Red and Processed Meat Effects on the Metabolome and Microbiome: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Red and Processed Meat Effects on the Metabolome and Microbiome (NCT05274906), a randomized na study. The primary outcome is Test the Effects of Red and Processed Meat on Aqueous Biomarkers of the Blood Metabolome.

2. Clinical Question

3. Trial Design

This was a randomized, double-blind, crossover controlled-feeding trial. In a crossover design, participants receive each condition in sequence, so the comparison can be made within the same participant rather than relying only on separate groups. Here, each participant completed both controlled diets, with the order randomized.

One sequence began with the 21-day HEI-2015-M diet containing red and processed meat, followed after a washout period of 1 week or longer by the 21-day HEI-2015 diet without red and processed meat. The other sequence reversed that order. Both diets were described as controlled HEI-2015 diets, with the meat component distinguishing the conditions.

The registry lists enrollment of 23 and a completed status. Its primary outcome timeframe is day 21, and the primary measure is described as the ratio of a biomarker's relative concentration on day 21 to its relative concentration on day 0. The record does not report the numerical primary outcome results, a between-diet estimate, or a confidence interval. It lists five outcome measures and no posted analyses.

Randomization of order can help address systematic order effects, while a washout period is intended generally to reduce carryover between periods. Those design features do not by themselves establish that order or carryover effects were absent. The registry record does not report diagnostics or analyses addressing those issues. It also does not report details of how masking was maintained or assessed.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Cross-over design; each participant completed each arm in random order

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

Population: Age in years at time of enrollment based on participant-reported questionnaire

6. Primary Endpoint

The registry lists the primary outcome as Test the Effects of Red and Processed Meat on Aqueous Biomarkers of the Blood Metabolome, measured over Day 21.

The primary endpoint concerns aqueous biomarkers in the blood metabolome. Plasma metabolomics were evaluated using Liquid Chromatography/Mass Spectrometry (LC/MS). The record defines each measurement as a relative concentration: the concentration of a specified biomarker relative to the concentration of all other biomarkers. It reports the outcome conceptually as the mean ratio of relative concentration on day 21 to relative concentration on day 0.

As described in the registry, a ratio above 1.0 indicates an increase in relative concentration from baseline by the end of the diet period; a ratio below 1.0 indicates a decrease; and a ratio of 1.0 indicates no change from baseline. This relative measure describes a biomarker's share in relation to the other measured biomarkers, rather than its absolute concentration in plasma.

Metabolomic biomarkers are used in this trial because the stated objective is to identify biological measures that may differ with the diet conditions. Such measurements can characterize patterns for further study, but the registry does not report which biomarkers changed, the size or uncertainty of any change, or a comparison between the diets. The endpoint description alone therefore establishes how the measure is defined, not what the trial found.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes a randomized crossover design, a continuous primary outcome summarized as a mean, and standard deviation as the dispersion measure. It does not report the numerical outcome summaries or the statistical analysis of the primary endpoint. The concepts below are general explanations of how these methods are commonly interpreted; they are not claims about analyses performed in this trial.

What does a crossover comparison use?

In general, a crossover study measures participants under more than one condition. A within-participant comparison can account for stable characteristics that differ between people, because each participant serves as their own comparator. The estimate of interest is typically based on the contrast between measurements from the same participant under the two conditions. This does not remove all sources of bias: period effects, order effects, and carryover from an earlier condition may matter. How those features are assessed and incorporated depends on the analysis plan. The registry record does not report the statistical model, the handling of sequence or period, or an assessment of carryover.

What do a mean and standard deviation describe?

In general, a mean describes the center of a set of observed values, while a standard deviation describes how spread out those values are around the mean. They are descriptive summaries, not by themselves a test of whether conditions differ. For a crossover comparison, summaries of each condition alone do not convey the within-participant relationship; a paired contrast and its uncertainty are needed to quantify the comparison. The record lists mean and standard deviation as the summary and dispersion types, but gives no numerical summaries for the primary outcome.

What would a confidence interval add?

