Bok choy is not the same species as cabbage or broccoli. It is Brassica rapa subsp. chinensis, the same species as turnip, napa cabbage, mizuna, tatsoi, komatsuna and choy sum, while cabbage and broccoli are Brassica oleracea. A 2014 analysis traces the two species to a shared lineage that arose about 3 million years ago in the northeastern Mediterranean, from where one branch spread through Europe and the other to Asia.
The name comes from Cantonese baak choi, “white vegetable”. In a study of 347 women in Shanghai, Brassica vegetables averaged about 98 g a day and were mostly bok choy. Raw bok choy has 13 kcal per 100 g, 45 mg of vitamin C (50% of the Daily Value) and 105 mg of calcium.
In a small trial, women absorbed about 52% of the calcium in bok choy leaves and stems, similar to milk. Bok choy itself is little studied, though. Most of the research below covers cruciferous or green leafy vegetables as a group, and each card says so.
Health benefits of bok choy
The top findings from 14 studies, strongest evidence first
What the stars mean
- Strong. Several randomized trials, pooled in a meta-analysis, point the same way, or regulators (FDA or EFSA) have approved the claim.
- Moderate. Good randomized trials support it, but there are fewer of them, or their results vary.
- Limited. Small, short or single trials, or mixed results. Promising, but it needs confirmation.
Population and lab studies get no stars: they show a link or a mechanism, not proof.
How we rate evidence →- ★★Slightly lower total cholesterol, from Brassica vegetablesAcross 9 trials of Brassica vegetables, the group bok choy belongs to, total cholesterol fell by a small amount. LDL, triglycerides and blood sugar did not change significantly.
- ★Calcium in bok choy is well absorbedWomen absorbed about 52% of the calcium in bok choy. The authors compare this with an earlier value of 46% for milk.
- ★No clear effect on blood sugar after riceIn 31 women, eating bok choy with rice did not significantly change the blood sugar response compared with rice alone.
- Population studyLinked to a lower risk of deathChinese adults who ate the most cruciferous vegetables had a 22% lower risk of dying than those who ate the least. This covers cruciferous vegetables as a group.
- Population studyLinked to lower colorectal cancer riskPeople who ate the most cruciferous vegetables had an 18% lower risk of colorectal cancer. In studies that followed people forward in time, the link was borderline.
All 14 studies, strongest evidence first
Eating Brassica vegetables as a group lowered total cholesterol in trials, but not LDL, triglycerides or blood sugar
Meta-analysis of 9 randomized trials (548 people) of Brassica vegetables, the group bok choy belongs to; the abstract does not say which vegetables were used. Total cholesterol fell by a small amount (a standardized difference of 0.28), while LDL, HDL, triglycerides, fasting blood sugar and HbA1c did not change significantly. The authors call for more high-quality trials.
Women absorbed about 52% of the calcium in bok choy, similar to milk
Absorption trial in 15 women who ate labeled bok choy, broccoli and kale, with about 83 mg of calcium in each test. Absorption was 0.52 from bok choy stems and from leaves, 0.48 from broccoli and 0.53 from kale, differences too small to matter. Milk was not retested; the authors compare with an earlier value of 0.46. The study measured absorption, not bone health.
Eating bok choy with rice did not significantly change the blood sugar response in 31 women
Study in 31 women who ate rice, rice with bok choy, or spinach (75 g of available carbohydrate) on separate occasions. Blood sugar responses varied widely from woman to woman, and the greens did not significantly reduce them. Responses tracked age and the activity of sirtuin-related genes, which the authors see as a lead for further work.
Among Shanghai women who ate about 98 g of Brassica vegetables a day, mostly bok choy, higher intake went with higher urinary isothiocyanates
Study of 347 healthy women in the Shanghai Breast Cancer Study, using a food questionnaire and a fasting morning urine sample. Isothiocyanates, the breakdown products of glucosinolates, rose across quarters of intake, and the link was stronger with some Phase II enzyme gene variants. It shows that the urine marker follows Brassica intake and did not test health outcomes.
