BioVariability/BioAvailability: Quercetin Part III. InterPersonal Drift & Quercefit?

by Anthony L. Almada, MSc, FISSN

"Bioavailability". When I first heard this word used in a nutritional biochemistry context I thought, "What a cool, polysyllabic term to sound and read cool and cutting edge". The early to mid-1980s context involved 'light metal': the nutritionally essential trace mineral zinc.

In the early 1980's this emerging trace metal (from a commercial vantage) was a Helen of Troy/Sparta, the axis of an epic, contentious, and personalized battle between a scientist at the University of California, Davis (the late Lucille Hurley, PhD) and one at the US Department of Agriculture (Gary Evans, PhD; USDA, out of Grand Forks, North Dakota). The crux of the conflict: Is picolinic acid--a metabolite of the essential amino acid tryptophan--the preferred "partner" (ligand) to enhance the absorption, delivery, and utilization of zinc?

Irrespective of the side one took, this war led to a Phyrric victory for Dr. Evans (then at USDA, moving to Bemidji State University in the later 80s) who attained commercial success and recognition through his patent for metal picolinates, first focused on zinc and then, to a later and much higher recognition, chromium. This US patent (4,315,927) was filed in 1980 by, and assigned to the USDA, later to be licensed to Nutrition 21.

The industrial translation of greater bioavailability (for zinc dipicolinate, back in the 80s) was simple: higher, greater, more...better. Apparent increases in tissue concentrations--relative to other forms of zinc e.g. citrate or gluconate--were communicated as a better way to supplement zinc. Notably, this first comparison study (funded by nutrition retail giant GNC!) with zinc dipicolinate (against citrate and gluconate forms), conducted at the Bastyr College of Naturopathic Medicine in Seattle, Washington, did not show increases in blood (serum) zinc; significant increases in hair, red blood cell, and urine concentrations were seen with zinc dipicolinate only, and only relative to placebo, not to the other zinc ligands.

In Part I of this series I described my early 1980s, bipolar II swing after finding (hypomanic zenith) and then reading (depressive nadir) the first human oral (4 grams, single dose) bioavailability study with quercetin (in 1975): reprising Part I...It was bioUNavailable. I also detailed a seminal 2006 study wherein the bioavailability of oral quercetin (as a polymolecular drink called FRS) in humans was obviated by a focus on assessing its bioactivity in humans, i.e. endurance cycling performance in trained cyclists.

Since this ostensibly crippling 1975 publication, which precluded this author from creating quercetin-containing dietary supplement innovations that included quercetin for decades , numerous quercetin (as a pure dietary supplement ingredient) bioavailability studies in humans have been conducted, inspired by the diverse pleiotropic effects of quercetin e.g. antihistamine, anti-inflammatory, antioxidant, anti-platelet, anti-cystitis, anti-________... These have been complemented by an even greater number of studies with quercetin delivered in food sources.

Non-Response/Non-Responders. Looming Behind the "Better Bioavailability" Curtain

If you’ve met one person who has tried "CBD", you’ve met one person who has tried "CBD". If you've met one person who has tried glucosamine...you've met one person who has tried glucosamine. If you've met one person who has tried quercetin...you have met one person who has tried quercetin. What is shared between these three ostensibly divergent, molecules of Nature origin?

They all are magnificently under-absorbed in a significant percentage of humans--they are malabsorbed.

The only way to modify this is to 1) take advantage of the "food effect" i.e. consume with a large meal (I have been advocating this to numerous "CBD"-centric companies, and consumers, for > two years), and/or 2) process the bioactive to a different particle size and/or "wrap" or mix it with something, and then demonstrate that either 1 or 2 produces greater/faster amounts in the blood (after oral ingestion) and, per definition, greater amounts appearing in/delivered to target tissues.

Read almost any biomedical journal article that is reporting on a bioavailability study and you will see the results of each group represented as a mean, or average, along with a second value ("SD" or "SEM") that describes the noise or variability between each of the subjects comprising Group 1 relative to the average or mean value for the group. In other words, the average "signal" for a group (as a whole) and the inter-individual "noise" or scatter between each subject in the group relative to the signal.

