Bok Choy

Food · Vegetable · Food, Typed Supps

Bok choy is a crunchy, low-calorie green that quietly packs a lot of bone-friendly vitamin K and immune-supporting vitamin C.

Stage by stage

Chewing & Chopping (Mouth): Chewing and cutting bok choy ruptures its cells, triggering the enzyme myrosinase to convert glucosinolates into protective isothiocyanate compounds.
Stomach Breakdown (Stomach): Stomach acid and mechanical churning break down the leafy matrix, freeing carotenoids, vitamin C, and minerals for downstream absorption.
Intestinal Absorption (Small intestine): In the small intestine, fat-soluble vitamin K and provitamin A (beta-carotene) are absorbed alongside dietary fat, while calcium and folate cross into the bloodstream.
Bone & Blood Support (Bone & liver): The liver uses absorbed vitamin K to activate blood-clotting proteins, while bone cells use it to activate osteocalcin, supporting mineralisation and skeletal strength.

Timing

Pairing bok choy with a source of fat, such as cooking oil in a stir-fry, improves absorption of its fat-soluble vitamin K and beta-carotene.

Time to effect

Weeks: Vitamin K status and related coagulation markers reflect roughly one to two weeks of recent dietary intake, so consistent, regular consumption is what produces a measurable nutritional effect rather than a single meal.

Allergens

None of the fourteen major allergens. Derived from what this food is, not from a product label.

Eating patterns

Fits: Vegan, Vegetarian, Pescatarian, Halal, Kosher, Keto, Low-FODMAP, Gluten-free.

In season

September to April in the northern hemisphere, March to October in the southern.

Satiety

The satiety index is measured on 240 kcal servings. At 19 kcal per 100 g that is 1.3 kg of this, which is not a serving anyone eats — so the index has nothing to say about it.

Environmental footprint

0.5 kg CO2e and 76 litres of freshwater per kg, matched to "Brassicas" in Poore & Nemecek (2018), Science 360.

Cost band

Cheap — roughly £2.5 per kg, as a band midpoint rather than a price.

Key nutrients

Nutrition per 100g

Calories: 18.9
Protein: 2.5g
Carbohydrate: 0.6g
of which sugars: 0.6g
Fat: 0.2g
of which saturated: 0g
Fibre: 2.4g
Sodium: 57mg

Food vs. supplement

Bok choy supplies vitamin K, provitamin A, and vitamin C together in a low-calorie, fiber-containing package, and whole-food sources like this are generally preferred over isolated supplements for these nutrients, particularly vitamin K given its narrow interaction margin with anticoagulant medications.

Kitchen tip

Steam or stir-fry bok choy briefly with a little oil rather than boiling it for long periods; this preserves more vitamin C and helps your body absorb its fat-soluble vitamins A and K.

Common myth

"Bok choy and other cruciferous vegetables are dangerous for your thyroid and should be avoided if you have thyroid problems." In reality: The clearest evidence of harm is an extreme documented case, a myxedema coma linked to eating roughly 1 to 1.5 kg of raw bok choy daily for months; cooking inactivates much of the goitrogenic potential, and normal culinary servings are not associated with thyroid dysfunction in people with adequate iodine intake.