Disorders of Lipid Metabolism and Carbohydrates

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:

Determine the effect a Western diet vs. a Therapeutic Lifestyle Change/Step 2 diet on lipid profiles in moderately hypercholesterolemic adults.

Inclusion Criteria:
  1. Understand and give written consent
  2. Age > 50 years
  3. LDL-C > 130 mg/dL
  4. Non-smokers
  5. Not taking medications known to affect lipid levels
  6. No evidence of chronic illness
  7. Women must be postmenopausal and not on HRT.
Exclusion Criteria:
  1. Refusal to consent
  2. Not meeting inclusion criteria
Description of Study Protocol:

Participants were randomized to one of two diet treatment groups, a Western-diet group (Control) and a Step 2 diet group. The study had two 32-day phases with a min 2 week interval between diet phases. Once subjects finished with/phase 1 and the 2 week interval, they began the other diet phase.

Diet Tx Details

Ctrl

Step2

%Pro

17

16

%Cho

45

56

%Fat

39

28

   SFA

15

7

   MUFA

15

8

   PUFA

8

12

Chol mg, per1000 kcal

164

66

Fiber g, per 1000 kcal

10

16

Food/drink prepared at research ctr for consumption on site or pkgd for take -out.  Subjects required to report to research ctr at least 4x/wk for BP, weight, and eat 1 meal on site.

3 fasting blood samples taken during final week of each diet. 1-4 hr postprandial blood sample obtained after dinner meal.

Subjects not to change physical activity during study period.

Data Collection Summary:

Following measured at baseline and during final week of each diet for chg within tx groups and between groups.

  • Total cholesterol (TC)
  • VLDL, HDL, LDL, TC/HDL
  • Tg
  • Apo B, ApoA-I, ApoA-II

Investigators, lab staff and subjects blinded to identity of diets.

Description of Actual Data Sample:

N = 36 adults (age range 55-74y)

  • Females n=18
  • Males n=18

Baseline Characteristics at Screening

 

Female

Male

All

Age

67

(4)

60

(7)

63

(6)

BMI

26.6

(2.4)

28.1

(3.4)

27.4

(3.0)

Total Chol

(mg/dL)

253

(32)

237

(33)

245

(33)

LDL-C

(mg/dL)

167

(30)

167

(26)

167

(28)

Summary of Results:

Mean caloric intake

  • Females: 2105 ± 314 kcal
  • Males: 2803 ± 506 kcal

Caloric levels determined by Harris-Benedict at baseline and adjusted for subjects to maintain body weight throughout study.

Mean cholesterol intake (mg/day)

Western Diet

  • Females: 345 ± 51
  • Males: 460 ± 80

Step 2 Diet

  • Females: 139 ± 21
  • Males: 185 ± 33

Cholesterol calculated for individual subjects on basis of total kcal instead of total amount per day.

Change in fasting total cholesterol & LDL-C (mg/dL) per diet group

 

Ctrl

N=18

Step 2

N=18

%Chg

Total Chol

250

(33)

225

(32)

-9% a

   Female

250

(30)

225

(29)

-10% a

   Male

249

(37)

226

(35)

-9% b

LDL-C

175

(31)

154

(28)

-11%a

   Female

173

(28)

153

(32)

-12%a

   Male

177

(34)

155

(25)

-11%c

ap<0.001, bp=0.005, cp=0.004

The Step 2 Diet significantly reduced non-fasting TC 9-10% and LDL-C 11-12% vs. Western Diet similarly in males and females.

Change in non-fasting total cholesterol & LDL-C (mg/dL) per diet group

 

Ctrl

N=18

Step 2

N=18

%Chg

Total Chol

235

(30)

217

(31)

-7% a

   Female

236

(33)

219

(32)

-7% a

   Male

233

(27)

216

(31)

-7% b

LDL-C

156

(25)

143

(26)

-8%c

   Female

158

(30)

142

(31)

-10%d

   Male

153

(20)

143

(22)

-5%e

ap<0.001, bp=0.065, cp=0.006, dp=0.002, ep=0.219

Serum lipid concentrations in non-fasting state were of smaller magnitude vs. fasting state, especially for LDL-C in males which was not significant.

Author Conclusion:

The TLC/Step 2 Diet, by decreasing sat fat by 8% of energy and chol by 98mg/1000kcal, resulted in an 11% decrease in LDL-C.

"For individuals in with LDL-C levels in the borderline high-risk range this response may be sufficient to forestall the use of lipid lowering medications."

"Potential limitation in broadening the interpretation of the study results...is that each diet was consumed over a relatively short period of time."

Funding Source:
Government: NIH, USDA
Not-for-profit
0
Foundation associated with industry:
Reviewer Comments:

Physical activity not monitored throughout the study period.

Food group servings per diet treatment not specified.

No "wash-in" period required before beginning 1st diet phase.

2-week period between diet treatments not standardized and subjects were allowed to consume whatever diet they chose. May impact lipid profile from second diet phase.

Unable to determine what element of Step 2 diet contributed to LDL-C lowering effect seen in this population (i.e. increased fiber, decreased saturated fat, decreased total fat, etc.).

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? Yes
  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