Diet trials depend on what participants eat when nobody is watching. Capture puts meal diaries and adherence questions on participants' phones, calculates anthropometrics at entry, and keeps biomarkers, glucose data and questionnaires on one schedule, including crossover designs with washouts.
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Meal diary
Day 9 · Intervention period 1
Which meal is this?
Time you started eating
Did you eat the study meal as provided?
Anything else eaten or drunk?
What matters in nutrition trials
Dietary assessment
Nutrition research has three classic tools for measuring intake: prospective food records or diaries, 24-hour recalls, and food frequency questionnaires. Each trades burden against accuracy. Detailed weighed records are accurate but demanding, and people change how they eat when they have to record it. Frequency questionnaires are easy but blunt. Most intervention trials need something simpler than full dietary assessment: evidence that participants followed the intervention, plus enough about background diet to interpret the results.
Short, structured meal or adherence diaries on participants' phones fit that need well. Asked at the right time (shortly after meals, or each evening) and kept brief, they get completed. Detailed intake can then be collected at a few time points with a specialised dietary assessment tool if the protocol requires it.
Where possible, pair self-reported adherence with an objective marker: returned supplement counts, a nutrient biomarker in blood or urine, or glucose response for a carbohydrate intervention. Record each on its own form so the analysis can compare them.
Precision nutrition studies often use continuous glucose monitors to measure responses to meals. Raw traces usually stay in the device platform; the eCRF captures the summary metrics and meal timings needed to link glucose responses to what was eaten. Meal time fields in the diary make that link possible. See EDC for metabolic studies for related designs.
Participants
32
Meals logged
91%
Off-protocol meals
6%
Evening entries drop at weekends
Crossover designs
Crossover trials compare interventions within the same participant, separated by washout periods. Capture's study design handles arms and epochs, and randomisation allocates each participant's sequence at enrolment, with visits and windows laid out across periods and washouts.
Weeks
Measurements
Weight, height, waist and hip circumference are entered once and BMI and waist-hip ratio appear read-only. Blood lipids, glucose and nutrient biomarkers use lab forms with reference ranges by sex and age, and out-of-range values are flagged at entry.
BMI (Body Mass Index)
Auto-derivedHeight (cm)
172
Weight (kg)
68.5
Result
23.2 kg/m²
Reference: WHO · shown read-only during data entry
Build both in the free sandbox and try the diary on your phone.
Supplements and foods
Studies of supplements and functional foods can often be blinded where whole-diet studies cannot, but only if the placebo is well matched in appearance, taste and packaging. Record the product batch dispensed to each participant, and ask participants at the end which product they think they received: a simple blinding assessment that reviewers find reassuring.
Compliance is usually measured by counting returned capsules or sachets at each visit and comparing with the number expected. Record dispensed and returned counts as numbers, so compliance percentages are calculated consistently rather than estimated by the site. For studies intended to support health claims, design endpoints and populations with the relevant regulator's expectations in mind from the start; see EDC for supplement clinical trials.
Participants' usual diets vary, and changes in background diet during a study can swamp the effect of a supplement. Ask participants to keep their usual diet, capture it briefly at baseline and at the end, and record major changes (such as starting a weight-loss diet) as protocol deviations if the protocol defines them.
Study build
Self-report plus an objective marker where one exists.
Short, structured questions at the right time rather than full intake records every day.
At baseline and key time points, with a validated method if the analysis needs it.
Long enough for the outcome to return to baseline between periods.
Glucose, lipids and biomarkers in one unit per field.
If results will support a health claim, design endpoints with the relevant regulator's expectations in mind.
With food records, 24-hour recalls or food frequency questionnaires for detailed intake, and short adherence or meal diaries for intervention compliance, often paired with objective biomarkers.
Yes. Meal and adherence diaries run in the phone browser from a secure link, with completion windows and reminders.
Yes. Arms and epochs define periods and washouts, and randomisation allocates sequences at enrolment.
Yes. BMI and waist-hip ratio are built-in calculated fields shown read-only during entry.
Record CGM summary metrics and meal times on structured forms. Raw traces usually remain in the device platform.
Yes. The free sandbox has every feature with no credit card.
Keep exploring
Meal diaries, crossover schedules and calculated anthropometrics. Free sandbox.