Vitamin C Foot Ulcer Protocol
This is a planned efficacy study, so its design and prior small-trial signal are informative, but they cannot establish whether vitamin C improves outcomes in the intended population.
This Skin & Dermatology briefing examines the FOOT-C study protocol, which evaluates oral vitamin C as an adjunct for healing diabetes-related foot ulcers. The supplied source presents a planned trial and cites earlier evidence; it does not provide outcome results from FOOT-C itself. pmid:42570250
Evidence
The reported design is a multi-site, parallel-group, randomised, placebo-controlled, double-blind trial in adults with a diabetes-related foot ulcer. The protocol plans to recruit 80 participants. pmid:42570250
Participants are to receive oral vitamin C or placebo for 8 weeks, while ulcer measurements are scheduled at baseline and at 2, 4, 6, and 8 weeks. The primary outcome is percentage reduction in ulcer size, measured as ulcer volume in mm3, at 8 weeks versus baseline; primary analyses are planned on an intention-to-treat basis. pmid:42570250
The protocol identifies changes in plasma vitamin C, time to 50% ulcer healing, time to complete ulcer healing, ulcer-healing rate, and adverse events as secondary outcomes. It also lists exploratory assessments including glycaemic status, blood lipids, blood pressure, peripheral arterial perfusion, mental health and well-being, scurvy signs and symptoms, and oxidative stress. pmid:42570250
The strongest treatment-comparator finding in the supplied material comes from a prior randomised controlled trial of 16 participants cited by the protocol. At 8 weeks, median percentage ulcer healing was 100% with vitamin C and −14% with placebo. The packet does not supply a confidence interval or p-value for that result. pmid:42570250
The protocol also states that its planned sample size provides 90% power to detect a minimum 3.5 hazard ratio for time to 50% ulcer healing, assuming 70% censoring in the control group. This is a design assumption and power statement for the planned study, rather than an observed FOOT-C treatment effect. pmid:42570250
Analysis — Protocol Interpretation
FOOT-C is best understood as a prospective test of an intervention signal, not as completed evidence of benefit. Its randomised, placebo-controlled, double-blind, multi-site design is intended to limit bias when comparing vitamin C with placebo, and repeated ulcer measurements create a defined assessment schedule. The primary endpoint focuses on relative change in ulcer size at 8 weeks, whereas the listed secondary outcomes broaden evaluation to healing milestones, biological exposure, and adverse events. pmid:42570250
The cited prior trial provides a notable directional comparison: median healing at 8 weeks was higher in the vitamin C group than in the placebo group. However, that earlier result came from 16 participants, and the supplied packet does not provide its confidence interval or p-value. Accordingly, the comparison should be treated as rationale for the new trial rather than a precise or definitive estimate of treatment benefit. Statistical planning for FOOT-C, including power for a specified time-to-healing effect, does not substitute for observed outcomes, clinical significance, or safety results. pmid:42570250
For this filing category, the relevant connection is wound healing in diabetes-related foot ulcers rather than a broad claim about dermatologic vitamin C use. The protocol’s planned outcomes can clarify whether the intervention changes ulcer-size reduction and other specified healing measures under the study conditions. Until trial findings are reported, neither efficacy nor a patient-level implication can be concluded from this protocol. pmid:42570250
Limitations
The central limitation is evidentiary stage: the supplied source is a study protocol, and no results from the planned FOOT-C trial are reported in the packet. The primary outcome is assessed at 8 weeks, and the authors state that this duration may be insufficient to capture complete ulcer healing in all participants. pmid:42570250
The protocol further states that the study is not likely sufficiently powered to determine whether there is a plasma vitamin C concentration threshold above which supplementation provides no wound-healing benefit. The prior 16-participant comparison lacks a supplied confidence interval and p-value, limiting interpretation of its precision and statistical uncertainty. pmid:42570250