Shanghai women in the top quarter of urinary isothiocyanates, a marker of Brassica intake, had about half the odds of breast cancer
Case-control study of 337 women with breast cancer, each matched to a population control, in Shanghai, where Chinese cabbage and other Brassica vegetables are eaten habitually (odds ratio 0.5). Intake from a food questionnaire alone was not linked to breast cancer. Urine was collected once, and in cases before surgery. A companion paper from the same Shanghai breast cancer study found that women’s Brassica intake was mostly bok choy.
In Shanghai, total cruciferous vegetable intake was not linked to breast cancer risk, though women who ate more Chinese cabbage or turnip had lower risk after menopause
Case-control study of 3,035 breast cancer cases and 3,037 controls. The lower postmenopausal risk showed for Chinese cabbage (P for trend 0.049) and turnip (P for trend below 0.001); the abstract does not say whether Chinese cabbage means bok choy or napa cabbage. The GSTP1 Val/Val gene variant carried a higher risk (odds ratio 1.50).
Chinese women who ate the most cruciferous vegetables had about half the odds of breast cancer (odds ratio 0.48)
Case-control study of 737 women with breast cancer and 756 controls, covering cruciferous vegetables as a group. Higher glucosinolate and isothiocyanate intake also went with lower odds (0.54 and 0.62). Case-control studies depend on people recalling past diet, and the gene-diet interactions the authors tested were not significant.
Chinese adults who ate the most cruciferous vegetables had a 22% lower risk of dying than those who ate the least
Two Shanghai cohorts with 134,796 adults, including 3,442 deaths among women and 1,951 among men. The link was mainly with cardiovascular deaths, not cancer deaths. It covers cruciferous vegetables as a group, from food questionnaires.
People who ate the most cruciferous vegetables had an 18% lower risk of colorectal cancer
Meta-analysis of 24 case-control and 11 prospective studies of cruciferous vegetables as a group. In the prospective studies alone the link was borderline, and case-control studies depend on people recalling past diet.
In an umbrella review of cruciferous vegetables, only gastric, lung and endometrial cancer and all-cause mortality had suggestive links to lower risk
Review of 41 meta-analyses covering 303 observational studies and about 13.4 million people. Sixteen more links were supported by weak evidence, and the authors say substantial uncertainty remains. It covers cruciferous vegetables as a group.
Higher intake of green leafy vegetables went with an 11% lower risk of cardiovascular disease in cohort studies, but 7 trials showed no better vascular function
Systematic review and meta-analysis of green leafy vegetables as a group; the abstract does not name bok choy. Cardiovascular deaths were 21% lower (relative risk 0.79), but results differed a lot between studies. Blood pressure did not change in the trials, and the authors call the trial evidence limited.
Stir-frying pak choi for 1 to 8 minutes at pan temperatures from 160 to 250°C kept its glucosinolates
Lab study of pak choi (Brassica rapa ssp. chinensis) and napa cabbage. One compound, glucobrassicanapin, made up 63% of the glucosinolates in fresh pak choi. The authors credit quick loss of the enzyme myrosinase and heat-stable glucosinolates, and say nothing leached out, unlike boiling. These are measurements of the vegetable, not a study in people.
Pak choy varieties differed widely in their glucosinolates, with 17 compounds found across one genebank collection
Lab analysis of leaves from pak choy accessions held in a Korean genebank. They fell into three groups: one high in glucobrassicin and gluconasturtiin, one high in glucoiberin, glucocheirolin and sinigrin, and a majority group high in glucoraphanin, progoitrin and glucotropaeolin. It shows that the mix varies by variety and did not test health effects.
