Assessing the Effect of Lettuce on Intestinal Water Content Through Magnetic Resonance Imaging of the Small Bowel: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Assessing the Effect of Lettuce on Intestinal Water Content Through Magnetic Resonance Imaging of the Small Bowel (NCT02939716), a randomized na study. The primary outcome is Small Bowel Water Content Measured by MRI.

2. Clinical Question

The registry record frames the work as an investigation of a possible food-related change in intestinal water and a possible relationship between bowel water and bloating. It is a study of imaging and symptom measures in healthy volunteers, not a direct test of stoma output, dehydration, or outcomes after surgery. Those distinctions matter when interpreting the scope of the clinical question.

3. Trial Design

The registry describes a completed, randomized, unmasked crossover study sponsored by the University of Nottingham. The record gives a study start of 2016-10 and primary completion of 2017-02. It lists 18 participants enrolled and identifies the population for the primary outcome as healthy volunteers free from gastrointestinal disorders. The phase is listed as NA.

A crossover design means participants receive more than one study condition in sequence, so each participant may contribute measurements under multiple conditions. The adverse-event group descriptions list different food sequences, consistent with the crossover structure. The registry record does not describe the sequence-generation method, the timing of periods, any washout interval, or procedures intended to address carryover between meals.

The study was not masked. This means participants and investigators were not described as blinded to the food condition. The meals themselves differed visibly and compositionally, so the study compared complete meal conditions rather than a masked intervention with an otherwise identical control meal.

Outcome means are posted for 15 participants in each food arm. The relationship between the enrollment of 18 and the participants represented in those outcome summaries is not reported in the registry record. The record also does not report how many participants completed every crossover period, how missing measurements were handled, or whether the posted means include all randomized participants.

The primary endpoint was MRI-measured small-bowel water over 0-3 hours. Four secondary outcomes are listed: ascending-colon water content, relaxation time in the ascending colon, bloating VAS score and satiety VAS score. No sponsor-reported statistical analyses are listed for the primary or secondary outcomes. The registry record does not report the original sample-size justification, a prespecified statistical analysis plan, interim analyses, or a primary analysis population definition.

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: 15 healthy volunteers free from GI disorders.

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.

6. Primary Endpoint

The registry lists the primary outcome as Small Bowel Water Content Measured by MRI, measured over 0-3 hours.

The primary endpoint is the area under the curve of postprandial change from fasting small-bowel water, measured by MRI over 0-3 hours and expressed in mL*min. An area under the curve combines the change in a measure over a defined observation period into one summary. In this study, it represents the accumulated change in MRI-measured small-bowel water relative to the fasting measurement across the stated period. It is not a single measurement at one moment.

MRI was used because the investigators wanted to assess water in the small bowel without relying only on a clinical symptom or on stoma output. The registry’s rationale describes the technique as a way to explore whether eating lettuce changes small-bowel water content. The primary endpoint therefore addresses an imaging-based physiological question. The listed endpoint does not itself establish a change in hydration status, stoma output, or clinical consequences.

The registry reports the endpoint as a mean with standard error. The posted mean is -5662.0 for bread, 3194.0 for lettuce and 10590.0 for rhubarb, each based on 15 participants. These values are area-under-the-curve measures of change from fasting, not absolute water volumes. The comparison with bread is a useful reference within this study because bread was the designated control condition. What makes bread a control, and the meal-specific rationale behind that choice, are described only in the study summary; detailed protocol reasoning is not reported in the registry record.

As an exploratory pilot endpoint, the measure can help characterize the scale and variability of MRI responses for further study. The registry does not report a threshold defining a clinically important difference, so the practical importance of a particular change cannot be inferred from the endpoint values alone.

7. Results Posted in the Registry

• Healthy Volunteers. Lettuce Arm: mean 3,194 versus -5,662 on control; difference 8,856 (95% CI 4,966 to 12,746), standardized effect d = 1.63; z-test p = <0.001.
• Healthy Volunteers. Rhubarb Arm: mean 10,586 versus -5,662 on control; difference 16,248 (95% CI 12,272 to 20,224), standardized effect d = 2.92; z-test p = <0.001.

