J. Philip Karl

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BACKGROUND Iron status degrades in female soldiers during military training. Inflammation-mediated up-regulation of hepcidin, a key mediator of iron homeostasis, may be a contributing factor. OBJECTIVE We measured the efficacy of an iron-fortified food product for maintaining iron status in female soldiers during basic combat training (BCT) and examined(More)
Fe is an essential micronutrient required for optimal cognitive and physical performance. Cross-sectional studies indicate that training degrades Fe status in female military personnel; however, longitudinal studies to measure the direct impact of military training on Fe status and performance have not been conducted. As such, the objective of the present(More)
Poor iron status affects billions of people worldwide. The prevalence of obesity continues to rise in both developed and developing nations. An association between iron status and obesity has been described in children and adults. The mechanism explaining this relationship remains unknown; however, findings from recent reports suggest that body mass index(More)
BACKGROUND Vitamin D is an essential nutrient for maintaining bone health, to include protecting against stress fracture during periods of rapid bone turnover. The objective of this longitudinal, observational study was to assess vitamin D status, biomarkers of bone turnover, and vitamin D and calcium intake in female Soldiers (n = 91) during US Army basic(More)
Military personnel and some athlete populations endure short-term energy deficits from reduced energy intake and/or increased energy expenditure (EE) that may degrade physical and cognitive performance due to severe hypoglycemia (<3.1 mmol/l). The extent to which energy deficits alter normoglycemia (3.9-7.8 mmol/l) in healthy individuals is not known, since(More)
New approaches to assess energy intake (EI) may have advantages over traditional written methods, but validity of these emerging methodologies must be demonstrated. This exploratory study compared EI obtained using a hand-held personal digital assistant (PDA) and traditional written records with total energy expenditure measured by doubly labeled water(More)
OBJECTIVE The objectives of this study were to use the healthy eating index (HEI) as a tool to characterize diet quality in Soldiers (n=135) during basic combat training (BCT), and to assess the effects of BCT on diet quality by comparing HEI scores before and after the training period. METHODS HEI scores were calculated from a 110-item semiquantitative(More)
The magnitude, temporal dynamics, and physiological effects of intestinal microbiome responses to physiological stress are poorly characterized. This study used a systems biology approach and a multiple-stressor military training environment to determine the effects of physiological stress on intestinal microbiota composition and metabolic activity, as well(More)
UNLABELLED The contributions of systemic versus local insulin-like growth factor-I (IGF-I) action for mediating fat-free mass (FFM) accretion have yet to be fully clarified, but circulating IGF-I is the preferred measure in clinical practice, and its merits as a biomarker have been demonstrated for a number of physiological outcomes. PURPOSE To test the(More)
Vitamin K exists in the food supply as phylloquinone, a plant-based form and as menaquinones (MKs), a collection of isoprenologues mostly originating from bacterial synthesis. Although multiple bacterial species used as starter cultures for food fermentations synthesize MK, relatively little is known about the presence and distribution of MK in the food(More)