Benefits
Antioxidant activity: shown in test tubes, not in people
Apple procyanidins are strong free radical scavengers in laboratory assays. In the trial cited here the antioxidant work was a test tube superoxide scavenging assay run on isolated procyanidin fractions, with a half maximal effective concentration of about 2.4 micrograms per millilitre for the whole procyanidin mixture; the authors reported no clear relationship between the size of the procyanidin molecules and their scavenging activity. No marker of oxidative stress in the body, such as malondialdehyde, isoprostanes or 8-OHdG, was measured in any human study cited here, so an antioxidant benefit for a person taking this extract has not been demonstrated.
Skin pigmentation after UV exposure: one small sponsor run trial of another brand
In 65 healthy women in Japan aged 20 to 39, of whom 59 were analysed, 12 weeks of apple polyphenol at 300 or 600 mg/day left the change from baseline in redness, melanin reading and skin lightness on ultraviolet exposed upper arm skin smaller than on placebo. Read this carefully: the absolute readings for those same measures did not differ significantly between the apple polyphenol and placebo groups at any timepoint, and 600 mg/day did not clearly beat 300 mg/day. Facial moisture and water loss through the skin did not change, and the paper reports no significant effect on any other facial skin measure. The tested material was another company's apple polyphenol, and the study was designed, funded and staffed by that company. Cardiometabolic markers were not measured in this trial.
Inflammation: not measured in anyone taking this extract
Apple procyanidins have been reported to reduce inflammatory signalling in cell and animal experiments. No inflammatory marker was measured in the human trial cited here, so this remains a laboratory observation rather than something shown in people taking the supplement.
Mechanism of action
Procyanidin antioxidants
Apple procyanidins scavenge superoxide radicals in test tube assays, with no clear relationship between the size of the procyanidin molecules and the strength of the effect. Whether that translates into measurable antioxidant protection inside the body at supplement doses has not been tested in any of the human studies cited here.
Vascular and metabolic signalling: preclinical only
Apple procyanidins alter cholesterol transport and vascular gene expression in animal models, including a rabbit study of arterial plaque. In people, the one randomised trial of an apple polyphenol extract on brachial artery flow mediated dilatation found no significant advantage over placebo, so improved blood vessel function has not been shown in humans for this class of extract.
Clinical trials
12 week randomised, double blind, placebo controlled trial in 65 healthy women in Japan aged 20 to 39, of whom 59 were included in the efficacy analysis. Participants took tablets supplying 300 mg/day or 600 mg/day of apple polyphenol, or placebo. The material tested was Applephenon, an apple polyphenol from Asahi Breweries, not this branded extract. Registered as UMIN000039612. (Shoji T, Masumoto S, Moriichi N, Ohtake Y, Kanda T. Nutrients 2020;12(4):1071.)
65 healthy women in Japan aged 20 to 39 with skin phototype II or III; 59 analysed (21 placebo, 20 at 300 mg/day, 18 at 600 mg/day). People with atopic dermatitis, dyslipidemia, diabetes or uncontrolled hypertension were excluded.
Skin on the upper arm was deliberately exposed to ultraviolet light. The change from baseline in redness, melanin reading and skin lightness was significantly smaller in the apple polyphenol groups than in placebo. However, the absolute values of those same three measures did not differ significantly between the apple polyphenol and placebo groups at any timepoint, and no clear dose response appeared between 300 and 600 mg/day. On the face, moisture content and water loss through the skin did not differ from placebo, and the authors report no significant effect on any other facial skin measure. The study was funded by the company that sells the tested extract and all five authors were employed by that company. No adverse events related to the supplement were reported.