EAL

AWM: High Calcium (2006)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To determine if calcium intake is associated with body weight and adiposity in Pima Indians, an obesity-prone population.

Inclusion Criteria:

All subjects found to be free of disease according to physical exam, medical history, and laboratory testing. Only nondiabetic subjects participated in this study.

Exclusion Criteria:

Excluded if not included above.

Description of Study Protocol:

Recruitment

Adults and children recruited from Gila River Indian Community. Adults were participants in an eating behavior study and children were participants in a childhood obesity study.

Design

Cohort.

Blinding used (if applicable)

Not applicable.

Intervention (if applicable)

Not applicable.

Statistical Analysis

Sex differences determined using Student's t test. Multiple linear regression analysis and correlation coefficients were used to determine the relationship between calcium intake and anthropometric variables.

Data Collection Summary:

Timing of Measurements

Height, weight, body composition and food intake assessed.

Dependent Variables

Height measured without shoes
Weight measured in adults wearing a preweighed robe and in children wearing light summer clothing
Body composition through DEXA
BMI calculated, BMI percentile determined using 2000 CDC growth charts

Independent Variables

Food intake in adults assessed through Block 1998 Food Questionnaire (100 item FFQ), food intake in children assessed using 24 hour recall with parental assistance

Control Variables

Description of Actual Data Sample:

Initial N: 65 Pima Indian adults (35 men, 30 women), 78 Pima Indian children (36 boys, 42 girls)

Attrition (final N): See above

Age: Adults mean age 33 +/- 8 years, children 10.4 +/- 0.3 years

Ethnicity: Pima Indian

Other relevant demographics: Mean BMI of adults was 33.3 +/- 8.1 and mean body fat percentage was 40% +/- 10%.

Anthropometrics: No significant differences between men and women in age, body weight, BMI, energy intake, or calcium intake.

Location: Arizona

Summary of Results:

	Male (n=35)	Female (n=30)	P-value
Age (years)	34.0 +/- 8.5	32.4 +/- 7.0	0.40
Body weight (kg)	96.6 +/- 26.7	88.1 +/- 20.2	0.16
Body fat (%)	33 +/- 8	47 +/- 6	0.0001
BMI	32.1 +/- 8.0	34.7 +/- 8.1	0.21
Energy intake (Kcal/day)	3083 +/- 1034	3268 +/- 1048	0.48
Calcium intake (mg/day)	876 +/- 336	974 +/- 345	0.25
Fat intake (% kcal)	39 +/- 7	42 +/- 8	0.15

Other Findings

No participants reported taking calcium supplements.

In adults, mean energy intake was 3163 +/- 1037 kcal/day, mean percentage of energy from fat was 41% +/- 7%, and calcium intake was 914 +/- 333 mg/day, close to the recommended intake of 1000 mg/day.

In children, mean energy intake was 1988 +/- 733 kcal/day, mean percentage of energy from fat was 36% +/- 9%, and calcium intake was 637 +/- 352 mg/day, half the recommended daily intake for this age group.

There were no significant associations between calcium intake and body weight (r = 0.05, P = 0.71; r= 0.04, P = 0.73), body fat (r = 0.16, P = 0.19; r = 0.12, P = 0.42), or BMI (r = 0.01, P = 0.97; r = 0.04, P = 0.77) in either adults or children, respectively.

In multiple linear regression models accounting for sex, age, and energy intake, calcium intake was not a significant determinant of BMI or adiposity in either adults or children.

Author Conclusion:

We were unable to find an association between calcium intake and obesity (assessed as either body weight, percentage body fat or BMI) in Pima Indian adults and children. Although the essentiality of calcium to bone health is well established, the role of calcium and dairy product intake in obesity and weight management remains uncertain. One explanation for the lack of association between reported calcium intake and body size in Pima Indians may be that the high-fat, high-energy diet consumed by the population overwhelmed the "anti-obesigenic" effect of calcium.

Funding Source:

Government:

NIDDK, NIH

Reviewer Comments:

Food intake based on self-report.

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?	Yes
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?	Yes
	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.)	Yes
	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?		N/A
	4.1.	Were follow-up methods described and the same for all groups?	N/A
	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%.)	N/A
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	N/A
	4.4.	Were reasons for withdrawals similar across groups?	N/A
	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?		N/A
	5.1.	In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate?	N/A
	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.)	N/A
	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?	N/A
	6.2.	In observational study, were interventions, study settings, and clinicians/provider described?	Yes
	6.3.	Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect?	N/A
	6.4.	Was the amount of exposure and, if relevant, subject/patient compliance measured?	N/A
	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?	N/A
	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?	N/A
	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)?	N/A
	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?	N/A
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?		Yes
	10.1.	Were sources of funding and investigators' affiliations described?	Yes
	10.2.	Was the study free from apparent conflict of interest?	Yes