Brussels Sprout.

The glucosinolates brussels sprouts store are inert until myrosinase cleaves them to isothiocyanates. Heat inactivates the plant's own enzyme, so added myrosinase restores conversion.

Sinigrin is a dominant glucosinolate in brussels sprouts, and its hydrolysis gives allyl isothiocyanate. Added sinigrin raises the same substrate pool the vegetable supplies.

Allyl isothiocyanate is the pungent product released when brussels sprout sinigrin is hydrolysed. Supplying it directly gives the end product without the conversion step.

Brussels sprouts carry glucobrassicin, which breaks down to indole-3-carbinol and condenses in stomach acid to diindolylmethane. DIM is the same end point reached by a different route.

Ascorbate is a cofactor for myrosinase and pushes glucosinolate hydrolysis toward isothiocyanates rather than nitriles. Brussels sprouts carry ascorbate themselves, which supports their own conversion.

Thiocyanate released from glucosinolate breakdown competes with iodide at the sodium iodide symporter, so it lowers how much iodide is taken up. The effect matters most when iodine intake is already low.

Brussels sprouts are among the highest phylloquinone foods, and phylloquinone is the cofactor for gamma carboxylation of clotting factors. Their intake adds to supplemental vitamin K1.

Isothiocyanates raise transcription of selenium dependent enzymes such as glutathione peroxidase and thioredoxin reductase. Selenium supply determines whether those induced enzymes can be assembled.

Brussels sprouts are a whole food source of the same glucosinolate family a cruciferous extract concentrates. Both arrive at the gut as intact thioglucosides awaiting hydrolysis.

Isothiocyanates are conjugated to glutathione for excretion and also drive glutathione synthesis upward. NAC supplies the cysteine that limits how fast that synthesis can run.

Brussels sprouts carry glucoraphanin, the glucosinolate that myrosinase converts to sulforaphane when plant tissue is damaged. A preformed sulforaphane supplement supplies the end product directly and does not depend on that conversion. Taken together the two routes converge on the same isothiocyanate pool. Cooking destroys myrosinase, which is why the vegetable and the isolate behave differently.

Brussels sprouts are among the denser vegetable sources of natural folate, which feeds one-carbon metabolism alongside B12 and B6. A supplemental folate adds to that dietary contribution rather than competing with it. Boiling leaches a meaningful share of the folate into the cooking water. The pairing is nutritional addition.

Dark green brassica leaves and sprouts carry lutein and zeaxanthin alongside chlorophyll. Because both are fat-soluble, absorption from the vegetable depends heavily on eating fat at the same meal. A lutein supplement contributes to the same pool. This is dietary addition, not a new mechanism.

Zeaxanthin accompanies lutein in green vegetable tissue and shares its absorption route through mixed micelles. Supplementation adds to what the vegetable supplies. The two carotenoids compete with each other and with beta-carotene for the same intestinal transport, so a very large single-carotenoid dose can crowd the others. Direction depends on relative dose.

Beta-carotene, lutein and zeaxanthin share micellar packaging and the SR-B1 transporter at the enterocyte. A high-dose beta-carotene supplement taken with a carotenoid-rich vegetable can lower the uptake of the others in that meal. The competition is established from human absorption studies of carotenoid mixtures. It is a within-meal effect, not a long-term depletion.

Carotenoids and vitamin K1 from a vegetable need dietary fat to form the mixed micelles that carry them across the gut wall. Adding fat to a meal that includes brussels sprouts raises the absorbed fraction substantially. Medium chain triglycerides are less effective at this than long chain fats because they bypass chylomicron packaging. Any fat source works for the purpose.

Brussels sprouts carry raffinose and stachyose, which humans lack the alpha-galactosidase to digest, so colonic bacteria ferment them and produce gas. An alpha-galactosidase enzyme preparation cleaves those sugars before they reach the colon. This changes tolerability, not nutrient content. It also reduces the prebiotic substrate reaching the bacteria.

The oligosaccharides and insoluble fibre in brussels sprouts feed colonic bacteria in the same way inulin does. Combining them raises the total fermentable load, which raises short chain fatty acid production and also raises gas. For someone new to either, the additive effect is felt as discomfort before it is felt as benefit. The direction is additive on both counts.

Brussels sprouts are unusually high in vitamin C for a vegetable, and ascorbate reduces ferric iron to the ferrous form and keeps it soluble in the duodenum. Eaten in the same meal as a plant iron source or an iron supplement, that raises the absorbed fraction. Boiling destroys much of the vitamin C and weakens the effect. The mechanism is well characterised in human absorption studies.

Brussels sprouts contribute meaningful potassium to a meal, which supports normal fluid and electrolyte handling. A potassium supplement adds to that dietary intake. Boiling leaches potassium into the cooking water, so preparation matters. The contribution is nutritional.

Brussels sprouts supply phylloquinone, the plant form of vitamin K, while MK-7 is the long-chain menaquinone form. Both feed the same gamma-carboxylation reaction that activates vitamin K dependent proteins, but they differ in half life and tissue distribution. Humans convert phylloquinone to menaquinone-4 to a limited extent. Anyone whose clotting is being managed by a clinician should keep vitamin K intake steady rather than variable.

Isothiocyanates released from brassica glucosinolates are conjugated to glutathione by glutathione S-transferases, and the conjugates are excreted as mercapturic acids. That pathway is both the clearance route and part of the signalling that follows. Glutathione status therefore shapes how long an isothiocyanate stays around. Individual GST genotype is a known source of person-to-person variation.

When cooking has destroyed plant myrosinase, glucosinolates arrive intact at the colon and are hydrolysed by bacterial thioglucosidase instead. That microbial step is why cooked brassicas still yield measurable isothiocyanate metabolites, at lower and more variable levels. Shifting the resident bacteria shifts the conversion. The step is absorption-side, not an added active.