EAL

AWM: High Calcium (2006)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

The purpose of the study was to investigate, prospectively, during a 2-year exercise intervention, the relationships of micronutrient intakes (including total dietary calcium, dairy and non-dairy calcium) to body weight and body composition in young women ages 18-31 years.

Inclusion Criteria:

Participants who had both body composition results and 9-18 days of completed dietary records between baseline and 30 months

Exclusion Criteria:

Participants who:

had chronic intake of medication which interferes with calcium metabolism
had irregular menses
had a history of high blood pressure, hear disease, or diabetes
were >20% overweight or 15% underweight

Description of Study Protocol:

Recruitment Sedentary Caucasian women (ages 18-31 years) were recruited via direct mail, radio announcements, and flyers for an exercise intervention study. None of the participants had engaged in more than 2 hours/week of exercisein the year prior to entry into the study.

Design This was a prospective non-concurrent analysis of effect of calcium intake on changes in body composition during a 2-year exercise intervention.

Blinding used (if applicable) Not indicated

Intervention (if applicable) Participants were randomized into either 3 sessions of resistance exercise + 60 minutes of jumping rope/week or a control group for 24 months. Overall compliance to the exercise protocoal was 45.2+4.6% over the 2-year period.

Statistical Analysis Regression methods were used to correlate body composition measures to dietary variables. Experimental variable for the primary analysis was exercise. Thus, influence and interaction of exercise were carefully examined. For secondary analysis, explanatory variables were dietary intakes of slected nutrients. and response variables were changes in weight, fat, and lean mass. Results were considered significant at the P<0.05 level.

Data Collection Summary:

Timing of Measurements Dietary intake was assessed at baseline and every 6 months for up to 30 months. Body composition variables were measured at baseline and at 24 months.

Dependent Variables

Weight change-weight was measured using a calibrated electronic scale and height was measured with a wall-mounted stadiometer. Participants wore light clothing and no shoes.
Fat mass, percent fat, and lean mass change-these variables were measured using a dual energy absorptiometer. Body composition measures are expressed as change from baseline to 24 months.

Independent Variables

Exercise Assignment
Selected Nutrient Intake (including total, dairy, and non-dairy calcium intakes)-assessed using 3-day diet record, including intake of vitamin and mineral supplements, at baseline and every 6 months for up to 30 months. Diet records were analyzed using Computrition. There were no significant differences in nutrient intake between baseline and 6,12,18, or 24 months; thus, a mean was calculated for each nutrient for each subject. Analyses indicated no significant differences in nutrient intakes withint or between, over time, in the exercisers of non-exercisers. Dairy calcium was determined from calcium content of dairy foods only. Non-dairy calcium was calculated as difference between total calcium intake and dairy calcium intake. Ratios were determined using mean of variables for each individual.

Description of Actual Data Sample:

Initial N: not indicated

Attrition (final N): 54 normal weight women

Age: 18-31 years

Ethnicity: Caucasian

Location: Purdue University

Summary of Results:

All participants were normal weight at baseline. Individual participants both gained and lost weight, fat, and lean mass over course of the 2-year study. At 2 years there were no significant differences in body composition between exercisers and non-exercisers.
The participants' mean calcium intake (781+212 mg/day) was below current recommendations of 1000 mg/day for this age group. Dairy calcium comprised 69% of the total calcium consumption. There were no significant differences in nutrient intakes between exercise and nonexercise groups.
Total calcium/kcal and vitamin A together predicted (negatively and positively, respectively) changes in body weight (R² =0.19) and body fat (R²=0.27). There also was an interaction of calcium and energy intake in predicting body weight changes, such that only at lower energy intake (<1876 kcal/day) did calcium intake (not adjusted for energy) predict changes in body weight.

Author Conclusion:

1. Regardless of exercise group assignment, calcium adjusted for kcal intake was negatively related and vitamin A intake was positively related to 2-year changes in total body weight and body fat in young women ages 18-31 years.

2. Participants with high calcium intake, corrected by total kcal intake, and lower vitamin A intake gained less weight and body fat over 2 years in this study.

