Benefits
Total and LDL cholesterol over 12 weeks
In a 12-week placebo-controlled trial in Japanese adults with a BMI of 23 to 30, apple polyphenol capsules at 600 mg/day (24 people in the apple arm) lowered total cholesterol versus placebo at week 4 and LDL cholesterol versus baseline at weeks 8 and 12. The trial was led by researchers at the extract maker, and a carefully controlled UK trial of lower-dose apple flavanol extracts found no change in blood fats.
Blood sugar rise after a starchy meal
In two UK crossover trials in healthy adults, drinks containing an apple extract taken with a starch and sugar meal lowered the blood glucose rise over the first 30 minutes, even at the lowest dose tested (0.9 g). Peak glucose and the 2-hour glucose response were mostly unchanged, so the effect is a short delay in the early rise rather than a lower overall sugar load.
Glucose tolerance in adults with high-normal fasting glucose
In a 12-week Japanese trial in 65 adults with fasting glucose of 100 to 125 mg/dL, 600 mg/day of apple polyphenol tablets lowered the 30-minute value in a glucose tolerance test compared with placebo; other blood fat measures and cytokines did not change significantly. In an 8-week Italian trial in 62 overweight adults with similar glucose levels, 300 mg/day lowered fasting glucose versus placebo.
Visceral body fat over 12 weeks
In a 12-week trial in 94 Japanese adults with a BMI of 25 to 30, a drink supplying 600 mg/day of apple polyphenols reduced visceral fat area compared with a placebo drink. Split by starting level, the drop was significant in people who began with high visceral fat (100 cm2 or more), not in those below. The trial was led by researchers at the extract maker, and an earlier 12-week trial by the same group found only a slight drop.
Endothelial function and blood pressure
Results with extracts disagree. An 8-week Italian trial of 300 mg/day reported better endothelial reactivity than placebo in 62 overweight adults. Two 4-week crossover trials in adults with raised blood pressure found no benefit over placebo: epicatechin-rich and procyanidin-rich extracts did not change blood pressure or arterial stiffness in one, and an epicatechin-rich extract did not improve flow-mediated dilation in the other.
Bowel movement frequency
In a 12-week trial in 23 analysed Japanese adults with overweight and constipation, run by an extract supplier, 600 mg/day of unripe apple polyphenols raised bowel movements to about 7 a week versus about 5 on placebo. Fecal levels of the bacterium Akkermansia muciniphila did not differ from placebo. This is a single small trial.
Whole apples and cholesterol (food evidence)
Whole-apple trials test the food, not an extract. In a UK crossover trial in 40 adults with mildly raised cholesterol, two apples a day for 8 weeks lowered total and LDL cholesterol and triglycerides versus a sugar-matched apple drink. A pooled analysis of 18 trials mixing apples, extracts and juice found only a non-significant trend overall, with significant drops in placebo-controlled comparisons.
Mechanism of action
Slows glucose transport in the gut
Phloridzin blocks SGLT1, the main sugar transporter in the small intestine, in frog egg cell and mouse gut tests, and apple extracts reduced glucose uptake in human gut cell lines. In volunteers, an apple extract taken before a glucose drink lowered blood glucose and insulin and slightly raised the glucose lost in urine.
Cholesterol and bile acid handling (proposed)
Researchers propose that apple procyanidins bind cholesterol and bile acids in the gut so more leave in the stool, and rat studies report lower activity of HMG-CoA reductase, the liver enzyme that makes cholesterol. These ideas come from animal work and have not been measured directly in people taking the extract.
Xanthine oxidase and uric acid
In laboratory tests an apple polyphenol extract blocked xanthine oxidase, the enzyme that makes uric acid. In one 8-week trial, uric acid fell compared with placebo. Whole apples, by contrast, slightly raised uric acid in a UK food trial.
Clinical trials
Randomized, double-blind, placebo-controlled three-arm trial led by Asahi Breweries researchers: apple polyphenol capsules, hop bract polyphenol capsules or placebo capsules, 600 mg/day for 12 weeks (Nagasako-Akazome et al. 2007, J Oleo Sci)
71 Japanese adults (45 men, 26 women) with a BMI of 23 to 30; 24 in the apple polyphenol arm, 24 on placebo and 23 on hop bract polyphenols.
