Benefits
Absorbed more readily than plain quercetin
A review of 31 human absorption studies found that quercetin with a chain of glucose units (as in EMIQ) gave about twice the blood quercetin of isoquercitrin and about 20 times that of plain quercetin powder. Food changes the picture: quercetin naturally spread through shallot skin was absorbed better than shallot glucosides. Blood levels show uptake, not a health benefit.
Endothelial function after a single dose
In 25 adults with at least one heart risk factor, a single EMIQ dose (2 mg quercetin equivalent per kg body weight) with breakfast raised flow-mediated dilation, a test of how well the arm artery widens, by 1.8 points versus placebo. Blood pressure and arterial stiffness did not change. A test of plain isoquercitrin at 50 to 400 mg in 15 healthy adults found no change in either. Daily use was not tested.
Eye comfort during cedar pollen season
Two small placebo-controlled Japanese trials gave EMIQ for 8 weeks to adults with cedar pollen allergy (20 and 24 people). Eye symptom scores were lower than on placebo, with less eye itching in one trial, but nose symptoms did not differ significantly, and blood IgE did not fall. Both trials came from one university research group.
Leg muscle mass in athletes using protein powder
In 39 university American football players, 20 g of whey with 42 mg EMIQ six days a week for 4 months raised leg muscle mass by about 0.93 kg versus 0.26 kg with whey alone. Body weight, total lean mass and fat mass did not differ between groups. The trial was funded by the food company Morinaga, and four of its seven authors were its employees.
Strength gains with resistance training in older adults
In 26 older adults doing 6 weeks of resistance training, 200 mg/day of EMIQ-type quercetin glycosides raised knee extension force by about 15% versus 5% on placebo, while muscle mass did not change in either group. In a 24-week trial of 48 adults aged 50 to 74, 200 or 500 mg/day did not increase thigh muscle size, the main outcome, though muscle stiffness was lower.
Blood markers of oxidative stress
In the 4-month athlete trial, the group taking EMIQ with whey ended with a higher ratio of antioxidant capacity to oxidative stress in the blood than the whey group. A 7-day crossover in 9 adults taking 42 mg EMIQ with soy protein also reported lower oxidative stress readings, and a pollen season trial reported lower oxidized LDL. These are lab markers, not health outcomes.
Reaction time in adults aged 60 to 75
In 80 healthy adults aged 60 to 75, a daily drink with 110 mg of quercetin glycosides (counted as isoquercitrin) for 40 weeks improved reaction time on a computer test versus placebo. Brain blood flow measures did not differ significantly between groups. The lead researcher worked at Suntory's research institute.
Mechanism of action
Glucose units help quercetin reach the blood
Plain quercetin dissolves poorly in the gut. With one glucose attached, isoquercitrin was absorbed quickly in volunteers, with blood quercetin peaking about 37 minutes after a dose. EMIQ is more water soluble again and was absorbed more efficiently than isoquercitrin or rutin, with the same pattern of quercetin breakdown products in the blood.
Effects on blood clotting proteins
Isoquercetin blocks protein disulfide isomerase, an enzyme involved in clot formation. In a cancer patient study, 500 to 1,000 mg/day lowered platelet-dependent thrombin generation and 1,000 mg/day lowered D-dimer. In a sickle cell study, 1,000 mg/day lowered whole-blood clotting and platelet aggregation from baseline. This is the reason for caution with blood thinners.
How the artery effect arises is unclear
Quercetin is proposed to support blood vessel function through nitric oxide. In both single-dose artery studies, however, blood markers of nitric oxide did not change, so the reason for the flow-mediated dilation result in the EMIQ study is not known.
Clinical trials
Randomized, controlled crossover study: one dose of EMIQ (2 mg quercetin equivalent per kg body weight) or placebo with a standard breakfast, with flow-mediated dilation of the arm artery measured before and 1.5 hours after (Bondonno et al. 2020, Br J Nutr)
25 adults (12 men, 13 women) with at least one cardiovascular risk factor.