In general, a confidence interval gives a range of values compatible with the data and the method used to calculate it. Its width conveys precision: wider intervals indicate less precision than narrower intervals. A confidence interval around a between-diet contrast would help readers judge which effect sizes remain plausible, while a point estimate alone would not show that uncertainty. No confidence interval or between-diet estimate is reported for this endpoint in the registry record.

How should the ratio be understood?

The registry defines the endpoint as a relative concentration on day 21 divided by the corresponding relative concentration on day 0. By that definition, a ratio above 1.0 indicates an increase in relative concentration, a ratio below 1.0 indicates a decrease, and 1.0 indicates no change from baseline. These are interpretations of the measure, not evidence of an observed change. Because the concentration is relative to the other biomarkers, it should not be treated as an absolute plasma concentration. The registry does not give individual biomarker values or a summary of the observed ratios.

What does statistical significance tell a reader?

In general, a p-value is calculated under a specified statistical model and a null hypothesis. It describes how unusual data at least as extreme as those observed would be if that model and null hypothesis were true; it does not measure the probability that the null hypothesis is true or quantify the size of an effect. A p-value is most informative alongside an effect estimate and its confidence interval. No primary-outcome p-value or inferential analysis is reported in the registry record, so statistical significance cannot be evaluated.

What is the relevance of multiple biomarkers?

In general, when many biomarkers or time points are examined, the chance of finding at least one apparently notable result can increase if each is tested separately. Multiplicity procedures can control error rates across a defined family of tests, but the appropriate approach depends on the questions and analysis plan. The registry indicates that the primary outcome has several categories or time points and was not reduced to one comparison. It does not report a multiplicity strategy, the set of tests, or the results for individual biomarkers.

The registry record does not report a model, test, variance estimate for paired differences, missing-data method, or analysis population for the primary outcome. Those details are necessary to reproduce or fully evaluate an inferential analysis. Their absence should be read as unavailable information in the registry record, not as evidence that a particular method was or was not used.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists five outcome measures and no posted analyses. It does not report a statistical analysis plan, a prespecified family of tests, or a method for adjusting comparisons across biomarkers, categories, or time points. The primary outcome is noted as having several categories or time points and not being reduced to one comparison. The registry record therefore does not show how multiplicity was handled or which comparisons were intended to be primary.

Multiplicity matters in general because examining many outcomes or time points can increase the chance of finding an apparently notable result by chance. How to account for that depends on the analysis questions and the planned testing strategy. No specific adjustment should be assumed for this trial from the information recorded.

The record describes the crossover population as participants who completed each arm in randomized order, but does not report an analysis population definition, the number of participants with primary endpoint data, or how incomplete measurements were handled. It does not report missing-data counts, reasons for missingness, imputation, or sensitivity analyses. Therefore, readers cannot assess whether the primary outcome analysis included all enrolled participants or how missing measurements might affect the result.

These are reporting gaps in the registry record. They do not establish that outcomes were missing, that an adjustment was omitted, or that an analysis was not conducted outside the posted registry information.

11. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

The registry records 0 serious adverse events and 0 deaths for the Controlled HEI-2015-M Diet, with 23 participants at risk. For the Controlled HEI-2015 Diet, it also records 0 serious adverse events and 0 deaths, with 23 participants at risk. The record additionally lists 0 other adverse events for each diet condition, with 23 participants at risk in each.

These are the safety counts recorded for the diet conditions; they are not a statistical comparison and do not quantify uncertainty around the counts. Because this was a crossover trial, participants completed both conditions, so the condition-specific at-risk figures should not be added to infer a count of distinct participants. The registry does not report further detail on event definitions, monitoring, severity categories beyond serious and other adverse events, or the timing of events. The absence of recorded events in these entries should be interpreted as what the registry reports, not as proof that no adverse experiences occurred outside the registry's recorded categories.

12. What the Result Does, and Does Not, Mean

The record establishes that a randomized, double-blind crossover controlled-feeding trial was completed, with each participant completing a healthy controlled diet with red and processed meat and a comparable diet without red and processed meat. Its primary question concerned changes in relative aqueous blood-metabolome biomarkers from day 0 to day 21. The endpoint definition clarifies how a reported ratio would be interpreted.