In the apple arm, total cholesterol was lower than placebo at week 4 and lower than baseline at week 12, and LDL cholesterol fell from baseline at weeks 8 and 12. Adiponectin fell significantly on placebo but not on apple polyphenols. Visceral fat decreased only slightly. Colds and digestive symptoms occurred in some participants, including on placebo, and were not attributed to the capsules.
Two randomized, double-blind, placebo-controlled trials led by Asahi Breweries researchers: a 12-week trial of a beverage with 600 mg apple polyphenols per day, and a 4-week test at three times that amount (Akazome et al. 2010, J Oleo Sci)
94 Japanese adults aged 20 to 65 with a BMI of 25 to 30 in the 12-week trial (87 in the efficacy analysis); 30 adults with a BMI of 18 to 30 in the excess-intake test.
Visceral fat area fell from baseline at weeks 8 and 12 in the apple group, and the change differed significantly from placebo. Split by starting level, the decrease appeared in people with visceral fat of 100 cm2 or more but not in those below. Adverse events occurred in both trials, but none was attributed to the beverage, and blood and physical exams showed no clinical problems.
Randomized, double-blind, placebo-controlled trial of apple polyphenol tablets (600 mg/day) for 12 weeks; primary outcome was insulin resistance in a 75 g oral glucose tolerance test (Shoji et al. 2017, Diabetes Res Clin Pract)
65 Japanese adults with fasting plasma glucose of 100 to 125 mg/dL at a recent health check.
Apple polyphenols reduced the rise in glucose 30 minutes into the glucose tolerance test compared with placebo; in the high-normal and borderline subgroup the 30-minute value was 164 versus 195 mg/dL. Other lipid measures and cytokines did not change significantly. The authors call for larger and longer trials.
Randomized, controlled, double-blind crossover trial of drinks containing 0, 0.9, 1.35 or 1.8 g of a phloridzin-rich apple extract taken before a 75 g starch and sucrose meal, plus cell studies (Prpa et al. 2020, J Nutr Biochem)
Healthy adults in the UK.
All three doses lowered the plasma glucose rise over the first 30 minutes and delayed the time to peak from 30 to 45 minutes, but did not lower peak glucose; the authors conclude the extract slightly delays early glucose without changing peak or total response. Gastric emptying and urinary glucose did not differ.
Randomized, controlled, double-blind crossover trial of a placebo drink, a drink with 1,200 mg apple polyphenols, or 600 mg apple polyphenols plus 600 mg blackcurrant anthocyanins, taken with a starch and sucrose meal (Castro-Acosta et al. 2017, J Nutr Biochem)
25 healthy adults in the UK (20 men, 5 postmenopausal women).
The apple drink lowered the glucose rise over 0 to 30 minutes versus placebo, but the difference over 120 minutes was not significant; the apple plus blackcurrant drink lowered it over both periods. Insulin, C-peptide and the gut hormone GIP were lower than with placebo.
Randomized, double-blind, placebo-controlled, 4-arm crossover trial of an apple flavanol extract at two doses, an apple procyanidin extract, or placebo, each once daily for 4 weeks (Hollands et al. 2018, Am J Clin Nutr)
42 healthy adults with moderately elevated blood pressure who completed the trial.
Compared with placebo, none of the apple extracts changed systolic or diastolic blood pressure, arterial stiffness or nitric oxide products at 2 hours or after 4 weeks. Total, HDL and LDL cholesterol, triglycerides, fasting glucose and insulin were also unchanged.
Single-centre, double-blind, placebo-controlled crossover trial of an apple polyphenol extract supplying 100 mg/day epicatechin for 4 weeks per period, funded by DuPont Nutrition and Health (Saarenhovi et al. 2017, Nutr J)
60 otherwise healthy adults aged 40 to 65 in Finland with borderline or unmedicated mild high blood pressure.
Maximum flow-mediated dilation rose acutely after extract doses, but neither the acute nor the 4-week change differed significantly from placebo. Nitrate-mediated dilation did not differ either. No safety concerns were raised.
Randomized, double-blind, parallel placebo-controlled trial of 300 mg/day apple polyphenols for 8 weeks, with a laboratory xanthine oxidase study (Cicero et al. 2017, Mol Nutr Food Res)
62 overweight adults in Italy with fasting plasma glucose of 100 to 125 mg/dL.
After 8 weeks, fasting glucose was 10.3% lower than baseline and differed from placebo; uric acid fell 14.0% and endothelial reactivity improved compared with placebo. At 4 weeks, fasting glucose had already fallen 6.1% and other blood measures had not changed significantly.