study, insufficient serum 25(OH)D at baseline was also associated with increased risk of ARI (odds ratio [OR], 2.1; 95% confidence interval [CI], 1.2-3.7) and also days-off duty (OR, 2.3; 95% CI, 1.3-4.0) and was inversely associated with cathelicidin concentration (OR, 0.49; 95% CI, .24-.99).

Conclusions

Sufficient serum 25(OH)D may be preventive against acute respiratory infection and the preventive effect could be mediated through the induction of cathelicidin production. Clinical Trial Registry number: NCT05014048. https://clinicaltrials.gov/study/NCT05014048?term=NCT05014048&rank=1.

Added γ-oryzanol boosted anti-inflammatory effects of canola oil in adult subjects with type 2 diabetes: a randomized controlled clinical trial

PURPOSE

This study was conducted to examine the effects of daily intake of γ-oryzanol (ORZ)-fortified canola oil, as compared with plain canola and sunflower oils, on certain inflammatory and oxidative stress biomarkers in adult subjects with Type 2 Diabetes (T2D).

METHODS

We randomly allocated 92 adult subjects with T2D from both sexes to one of the following groups to receive: (a) ORZ-fortified canola oil (ORZO; n1 = 30); (b) unfortified canola oil (CANO; n2 = 32); or (c) sunflower oil (SUFO; n3 = 30) for 12 weeks. Dietary and laboratory evaluations were performed initially and finally.

RESULTS

Serum hs-CRP concentrations significantly decreased in ORZO group (from 3.1 ± 0.2 to 1.2 ± 0.2 mg/L), as compared with CANO (p = 0.003) and SUFO (p < 0.001) groups. Serum IL-6 significantly decreased just in ORZO (- 22.8%, p = 0.042) and CANO groups (- 19.8%, p = 0.038). However, the between-group differences were not significant. Serum IL-1β slightly decreased in ORZO (- 28.1%, p = 0.11) and increased in SUFO (+ 20.6%, p = 0.079) but between-group difference was statistically significant (p = 0.017). Serum IFN-γ concentrations decreased significantly only in ORZO (from 3.3 ± 0.08 to 2.9 ± 0.21 IU/mL, p = 0.044). Salivary IgA concentrations increased significantly in all three intervention groups. Notwithstanding, only the difference between ORZO and CANO groups was statistically significant (p = 0.042). Similarly, circulating malondialdehyde concentrations significantly decreased in all three groups but with no between-group significant difference.

CONCLUSIONS

Daily consumption of ORZ-fortified canola oil, compared with unfortified canola and sunflower oils, for 12 weeks resulted in boosting of certain anti-inflammatory effects of canola oil. These findings may have preventive implications for both clinicians and policy makers. This clinical trial was registered at clinicaltrials.gov (03.08.2022; NCT05271045).

Nutrition, Immune Function, and Infectious Disease in Military Personnel: A Narrative Review

Consuming a diet that meets energy demands and provides essential nutrients promotes a healthy immune system, while both under- and over-nutrition have been associated with immune dysfunction. Military personnel comprise a unique population who frequently endure multi-stressor environments, predisposing them to immune decrements. Additionally, 49% and 22% of active duty U.S. military personnel are classified as overweight and obese, respectively. A literature search on PubMed was conducted to identify studies, reports, review papers, and references within those sources relevant to the topic area. Military personnel experiencing either under- or over-nutrition can suffer from degraded health, readiness, and performance. Insufficient intake of nutrients during military operations increases infection risk and negatively impacts infection recovery. Energy, protein, iron, zinc, and vitamins C and D are nutritional areas of concern that may impact immune competence in a multi-stressor environment. Over-nutrition can promote accretion of excess body fat and obesity, which contributes to a chronic inflammatory state that coincides with immune impairments. Prioritizing efforts to optimize nutrient intake is one approach for reducing disease burden and improving readiness. This review discusses nutritional concerns concomitant to multi-stressor environments that impact immune function, and the relevance of obesity to infectious disease risk in the military population.

