Yu Mi Xu

Newly diagnosed type 2 diabetes patients were randomised to corn silk water extract or placebo. After three months the corn silk group had significantly lower glycated haemoglobin and fasting blood glucose than placebo. Untargeted metabolomics identified 73 differential metabolites enriched in oxidative phosphorylation, purine metabolism and endocrine resistance pathways. This is the clearest human evidence that the herb lowers glucose on its own rather than as part of a combination, though the trial is single-centre and the sample small.

Five randomised trials with 567 participants comparing corn silk tea plus conventional antihypertensive drugs against those drugs alone. The combination was more effective at lowering blood pressure, relative risk 1.27 (95 per cent confidence interval 1.17 to 1.38), with no heterogeneity between trials. The authors classed this as limited evidence because most included trials were methodologically poor, and found no evidence that adding corn silk tea reduced adverse events. All trials are add-on designs, so the review says nothing about corn silk used alone.

Randomised crossover trial in 11 prediabetic adults across four milk-based interventions. Mulberry leaf and corn silk extracts inhibited alpha-amylase and alpha-glucosidase dose-dependently and synergistically in vitro. No significant difference in postprandial glycaemic response was seen in the group overall; in the overweight subgroup the corn silk and mulberry leaf combination in a galacto-oligosaccharide milk matrix reduced one-hour glucose by a median of 0.84 mmol per litre, maximum glucose by 0.54 and glucose excursion by 0.62 against pure milk. A negative primary result rescued by a subgroup, in eleven people, with corn silk never given alone.

Twenty-eight adults with type 2 diabetes completed a four-arm crossover with continuous glucose monitoring. The mulberry leaf and corn silk extract combination lowered maximum glycaemia by a median 0.9 mmol per litre and maximum excursion by 0.9 against water, and added to lactose-hydrolysed milk it lowered one-hour glucose, maximum glycaemia and maximum excursion against the milk alone. Registered as ChiCTR2400086442. Again a two-herb combination, so the corn silk contribution is not isolated.

Pregnant Wistar rats received a standardised corn silk dry extract, maysin-predominant with 1.698 per cent total flavonoids, at 300, 600 or 1200 mg per kilogram from gestational day 0 to 20. No clinical toxicity, weight, genotoxicity, histopathological or biochemical changes were seen, and no fetal malformations. The 1200 mg per kilogram dose increased pre-implantation losses, which the authors flag as possible interference with early pregnancy. Relevant because corn silk is treated as a food and is drunk freely in pregnancy for oedema.

Spontaneously hypertensive rats received oral corn silk extract for four weeks followed by four weeks off treatment. Blood pressure fell and the effect was attributed to prebiotic modulation of the gut microbiota by the polysaccharide fraction rather than to a direct vascular mechanism. Offers a plausible route for the clinical blood pressure findings, but it is a rat model and the proposed mechanism has not been tested in humans.