Adding 7% bok choy to a high-fat hamster diet lowered total and LDL cholesterol and triglycerides
Study in hamsters, not people. Fifty-six hamsters ate a normal diet, a high-fat diet, or a high-fat diet with 5% or 7% of a green or a purple bok choy for 56 days. The 7% green and both purple doses also lowered liver enzymes and raised HDL cholesterol, and the 5% green dose is not reported as significant. The authors are plant scientists.
Who should be careful with bok choy
Most people can eat bok choy freely. Take a little care if one of these applies:
- Warfarin. Bok choy contains vitamin K, about 38% of the Daily Value in 100 g, which can change how this blood thinner works. You do not need to avoid it; keep the amount steady from week to week and check with your clinic before big changes.
- Very large amounts of raw bok choy. A 2010 case report described an 88-year-old woman who ate 2 to 3 pounds (about 0.9 to 1.4 kg) of raw bok choy a day for several months and developed myxedema coma, a severe form of underactive thyroid. She recovered with treatment. That is roughly 13 to 19 cups a day, so it is one extreme case, but if you have a thyroid condition, ask your doctor before eating large amounts.
- Irritable bowel syndrome. Monash University lists bok choy among the low-FODMAP leafy vegetables at a standard serve of 75 g, so a normal portion should suit a low-FODMAP diet.
How to choose, store and eat bok choy
- Stir-fried: in lab tests, stir-frying pak choi at pan temperatures from 160 to 250°C for 1 to 8 minutes kept its glucosinolates, with no leaching into water as in boiling.
- Raw or cooked: heat switches off the plant enzyme that turns glucosinolates into isothiocyanates, and gut bacteria can make some instead, from about 1% to over 40% of a dose between people in one study of broccoli sprout extract. No study here compares raw and cooked bok choy.
- Stems and leaves: eat both, since calcium absorption was about 52% from each. Stems need about 5 minutes of steaming and leaves 2 to 3 minutes.
Pick bok choy with firm stalks and fresh green leaves, and avoid wilted heads. Keep it unwashed in a loose plastic bag, or wrapped in paper towels, in the fridge drawer for up to five days.
Sources
- Anticoagulant medicines: considerations. NHS.
- Chu M, Seltzer TF. Myxedema coma induced by ingestion of raw bok choy. N Engl J Med. 2010.
- Back away from the bok choy, ma’am. NBC News. Report on the case above, with the amount eaten.
- Low FODMAP shopping list. Monash FODMAP blog.
- Nugrahedi PY, Oliviero T, Heising JK, Dekker M, Verkerk R. Stir-frying of Chinese cabbage and pakchoi retains health-promoting glucosinolates. Plant Foods Hum Nutr. 2017.
- Fahey JW, Wehage SL, Holtzclaw WD, et al. Protection of humans by plant glucosinolates: efficiency of conversion of glucosinolates to isothiocyanates by the gastrointestinal microflora. Cancer Prev Res (Phila). 2012.
- Heaney RP, Weaver CM, Hinders SM, Martin B, Packard PT. Absorbability of calcium from Brassica vegetables: broccoli, bok choy, and kale. J Food Sci. 1993.
- Bok choy. Purdue Extension FoodLink.
History of bok choy
Bok choy has two names with one meaning. English borrowed “bok choy” from Cantonese baak choi, “white vegetable”, and the Mandarin name xiǎo bái cài means “small white vegetable”. Carl Linnaeus described it as Brassica chinensis in 1755, and botanists now treat it as a subspecies of Brassica rapa.
Its species has a long farming past. A 2021 genetic study of 416 samples concluded that turnips were probably the first Brassica rapa crop, and that leafy types in East Asia and in Europe were later selected from separate lineages. Bok choy belongs to the East Asian leafy group.
Wikipedia says bok choy has been grown in China since the 5th century CE. Two main kinds exist: dark green leaves on white stalks, mostly grown in southern China, and lighter leaves on green stalks, common in eastern China, where it is known as “Shanghai green”.
From China it spread across Asia, to Japan, Malaysia, Indonesia and the Philippines. Wikipedia reports plantations in Japan and Malaya by the early 19th century, and says it reached North America in the 19th century but took about another century to catch on.