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

Ascending Colon Water Content

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard errors.
• Result:
  • Lettuce: mean 409.00 versus 78.00 on control; difference 331.00 (95% CI -129.53 to 791.53), standardized effect d = 0.51; z-test p = 0.159.
  • Rhubarb: mean 291.00 versus 78.00 on control; difference 213.00 (95% CI 19.27 to 406.73), standardized effect d = 0.79; z-test p = 0.031.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Lettuce and the control. The interval gives the range of effects that remain compatible with the data.
  • The 95% confidence interval excludes no difference, so the mean is statistically higher for Rhubarb than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

Relaxation Time in Ascending Colon

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard errors.
• Result:
  • Lettuce: mean 18,990 versus 15,188 on control; difference 3,802 (95% CI -16,498 to 24,102), standardized effect d = 0.13; z-test p = 0.714.
  • Rhubarb: mean 35,744 versus 15,188 on control; difference 20,556 (95% CI -1,475 to 42,587), standardized effect d = 0.67; z-test p = 0.067.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Lettuce and the control. The interval gives the range of effects that remain compatible with the data.
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Rhubarb and the control. The interval gives the range of effects that remain compatible with the data.

Bloating VAS Score

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard errors.
• Result:
  • Lettuce: mean 7,071 versus 4,196 on control; difference 2,875 (95% CI 705.90 to 5,044), standardized effect d = 0.95; z-test p = 0.009.
  • Rhubarb: mean 5,113 versus 4,196 on control; difference 917.00 (95% CI -1,288 to 3,122), standardized effect d = 0.30; z-test p = 0.415.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically higher for Lettuce than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Rhubarb and the control. The interval gives the range of effects that remain compatible with the data.

The secondary outcomes cover more than one aspect of bowel response: ascending-colon water content and relaxation time are imaging-related measures, while bloating and satiety are symptom ratings. Across these outcomes, the posted comparisons do not form a uniform pattern. Some estimates are accompanied by intervals spanning zero, while others are not. This variation is compatible with the fact that the outcomes measure different phenomena and may have different variability.

The secondary findings add context to the primary MRI result but do not independently establish the same conclusion. In particular, the secondary outcomes are not interchangeable with small-bowel water content, and none is a direct measure of stoma output or dehydration. The relationship between bowel water and feelings of bloating was part of the study’s stated interest, but the registry does not post a reported association analysis linking those measures.

Unadjusted secondary results carry less weight because several outcomes and comparisons create multiple opportunities for apparently notable findings. If many hypotheses are examined without a prespecified testing hierarchy or adjustment, the chance of at least one chance finding can increase. The registry does not report a multiplicity plan, a hierarchy of outcomes, or sponsor-reported analyses for the secondary endpoints. The posted unadjusted comparisons should therefore be treated as exploratory rather than as definitive evidence across outcomes.

The sample sizes and uncertainties also matter. Each secondary arm mean is based on 15 participants, and some measures have substantial uncertainty relative to their estimated differences. A result that does not rule out zero is not proof of no effect, while a result that excludes zero under an unadjusted interval does not establish clinical importance. Replication with a prespecified analysis plan and a population relevant to the clinical motivation would be needed to clarify the broader pattern.

Secondary outcomes registered for this trial, for reference (only those above were recalculated):

• Ascending Colon Water Content
• Relaxation Time in Ascending Colon
• Bloating VAS Score
• Satiety VAS Score

9. Statistical Interpretation

10. Statistical Methods Explained

The registry posts continuous outcomes as means with standard errors. A mean is a summary of the observed values in a group. A standard error describes uncertainty in the estimated mean; it is not the same as the spread of individual participant measurements. General statistical interpretation: a smaller standard error, all else being equal, indicates a more precisely estimated mean. In a small pilot, standard errors can still be substantial, and the mean does not describe the full distribution of individual responses.