It does not establish whether the diets differed on the primary outcome. Numerical biomarker results, a between-diet estimate, a confidence interval, and inferential test results are not reported in the registry record. The absence of those results is not evidence of no effect, and it does not permit a conclusion that an effect was present. The record also does not show which biomarkers, if any, differed or how consistent any pattern was across outcomes.

The endpoint measures relative concentrations, not absolute amounts. A change in relative concentration describes a biomarker in relation to the other measured biomarkers. It cannot, by itself, be interpreted as a change in absolute concentration or as a clinical outcome. The trial's stated objective is to identify biomarkers that may differ between diet conditions; the registry information does not establish the clinical meaning of any biomarker pattern.

The crossover design offers the possibility of comparing conditions within the same participants, but design alone cannot establish the size, precision, or validity of a treatment contrast. Assessment requires reported outcome data and an analysis that addresses the paired design and relevant period or sequence issues. Those results and methods are not reported in the registry record.

Thus, the available record describes the question, design, outcome definition, and recorded adverse-event counts. It does not support a conclusion about whether either diet changed metabolomic biomarkers relative to the other.

13. Why This Trial Matters Statistically

This trial is statistically notable for asking a within-participant question. In a crossover design, participants receive both conditions, making it possible to compare measurements from the same person under each diet. In general, such comparisons can reduce the influence of stable differences between participants. They also require attention to the ordering of conditions, period effects, and potential carryover; the registry describes randomized order and a washout period of 1 week or longer, but does not report analyses of those design features.

The endpoint also illustrates an important distinction between relative and absolute measurement. A relative metabolite concentration is defined in relation to the other biomarkers, so a change in the ratio cannot automatically be read as a change in absolute concentration. Clear endpoint definitions are essential when interpreting high-dimensional biological measurements.

Finally, this record illustrates the difference between a registered question and an interpretable result. The trial is marked completed and the primary endpoint is described, but the registry does not report numerical outcome results or analyses. Without estimates and uncertainty, readers cannot evaluate the magnitude, precision, or statistical evidence for a between-diet difference. The record also notes multiple categories or time points without reducing the primary outcome to one comparison, making clear reporting of the analysis strategy especially relevant. These features make transparent reporting of outcome data and methods central to statistical interpretation.

14. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The registry record does not report numerical results for the primary metabolomics endpoint. It provides no biomarker-specific estimates, standard deviations, between-diet contrasts, confidence intervals, or p-values. The primary outcome is described as having several categories or time points and is not reduced to one comparison, so no single summary can be interpreted as the trial's overall primary result from this record.

The available information does not specify how the crossover data were analyzed, how period or sequence effects were handled, or whether carryover was assessed. It also does not report a statistical analysis plan, multiplicity approach, missing-data handling, or analysis population for the primary outcome. These omissions prevent assessment of the model, assumptions, and robustness of any inferential findings.

The endpoint is a relative concentration measure. It does not directly report absolute plasma concentrations, and the registry does not provide additional details about assay performance or the handling of the measured biomarker data. The information available also does not provide participant characteristics beyond describing a healthy-participant controlled feeding trial, limiting assessment of how broadly the findings might apply.

These limitations concern what is not reported in the registry record. They do not establish that the underlying study lacked these methods or information, only that they cannot be evaluated from the posted record.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Red and Processed Meat Effects on the Metabolome and Microbiome — NCT05274906.
• Registry record last updated 2024-09-05; status last verified 2024-08.
• Results first posted 2024-09-05.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

18. Record Summary

The registry describes a completed randomized, double-blind crossover controlled-feeding trial comparing controlled HEI-2015 diets with and without red and processed meat. Each participant completed both diet conditions in randomized order, with a washout period of 1 week or longer between the 21-day diet periods. Enrollment is listed as 23.

The primary outcome concerns mean ratios of day 21 to day 0 relative aqueous plasma metabolite concentrations measured using LC/MS. The registry explains that values above 1.0 indicate an increase from baseline, values below 1.0 indicate a decrease, and 1.0 indicates no change. Numerical primary outcome results and analyses are not reported in the registry record. It records 0 serious adverse events, 0 other adverse events, and 0 deaths for each diet condition.