The effects of exercise training programs on plasma concentrations of proenkephalin Peptide F and catecholamines.

To determine if exercise training alters the pattern and magnitude of plasma concentrations of proenkephalin Peptide F and epinephrine, plasma proenkephalin [107-140] Peptide F(ir) and catecholamines were examined pre-training (T-1), and after 4- (T-2), 8- (T-3), and 12-weeks (T-4) of training. 26 healthy men were matched and randomly assigned to one of three groups: heavy resistance strength training (Strength, n=9), high intensity endurance training (Endurance, n=8), or both training modalities combined (Combined, n=9). Blood was collected using a syringe with a cannula inserted into a superficial arm vein with samples collected at rest, after each 7 min stage and 5 and 15 min into recovery. With training, all groups observed shifted plasma Peptide F responses to graded exercise, where significant increases were observed at lower exercise intensities. Increases in plasma epinephrine with exercise were observed in all groups. The Combined group saw increases at 25% at T-3 and for 50% at T-2, T-3, and T-4 which was higher than T-1. The Endurance group demonstrated increases for 50% at T-1, T-2, T-3 but not at T-4. The plasma epinephrine response to graded exercise was reduced in the Strength group. Increases in plasma norepinephrine above rest were observed starting at 50% . The Strength group demonstrated a significant reduction in norepinephrine observed at 100% at T-3 and T-4. Peptide F and catecholamines responses to graded exercise can be altered by different types of physical exercise training. Simultaneous high intensity training may produce adrenal medulla exhaustion when compared to single mode training.

Phytase supplementation increases bone mineral density, lean body mass and voluntary physical activity in rats fed a low-zinc diet.

Phytic acid forms insoluble complexes with nutritionally essential minerals, including zinc (Zn). Animal studies show that addition of microbial phytase (P) to low-Zn diets improves Zn status and bone strength. The present study determined the effects of phytase supplementation on bone mineral density (BMD), body composition and voluntary running activity of male rats fed a high phytic acid, low-Zn diet. In a factorial design, rats were assigned to ZnLO (5 mg/kg diet), ZnLO+P (ZnLO diet with 1500 U phytase/kg) or ZnAD (30 mg/kg diet) groups and were divided into voluntary exercise (EX) or sedentary (SED) groups, for 9 weeks. SED rats were significantly heavier from the second week, and no catch-up growth occurred in EX rats. Feed intakes were not different between groups throughout the study. ZnLO animals had decreased food efficiency ratios compared to both phytase-supplemented (ZnLO+P) and Zn-adequate (ZnAD) animals (P<.01 compared to ZnLO). The ZnLO+P and ZnAD rats ran 56-75 km more total distance than ZnLO rats (P<.05), with the ZnLO+P rats running more kilometers per week than the ZnLO rats by Week 6. In vivo DEXA analyses indicate that rats fed phytase-supplemented diets had higher lean body mass (LBM) than those fed ZnLO diets; and that rats fed the Zn-adequate diets had the highest LBM. Body fat (%) was significantly lower in EX rats and was both Zn- and phytase insensitive. Rats fed phytase-supplemented diets had higher bone mineral content (BMC), bone area (BA) and BMD than rats fed ZnLO diets; and in rats fed ZnAD diets these indices were the highest. The dietary effects on BMC, BA and BMD were independent of activity level. We conclude that consuming supplemental dietary phytase or dietary Zn additively enhances Zn status to increase BMD, LBM and voluntary physical activity in rats fed a low-Zn diet. While the findings confirm that bone health is vulnerable to disruption by moderate Zn deficiency in rats, this new data suggests that if dietary Zn is limiting, supplemental phytase may have beneficial effects on LBM and performance activity.

Moderate zinc deficiency negatively affects biomechanical properties of rat tibiae independently of body composition.

