D. Travis Thomas

Position of the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and Athletic Performance

It is the position of the Academy of Nutrition and Dietetics (Academy), Dietitians of Canada (DC), and the American College of Sports Medicine (ACSM) that the performance of, and recovery from, sporting activities are enhanced by well-chosen nutrition strategies. These organizations provide guidelines for the appropriate type, amount, and timing of intake of food, fluids, and supplements to promote optimal health and performance across different scenarios of training and competitive sport. This position paper was prepared for members of the Academy, DC, and ACSM, other professional associations, government agencies, industry, and the public. It outlines the Academys, DCs, and ACSMs stance on nutrition factors that have been determined to influence athletic performance and emerging trends in the field of sports nutrition. Athletes should be referred to a registered dietitian nutritionist for a personalized nutrition plan. In the United States and in Canada, the Certified Specialist in Sports Dietetics is a registered dietitian nutritionist and a credentialed sports nutrition expert.

Relationship between 25-hydoxyvitamin D, muscle strength, and incidence of injury in healthy adults: a systematic review

The purpose of this systematic review is to answer the following clinical questions in healthy adults: is vitamin D status related to (1) muscle strength? (2) or incidence of injury? A literature search was performed using Pubmed, SPORTDiscus, and Web of Science to capture relevant articles that have examined these outcomes. Inclusion criteria required studies to address at least one of the 2 questions stated above, enroll healthy human subjects with a mean age of 18 to 65 years of age, and include serum 25-hydoxyvitamin D measures. Study characteristics such as vitamin D status, study design, and study population were documented. Measured assessors and outcomes from all studies were extracted to answer at least one of the two questions. When applicable, data were used to compute effect sizes at a 95% confidence interval for comparisons across studies to answer the 2 questions. The results of these studies indicate a weak to moderate effect of higher 25-hydoxyvitamin D levels on greater muscle strength and reduced incidence of injury. Randomized controlled clinical trials examining these questions are scarce when compared with the popularity of vitamin D testing; therefore, future trials are necessary to advance our understanding and to clarify the effect vitamin D has on extraskeletal outcomes in healthy adults.

The effect of sex on immune cells in healthy aging: Elderly women have more robust natural killer lymphocytes than do elderly men.

Immune gender differences have been reported, but are little studied in elderly humans. We compared monocyte and lymphocyte subsets, along with soluble immune mediators in healthy men and women over the age of 70. We also measured natural killer (NK) lymphocyte cytotoxic granule exocytosis, chemokine synthesis, and cytokine synthesis in response to a variety of stimuli. Elderly women had significantly more circulating B cells than men, whereas men had more CD4 central memory T cells and higher monocyte levels. Plasma adiponectin levels were higher in women, plasma retinol-binding protein 4 levels were higher in men, but there were no significant gender differences in C-reactive protein, IL-15, or sphingosine-1-phosphate. Women had a higher ratio of immature CD56(bright) NK cells to mature CD56(dim) NK cells, indicating a gender difference in NK cell maturation in the elderly. Comparing sexes, female mature NK cells had more vigorous cytotoxic granule responses to K562 leukemia cells and IFN-γ responses to NKp46 crosslinking. Moreover, female NK cells were more likely to produce MIP-1β in response to a variety of stimuli. These data show that gender influences NK cell activity in elderly humans.

Nutrition intervention to decrease symptoms in patients with advanced heart failure.

For a majority of patients with advanced heart failure, there is a need for complementary, non-pharmacologic interventions that could be easily implemented by health care providers to provide palliative care. Three major pathologic pathways underlying heart failure symptoms have been identified: fluid overload, inflammation, and oxidative stress. Prior research has demonstrated that three nutrients-sodium, omega-3 fatty acids, and lycopene-can alter these pathologic pathways. Therefore, the purposes of this study are to test the effects of a 6-month nutrition intervention of dietary sodium reduction combined with supplementation of lycopene and omega-3 fatty acids on heart failure symptoms, health-related quality of life, and time to heart failure rehospitalization or all-cause death. The aims of this double blind-placebo controlled study are (1) to determine the effects of a 6-month nutrition intervention on symptom burden (edema, shortness of air, and fatigue) and health-related quality of life at 3 and 6 months, and time to heart failure rehospitalization or all-cause death over 12 months from baseline; (2) compare dietary sodium intake, inflammation, and markers of oxidative stress between the nutrition intervention group and a placebo group at 3 and 6 months; and (3) compare body weight, serum lycopene, and erythrocyte omega-3 index between the nutrition intervention group and a placebo group at 3 and 6 months. A total of 175 patients with advanced heart failure will be randomized to either the nutrition intervention or placebo group.

