Adjusting Ferritin Concentrations for Nonclinical Inflammation in Adolescents with Overweight or Obesity.

OBJECTIVE: To compare approaches for adjusting serum ferritin concentrations for inflammation in Chilean adolescents with overweight and obesity. STUDY DESIGN: Cross-sectional data from 518 adolescents (aged 16-17 years; 48% females) from Santiago, Chile were analyzed. Several approaches were compared for estimating the prevalence of depleted iron stores (defined as serum ferritin <15 µg/L), including unadjusted prevalence and higher cutoffs for various subgroups (excluding participants with inflammation), correction factors, and regression corrections. A "reference" prevalence estimate was calculated as the prevalence of serum ferritin <15 µg/L in normal weight individuals without inflammation. Each adjustment approach was compared with this reference prevalence. RESULTS: The sample comprised 61.2% normal weight, 23.7% overweight, and 15.1% obese individuals. The prevalence of inflammation (marked by C-reactive protein level >5.0 mg/L) was 6.3%, 8.1%, and 14.1% in the 3 groups, respectively. The correction factor approaches produced adjusted estimates closest to the reference estimate (24.1%-24.7% vs 22.9%), followed by the regression corrections (24.7%-25.1% vs 22.9%). Applying a higher serum ferritin cutoff (30 µg/L) to all participants or to participants with overweight/obesity produced adjusted estimates farthest from the reference (59.5% and 35.3%, respectively). CONCLUSIONS: Adjusting serum ferritin concentration may be necessary when assessing iron status in populations with high rates of overweight/obesity. After reviewing 6 approaches for adjusting for the influence of inflammation, this study suggests that using correction factors may be the most appropriate approach for adjusting serum ferritin in Chilean adolescents. Further research is needed to determine the optimal approach for adjusting serum ferritin concentrations for weight-related inflammation in broader populations.

Iron-biofortified pearl millet consumption increases physical activity in Indian adolescent schoolchildren after a 6-month randomised feeding trial.

Fe deficiency has negative effects on voluntary physical activity (PA); however, the impact of consuming Fe-biofortified staple foods on voluntary PA remains unclear. This study compared the effects of consuming Fe-biofortified pearl millet or a conventional pearl millet on measures of voluntary PA in Indian schoolchildren (ages 12-16 years) during a 6-month randomised controlled feeding trial. PA data were collected from 130 children using Actigraph GT3X accelerometers for 6 d at baseline and endline. Minutes spent in light and in moderate-to-vigorous PA were calculated from accelerometer counts using Crouter's refined two-regression model for children. Mixed regression models adjusting for covariates were used to assess relationships between intervention treatment or change in Fe status and PA. Children who consumed Fe-biofortified pearl millet performed 22·3 (95 % CI 1·8, 42·8, P = 0·034) more minutes of light PA each day compared with conventional pearl millet. There was no effect of treatment on moderate-to-vigorous PA. The amount of Fe consumed from pearl millet was related to minutes spent in light PA (estimate 3·4 min/mg Fe (95 % CI 0·3, 6·5, P = 0·031)) and inversely related to daily sedentary minutes (estimate -5·4 min/mg Fe (95 % CI -9·9, -0·9, P = 0·020)). Consuming Fe-biofortified pearl millet increased light PA and decreased sedentary time in Indian schoolchildren in a dose-dependent manner.

Increased Iron Status during a Feeding Trial of Iron-Biofortified Beans Increases Physical Work Efficiency in Rwandan Women.

