Flattened cola improves high-intensity interval performance in competitive cyclists.

PURPOSE: Some cyclists consume flattened cola during competitive events, but limited research has investigated if cola beverages elicit ergogenic effects, particularly on high-intensity exercise performance. Whether the potentially beneficial effects of cola are due to the caffeine and/or the carbohydrate content is also unclear. This study assessed the ergogenic effects of different cola beverages on performance during a constant power bout (CPB) and subsequent high-intensity interval efforts in competitive cyclists. METHODS: In a randomized, double-blind, cross-over design, competitive cyclists (n = 13; [Formula: see text]O2max 65.7 ± 5.9 ml kg-1 min-1) completed a 45-min CPB at 69% of maximum workload (Wmax), followed by four maximal 1-min high-intensity intervals (HII) against a resistance of 0.5 N kg-1. Participants consumed 16 ml kg-1 total (intermittantly at four time points) of flattened decaffinated diet cola (PLA), caffeinated diet cola (CAF) or cola containing caffeine and carbohydrates (CAF + CHO). RESULTS: During the CPB, ratings of perceived exertion were lower in the CAF + CHO and CAF conditions compared to PLA (both, P < 0.04). Compared to PLA, CAF + CHO and CAF similarly increased (all, P < 0.049) mean power (CAF + CHO: 448 ± 51 W; CAF: 448 ± 50 W; PLA: 434 ± 57 W), minimum power (CAF + CHO: 353 ± 45 W; CAF: 352 ± 51 W; PLA: 324 ± 49 W) and total work (CAF + CHO: 26.9 ± 3.1 kJ; CAF: 26.9 ± 3.0 kJ; PLA: 26.0 ± 3.4 kJ), but not peak power (CAF + CHO: 692 ± 117 W; CAF: 674 ± 114 W; PLA: 670 ± 113 W; all, P > 0.57) during the HII. CONCLUSION: Cola containing caffeine with or without carbohydrates favorably influenced perceived effort during the CPB and enhanced mean and minimum power during repeated maximal intervals. We provide evidence supporting the consumption of commercially available cola for high-intensity cycling in competitive cyclists.

Impact of Vitamin D Supplementation on Gross Motor Development of Healthy Term Infants: A Randomized Dose-Response Trial.

UNLABELLED: In addition to benefits for bone health, vitamin D is implicated in muscle function in children and adults. AIMS: To determine if vitamin D dosage positively correlated with gross motor development at 3 and 6 months of age. We hypothesized that higher doses would be associated with higher scores for gross motor skills. METHODS: A consecutive sample of 55 healthy, term, and breastfed infants from Montreal, Canada were recruited from a randomized trial of vitamin D supplementation between 2009 and 2012. Infants were randomized to 400 International Units (IU) (n = 19), 800 IU (n = 18) or 1,200 IU (n = 18) vitamin D3/day. Motor performance at 3 and 6 months was quantified by the Alberta Infant Motor Scale (AIMS). Plasma vitamin D3 metabolites were measured by tandem mass spectrometry. RESULTS: AIMS scores did not differ at 3 months. However, total AIMS scores and sitting subscores were significantly higher at 6 months in infants receiving 400 IU/day compared to 800 IU/day and 1,200 IU/day groups (p < .05). There were weak negative correlations with length and C-3 epimer of 25(OH)D. CONCLUSIONS: In contrast to our hypothesis, gross motor achievements were significantly higher in infants receiving 400 IU/day vitamin D. Our findings also support longer infants being slightly delayed.

Effect of different dosages of oral vitamin D supplementation on vitamin D status in healthy, breastfed infants: a randomized trial.