To guide development of novel nutritional strategies aimed at reducing the incidence of stress fractures, we observed the effects of manipulating dietary zinc (Zn) content on bone integrity in Sprague-Dawley rats fed either a severely Zn-deficient (ZnD; 1 ppm), a moderately Zn-deficient (MZnD; 5 ppm) or a Zn-adequate (ZnAD; 30 ppm) diet for 6 weeks. At the completion of the diet period, body composition, bone mineral content (BMC), bone area (BA) and bone mineral density (BMD) were determined in vivo by using dual-energy X-ray absorptiometry. Following euthanasia, long bones were collected for determination of Zn content and biomechanical strength testing. Despite significant positive correlations between dietary Zn and both body weight (BW) and bone Zn content for the entire cohort (r = .77 and r = .83, respectively), rats fed MZnD or ZnAD diets did not differ in feed intakes, body composition, BMC, BA, BMD or BW. Tibial bones, but not femur bones, appear to be more responsive to dietary Zn manipulation, as all bone biomechanical strength indices in the ZnAD-fed rats were significantly greater than in rats fed the ZnD diets. Rats fed either MZnD or ZnAD diets had stronger tibiae (129% increase in maximum load and stress at maximum load, P<.01) compared with those fed ZnD diets. The load at breakage for the tibial bones of rats fed MZnD diets was not different from the ZnD rats, but lower (P<.05) than that of the ZnAD rats. These results suggest that since feed intakes, body composition, BMC, BA, BMD and BW were not significantly different between the MZnD- and ZnAD-fed animals, the reduced bone integrity observed in the MZnD-fed rats resulted from dietary Zn inadequacy, and not as a result of the reduced growth that is typically associated with Zn deficiency.

Prevalence of iron deficiency and iron deficiency anemia among three populations of female military personnel in the US Army.

BACKGROUND: Iron deficiency is the most prevalent micronutrient deficiency disease in the world and occurs in young women in the United States. Female military personnel represent a unique population faced with intense physical and cognitive demands. OBJECTIVE: The objective of this study was to determine the prevalence of iron deficiency and iron deficiency anemia among three populations of female military personnel in the US Army. METHODS: Iron status was assessed in 1216 volunteers. Volunteers were recruited from three groups: immediately following initial entry to the Army (IET), immediately following basic combat training (AIT), or following at least six months of permanent assignment (PP). Iron deficiency was determined using a three variable model, including cut-off values for serum ferritin, transferrin saturation, and red cell distribution width (RDW). Iron deficiency anemia was categorized by iron deficiency and a hemoglobin (Hgb) value of <12 g/dL. RESULTS: The prevalence of iron deficiency was greater in women in the AIT group (32.8%) than in the IET and PP groups (13.4 and 9.6%, respectively). The prevalence of iron deficiency anemia was greater in the AIT group (20.9%) than in the IET and PP groups (5.8 and 4.8%, respectively). Furthermore, the prevalence of iron deficiency anemia was greater in Hispanic (21.9%) and African-American military personnel (22.9%) than in Caucasian military personnel (10.5%). CONCLUSIONS: These data indicate that female military personnel experience diminished iron status following training, and that iron nutriture is an important issue facing females in the military.

Effects of dietary phytase on body weight gain, body composition and bone strength in growing rats fed a low-zinc diet.

Phytic acid, a major phosphorous storage compound found in foodstuffs, is known to form insoluble complexes with nutritionally essential minerals, including zinc (Zn). Phytases are enzymes that catalyze the removal of these minerals from phytic acid, improving their bioavailability. The objective of the present study was to determine the ability of dietary phytase to affect body weight, body composition, and bone strength in growing rats fed a high phytic acid, low Zn diet. Rats (n = 20) were fed either a control (AIN-93) or phytase supplemented (Natuphos, BASF, 1,500 phytase units (FTU)/kg) diet for a period of 8 weeks. Phytase supplementation resulted in increased (P<.05) bone and plasma Zn, but no change in plasma inorganic phosphorous or bone levels of Ca, Fe, or Mg. The addition of phytase to the diets resulted in a 22.4% increase (P<.05) in body weight at the end of the study as compared with rats fed a control diet. Dual x-ray absorptiometry (DXA) revealed that phytase supplementation resulted in increase lean body mass (LBM, P<.001) and increased bone mineral content (BMC, P<.001) as compared with feeding the control diet. Bone studies indicated that femurs and tibias from phytase supplemented rats had greater mass (P<.05) and were stronger (P<.05) than rats fed the control diet. This data suggest that the addition of phytase to low Zn diets results in improved Zn status, which may be responsible for beneficial effects on growth, body composition, and bone strength.