Consider a bullseye target at a field archery range. The target face is a series of (usually ten) concentric rings of differing colors.

Figure 1. A field archery target. Image: Ich28

In bioavailability/absorption context, think of one arrow entering the "bullseye" (AKA the ten ring), the centermost (usually yellow) and smallest circle, as being equivalent to a score or value associated with the highest blood concentration increase (at a specific time, or accumulated over a specific time interval) of a certain bioactive agent (e.g. quercetin) after ingestion of a single oral dose in one individual.

As the number of "archers" firing at the target (or the number of subjects each taking a single dose of quercetin) increases, one will see a scattered distribution of arrows (or, quercetin blood concentration values).

As one moves away from the bullseye center into each successively outer, larger diameter ring, each arrow/subject dose response represents a lesser/lower blood concentration increase (relative to baseline, pre-supplementation) of quercetin for each respective individual. Arrows that do not hit the target at any scoring location i.e. they hit the white area (AKA a "petticoat") are equivalent to blood concentration changes/values that are equal to or less than zero.

Figure 2. Field archery target showing a variety of scoring (non-white colored rings) and non-scoring (white rings) arrows; each arrow (for this article) represents a single individual's blood quercetin concentration change after a single oral dose of supplement form quercetin i.e. quercetin aglycone, quercetin lacking a sugar molecule(s) attached to it (as it occurs in many plant foods). Image: Giovanna Orlando

Quercetin is the most abundant flavonoid in the diet. Thus, for a person eating plant foods e.g. onions, drinking grape-derived products e.g, red wine, or ingesting Ginkgo biloba or Hypericum perforatum [St. John's wort]-containing supplements, a background, above zero concentration of blood quercetin would be likely/expected. A well-controlled bioavailability/"pharmacokinetics" study assessing a quercetin dosage form would/should require subjects to avoid these types of foods/beverages/supplements for a period of time before the study and through the completion of the supplementation and collection of body fluids (blood, urine).

Taking this target practice out of the field and into the university research laboratory, a number of human studies have been undertaken and assessed the person to person variability in the oral bioavailability/absorption of quercetin.

The first study profiled below hails from Professor Marilyn Morris' lab, University at Buffalo (New York). Six male and four female adult subjects ingested capsules labeled to contain 500 mg of quercetin (the average, measured quercetin content of six capsules was 589 mg) three times daily with meals (see below for food/fat effect), for seven consecutive days. On the eighth day the subjects reported to the clinical research center in a fasted state, consumed a standardized breakfast (macronutrient and calorie content not described; it likely contained a notable amount of fat; such a meal [≈ 15 grams, 30% of calories] can increase the absorption/bioavailability of quercetin administered in a supplement, non-food form, relative to a low [≈ 5 grams] or zero fat meal), and then took a single, 500 mg quercetin capsule with water.

The graphs below show 1) the "baseline" (prior to the day 8, single 500 mg quercetin capsule after breakfast, and after seven days [168 hours] of 500 mg quercetin, thrice daily), and 2) the acute blood quercetin response to the single, 500 mg, post-breakfast dose. These are from four of the ten subjects. Note the variability in the baseline (vertical axis) plasma quercetin concentrations (dotted line arrow tip; 7 days of 1,500 mg of quercetin in a capsule, with meals) and acute blood quercetin responses (solid, vertical arrows in two of the subjects; the other two had increases that are too small to depict).

Figure 3. Individual blood plasma free quercetin concentrations after a) seven days of supplementing with 500 mg of quercetin, 3x daily, with meals [arrows], and b) following a single, post-breakfast dose of 500 mg of quercetin. From Moon et al., 2008. Note: Most quercetin ingested is metabolically transformed (by the gut microbiota, and intestinal and liver cells) into quercetin connected (conjugated) to water solubilizing substrates (e.g. quercetin glucuronide; quercetin sulfate), among other forms; unmodified, free quercetin represents a minority of quercetin appearing in the blood shortly after ingestion. Total quercetin is typically defined as the sum of free + conjugated quercetin. Thus, free quercetin is always markedly lower than TOTAL quercetin values: compare the values in the vertical axes of these graphs [range of 0.0625 - 64 ng/ml] to those in Figures 5-6 [range of 0 - 3000 ng/ml].

