EAL

DLM: Diet Composition (2010)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

Determine the effect of specific diets - DASH diet, fruit and vegetable diet, vs a control diet - on plasma lipid levels in middle-aged adults.

Inclusion Criteria:

Understand and give written consent
³ 22 years old
Diastolic BP btwn 80-95mmHg, systolic BP < 160mmHg
Plasma total chol > 260mg/dL OR
On repeat testing LDL ³ 160mg/dL or LDL 130-159mg/dL w/³2 other CHD risk factors.

Exclusion Criteria:

Refusal to consent
Not meeting inclusion criteria
Uncontrolled DM, CV event w/in previous 6 mo., BMI>35.
On medications affecting BP, nutrient metabolism.
Unwillingness to d/c use of multivitamins or antacids.
Alcohol > 14 drinks/wk.

Description of Study Protocol:

Participants given a 3-week control diet as run-in period and energy level to keep weight stable was determined.

Participants randomly assigned to 1 of 3 diet treatments (Control, DASH, Fruit and Vegetable Diet (FV) for 8 weeks and assessed for changes in plasma lipids.

Diet Tx Details

	Ctrl	DASH	FV
Energy kcal	2100	2100	2100
%Pro	14	18	15
%Fat	37	27	37
%Cho	50	58	52
%SF	14	7	13
Chol mg	246	141	188
Fiber g	10.8	29.7	29.9
K mg	1454	4589	4334
Ca mg	379	1220	468
Servings
Fruit	1.6	5.2	5.2
Veg	2.0	4.4	3.3
Grains	8.2	7.5	6.9
Dairy (RegF)	0.4	0.7	0.3
Dairy (LF)	0.1	2.0	0
Nuts/seeds	0	0.7	0.6
Beef/pork	1.5	0.5	1.8
Poultry/fish	1.0	1.1	0.7
Fats/oils	5.8	2.5	5.3
Snack/sweet	4.1	0.7	1.4

Data Collection Summary:

Primary outcome: change in lipids from run-in to the end of the intervention.

12-hr fasting blood samples at end of run-in period and end of 8 wk intervention:
Total cholesterol, LDL, HDL, TG, TC:HDL, LDL:HDL

Other measures: Keys score for atherogenicity of diet; Food frequency questionnaire; 7-day physical activity recall; Daily diary of diet deviations.

Blinding: Measurement staff blinded to the diet assignments.

Description of Actual Data Sample:

N = 436 adults aged 44.6 ± 10.7 years

Women 48.9%
African American (AA) 59.9%
Smokers 10.3%; Drink ETOH 56.7%; Women on HRT 14.2%; Taking cholesterol meds 0.7%
BMI: 28.2 ± 3.9

Diet Groups

Control (n = 145)
DASH (n = 145)
Fruit/Veg (n = 146)

459 randomized, 436 completed (95% completion rate)

Summary of Results:

No significant differences among treatment groups at baseline except:

Women had lower LDL (p<0.05) vs men
Women had lower LDL:HDL (p<0.0001) vs men

Change in LDL (mg/dL) from baseline by group.

	Baseline Mean (SD)	? Post-Treat Mean (95% CI)
DASH	118.5 (30.2)	-13.7 (-18.8, -8.6)*
F/V	124.4 (32.3)	-1.9 (-6.6, 2.7)
CTRL	121.7 (31.6)	Data not available

*Sig difference (<0.0001)

Change in LDL (mg/dL) from baseline by diet and subgroup.

	Baseline (Tx Combined)	? Post-Treat
DASH	*Mean (SD)*	*Mean (95%CI)*
Women	118.3 (32.1)	-5.4 (-12.1,1.3)^a
Men	124.7 (30.5)	-16.5 (-23.0,-10.1)^a
AA	121.0 (32.3)	-11.2 (-17.1,-5.3)
Non-AA	122.3 (30.2)	-11.0 (-18.4,-3.6)
FV
Women	See above	2.1 (-4.6,8.8)
Men		-4.7 (-11.1,1.8)
AA		0.0 (-0.15,6.0)
Non-AA		(-3.5, -10.7,3.8)

^aSig difference in subgroup (p<0.05)

DASH

Total Cholesterol significantly (p<0.0001) decreased 7.30% overall [-13.7 (-18.8, -8.6) mg/dL].
LDL significantly (p<0.0001) decreased 9.0% overall [-10.7 (-15.4, -6.0) mg/dL].
LDL reduction in men significantly greater than in women (p<0.05).

FRUIT/VEG DIET

Compared to control, no significant reductions observed in Total Cholesterol or LDL overall or by subgroup.

Author Conclusion:

Relative to the control diet, the DASH diet resulted in lower LDL cholesterol (-10.7mg/dL), as part of lowering total cholesterol, in the absence of changes in weight and physical activity among all subgroups.

Reductions in LDL were greater in men than women (-11.2 mg/dL vs -10.3 mg/dL respectively), but lipid responses did not differ significantly between African-Americans and non-African Americans.

Relative to the control diet, the fruit and vegetable diet did not significantly reduce LDL in this sample.

"The present study suggests that changes in total and LDL cholesterol are minimal without concomitant reductions in fat intake when dietary fiber is increased by 20g/d."

Authors applied the Framingham risk equation to estimate CHD risk and found the "10-year risk [of developing CHD] was decreased by 12.1% in participants consuming the DASH diet compared with a 0.9% increase in risk in participants consuming the control diet (p<0.01).

Funding Source:

Government:

NHLBI, NIH Office of Research and Minority Health

Industry:

Merck & Co, Kaiser Permanente Center for Health Research,

Pharmaceutical/Dietary Supplement Company:

Other:

University/Hospital:

Harvard Medical School, Louisiana State Unviersity, Johns Hopkins University, Duke University School of Medicine, VA Medical Center

Reviewer Comments:

Did not track physical activity throughout the study only at baseline at post-treatment. Changes in PA could bias results when not accounted for.

Included subjects with characteristics potentially affecting TC and LDL (e.g smokers, women on ERT, alcohol drinkers). Although a small proportion, these characteristics were not controlled for during analysis.

Well designed study with balanced mix of gender and race. Diet and participant intake well controlled.

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?	N/A
	1.2.	Was (were) the outcome(s) [dependent variable(s)] clearly indicated?	N/A
	1.3.	Were the target population and setting specified?	N/A
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?	N/A
	2.2.	Were criteria applied equally to all study groups?	N/A
	2.3.	Were health, demographics, and other characteristics of subjects described?	N/A
	2.4.	Were the subjects/patients a representative sample of the relevant population?	N/A
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)	N/A
	3.2.	Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?	N/A
	3.3.	Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.)	N/A
	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?	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?		Yes
	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?	N/A
	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?	N/A
	7.2.	Were nutrition measures appropriate to question and outcomes of concern?	N/A
	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?	N/A
	7.5.	Was the measurement of effect at an appropriate level of precision?	N/A
	7.6.	Were other factors accounted for (measured) that could affect outcomes?	N/A
	7.7.	Were the measurements conducted consistently across groups?	N/A
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?	N/A
	8.2.	Were correct statistical tests used and assumptions of test not violated?	N/A
	8.3.	Were statistics reported with levels of significance and/or confidence intervals?	N/A
	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)?	N/A
	8.6.	Was clinical significance as well as statistical significance reported?	N/A
	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?	N/A
	9.2.	Are biases and study limitations identified and discussed?	N/A
10.	Is bias due to study's funding or sponsorship unlikely?		Yes
	10.1.	Were sources of funding and investigators' affiliations described?	N/A
	10.2.	Was the study free from apparent conflict of interest?	N/A