BACKGROUND: Iron-biofortified staple foods can improve iron status and resolve iron deficiency. However, whether improved iron status from iron biofortification can improve physical performance remains unclear. OBJECTIVE: This study aimed to examine whether changes in iron status from an iron-biofortified bean intervention affect work efficiency. METHODS: A total of 125 iron-depleted (ferritin <20 µg/L) female Rwandan university students (18-26 y) were selected from a larger sample randomly assigned to consume iron-biofortified beans (Fe-Bean; 86.1 mg Fe/kg) or conventional beans (control: 50.6 mg Fe/kg) twice daily for 18 wk (average of 314 g beans consumed/d). Blood biomarkers of iron status (primary outcome) and physical work efficiency (secondary outcome) were measured before and after the intervention. Work performed was assessed during 5-min steady-state periods at 0-, 25-, and 40-W workloads using a mechanically braked cycle ergometer. Work efficiency was calculated at 25 W and 40 W as the work accomplished divided by the energy expended at that workload above that expended at 0 W. General linear models were used to evaluate the relation between changes in iron status biomarkers and work efficiency. RESULTS: The Fe-Bean intervention had significant positive effects on hemoglobin, serum ferritin, and body iron stores but did not affect work efficiency. However, 18-wk change in hemoglobin was positively related to work efficiency at 40 W in the full sample (n = 119; estimate: 0.24 g/L; 95% CI: 0.01, 0.48 g/L; P = 0.044) and among women who were anemic (hemoglobin <120 g/L) at baseline (n = 43; estimate: 0.64 g/L; 95% CI: 0.05, 1.23 g/L; P = 0.036). Among women who were nonanemic at baseline, change in serum ferritin was positively related to change in work efficiency at 40 W (n = 60; estimate: 0.50 µg/L; 95% CI: 0.06, 0.95 µg/L; P = 0.027). CONCLUSIONS: Increasing iron status during an iron-biofortified bean feeding trial improves work efficiency in iron-depleted, sedentary women. This trial was registered at clinicaltrials.gov as NCT01594359.

Increasing Iron Status through Dietary Supplementation in Iron-Depleted, Sedentary Women Increases Endurance Performance at Both Near-Maximal and Submaximal Exercise Intensities.

BACKGROUND: Iron deficiency persists as the most common micronutrient deficiency globally, despite having known detrimental effects on physical performance. Although iron supplementation and aerobic exercise have been examined individually and are known to improve physical performance, the impact of simultaneous iron supplementation and aerobic training remains unclear. OBJECTIVE: The aim of this study was to examine the individual and combined effects of iron supplementation and aerobic training on improving maximal and submaximal physical performance in iron-depleted, nonanemic (IDNA) women. We hypothesized that women receiving iron would improve their endurance performance but not their estimated maximal oxygen consumption (eVO2max). METHODS: Seventy-three sedentary, previously untrained IDNA (serum ferritin <25 µg/L and hemoglobin >110 g/L) women aged 18-26 y with a body mass index (kg/m2) of 17-25 participated in a double-blind, 8-wk, randomized controlled trial with a 2 × 2 factorial design including iron supplementation (42 mg elemental Fe/d) or placebo and aerobic exercise training (5 d/wk for 25 min at 75-85% of age-predicted maximum heart rate) or no training. Linear models were used to examine relations between training, supplement, and changes in the primary outcomes of observed maximal oxygen consumption (VO2peak) and eVO2max and ventilatory threshold (absolute oxygen consumption and percentage of maximum). Re-evaluation of a published meta-analysis was used to compare effects of iron supplementation on maximal oxygen consumption (VO2max) and VO2peak. RESULTS: There were significant training-by-supplement interactions for VO2peak, volume of oxygen consumption at the ventilatory threshold, and the percentage of eVO2max where the threshold occurred, with the iron-untrained group performing better than the placebo-untrained group. There was no beneficial effect of iron supplementation for VO2max (mean difference: 0.53; 95% CI: -0.75, 1.81; P = 0.42), but a significant benefit was observed for VO2peak (mean difference: 1.87; 95% CI: 0.15, 3.60; P = 0.03). CONCLUSIONS: Iron supplementation increases endurance performance at submaximal and maximal (VO2peak) exercise intensities in IDNA women. However, increasing iron status does not increase eVO2max. This trial was registered at clinicaltrials.gov as NCT03002090.

Effects of Dose and Duration of Zinc Interventions on Risk Factors for Type 2 Diabetes and Cardiovascular Disease: A Systematic Review and Meta-Analysis.

