Asian leafy greens like bok choy are nitrate-dense, and a fast, hot stir-fry keeps far more of that nitrate than a pot of boiling water would.

Bok choy belongs to the same family as broccoli and cabbage, but as a leafy green it also sits high on published nitrate tables (American Journal of Clinical Nutrition, 2009). Dietary nitrate is the raw material your body uses to make nitric oxide, the signal that lets blood vessels widen and relax.
In a randomized controlled trial, nitrate-rich vegetables raised nitric-oxide status and improved endothelial function in healthy adults (Free Radical Biology and Medicine, 2012), and in a large cohort study, higher vegetable nitrate intake tracked with lower blood pressure and less cardiovascular disease (European Journal of Epidemiology, 2021). Cohort findings are associations, not proof, and the trial effects are modest. Still, the direction is consistent, and the cooking lesson is simple: nitrate is water-soluble, so speed beats a pot of boiling water.
The bok choy is the point, and the method is what protects it. Searing the halves cut-side down in a very hot pan, then covering them for a single minute with a splash of water, cooks the thick stems through without ever submerging the leaves. Garlic and ginger go in late because both turn bitter if they scorch. Toasted sesame oil and sesame seeds carry most of the flavor, which means you need very little tamari — and rice vinegar at the end does the job that extra salt would otherwise be asked to do. Scallions add a raw, fresh edge.

The soy sauce is the one thing here that can work against you: use low-sodium tamari, measure it rather than pouring, and lean on the vinegar and sesame instead if you want more flavor. Get the pan properly hot before anything goes in, or the bok choy will steam and slump. Buy baby heads with tight white stems and no yellowing, and halve them just before cooking.
Calculated for one serving from USDA FoodData Central values for the ingredients above. An estimate, not a lab analysis.
How this was calculated. Each ingredient was converted to grams, matched to a food in USDA FoodData Central (SR Legacy, April 2018), summed, and divided by 3 servings. Cooking losses, draining and the real size of a handful all move these numbers, so treat them as a good estimate rather than a measurement. Added sugars count honey, maple syrup and table sugar only; sugar from whole fruit is not an added sugar.
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Primary sources for the claims above. Effects reported in these papers describe the compound or the dietary pattern studied — not this specific dish.
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