Land Cress.

Land cress is eaten raw and carries ascorbic acid, which keeps dietary non-heme iron in the ferrous state at duodenal pH. That is the form the DMT1 transporter moves across the enterocyte. The effect is on absorption of iron eaten in the same meal, not on iron status measured weeks later. Cooking the leaf hard enough to destroy the vitamin C removes the interaction.

Some glucosinolates in brassica leaves break down to thiocyanate, which competes with iodide for uptake at the sodium-iodide symporter. The competition matters mainly when iodine intake is already low, because adequate iodide outcompetes the thiocyanate. Anyone eating large daily volumes of raw cress with a low-iodine diet has a reason to keep iodine intake steady. At ordinary culinary amounts with adequate iodine this is mechanistic rather than clinical.

Land cress supplies glucosinolates that myrosinase converts to isothiocyanates when the leaf is chewed or chopped. Sulforaphane is the isothiocyanate from broccoli glucoraphanin and reaches the same Nrf2 signalling step. Stacking them raises total isothiocyanate exposure rather than adding a second mechanism. This is a pathway argument, not a measured clinical outcome for the pairing.

The ascorbate in fresh cress sits in the aqueous phase and can hand an electron to the tocopheroxyl radical formed when vitamin E quenches a lipid radical. That returns vitamin E to its active form at the membrane surface. The pairing is a laboratory-grade redox relationship measurable in plasma antioxidant assays. Markers of recycling are not the same as an outcome anyone feels.

Isothiocyanates from brassica leaves raise transcription of glutathione-linked enzymes, and glutathione peroxidase cannot function without a selenocysteine residue. Low selenium status caps what the induced transcription can deliver in enzyme activity. The relationship is a cofactor dependency rather than a demonstrated combined effect. It matters most where soil selenium is low.

Land cress leaf contains phylloquinone, the cofactor for gamma-glutamyl carboxylase. Taking a vitamin K1 supplement alongside a large raw-cress intake stacks two sources of the same vitamer. Anyone whose clotting medication has been titrated against a steady vitamin K intake should keep that intake steady rather than swinging it. The point is consistency of intake, not avoidance.

Oxalate binds calcium in the gut lumen and forms a poorly absorbed complex. Brassica leaves including cress sit low on the oxalate scale relative to spinach and chard, so calcium taken with them is less bound than the leafy-green reputation suggests. The row is here to correct the assumption rather than to claim a benefit. Fibre and phytate in a mixed meal still matter separately.