No meta-analysis has examined the effect of dose and duration of zinc interventions on their impact on risk factors for type 2 diabetes (T2D) or cardiovascular disease (CVD). This study aimed first to compare the effects of zinc interventions dichotomized as low versus high dose (<25 mg/d and ≥25 mg/d, respectively) and short versus long duration (<12 wk and ≥12 wk, respectively) on risk factors for T2D and CVD. Second, it discusses the results from the low-dose and long-duration meta-analyses as a foundation for understanding what impact a zinc-biofortification intervention could have on these risk factors. The PubMed and Cochrane Review databases were searched through January 2020 for full-text, human studies providing zinc supplements (alone) at doses ≤75 mg/d and a placebo. Data on study and sample characteristics and several T2D and CVD risk factors were extracted. There were 1042 and 974 participants receiving zinc and placebo, respectively, from 27 studies. Low-dose zinc supplementation (<25 mg/d) significantly benefited fasting blood glucose, insulin resistance, triglycerides, total cholesterol, and LDL cholesterol. High-dose zinc supplementation (≥25 mg/d) benefited glycated hemoglobin and insulin resistance. Short-duration interventions (<12 wk) benefited fasting blood glucose, insulin resistance, and triglycerides, while long-duration studies (≥12 wk) benefited fasting blood glucose, triglycerides, and total and LDL cholesterol. Effect sizes for low-dose and long-duration interventions were of equal or greater magnitude to those from high-dose or short-duration interventions. Low-dose and long-duration zinc supplementation each improved more risk factors for T2D and CVD than high-dose and short-duration interventions, respectively. It is currently unknown whether low doses of zinc delivered over long durations via a biofortified crop would similarly impact these risk factors. However, this review suggests that low-dose, long-duration zinc intake from supplements, and potentially biofortification, can benefit risk factors for T2D and CVD.

Efficacy of iron supplementation may be misinterpreted using conventional measures of iron status in iron-depleted, nonanemic women undergoing aerobic exercise training.

Background: Despite its known detrimental effects, iron deficiency remains the most common micronutrient deficiency in the world. Many interventions that aim to improve iron status involve physically active populations. Intense aerobic exercise training negatively affects iron status; however, the impact of regular moderate aerobic exercise on the effectiveness of iron supplementation remains unclear.Objective: This study aimed to determine whether aerobic training modifies the assessment of the effectiveness of iron supplementation in improving conventional iron status measures.Design: Seventy-two iron-depleted, nonanemic Chinese women [serum ferritin (sFer) <25 µg/L and hemoglobin >110 g/L] were included in an 8-wk, partially blinded, randomized controlled trial with a 2 × 2 factorial design including iron supplements (42 mg elemental Fe/d) or placebo and aerobic training (five 25-min sessions/wk at 75-85% of maximum heart rate) or no training. Linear mixed models were used to evaluate the relation between supplement type, training, and changes in iron status over time, measured by sFer, hemoglobin, soluble transferrin receptor (sTfR), and estimated total body iron.Results: After treatment, both the iron-supplemented trained and untrained groups showed significantly improved sFer, sTfR, and body iron values compared with either of the placebo groups. Similarly, trained participants had significantly higher aerobic fitness measures than untrained participants. Training modified the sFer response to supplementation (training by supplement interaction, P = 0.07), with the iron-supplemented trained group having significantly lower sFer than the iron-supplemented untrained group at week 8 (mean ± SD: 31.8 ± 13.5 and 47.6 ± 15.7 µg/L, respectively; P = 0.042), whereas there was no significant difference between the placebo trained and untrained groups (21.3 ± 12.2 and 20.3 ± 7.0 µg/L, respectively; P = 1.00).Conclusions: Regular aerobic training reduces the apparent effectiveness of iron supplementation in improving sFer and calls into question whether conventional measures of iron status accurately reflect iron metabolism in physically active, nonanemic women. This trial was registered at clinicaltrials.gov as NCT03002090.