IMPORTANCE: Vitamin D supplementation in infancy is required to support healthy bone mineral accretion. A supplement of 400 IU of vitamin D per day is thought to support plasma 25-hydroxyvitamin D (25[OH]D) concentrations between 40 and 50 nmol/L; some advocate 75 to 150 nmol/L for bone health. OBJECTIVE: To investigate the efficacy of different dosages of vitamin D in supporting 25(OH)D concentrations in infants. DESIGN, SETTING, AND PARTICIPANTS: Double-blind randomized clinical trial conducted among 132 one-month-old healthy, term, breastfed infants from Montréal, Québec, Canada, between March 2007 and August 2010. Infants were followed up for 11 months ending August 2011 (74% completed study). INTERVENTION: Participants were randomly assigned to receive oral cholecalciferol (vitamin D3) supplements of 400 IU/d (n=39), 800 IU/d (n=39), 1200 IU/d (n=38), or 1600 IU/d (n=16). MAIN OUTCOMES AND MEASURES: The primary outcome was a plasma 25(OH)D concentration of 75 nmol/L or greater in 97.5% of infants at 3 months. Secondary outcomes included 25(OH)D concentrations of 75 nmol/L or greater in 97.5% of infants at 6, 9, and 12 months; 25(OH)D concentrations of 50 nmol/L or greater across all times; growth; and whole body and regional bone mineral content. Data were analyzed by intention to treat using available data, logistic regression, and mixed-model analysis of variance. RESULTS: By 3 months, 55% (95% CI, 38%-72%) of infants in the 400-IU/d group achieved a 25(OH)D concentration of 75 nmol/L or greater vs 81%(95% CI, 65%-91%) in the 800-IU/d group, 92% (95% CI, 77%-98%) in the 1200-IU/d group, and 100% in the 1600-IU/d group. This concentration was not sustained in 97.5% of infants at 12 months in any of the groups. The 1600-IU/d dosage was discontinued prematurely because of elevated plasma 25(OH)D concentrations. All dosages established 25(OH)D concentrations of 50 nmol/L or greater in 97% (95% CI, 94%-100%) of infants at 3 months and sustained this in 98% (95% CI, 94%-100%) to 12 months. Growth and bone mineral content did not differ by dosage. CONCLUSIONS AND RELEVANCE: Among healthy, term, breastfed infants, only a vitamin D supplement dosage of 1600 IU/d (but not dosages of 400, 800, or 1200 IU/d) increased plasma 25(OH)D concentration to 75 nmol/L or greater in 97.5% of infants at 3 months. However, this dosage increased 25(OH)D concentrations to levels that have been associated with hypercalcemia. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT00381914.

Parathyroid hormone-ionized calcium dynamics over the first year of life.

BACKGROUND: Ionized calcium (iCa) is believed to be the principle determinant of parathyroid hormone concentration (PTH). However, previous studies contained few infants. METHODS: This ancillary study from our vitamin D3 dose-response trial in healthy, breastfed infants measured calcium, phosphorus, PTH and 25(OH)D (25-hydroxyvitamin D) at 1, 2, 3, 6, 9 and 12 months of age. The relationship between iCa and PTH was assessed by Pearson correlation and a mixed effects regression model to account for repeated measures. RESULTS: No significant correlations were observed between iCa and PTH at individual visits (p>0.2). After accounting for repeated measures, PTH decreased with increasing iCa (slope -5.25; 95% confidence intervals (CI) -8.78 to -1.73), decreased with increasing 25(OH)D (slope -0.006; 95% CI -0.009 to -0.002, and increased with later visits (6-12 months, p<0.001), CONCLUSIONS: We observed a weak negative relationship between iCa and PTH and an increase with age consistent with physiologic maturation.

Methodological issues in assessing plasma 25-hydroxyvitamin D concentration in newborn infants.

BACKGROUND: Although no gold standard exists, liquid chromatography tandem mass spectrometry (LC-MS/MS) is a precise and accurate method for the analysis of plasma 25-hydroxyvitamin D (25(OH)D). Immunoassays are more readily available and require small volume sampling, ideal for infant testing. The objective was to compare two commercially available immunoassays for measuring circulating 25(OH)D concentration in infant plasma against LC-MS/MS. METHODS: Capillary blood samples from 103 infants were analyzed for plasma 25(OH)D using an enzyme immunoassay (EIA, Octeia, IDS Ltd.) and radioimmunoassay (RIA, DiaSorin). Plasma 25(OH)D(3), C-3 epimer of 25(OH)D(3) (3-epi-25(OH)D(3)) and 24,25-dihydroxyvitamin D (24,25(OH)(2)D(3)) were measured on the same samples using LC-MS/MS. To establish whether plasma 24,25(OH)(2)D(3) or 3-epi-25(OH)D(3) interferes with these immunoassay results, the zero 25(OH)D calibrator from each assay kit was spiked with increasing amounts of 24,25(OH)(2)D(3) or 3-epi-25(OH)D(3). RESULTS: Classifying infants below the common vitamin D status targets of 50 nmol/L and 75 nmol/L respectively, 58% and 99% fell below using the RIA, 19% and 56% with the EIA and 31% and 76% with LC-MS/MS. Compared to LC-MS/MS, both immunoassays showed poor Bland-Altman limits of agreement for 25(OH)D concentrations (RIA: limits of agreement -27 to +13%; EIA: -12 to +41%), and mountain plots (folded cumulative distribution) depicted significant skew and bias. Spiked 24,25(OH)2D3 concentrations, but not 3-epi-25(OH)D3, appeared as >100% of known values on the EIA but not on the RIA thus, suggesting that the EIA may cross-react with 24,25(OH)(2)D(3) to a greater extent than 3-epi-25(OH)D(3). CONCLUSION: Two common immunoassays resulted in very different classifications of vitamin D status possibly related to the interference of other vitamin D metabolites. Based on these data, LC-MS/MS assessment of vitamin D status is recommended in young infants (4-6 weeks of age).