What does a mean difference represent?

The recalculated comparisons express the difference between a meal’s posted mean and the bread mean. For the primary MRI endpoint, the lettuce-versus-bread mean difference is 8856.0, and the rhubarb-versus-bread mean difference is 16250.0. The comparison is stated in the endpoint’s units, mL*min. A positive difference means the posted mean for the named meal is higher than the bread mean on this endpoint. That direction is a description of the numerical scale, not evidence on its own of clinical benefit or harm.

These values are labelled recalculated because they are simple, unadjusted calculations from the posted summaries. They do not replace a sponsor’s analysis. The registry does not list sponsor-reported analyses for these outcomes, so no model-based estimate from the original study is available in the record. The recalculated comparisons also do not establish that the crossover structure was fully represented in the calculation.

How should a p-value be read?

A p-value describes how compatible the observed data are with a specified null model, under the assumptions used for that test. It is not the probability that the null hypothesis is true, and it does not measure the size or clinical importance of a difference. The primary unadjusted recalculated p-values are p < 0.001 for lettuce versus bread and p < 0.001 for rhubarb versus bread. These values describe the unadjusted comparisons, not a correction for multiple outcomes or comparisons. The registry does not report the original test specification or a multiplicity adjustment.

General statistical explanation: p-values depend on both the estimated difference and its uncertainty. A small p-value does not mean the estimate is precise enough for every practical decision, and a larger p-value does not demonstrate that conditions are equivalent. Effect estimates and their intervals are important complements to p-values.

Why does crossover structure matter?

In a crossover study, the same participant may provide measurements under different conditions. Those measurements can be correlated because they come from the same person. A paired or otherwise appropriate crossover analysis can use that relationship and may also need to account for period, sequence, and carryover effects. General statistical explanation: ignoring within-participant correlation can make uncertainty estimates inaccurate, while accounting for it appropriately can improve efficiency. The registry record does not describe the sponsor’s analysis model, period effects, carryover assessment, or handling of sequence. The recalculated unadjusted comparisons should therefore be read as summary-based comparisons rather than as a complete reanalysis of the crossover design.

Random allocation is listed, but the record does not give the allocation procedure or details of concealment. Masking is listed as none. In an unmasked food study, expectations or knowledge of the food condition could influence subjective outcomes such as bloating or satiety. MRI measures are less directly subjective, but that does not resolve questions about measurement procedures or analysis, which are not fully described in the registry.

What do the intervals contribute?

An interval around an estimate displays a range of values compatible with the data and the interval method, under its assumptions. Wider intervals indicate less precision than narrower intervals. The registry does not state the confidence level or method for the recalculated comparison intervals, so those details should not be assumed. Where an interval includes zero, the data do not rule out a zero mean difference under the interval’s method; where it lies entirely to one side, it is inconsistent with zero under that method. This interpretation does not establish clinical importance.

The intervals and p-values in the recalculated comparisons are unadjusted. In general, testing multiple hypotheses increases the chance of seeing at least one apparently unusual result by chance if no adjustment or prespecified hierarchy is used. The record does not report how many outcomes or comparisons were prespecified for formal testing, whether any outcome hierarchy was used, or whether corrections were planned.

General statistical explanation: over-dispersion means that variability is greater than a model expects. It can make standard errors too small if a model fails to allow for the extra variability. The posted continuous outcomes are summarized by means and standard errors, but the registry does not report a model-based dispersion assessment. There is not enough information in the record to determine whether over-dispersion was relevant or how it was handled.

The study’s summaries can inform planning for later research, but estimates from a pilot may be optimistic or unstable. The posted planning figures are illustrations derived from the observed effects, not documentation of the trial’s original design rationale. The original sample-size assumptions and the protocol’s statistical methods are not reported in the registry record.