Flow-mediated dilation was 1.80 percentage points higher after EMIQ than after placebo (95% CI 0.23 to 3.37; P = 0.025), and blood quercetin metabolites were higher. Blood pressure, arterial stiffness, cognitive function and biochemical markers, including oxidative stress and nitric oxide markers, did not change. This was a single dose; longer use was not tested.
Randomized, controlled crossover dose-response study of 0, 50, 100, 200 or 400 mg quercetin-3-O-glucoside (isoquercitrin), each given on a separate visit at least 1 week apart (Bondonno et al. 2016, Am J Clin Nutr)
15 healthy men and women.
Blood quercetin rose with dose, but there was no improvement in flow-mediated dilation or blood pressure, and no change in nitric oxide markers, at any dose. The primary outcomes were null.
Randomized, double-blind, placebo-controlled parallel-group trial: two capsules a day of 100 mg EMIQ or placebo for 8 weeks during the pollen season (Kawai et al. 2009, Int Arch Allergy Immunol)
20 adults with Japanese cedar pollen allergy.
Over the whole study, total eye symptom and eye itching scores were lower with EMIQ (P < 0.05). Total symptom score was lower only in weeks 4 to 5, and nasal scores only trended lower (P = 0.06 to 0.08). IgE and blood cytokines did not fall significantly; oxidized LDL and the chemokine TARC fell. Same university group as the pre-season pollen trial.
Randomized, double-blind, placebo-controlled parallel-group trial: 100 mg EMIQ or placebo for 8 weeks, starting 4 weeks before pollen release (Hirano et al. 2009, Allergol Int)
24 adults with Japanese cedar pollen allergy.
The combined eye symptom plus medication score over the whole study was lower with EMIQ (P < 0.05), and eye symptom and eye congestion scores were lower in weeks 5 to 6. Nasal symptoms did not differ between groups, and IgE did not fall significantly. Same research group as the 8-week pollen season trial.
Randomized, placebo-controlled, double-blind parallel trial: 20 g whey protein with 42 mg EMIQ or whey alone, 6 days a week for 4 months, body composition by DXA; funded by Morinaga, with four company employees among the authors (Omi et al. 2019, J Int Soc Sports Nutr)
39 Japanese male university American football players randomized (19 EMIQ, 20 whey alone), mean age 19.8; 40 were recruited and one was excluded before randomization.
Leg fat-free mass and leg muscle mass rose more with EMIQ (muscle about 0.93 vs 0.26 kg; P = 0.021), and an antioxidant index (BAP/d-ROMs) was higher. Body mass, whole-body lean mass, fat mass and leg fat mass did not differ. No adverse events were linked to the product.
Randomized, double-blind, controlled trial: 200 mg/day of enzymatically made quercetin glycosides or placebo during 6 weeks of resistance training (Nishikawa et al. 2025, Eur J Nutr)
26 healthy older adults in Japan.
Knee extensor force rose in both groups, more with quercetin glycosides (115.1% vs 105.3% of baseline; P < 0.001). Muscle mass did not change in either group. Firing rates of higher-threshold motor units were higher with the supplement. A small, short trial.
Randomized, controlled trial of placebo or 200 or 500 mg/day enzymatically made quercetin glycosides with low-intensity resistance training 3 days a week for 24 weeks; funded by Suntory Wellness, with four employee authors (Otsuka et al. 2022, Front Nutr)
Community-dwelling Japanese adults aged 50 to 74; 48 completed the 24 weeks.
There was no difference in thigh muscle cross-sectional area, the primary outcome, or in lean mass. Thigh muscle stiffness in a stretched position was lower in both supplement groups than with placebo (P < 0.05), a secondary outcome.
Randomized, double-blind, placebo-controlled parallel-group trial: 500 mL a day of a drink with 110 mg quercetin glycosides (as isoquercitrin) for 40 weeks; lead author from Suntory's research institute (Nakamura et al. 2022, Eur Rev Med Pharmacol Sci)
80 healthy men and women aged 60 to 75 without cognitive impairment who noticed age-related forgetfulness.
Reaction time on the Cognitrax test, the study endpoint, improved significantly with the quercetin drink. Brain blood volume, blood flow and activity measures did not differ significantly between groups.