Perspective: Council for Responsible Nutrition Science in Session. Optimizing Health with Nutrition-Opportunities, Gaps, and the Future

Achieving optimal health is an aspirational goal for the population, yet the definition of health remains unclear. The role of nutrition in health has evolved beyond correcting malnutrition and specific deficiencies and has begun to focus more on achieving and maintaining 'optimal' health through nutrition. As such, the Council for Responsible Nutrition held its October 2022 Science in Session conference to advance this concept. Here, we summarize and discuss the findings of their Optimizing Health through Nutrition - Opportunities and Challenges workshop, including several gaps that need to be addressed to advance progress in the field. Defining and evaluating various indices of optimal health will require overcoming these key gaps. For example, there is a strong need to develop better biomarkers of nutrient status, including more accurate markers of food intake, as well as biomarkers of optimal health that account for maintaining resilience-the ability to recover from or respond to stressors without loss to physical and cognitive performance. In addition, there is a need to identify factors that drive individualized responses to nutrition, including genotype, metabotypes, and the gut microbiome, and to realize the opportunity of precision nutrition for optimal health. This review outlines hallmarks of resilience, provides current examples of nutritional factors to optimize cognitive and performance resilience, and gives an overview of various genetic, metabolic, and microbiome determinants of individualized responses.

Seven-month wintertime supplementation of 1200 IU vitamin D has no effect on hand grip strength in young, physically active males: A randomized, controlled study

Background

Study Design

Methods

Results

Conclusion

The effect of antiretroviral therapy initiation on vitamin D levels and four oral diseases among Kenyan children and adolescents living with HIV

OBJECTIVES

The impact of antiretroviral treatment (ART) on the occurrence of oral diseases among children and adolescents living with HIV (CALHIV) is poorly understood. The aim of this study was to determine the effect of ART timing on vitamin D levels and the prevalence of four oral diseases (dry mouth, dental caries, enamel hypoplasia, and non-herpes oral ulcer) among Kenyan CALHIV from two pediatric HIV cohorts.

METHODS

This nested cross-sectional study was conducted at the Kenyatta National Hospital, Nairobi, Kenya. CALHIV, 51 with early-ART initiated at <12 months of age and 27 with late-ART initiated between 18 months-12 years of age, were included. Demographics, HIV diagnosis, baseline CD4 and HIV RNA viral load data were extracted from the primary study databases. Community Oral Health Officers performed oral health examinations following standardized training.

RESULTS

Among 78 CALHIV in the study, median age at the time of the oral examination was 11.4 years old and median ART duration at the time of oral examination was 11 years (IQR: 10.1, 13.4). Mean serum vitamin D level was significantly higher among the early-ART group than the late-ART group (29.5 versus 22.4 ng/mL, p = 0.0002). Children who received early-ART had a 70% reduction in risk of inadequate vitamin D level (<20 ng/mL), compared to those who received late-ART (p = 0.02). Although both groups had similar prevalence of oral diseases overall (early-ART 82.4%; late-ART 85.2%; p = 0.2), there was a trend for higher prevalence of dry mouth (p = 0.1) and dental caries (p = 0.1) in the early versus late ART groups. The prevalence of the four oral diseases was not associated with vitamin D levels (p = 0.583).

CONCLUSIONS

After >10 years of ART, CALHIV with early-ART initiation had higher serum vitamin D levels compared to the late-ART group. The four oral diseases were not significantly associated with timing of ART initiation or serum vitamin D concentrations in this cohort. There was a trend for higher prevalence of dry mouth and dental caries in the early-ART group, probably as side-effects of ART.

Supplemental Protein and a Multinutrient Beverage Speed Wound Healing after Acute Sleep Restriction in Healthy Adults

BACKGROUND

Physiologic and psychologic stress slow healing from experimental wounds by impairing immune function.

OBJECTIVES

We aimed to determine whether supplemental protein and multinutrient supplementation improved wound healing markers after acute stress induced by acute sleep restriction.

METHODS

In this single-blind, crossover study in generally healthy young adults (18 males/2 females; mean ± SD age: 19.7 ± 2.30 y), experimental wounds were created by removing the top layer of forearm blisters induced via suction after 48 h of 72-h sleep restriction (2-h nightly sleep), a protocol previously shown to delay wound healing. Skin barrier restoration (measured by transepidermal water loss) assessed wound healing ≤10 d postblistering, and local immune responses were evaluated by serial measurement of cytokine concentrations in fluid collected at wound sites for 48 h postblistering. Participants consumed controlled, isocaloric diets with either 0.900 g · kg-1 · d-1 protein plus placebo (PLA) or 1.50 g · kg-1 · d-1 protein plus multinutrient beverage [l-arginine: 20.0 g/d; l-glutamine: 30.0 g/d; omega-3 (n-3) fatty acids: 1.00 g/d; zinc sulfate: 24.0 mg/d; cholecalciferol: 800 IU/d; and vitamin C: 400 mg/d] (NUT) during sleep restriction and for 4 d afterwards.