11. Confidence Intervals and Precision

The recalculated primary mean differences are accompanied by intervals that quantify uncertainty under the calculation method. For lettuce versus bread, the estimate is 8856.0 and the interval runs from 4966.0 to 12750.0. For rhubarb versus bread, the estimate is 16250.0 and the interval runs from 12270.0 to 20220.0. Both intervals lie above zero, so the unadjusted recalculated comparisons are inconsistent with a zero difference under the interval method used. The registry record does not state the confidence level or interval method, and those details should not be inferred.

Precision is not the same as importance. An interval can be used to assess how much uncertainty surrounds an estimate, but it cannot say whether a difference matters clinically without a meaningful threshold and relevant clinical context. The registry does not report a minimally important difference for MRI-measured small-bowel water content. Nor does the primary endpoint directly measure stoma output, dehydration, or patient outcomes after surgery.

The standard errors attached to the group means are 1209.0 for bread, 1574.0 for lettuce and 1629.0 for rhubarb. They show that the estimated means have sampling uncertainty. They are not individual-level standard deviations and should not be interpreted as describing the range of values among participants.

The interval estimates are recalculated from posted summary statistics, and the design is a crossover. The registry does not report whether the original analysis used within-participant information or how it accounted for sequence and period. If the original crossover data are analyzed with a suitable participant-level model, its estimate and precision may differ from an unadjusted recalculation. No sponsor-reported analysis is posted for comparison. The small pilot population and the gap between listed enrollment and the outcome summaries also limit how definitively the precision can be assessed.

12. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The planning figures are participants per arm for 80% power and participants per arm for 90% power. They are not total sample sizes and they are not event counts. The registry’s planning assumptions are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. Each row considers an effect equal to the stated fraction of the observed effect. The original trial’s own sample-size assumptions are not reported in the registry record.

In plain terms, the 80% power column gives an illustrative number of participants per arm for a study designed to have an 80% chance of detecting the specified effect under the stated assumptions, if that effect is the true one and the model assumptions hold. The 90% power column uses a higher target chance of detection and therefore generally requires more participants per arm. These are planning calculations based on the observed effect in this pilot; they are not observed power.

Rows planning for 75% or 50% of the observed effect ask what sample size would be needed if a later study aimed to detect a smaller difference than the one estimated in this study. Smaller effects are harder to distinguish from random variation, so they need more participants under the same planning assumptions. The figures can change substantially when the assumed effect changes.

These illustrations are not a substitute for a design calculation using a clinically meaningful target, appropriate variance assumptions and an analysis plan suited to the crossover design. In particular, the registry does not report the original protocol’s sample-size justification or how within-participant correlation was treated. The planning numbers should be read as exploratory illustrations rather than as proof that the study was adequately or inadequately sized for its original question.

13. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = 8856.000; pooled standard deviation σ = 5435.410.
2. n = 2 × (1.96 + 0.842)² × 5435.410² / 8856.000² = 5.9, rounded up to 6 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
delta <- 8856                      # observed difference in means
sigma <- 5435.40959818117                     # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
  ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")

# Simulation: exact two-sample t-test using simulated means and variances
set.seed(2939716)
n    <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n))             # difference in sample means
s2     <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1))   # pooled sample variance
tstat  <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))

Output from running the code

100% of observed effect: n per arm = 6 (80% power), 8 (90% power)
 75% of observed effect: n per arm = 11 (80% power), 15 (90% power)
 50% of observed effect: n per arm = 24 (80% power), 32 (90% power)
power.t.test: 7 
Simulated power at n = 6 per arm: 0.726 (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

14. Multiplicity, Missing Data and Analysis Populations

The registry record lists one primary outcome and four secondary outcomes, but it does not report a strategy for controlling multiplicity. It does not state whether the primary comparison was intended to be tested against each food, whether secondary comparisons were exploratory, whether a testing hierarchy was specified, or whether any adjustment was planned. The recalculated comparisons are unadjusted, so their p-values and intervals do not account for the number of outcomes and comparisons considered.