Funding Source:

Industry:

National Dairy Council

Commodity Group:

Reviewer Comments:

No information was provided about initial N and attrition rate.
This study was supported in part by the National Dairy Council.

Quality Criteria Checklist: Primary Research
Relevance Questions
	1.	Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies)	Yes
	2.	Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about?	Yes
	3.	Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice?	Yes
	4.	Is the intervention or procedure feasible? (NA for some epidemiological studies)	Yes

Validity Questions
1.	Was the research question clearly stated?		Yes
	1.1.	Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified?	Yes
	1.2.	Was (were) the outcome(s) [dependent variable(s)] clearly indicated?	Yes
	1.3.	Were the target population and setting specified?	Yes
2.	Was the selection of study subjects/patients free from bias?		Yes
	2.1.	Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study?	Yes
	2.2.	Were criteria applied equally to all study groups?	Yes
	2.3.	Were health, demographics, and other characteristics of subjects described?	Yes
	2.4.	Were the subjects/patients a representative sample of the relevant population?	???
3.	Were study groups comparable?		Yes
	3.1.	Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT)	Yes
	3.2.	Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?	Yes
	3.3.	Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.)	Yes
	3.4.	If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis?	N/A
	3.5.	If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.)	N/A
	3.6.	If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")?	N/A
4.	Was method of handling withdrawals described?		No
	4.1.	Were follow-up methods described and the same for all groups?	???
	4.2.	Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.)	No
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	???
	4.4.	Were reasons for withdrawals similar across groups?	???
	4.5.	If diagnostic test, was decision to perform reference test not dependent on results of test under study?	N/A
5.	Was blinding used to prevent introduction of bias?		???
	5.1.	In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate?	???
	5.2.	Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.)	???
	5.3.	In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded?	N/A
	5.4.	In case control study, was case definition explicit and case ascertainment not influenced by exposure status?	N/A
	5.5.	In diagnostic study, were test results blinded to patient history and other test results?	N/A
6.	Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described?		Yes
	6.1.	In RCT or other intervention trial, were protocols described for all regimens studied?	Yes
	6.2.	In observational study, were interventions, study settings, and clinicians/provider described?	N/A
	6.3.	Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect?	Yes
	6.4.	Was the amount of exposure and, if relevant, subject/patient compliance measured?	Yes
	6.5.	Were co-interventions (e.g., ancillary treatments, other therapies) described?	N/A
	6.6.	Were extra or unplanned treatments described?	N/A
	6.7.	Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups?	Yes
	6.8.	In diagnostic study, were details of test administration and replication sufficient?	N/A
7.	Were outcomes clearly defined and the measurements valid and reliable?		Yes
	7.1.	Were primary and secondary endpoints described and relevant to the question?	Yes
	7.2.	Were nutrition measures appropriate to question and outcomes of concern?	Yes
	7.3.	Was the period of follow-up long enough for important outcome(s) to occur?	Yes
	7.4.	Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures?	Yes
	7.5.	Was the measurement of effect at an appropriate level of precision?	Yes
	7.6.	Were other factors accounted for (measured) that could affect outcomes?	Yes
	7.7.	Were the measurements conducted consistently across groups?	Yes
8.	Was the statistical analysis appropriate for the study design and type of outcome indicators?		Yes
	8.1.	Were statistical analyses adequately described and the results reported appropriately?	Yes
	8.2.	Were correct statistical tests used and assumptions of test not violated?	Yes
	8.3.	Were statistics reported with levels of significance and/or confidence intervals?	Yes
	8.4.	Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)?	No
	8.5.	Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)?	Yes
	8.6.	Was clinical significance as well as statistical significance reported?	Yes
	8.7.	If negative findings, was a power calculation reported to address type 2 error?	No
9.	Are conclusions supported by results with biases and limitations taken into consideration?		Yes
	9.1.	Is there a discussion of findings?	Yes
	9.2.	Are biases and study limitations identified and discussed?	Yes
10.	Is bias due to study's funding or sponsorship unlikely?		???
	10.1.	Were sources of funding and investigators' affiliations described?	Yes
	10.2.	Was the study free from apparent conflict of interest?	No