RESULTS

Skin barrier restoration (primary outcome) was shorter for NUT (median: 3.98 d; IQR: 1.17 d) than for PLA (median: 5.25 d; IQR: 1.05 d) (P = 0.001). Cytokines from wound fluid (secondary outcome) increased over time (main effect of time P ≤ 0.001), except IL-13 (P = 0.07); however, no effects of treatment were observed.

CONCLUSIONS

Supplemental nutrition may promote wound healing after sleep restriction in healthy adults including military personnel, the latter of which also have a high incidence of wounds and infection.This trial was registered at clinicaltrials.gov as NCT03525184.

Influence of Vitamin D Supplementation by Simulated Sunlight or Oral D3 on Respiratory Infection during Military Training

PURPOSE

This study aimed to determine the relationship between vitamin D status and upper respiratory tract infection (URTI) of physically active men and women across seasons (study 1) and then to investigate the effects on URTI and mucosal immunity of achieving vitamin D sufficiency (25(OH)D ≥50 nmol·L-1) by a unique comparison of safe, simulated sunlight or oral D3 supplementation in winter (study 2).

METHODS

In study 1, 1644 military recruits were observed across basic military training. In study 2, a randomized controlled trial, 250 men undertaking military training received placebo, simulated sunlight (1.3× standard erythemal dose, three times per week for 4 wk and then once per week for 8 wk), or oral vitamin D3 (1000 IU·d-1 for 4 wk and then 400 IU·d-1 for 8 wk). URTI was diagnosed by a physician (study 1) and by using the Jackson common cold questionnaire (study 2). Serum 25(OH)D, salivary secretory immunoglobulin A (SIgA), and cathelicidin were assessed by liquid chromatography-mass spectrometry LC-MS/MS and enzyme-linked immunosorbent assay.

RESULTS

In study 1, only 21% of recruits were vitamin D sufficient during winter. Vitamin D-sufficient recruits were 40% less likely to suffer URTI than recruits with 25(OH)D <50 nmol·L-1 (OR = 0.6, 95% confidence interval = 0.4-0.9), an association that remained after accounting for sex and smoking. Each URTI caused, on average, three missed training days. In study 2, vitamin D supplementation strategies were similarly effective to achieve vitamin D sufficiency in almost all (≥95%). Compared with placebo, vitamin D supplementation reduced the severity of peak URTI symptoms by 15% and days with URTI by 36% (P < 0.05). These reductions were similar with both vitamin D strategies (P > 0.05). Supplementation did not affect salivary secretory immunoglobulin A or cathelicidin.

CONCLUSION

Vitamin D sufficiency reduced the URTI burden during military training.

The Influence of Nutritional Factors on Immunological Outcomes

Through food intake, humans obtain a variety of nutrients that are essential for growth, cellular function, tissue development, energy, and immune defense. A special interaction between nutrients and gut-associated lymphoid tissue occurs in the intestinal tract. Enterocytes of the intestinal barrier act as sensors for antigens from nutrients and the intestinal microbiota, which they deliver to the underlying immune system of the lamina propria, triggering an immune response. Studies investigating the mechanism of influence of nutrition on immunological outcomes have highlighted an important role of macronutrients (proteins, carbohydrates, fatty acids) and micronutrients (vitamins, minerals, phytochemicals, antioxidants, probiotics) in modulating immune homeostasis. Nutrients exert their role in innate immunity and inflammation by regulating the expression of TLRs, pro- and anti-inflammatory cytokines, thus interfering with immune cell crosstalk and signaling. Chemical substrates derived from nutrient metabolism may act as cofactors or blockers of enzymatic activity, influencing molecular pathways and chemical reactions associated with microbial killing, inflammation, and oxidative stress. Immune cell function appears to be influenced by certain nutrients that form parts of the cell membrane structure and are involved in energy production and prevention of cytotoxicity. Nutrients also contribute to the initiation and regulation of adaptive immune responses by modulating B and T lymphocyte differentiation, proliferation and activation, and antibody production. The purpose of this review is to present the available data from the field of nutritional immunology to elucidate the complex and dynamic relationship between nutrients and the immune system, the delineation of which will lead to optimized nutritional regimens for disease prevention and patient care.