General statistical explanation: multiplicity arises when several statistical hypotheses are examined. Without a prespecified strategy, the chance of at least one result appearing notable by chance can be higher than for a single test. Adjustments or a clear hierarchy can address this issue, but the appropriate approach depends on the research question and analysis plan. The registry record does not provide enough information to assess whether such methods were used in the original study.

Missing-data handling is also not reported in the registry record. Enrollment is listed as 18, while the posted means use 15 participants per food arm. The record does not explain whether the other enrolled participants did not contribute outcome data, whether some measurements were unavailable, or whether a particular analysis population was used. It does not report imputation, exclusions, or sensitivity analyses.

The analysis population is not defined beyond the primary outcome population description of healthy volunteers free from gastrointestinal disorders. The record does not state whether analyses followed an intention-to-treat principle, included participants with complete crossover data only, or used another population definition. The number of sponsor-reported analyses is listed as zero, and no reported outcome analyses are posted. As a result, the recalculated summary comparisons cannot resolve how the original investigators handled missing observations, repeated measures, or multiplicity.

These omissions do not establish that the original study lacked an analysis plan; they mean that the relevant details are not reported in the registry record. Without them, the statistical interpretation should distinguish the posted unadjusted recalculations from any analysis that may have been conducted outside the record.

15. 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 adverse-event record organizes participants by food sequence. Each listed sequence group has 3 participants at risk for serious adverse events and 3 at risk for other adverse events. The posted counts are 0 serious adverse events, 0 other adverse events and 0 deaths in each listed group. The registry lists no serious-event terms.

These figures describe the adverse-event counts recorded for the listed groups; they do not demonstrate that no events of any kind occurred outside the record or establish safety for other populations. The groups are small, and the registry record does not provide additional event narratives, definitions, severity assessments, or a detailed observation period for safety reporting. It also does not explain the relationship between these group counts and the overall enrollment figure.

Absence of a recorded event in a small group is not precise evidence that an event cannot occur. The figures should be read as a limited description of what the registry reports, not as a broad estimate of risk. The population was healthy volunteers, and the safety summaries do not directly address people with a stoma or people recovering from bowel surgery.

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

The posted primary outcome supports a narrow conclusion about the MRI measure in this study: the mean area-under-the-curve values were higher for lettuce and rhubarb than for bread, and the unadjusted recalculated intervals for both comparisons lie above zero. This describes the measured response over 0-3 hours in healthy volunteers. It does not establish the clinical meaning of the difference because the registry does not report a threshold for an important change in this measure.

The results do not establish that lettuce increases stoma output, causes dehydration, or has a particular effect in people after bowel surgery. Those issues motivated the research, but they are not the primary outcome reported. The study measured small-bowel water by MRI and included other imaging and symptom outcomes. A physiological measurement in healthy volunteers cannot by itself be treated as an estimate of a patient outcome in a different population.

The comparisons also do not isolate a single ingredient. The intervention conditions were complete meals, with different accompanying foods and preparations. The posted result is therefore a contrast among the meals as used in the study. The registry does not report a design that separates the effect of lettuce itself from the rest of its meal, nor does it report a dose-response analysis.

The crossover design could allow within-person comparisons, but the registry does not report the sponsor’s analysis method or whether within-person dependence, period, sequence and carryover were modeled. The unadjusted recalculations are not a substitute for a full crossover analysis. The sample is small, the reported population is healthy volunteers, and the difference between enrollment and the posted outcome sample is unexplained in the registry record.

Finally, statistical evidence against a zero mean difference is not the same as proof of an important or reproducible effect. The intervals convey uncertainty, and unadjusted secondary findings add exploratory context rather than independent confirmation. The record does not report a prespecified clinical threshold, an original sample-size rationale, a multiplicity plan, or sponsor-reported analyses. The findings are best understood as preliminary estimates from a pilot study that motivate further evaluation, not as a basis for clinical recommendations.

