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Study Title and Description

Use of oral contraceptives blunts the calciuric effect of caffeine in young adult women.



Key Questions Addressed
1 For [population], is caffeine intake above [exposure dose], compared to intakes [exposure dose] or less, associated with adverse effects on bone and calcium balance outcomes?
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Primary Publication Information
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TitleData
Title Use of oral contraceptives blunts the calciuric effect of caffeine in young adult women.
Author MA Ribeiro-Alves,LC Trugo,CM Donangelo,
Country
Year 2003
Numbers

Secondary Publication Information
There are currently no secondary publications defined for this study.


Extraction Form: Bone & Calcium Outcomes
Design Details
Question... Follow Up Answer Follow-up Answer
Refid 12566473
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What outcome is being evaluated in this paper? Bone and Calcium
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What is the objective of the study (as reported by the authors)? The purpose of this study was to evaluate the effect of use of oral contraceptives on the urinary excretion of calcium, magnesium, phosphorous, zinc, sodium, potassium and caffeine metabolites, and their relationship, in response to an acute caffeine load.
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Provide a general description of the methods as reported by the authors. Information should be extracted based on relevance to the SR (i.e., caffeine related methods) Thirty women, 20–29 y of age: fifteen women were users of oral contraceptives (OC) (ethinylestradiol daily combined with a progestagen agent, +OC group), the other 15 women were nonusers of OC (-OC group). Each woman participated in two different tests, caffeine load and no caffeine, in a randomized crossover design in which each woman was her own control. The caffeine load (5 mg/kg body weight) was ingested as coffee beverage (regular instant coffee, 36 mg caffeine/g) and the no-caffeine control consisted of ingestion of decaffeinated instant coffee beverage (<0.4 mg caffeine/g), providing an identical weight of coffee powder. Caffeine load ranged from 245 to 345 mg (mean 285 mg). Also, before participation in the study, customary dietary intake of calcium, other minerals and caffeine was assessed by a food frequency questionnaire. Daily intakes were estimated using the program "The Food Processor" with database adapted to Brazilian foods based on published information All the urine produced during the following 4 h was collected into appropriate plastic containers. Plasma samples were obtained by centrifugation of the blood samples immediately after being drawn. Laboratory analyses included: hematocrit, hemoglobin, mineral (calcium, phosphorus, magnesium, zinc, sodium, and potassium) in plasma and urine, and caffeine metabolites in urine. _x000C_ For urinary minerals, responses to caffeine load compared to no caffeine within each group (+OC or -OC) were assessed by paired t-test, with each woman being her own control. Differences by OC use in net increase (caffeine load corrected by no caffeine) in urinary excretions were examined by unpaired t-test. The relationship between urinary mineral excretions and caffeine metabolites was examined using the Pearson correlation matrix (minerals vs. minerals), and the Spearman correlation matrix(minerals vs. caffeine metabolites).
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How many outcome-specific endpoints are evaluated? 1
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What is the (or one of the) endpoint(s) evaluated? (Each endpoint listed separately) Impact of caffeine on calcium excretion
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Clinical, physiological, other Physiological
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What is the study design? Controlled Trial
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Randomized or Non-Randomized? RCT
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What were the diagnostics or methods used to measure the outcome? Objective
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Optional: Name of Method or short description various analytical methods
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Caffeine (general) Caffeine (general)
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Coffee, Chocolate, energy drink, gum, medicine/supplement, soda, tea, other? coffee
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Measured or self reported? Measured
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Children, adolescents, adults, or pregnant included? Adults
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What was the reference, comparison, or control group(s)? (e.g. high vs low consumption, number of cups, etc.) Each woman served as own control; +OC and -OC
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What were the listed confounders or modifying factors as stated by the authors? (e.g. multi-variable components of models.  Copy from methods) Not evaluated in this study
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What were the sources of funding? Not addressed by authors
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What conflicts of interest were reported? Not addressed by authors
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Results & Comparisons

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