Strawberry.

Strawberries carry a high ascorbate content per gram, so the fruit and a vitamin C supplement feed the same pool. Ascorbate also protects the fruit's anthocyanins from oxidation in a liquid formula.

Strawberry polyphenols are dominated by ellagitannins, chiefly sanguiin H-6 and its relatives. These are the molecules that carry most of the fruit's polyphenol load into the gut.

Strawberry ellagitannins are hydrolysed in the gut to release free ellagic acid. Supplying ellagic acid directly and eating the fruit therefore reach the same intermediate.

Gut bacteria convert ellagic acid from strawberries into urolithins, which are the forms actually found in circulation. Not everyone carries the bacteria that make urolithin A, which is why the finished metabolite is supplied directly.

Pelargonidin-3-glucoside is the dominant strawberry anthocyanin and gives the fruit its colour. It enters the same absorption and glucuronidation route as anthocyanins from other berries.

Among ordinary foods strawberry carries the highest measured fisetin content. Food and supplement intakes feed one flavonol pool, though the supplement dose is far larger than any realistic serving of fruit.

The ascorbate in strawberry reduces ferric iron to the ferrous form and keeps it soluble in the upper gut. Taking iron with a vitamin C rich fruit raises the fraction that crosses the mucosa.

Ellagitannins in strawberry are hydrolysed to ellagic acid and then converted by colonic bacteria into urolithins, and people differ widely in whether their microbiota carry out that final step. That conversion is a settled part of polyphenol metabolism. Whether adding a commercial probiotic changes an individual's urolithin output has not been shown, so the mechanism is established while the intervention is not.

Bifidobacteria deglycosylate anthocyanins and ferment the associated fibre and polyphenol residues that reach the colon intact. Most anthocyanin from a berry serving is never absorbed as such and arrives in the colon for exactly this. The pairing rests on documented microbial metabolism rather than on a combination trial.

Inulin is fermented by colonic bacteria that also handle ellagitannin and anthocyanin residues arriving from the upper gut. Supplying both a fermentable fibre and a polyphenol load gives those populations substrate and precursor at once. This is mechanistic reasoning; no trial has paired strawberry with inulin specifically.

Anthocyanins associate with whey and casein proteins, which changes colour stability in a blended product and can alter how much free polyphenol is available in the upper gut. The binding is well characterised in food chemistry. Whether it changes anything measurable in a person is not established, so read it as a formulation consideration.

Casein binds anthocyanins and other berry polyphenols readily, which is why strawberry and dairy blends lose colour intensity over shelf life. The interaction is a food-chemistry fact, not a clinical one. Any claim that dairy blocks berry polyphenol effects in people goes beyond what has been measured.

Strawberry supplies ascorbate, and ascorbate reduces the tocopheryl radical back to alpha-tocopherol, which is settled redox chemistry in lipid systems. Certain berry polyphenols can act in the same direction in vitro. The chemistry is established; an effect on any health outcome from combining them is not.

Quercetin and strawberry flavonoids compete for the same UDP-glucuronosyltransferase and sulfotransferase capacity, so a large simultaneous dose of one can slow conjugation of the other. This is a handling interaction and can raise or lower circulating levels of either. It has not been quantified for this pair.

Piperine slows UGT-mediated glucuronidation, which is the dominant clearance route for anthocyanins and their aglycones. Formulators add it to polyphenol blends for that reason. Higher circulating polyphenol is a pharmacokinetic marker, not by itself a benefit, and the pairing has not been tested with strawberry.

Resveratrol and strawberry anthocyanins appear together in polyphenol blends and share overlapping conjugation and efflux handling. The pairing is commercial practice rather than a measured combination. Nothing about additive effect follows from co-formulation.

Pterostilbene is the dimethylated stilbene analogue used alongside berry extracts in blends, where its greater lipophilicity is the stated reason for its inclusion. The combination has commercial precedent, not trial precedent. Read it as formulation practice.

EGCG occupies sulfotransferase and glucuronosyltransferase capacity that also handles berry flavonoids, so a large simultaneous dose changes the clearance of both. Whether that shifts anything a person would notice has not been shown. The competition itself is well documented in polyphenol pharmacokinetics.

Pectin from the fruit and any added pectin reach the colon largely intact and are fermented there, which is also where a large share of ingested anthocyanin ends up. The two arrive at the same place and feed the same populations. This describes where the material goes, not an outcome.

Psyllium raises luminal viscosity, which slows how quickly the simple sugars in a fruit or fruit powder serving are absorbed. Blood sugar response is a measured parameter, not a clinical endpoint. The effect of viscous fibre on that parameter is well established; the pairing with strawberry specifically is not trial-tested.

Berry powders and marine oils are combined in blended products, where the polyphenol fraction is also used to slow oxidation of the oil during shelf life. That antioxidant role is a stability function inside the product. No combination effect in people has been measured.