CKD: Protein Requirements (2010)


Fujimori K, Satomi S, Okazaki H, Taguchi Y, and Mori S. The effect of protein intake on creatinine clearance in transplanted kidneys. Transplantation Proceedings. 1989; 21: 2,048-2,049.

PubMed ID: 2652671
Study Design:
Before-After Study
D - Click here for explanation of classification scheme.
Quality Rating:
Negative NEGATIVE: See Quality Criteria Checklist below.
Research Purpose:

To evaluate the effect of three types of Japanese diets on 24-hour creatinine clearance (CrCl).

Inclusion Criteria:

Renal transplant recipients were studies as inpatients. All were treated with 10mg to 20mg prednisone and 3.0mg to 6.0mg per kg per day cyclosporin. All showed less than 2.0mg per dL serum creatinines (SCr) and more than 45 ml per minute CrCl.

Exclusion Criteria:

None stated.

Description of Study Protocol:


Not described.


Before-and-after study: All patients were given two kinds of Japanese diets; the subjects were first placed on a 90g-per-day protein diet (90-PROT) for two days and then on a 30g-per-day protein diet (30-PROT). Two patients received a diet containing 120g of protein per day. (Note: It was not clear when was this diet started.)


The subjects were first placed on a 90g-per-day protein diet (90-PROT) for two days, then on a 30g-per-day protein diet (30-PROT) for two days.

All diets contained 2,000kcal and five to eight grams of salt.

Statistical Analysis

Paired T-test.

Data Collection Summary:

Timing of Measurements

Blood samples were collected at fasting time. In the morning, 24-hour urine collections were obtained from 6:00 A.M. to 6:00 A.M. the next day for CrCl and UPE measurements.

Dependent Variables

  • Serum creatinine
  • Blood urea nitrogen
  • Total protein
  • Serum albumin
  • Hematocrit.

Independent Variables

  • 90g-per-day protein diet (90-PROT) for two days
  • 30g-per-day protein diet (30-PROT) for two days.


Description of Actual Data Sample:
  • Initial N: 12 (9 males, 3 females)
  • Attrition (final N): 12
  • Age: 36±6.0 (range, 27 to 48) years old
  • Other relevant demographics: Six cadavers and six living donors. Mean day post-transplant, 55±29 (range, 33 to 133) days. Although some had hypertension, they were controlled at less than 160mm Hg SBP. Mean SCr, 1.5±0.4mg dL.
  • Anthropometrics: Mean body weight, 54.8±29kg
  • Location: Japan.
Summary of Results:



90g-per-day Protein Intake for Two Days

30g-per-day Protein Intake for Two Days

Paired T-test

SCr (mg per dL)




BUN (mg per dL)




CrCl (ml per minute)




Other Findings

No significant variations in total protein, albumin or hematocrit were found throughout the observation period.

Author Conclusion:

In this study, there were no patients with severely deteriorating kidney transplant function. Whether the same phenomenon could be found in chronic renal transplant failure is not known.

It is still early to discuss possible long-term effects of variations in protein intake. Since the usual meals increase the CrCl, it suggested that such meals may cause hyperfiltration in functioning grafts.

Funding Source:
Other: No data
Reviewer Comments:

Very short duration of interventions (two days); unclear whether it would result in changes in SCr and CrCl. There was no wash-out period between two protein diet interventions.

Paired T-test was done to test the difference between the two protein intake periods, not compared to the baseline (before intervention).

No description on how patients were selected.

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) ???
  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? No
  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? No
  2.2. Were criteria applied equally to all study groups? N/A
  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? No
3. Were study groups comparable? No
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) No
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? No
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) No
  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? 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? No
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? No
  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.) Yes
  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? No
  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? No
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? No
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? No
  6.6. Were extra or unplanned treatments described? No
  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? No
  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? No
  7.6. Were other factors accounted for (measured) that could affect outcomes? No
  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)? No
  8.6. Was clinical significance as well as statistical significance reported? No
  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? No
  9.1. Is there a discussion of findings? No
  9.2. Are biases and study limitations identified and discussed? No
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? ???