Science mapped the species more recently. The first Brassica rapa genome, published in 2011, came from a Chinese cabbage, and it showed a genome that had tripled at some point in its past. The authors suggest that changes in gene families may help explain the wide range of shapes in the species.
Sources
- Arias T, Beilstein MA, Tang M, McKain MR, Pires JC. Diversification times among Brassica (Brassicaceae) crops suggest hybrid formation after 20 million years of divergence. Am J Bot. 2014.
- McAlvay AC, Ragsdale AP, Mabry ME, et al. Brassica rapa domestication: untangling wild and feral forms and convergence of crop morphotypes. Mol Biol Evol. 2021.
- Wang X, Wang H, Wang J, et al. The genome of the mesopolyploid crop species Brassica rapa. Nat Genet. 2011.
- Fowke JH, Shu XO, Dai Q, et al. Urinary isothiocyanate excretion, brassica consumption, and gene polymorphisms among women living in Shanghai, China. Cancer Epidemiol Biomarkers Prev. 2003.
- Bok choy. Wikipedia.
- Brassica rapa. Wikipedia.
Frequently asked questions about bok choy
Is bok choy good for you?
For most people, yes. Raw bok choy has 13 kcal per 100 g, with 45 mg of vitamin C (50% of the Daily Value) and 45.5 µg of vitamin K (38%). Research on bok choy itself is thin: women absorbed about 52% of its calcium in one small trial, and Shanghai cohorts link cruciferous vegetables to a 22% lower risk of dying. That is a link, not proof, and no bok choy finding here reaches strong evidence.
Is bok choy the same as pak choi?
Yes. Bok choy and pak choi are two spellings of the same vegetable, Brassica rapa subsp. chinensis. “Bok choy” is the usual name in the US, Canada and Australia, and “pak choi” in the UK and South Africa. Baby bok choy is simply young plants.
Is bok choy healthier raw or cooked?
No study here compares them. Heat switches off the plant enzyme that makes isothiocyanates, though stir-frying pak choi at up to 250°C kept its glucosinolates, and boiling can lose them to the water. Gut bacteria can make some isothiocyanates from cooked vegetables, but people differ a lot: from about 1% to over 40% of a dose in one study of broccoli sprout extract.
Is bok choy a good source of calcium?
It is a modest source that the body absorbs well. Raw bok choy has 105 mg of calcium per 100 g (8% of the Daily Value), or 73.5 mg in a cup (70 g). In 15 women, about 52% of the calcium in bok choy leaves and stems was absorbed, against an earlier milk value of 46%, so it counts toward your calcium without being a large source.
Is bok choy high in vitamin K?
Fairly high. Raw bok choy has 45.5 µg of vitamin K per 100 g (38% of the Daily Value) and 31.8 µg in a cup (27%). If you take warfarin, the NHS says you do not need to avoid vitamin K foods, but you should keep the amount steady and ask your clinic.
Is bok choy good for weight loss?
No study here tested weight loss. Raw bok choy has 13 kcal and 1 g of fiber per 100 g, or 9 kcal in a cup (70 g), so it fills a plate cheaply. That is a swap effect for higher-calorie foods, not a proven effect of bok choy itself.
Is bok choy a cabbage?
Sort of. It is called Chinese cabbage in some places, but it is a different species from the green cabbage on most shelves. Bok choy and napa cabbage are both Brassica rapa, while green cabbage and broccoli are Brassica oleracea. In Cantonese, bok choy is “small white vegetable” and napa cabbage is “big white vegetable”.
Can you eat too much bok choy?
In extreme amounts, possibly. One 2010 case report described an 88-year-old woman who ate 2 to 3 pounds of raw bok choy a day for several months and developed myxedema coma, a severe form of underactive thyroid. That is roughly 13 to 19 cups a day, so it says little about normal servings. If you have a thyroid condition, ask your doctor.