Data correlations between gender, cytomegalovirus infection and T cells, NK cells, and soluble immune mediators in elderly humans.

We describe a cohort of 50 elderly subjects, age at least 70 years. We present gender-specific findings in T lymphocyte markers and soluble immune mediators. We show the correlation between cytomegalovirus infection status with CD56dim NK cell responses to a variety of stimuli and with CD56bright/CD56dim NK cell ratio. We also present the correlation of retinol binding protein (RBP)−4 plasma levels with NK cell responses and we explore the relationship between gender and adiponectin, 25(OH)D (vitamin D), and RBP4 in affecting CD56dim NK cell responses. These data are discussed in Al-Attar et al. (2016) [1].

Hybrid diffuse optical techniques for continuous hemodynamic measurement in gastrocnemius during plantar flexion exercise

Abstract. Occlusion calibrations and gating techniques have been recently applied by our laboratory for continuous and absolute diffuse optical measurements of forearm muscle hemodynamics during handgrip exercises. The translation of these techniques from the forearm to the lower limb is the goal of this study as various diseases preferentially affect muscles in the lower extremity. This study adapted a hybrid near-infrared spectroscopy and diffuse correlation spectroscopy system with a gating algorithm to continuously quantify hemodynamic responses of medial gastrocnemius during plantar flexion exercises in 10 healthy subjects. The outcomes from optical measurement include oxy-, deoxy-, and total hemoglobin concentrations, blood oxygen saturation, and relative changes in blood flow (rBF) and oxygen consumption rate (rV˙O2). We calibrated rBF and rV˙O2 profiles with absolute baseline values of BF and V˙O2 obtained by venous and arterial occlusions, respectively. Results from this investigation were comparable to values from similar studies. Additionally, significant correlation was observed between resting local muscle BF measured by the optical technique and whole limb BF measured concurrently by a strain gauge venous plethysmography. The extensive hemodynamic and metabolic profiles during exercise will allow for future comparison studies to investigate the diagnostic value of hybrid technologies in muscles affected by disease.

Could vitamin D and bicarbonate supplementation synergize to mitigate age-related loss of muscle?

In patients with kidney disease receiving hemodialysis, metabolic acidosis is closely tied to muscle pathology and is known to exacerbate age-related loss of muscle mass and function. To a lesser extent, the ‘‘Western’’ diet is thought to contribute to mild (sub-clinical) metabolic acidosis via the supply of acid precursors from foods [1], but the clinical significance to chronic age-related muscle degeneration has received little attention. This may partly be due to equivocal data on the benefits of neutralizing diet-induced metabolic acidosis for improving muscle-related outcomes in patients without kidney disease [2]. Despite limited data, acidosis has been shown to stimulate muscle proteolysis and is associated with negative functional outcomes including reduced peak torque and lower gait speed [3]. This is important to note because aged adults are less able to excrete excess H ions and are more prone to develop mild, but slowly increasing metabolic acidosis that may be exacerbated by a ‘‘Western’’ diet [1]. Furthermore, approximately one out of four adults older than 50 years of age have low serum bicarbonate levels to neutralize an acidogenic diet. Because of these factors, recommendations for future work include examining the effects of alkali therapy on functional outcomes, nitrogen balance, strength and other relevant measures of physical function, in aged healthy adults [3]. Vitamin D status (measured as 25(OH)D) is also garnering interest as a player in preserving skeletal muscle mass and function in aging. Although, the study of vitamin D deficiency and repletion, in relation to muscle metabolic function in aging is relatively new, vitamin D deficiency has already been associated with several negative muscle outcomes including muscle degeneration with fat infiltration [4]. Loss of muscle fiber size and reduction in muscle protein synthesis have also been documented and is thought to be clinically significant since vitamin D deficiency is considered as a worldwide epidemic [5]. In this issue of Endocrine, Ceglia et al. [6] investigated the interactions between potassium bicarbonate and vitamin D supplementation to shed light on the underlying mechanisms associated with muscle atrophy, conservation, and fiber morphology in male rats. The author’s rationale for examining the vitamin D/bicarbonate interaction was based on research from the 1970s citing that depletion of vitamin D resulted in metabolic acidosis, whereas repletion resulted in a metabolic alkalosis by changes in renal tubule bicarbonate reabsorption. An additional cited study provided support that acute metabolic acidosis resulted in suppression of 1-alpha hydroxylase activity, collectively suggesting that the alterations in either vitamin D status or acid–base balance may affect the other and, thus, have detrimental impact on muscle tissue [6]. Ceglia et al. [6] found that potassium bicarbonate supplementation resulted in 35 % lower urinary nitrogen to creatinine (UNi/Cr) ratio independent of vitamin D status. In vitamin D deficient rats, potassium bicarbonate resulted in 28 % increase in UNi/Cr compared to rats with normal vitamin D levels, but the findings did not reach the statistical significance. Furthermore, in rats experiencing metabolic acidosis, higher vitamin D status seemed to work synergistically with bicarbonate to potentiate Akt activation, a protein kinase involved in several anabolic pathways. As a result of their findings, the authors suggested that longer more comprehensive investigation is required to advance and confirm the impact of a dietary intervention on ubiquitin–proteasome pathway at different pathway time points and to fully D. Travis Thomas (&) Division of Clinical Nutrition, University of Kentucky, Lexington, KY, USA e-mail: david.t.thomas@uky.edu