A factor of almost 100 defines the difference between the hour 168 value for subject ID 7 (yellow arrow) and subject ID 8 (black arrow), suggesting subject 8 is a non-responder to a week of thrice daily quercetin (1,500 mg/day) supplementation. Although the increment in plasma quercetin (depicted by the blue vertical arrow for subject ID 8) seems substantial, a closer look at the vertical [quercetin] plasma concentration axis reveals a rather trivial increase a few hours post-dose: from ≈ 0.35 to ≤ 1.5 nanograms/milliliter of plasma.

This study calculated interpersonal variability in the response to oral quercetin supplementation, noting it to be 190%, while the rate of quercetin absorption showed a 91% variability between subjects. This strongly suggests that one to three of the ten subjects had very little to no quercetin absorption, with a few others displaying modest absorption, at best.

The next study, a collaboration between Rutgers Univeristy, the Univeristy of Massachusetts at Amherst, and the US Army research center in Natick, Massachusetts, was conducted with various dosage formats for quercetin, each format serving delivering 500-531 mg of quercetin (measured in each format):

Figure 4. Composition of three different quercetin delivery formats, used to compare bioavailability and pharmacokinetics in adult males after a single serving. From Kaushik et al., 2012.

Similar to the prior study, this group also commented on substantial intersubject variability (in each group) in the absorption/bioavailability of quercetin, being least in the group receiving the chews. However, variability was not calculated/provided in the paper so I calculated the values.

Below are coefficients of variation for peak plasma (Cmax) quercetin concentration, and cumulative plasma quercetin changes over 32 hours post-dose [AUCtotal] Note: Coefficient of Variation (CV) is expressed as a percentage, representing the dispersion of values within a group around the average (mean) value of the group. The higher the percentage the greater the dispersion away from the average and the higher likelihood of persons being non-responders, i.e. showing minimal to no increases in blood quercetin concentration:

1. Quercetin/Tang: (60.5%) [43.9%]
2. Quercetin/Bar: (66.5%) [66.0%]
3. Quercetin/Chew: (91.5%) [39.7%]

The figures below show the individual blood quercetin responses to the quercetin-loaded bar and chews:

Figure 5. Plasma total quercetin changes over 32 hours after ingestion of a quercetin-loaded bar, containing approximately 500 mg of quercetin. Each line represents one subject. The hashed blue arrow highlights the single outlier subject (UM3) that displayed a dramatically greater peak plasma quercetin response; the hashed red arrow approximates the average peak plasma quercetin concentrations among the remains five subjects. From Kaushik et al., 2012.

Figure 6. Plasma total quercetin changes over 32 hours after ingestion of quercetin-loaded chews (2), containing approximately 500 mg of quercetin. Each line represents one subject. The hashed blue arrow highlights the single outlier subject (UM2) that displayed a dramatically greater peak plasma quercetin response; the hashed green arrow approximates the average peak plasma quercetin concentrations among the remaining five subjects; the hashed red arrow focuses on two of the (non-responder?) subjects (UM8, UM14) that displayed negligible increases in plasma total quercetin. From Kaushik et al., 2012.

Quercetin Absorption/Bioavailability Solvation: More Quercetin for More Persons

Many natural product bioactives, especially those from plants, are poorly water soluble--they are often water insoluble (hydrophobic; "afraid" of water). Rather, they are very fat-loving (lipophilic). The intestinal contents are very water-rich and lipid-poor, unless one consumes a notable amount of dietary lipid (fats). Quercetin, like most flavonoids, is very hydrophobic and lipophilic (this may partly explain why a fat-rich meal can increase its absorption/bioavailability; see above). The pioneering delivery system technology of Phytosome?, as developed and patented by Indena in the late 1980s and first applied to various naturally-occurring flavonoids, is designed to render hydrophobic bioactives hydrophilic, with the intent of increasing delivery to the blood.