17. Why This Trial Matters Statistically

This study is statistically interesting because it combines a physiological imaging endpoint with a randomized crossover comparison of food conditions. MRI-measured small-bowel water provides a quantitative measure over time, while the crossover structure can, in principle, support comparisons within the same participant. Such designs can be efficient when repeated measurements and their dependence are handled appropriately.

The record also illustrates why the analysis method matters as much as the design label. A crossover is not simply a set of independent groups: a participant’s responses across meals may be related, and period or sequence effects may matter. The registry does not report the sponsor’s analysis model, so unadjusted comparisons from group summaries cannot show whether the potential advantages of the crossover design were used.

The pilot offers estimates that can inform future planning, including the scale of the posted primary differences and their uncertainty. At the same time, planning based on an observed pilot effect can be sensitive to sampling variation. The illustrative sample-size figures are not the original design justification and do not establish what effect would be clinically important.

The study also highlights the distinction between statistical and clinical questions. A detectable change in an MRI endpoint is not automatically a meaningful difference in stoma output or hydration. The population and outcomes must match the intended clinical use. The registry’s background gives a practical motivation, but the reported participants were healthy volunteers and the primary endpoint was an imaging measure.

Finally, the record demonstrates the value of transparent reporting. Information about missing data, outcome populations, multiplicity, crossover analysis and original sample-size assumptions would help readers judge the posted results more fully. Their absence limits interpretation without proving that the original investigators did not consider them.

18. 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 trial is a pilot with 15 participants contributing to each posted food-arm mean, and the registry lists 18 enrolled. The reason for that difference and the handling of any unavailable outcomes are not reported in the registry record. With a small dataset, estimates and standard errors may be sensitive to individual observations, and the registry does not provide participant-level data for further assessment.

The primary population was healthy volunteers free from gastrointestinal disorders. The motivation includes questions about people with a stoma, but the posted population and endpoint do not directly represent that group or measure stoma output. Generalizability to people after bowel surgery is therefore limited by the population and outcomes studied.

The foods were administered as complete meals with different accompaniments and preparation. The meal comparisons cannot isolate the effect of one ingredient from the other components. The study was unmasked, and the registry does not describe procedures for standardizing participant expectations or subjective ratings.

Although the design is crossover, the registry does not report the original analysis model, period or sequence handling, a washout interval, or an assessment of carryover. The unadjusted recalculations do not account for those features. No sponsor-reported analyses are listed, and the original analysis plan, missing-data procedures and analysis population are not reported in the registry record.

The registry also does not report a multiplicity strategy for the secondary outcomes, a clinically meaningful threshold for the primary measure, or the protocol’s sample-size justification. The primary endpoint is an imaging-based area-under-the-curve measure over 0-3 hours, so these results do not address longer-term responses or clinical consequences. Together, these limitations make the findings preliminary and narrow in scope.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Assessing the Effect of Lettuce on Intestinal Water Content Through Magnetic Resonance Imaging of the Small Bowel — NCT02939716.
• Registry record last updated 2020-07-31; status last verified 2020-07.
• Results first posted 2020-07-31.
• 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.

22. Record Summary

The registry describes a completed, randomized, unmasked crossover pilot study of lettuce, rhubarb and bread in healthy volunteers. The primary outcome was MRI-measured small-bowel water, expressed as the area under the curve of postprandial change from fasting over 0-3 hours. The record lists 18 participants enrolled and posts primary outcome means for 15 participants in each food arm.

The unadjusted recalculated primary comparisons show higher mean values for lettuce and rhubarb than bread, with intervals above zero and p < 0.001 for both comparisons. The record lists four secondary outcomes and posts no sponsor-reported analyses. Details of the original statistical plan, crossover analysis, missing-data handling, multiplicity strategy and sample-size justification are not reported in the registry record.

The results describe an MRI response in healthy volunteers. They do not directly establish effects on stoma output, dehydration, or outcomes in people after bowel surgery.