Physical, Physiological, and Dietary Comparisons Between Marine Corps Forces Special Operations Command Critical Skills Operators and Enablers

Introduction Tactical demands of a Marine Corps Forces Special Operations Command (MARSOC) Critical Skills Operator (CSO) require high levels of physical performance. During combat deployments, teams of CSOs are supplemented with enablers who specialize in mission-specific tasks. MARSOC CSOs and enablers serve alongside each other in extreme combat environments, often enduring the same physical demands, but the selection process for each group is very different. The purpose of this observational study was to quantify the physical, physiological, and dietary differences of MARSOC CSOs and enablers, as this may have a direct impact on tactical performance and provide important information to shape future research. Materials and Methods Fat free mass (FFM), fat mass (FM), fat mass index (FMI), fat free mass index (FFMI), anaerobic power (AP), anaerobic capacity (AC), aerobic capacity (VO2max), knee flexion (KF), knee extension (KE), trunk extension (TE), and trunk flexion (TF) isokinetic strength were collected. Dietary intake was collected using automated self-administered 24-hr dietary recalls (ASA24) for a subgroup of subjects. Results Testing on 164 male CSOs (age: 27.5 ± 3.8 yr, height: 178.7 ± 6.5 cm, mass: 85.7 ± 9.1 kg, and 7.6 ± 2.9 yr of military service) and 51 male enablers (age: 27.8 ± 5.4 yr, height: 178.4 ± 8.5 cm, mass: 83.8 ± 11.8 kg, and 7.9 ± 5.4 yr of military service) showed there were no significant differences for age, height, mass, or years of military service. (p > 0.05). CSOs demonstrated greater physiological performance in AP (W/kg) (p = 0.020), AC (W/kg) (p = 0.001), and VO2max (ml/kg/min) (p = 0.018). There were no significant differences in FM and FFM (p > 0.05), however CSOs demonstrated significantly higher FFMI (p = 0.011). CSOs also demonstrated greater KF (%BW) (p = 0.001), KE (%BW) (p = 0.001), TE (%BW) (p = 0.010), and TF (%BW) (p = 0.016). No differences in energy or macronutrient intake were observed in the subgroup. Conclusions MARSOC CSOs demonstrated significantly greater FFMI, AP, AC, VO2max, KF, KE, TE, and TF compared with enablers. Dietary intake was consistent between groups, but fueling concerns were identified for all personnel in the subgroup. These findings suggest the need for future studies to examine what physiological and strength thresholds are necessary to operate effectively as a member of a MSOT and determine the relationship between specific performance deficits and risk of injury. In addition, the integration of nutrition strategies that augment and optimize the performance of both CSOs and enablers may be beneficial.

Vitamin D and Athletes, Part I: A Growing Interest

Part I of this Pearls of Practice series highlights the growing interest in the status and needs of athletes in relation to vitamin D. Part II of the series will outline the relationship between vitamin D and injury prevention and identifi es take-home practice points for clinicians. Scientifi c inquiry involving vitamin D has sparked both public interest and controversy surrounding how much vitamin D is needed to promote good health. Vitamin D appears not only to maintain bone health but also to impact extraskeletal health by mediating infl ammatory and immune pathways and contributing to optimal muscle function. Given these fi ndings, it is no surprise that athletes’ interest in vitamin D supplementation has increased. It is conceivable that reversing compromised vitamin D status may affect muscle function, creating signifi cant implications for individuals in the highly competitive world of athletics. Conversely, athletes with chronic vitamin D defi ciency or insuffi ciency may experience impaired strength-gaining potential and increased risk of both hard and soft tissue injury. What are the key aspects of the vitamin D literature that clinicians should understand to help guide responsible supplementation decisions?