Indena's Phytosome? technology creates a unique composition between plant-derived phospholipids and the selected botanical bioactive(s), here being quercetin. With a super-hydrophilic (water-liking/soluble) “head” and super-hydrophobic (water-fearing/insoluble) “tails”, phospholipids like lecithins easily combine with bioactive molecules, improving their wetting capacity, and preventing them from self-aggregating and "shape-shifting" i.e. changing their physical state.

Phytosome? formulations are an emulsion in which lecithins break up, in a soft and fluid way, the interactions that foster the self-aggregation of botanical bioactives. The human body readily embraces and recognizes phospholipids as "self" or native (cell membranes are phospholipid "walls"), which fosters the transmembrane (through cell membranes) delivery of the bioactive payloads within Phytosomes. This optimizes bioavailability in its most relevant form, which transcends "absorption": making the bioactives available to interact with the metabolic and signaling machinery inside cells.

Phytosome? is not a mechanical blend but a physical process-- state-of-the art "diagnostic" techniques like solid-state NMR have failed to reveal the presence of ordered structures as seen in liposomes. A Phytosome? is distinctively more water soluble (see below, and able to be manufactured into a dry powder form--a significant advantage that obviates the need for softgel costs and lead times), while the bioactive(s) is(are) relatively protected from digestive enzymes, gut microbes (a significant "consumer"/degrader of quercetin before it can be absorbed), and moisture.

Even though quercetin was named as a specific flavonoid in the first (January 1987) patent application for Phytosome? technology, only very recently has the composition been validated by systematic chemical and pharmacological studies (some of which I described in Part I). Note: The trade name for Quercetin Phytosome is Quercefit? and it will be referred to herein. It is composed of (in descending order) quercetin (from the flowering parts of Styphnolobium japonicum; formerly referred to as Sophora japonica; AKA Japanese pagoda tree), non-GM sunflower lecithin (phospholipids extract), potato maltodextrin, and silicon dioxide.

The first demonstration of distinction was assessing solubility in vitro. Below is a table comparing the solubility (in simulated, fasting state intestinal fluid; ≈ 99% water) of quercetin (unmodified) to Quercefit? and quercetin plus the Phytosome? components (lacking the manufacturing/processing steps used to create Quercefit?from these components):

Figure 7. Comparative solubility of different quercetin-containing compositions: Quercefit?; a mixture of quercetin, sunflower lecithin, maltodextrin, and silicon dioxide, and unmodified quercetin, in a solution simulating the contents of the upper small intestine in a fasted state. Quercefit?-derived quercetin solubility was 4.2x greater than the unmanufactured components of Quercefit?, and 11.2x greater than quercetin alone. From: Riva et al., 2018.

These same compositions were also compared in a simulated fasting state in the stomach (very acidic; pH = 1.6) and a simulated fed state in the upper small intestine (pH = 5.0). i chose to depict the fasted state, simulated intestinal fluid conditions as this may reflect the conditions in the gut when Quercefit? would be ingested e.g. empty stomach before physical exercise/competition; upon arising or prior to sleep (for supporting a healthy response to allergens).

Test tube/in vitro/ex vivo data are nice but they are like operating a Formula 1 racing car or Boeing jet in a simulator: even though the conditions appear very similar they do not approach the complexity of a living human system interacting with its environment, and any perturbations (like ingestion of a quercetin-containing supplement). In the second part of this Quercefit?study, two different doses of Quercefit? (delivering either 100 or 200 mg of quercetin), and 500 mg of unmodified quercetin, were ingested (in a fasted state) as a single dose by twelve healthy male and female subjects (average age of 25), at three different times (crossover design), with a minimum one week washout between each different treatment. All treatments were delivered in identical, film-coated tablets. Blood (plasma) quercetin was measured out to 24 hours post-dose.

Figure 8. Bar graph comparison of cumulative plasma quercetin increment over 24 hours post-dose (AUC). *§AUC values for Quercefit? 500 mg [200 mg of quercetin] were significantly greater than both Quercefit? 250 mg [100 mg of quercetin] (P < 0.005) and unmodified quercetin (P < 0.0001); *Quercefit? 250 mg [100 mg of quercetin] AUC values for the group were significantly greater than 500 mg of unmodified quercetin (P < 0.0001). From: Riva et al., 2018.

