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Iron (Fe) deficiency is endemic worldwide. Little data are available regarding acute effects of dietary protein on intestinal Fe absorption. The current study evaluated the short-term effects of increasing dietary protein on Fe absorption and expression of genes involved in Fe homeostasis. Sprague Dawley rats (24, female) were randomly assigned to custom-formulated isocaloric diets containing 40, 20 (control), or 5% protein (as percentage of total kilocalories) for 7 d. Whole-body Fe balance studies demonstrated that Fe retention was greater in the 40% group than in the 5% group (30.8 vs. 7.3%; P0.01). In a separate study utilizing stable iron isotopes, the 40% group absorbed 30% of ingested Fe, while the 20% group absorbed 18% (P=0.005). Whole-genome profiling revealed that increasing dietary protein from 5 to 40% increased duodenal transcript expression of divalent metal transporter 1 (DMT1) 3.2-fold, duodenal cytochrome b (Dcytb) 1.8-fold, and transferrin receptor (TfR) 1.8-fold. Consistent with these findings, DMT1 transcript expression was 4-fold higher in RNA prepared from duodenal mucosa in the 40% group compared to the 20% group (P0.001). These data suggest that increasing dietary protein increases intestinal Fe absorption in part by up-regulating DMT1, Dcytb, and TfR.

Acute high protein intake results in increased intestinalcalcium absorption in humans and animals. Calcium is absorbed through both passive paracellular and facilitated trans cellular pathways. In rats, the increase in intestinal calcium absorption observed during a high protein dietis mediated at least in part through increased apical intestinal calcium uptake suggesting involvement of the transcellular pathway. However, we previously found that the expression of a paracellular calcium-permissive tight junction protein, Claudin-2, is higher in the duodenum of rats consuming a high compared to lowprotein diet. Whether dietary protein affects paracellular calcium flux has not been evaluated. Furthermore, the bioactive amino acids that might underlie this effect have not been identified. The purpose of this study was to evaluate the direct effects of mixed and individual amino acids on paracellular calcium flux across a small intestinal absorptive cell model. MethodsCaco-2 Bbe cells were used as a model of ...

Initial military training (IMT) is associated with elevated bone turnover and an increased risk for stress fractures. Supplemental Ca and vitamin D during IMT improves bone health, although previous studies indicate that supplemental Ca intake may interfere with iron absorption, affecting iron status. The objective of this study was to determine the effect of daily Ca and vitamin D supplementation (2000 mg and 1000 IU/day, respectively) on biochemical indicators of iron status during IMT. Biomarkers (hemoglobin, Hgb; serum ferritin, SF; soluble transferrin receptor, sTfR; transferrin saturation TS) were assessed in fasted volunteers (n = 152, males = 98, females = 54; age [mean ± SD] = 21 ± 4 yrs) at the start and end of a 9-wk IMT course. Supplemental Ca and vitamin D were provided in a fortified snack food, which was consumed between meals 2x/day throughout IMT. Iron status declined over the course, as Hgb, SF and TS declined (8, 50, and 37%, respectively; P < 0.05; main effect of time) and sTfR increas...

Stress fracture incidence is high during initial military training (IMT) with 2-6% of male and 8-21% of female recruits sustaining fractures. Identification and mitigation of risk factors is critic...

Consuming high protein during energy restriction (ER) promotes glycemic control. However, the extent to which protein source modulates the glycemic response and the intracellular mechanisms by which hepatic regulation of blood glucose is maintained during ER is not well described. Eighty male Sprague-Dawley rats (12 weeks old) were randomly divided into 8 treatment groups and fed energy adequate (EA) or ER (60% of the ad libitum feed intake for EA) diets containing two levels (control: CP, 10%; and high protein: HP, 35%) and sources (milk protein concentrate: MPC; and low isoflavone soy concentrate: SOY) of protein for 16 weeks. Fasting serum insulin and glucose concentrations were assessed, and hepatic regulators of gluconeogenesis were analyzed using Western blot. Blood glucose was similar across groups (group mean ± SD, 109 ± 11 mg/dL, P > 0.05). However, insulin levels were lower (P < 0.05) for HP (162 ± 63 pmol/L) than CP (208 ± 80 pmol/L); ER (165 ± 65 pmol/L) than EA (204 ± 80 pmol/L); and MPC (160...

Poor vitamin D status is linked to musculoskeletal injuries, such as stress fracture, during military training. The objective of this trial was to determine the effect of daily calcium (Ca) and vit...