The between treatment peak blood concentrations and 24 hour plasma quercetin excursions are illustrated by this graph from the 2018 paper:

Figure 9. Line drawing comparison of cumulative plasma quercetin increment over 24 hours post-dose (AUC). The red hashed arrows identify the approximate peak plasma quercetin concentration from two different Quercefit? doses; the green hashed arrow approximates the peak plasma quercetin concentration obtained from unmodified quercetin. Time point values: *§ AUC significantly greater than both Quercefit? 250 mg (P < 0.005) and unmodified quercetin (P < 0.0001); * significantly greater than unmodified quercetin (P < 0.0001). Note: Each subject took each treatment at separate times, thus minimizing inter-subject variability. From: Riva et al., 2018.

Quo Vadis, Variability? Intersubject Variability of Absorption/Bioavailability with Quercefit?

The impact of solubility (or relative insolubility) upon absorption/bioavailability of quercetin is striking and self-evident. Moreover, the two step dose escalation (250 to 500 mg of Quercefit?; 100 and 200 mg of quercetin payload) showed a nearly linear increment (in relation to AUC 24 hour values [Figure 8]. What about inter-subject variability, the differences between how you respond and how I respond? The authors did not calculate/report it, so I calculated coefficients of variation for peak plasma (Cmax) quercetin concentration, and cumulative plasma quercetin changes over 24 hours post-dose [AUCtotal]:

1. Quercetin [500 mg, unmodified]: (20.3%) [24.9%]
2. Quercefit? [250 mg; 100 mg quercetin equivalent]: (11.7%) [12.7%]
3. Quercefit? [500 mg; 200 mg quercetin equivalent]: (7.3%) [9.7%]

CV values greater than 20%, in the pharma world, are considered very problematic and difficult to interpret and make informed, guided decisions from. Above I have described CV values (from two notable quercetin bioavailability/absorption studies, evaluating a total of four different delivery formats) that range from 40 - 190%. Harnessing the solubilizing efficiency of Phytosome? technology for a quercetin delivery system translates into both a dramatic increase in in vitro solubility and in vivo absorption/bioavailability, with 2-3+-fold lesser variability.

Biovariability: A New Opportunity for Quercefit??

I was spawned in the fertile rivers of biochemical individuality in 1980-1981, as first articulated by Roger Williams, PhD in the late 1950's and later eloquently disseminated by Jeffrey Bland, PhD (Dr. Bland also wrote the introduction to the 1988 edition of Williams' seminal book, Biochemical Individuality). Is it plausible to believe that any one dietary bioactive or natural product would display the same absorption/bioavailability (let alone safety and efficacy...) across an entire population, let alone a family sharing a biological surname? The dawn of the genOmics generation (Gen-O, as I call it: 23andMe, Ancestry?, et al.) is missing out on the more relevant, functional expression of genes, which requires an integrated interrogation of phenotype (the outward, functional manifestation in an organism), and the RNA and protein-enzyme underpinnings. And then there is the holobiome, starting with the oral/gut microbiota and working outward to the skin microbiota...too much to contemplate, even with AI, computational biology power, and metagenomic robots.

Person to person variability in blood responses to oral quercetin supplementation could explain the equivocal findings described in the dozens of clinical studies conducted with this queen of flavonoids. Similarly, glucosamine, which has also accumulated an equivocal body of evidence in relation to efficacy, also displays "enormous variability" [120-fold] between persons after oral supplementation. Could these disparate response between subjects, where some are bioavailability and efficacy responders and others are not, yet the average of both is not greater than placebo, explain studies that report "no effect"? Alternatively, could a bioavailability-enhanced quercetin like Quercefit?translate into a greater percentage of responders manifesting as whole body biological responses (allergic response, immune response, exercise bioenergetic response, senolytic response)? As more studies are conducted on Quercefit? more answers to this question will manifest.

Disclosure: Mr. Almada is a paid consultant to Indena SpA, developers and marketers of QuerceFit?, a quercetin formulation exploiting the Phytosome? delivery system.