Bok Choy is one of many Chinese cabbage varieties original Asia, and was introduced to the US by Chinese who participated in the great gold rush in the late nineteenth century. Its veined leaves are dark green and have a taste less pronounced than that of cabbage. It looks like Swiss chard. Its whitish stems are sweet, juicy and crunchy. Bok Choy, which is part of the great family of crucifers, contains a multitude of vitamins and minerals as well as active compounds which have many health properties.
This vegetable is very nutritious. It is an excellent source of vitamins A, K and C, as well as vitamins B2, B6, and folate (vitamin B9), which is involved in the production of all cells in the body, including red blood cells. Folate is also essential in the production of genetic material (DNA, RNA), in the functioning of the nervous system and immune system, as well as in the healing of wounds and sores.
Bok Choy and Lung Cancer
Studies have shown a link between Chinese cabbage consumption and reduced risk of certain cancers. In a recent study conducted in China, subjects consuming the highest amounts of Bok Choy (more than 27 kg per year) had 50% lower risk of lung cancer than those who consumed the least (less than 18 kg per year). Note that in this study, the same type of association was obtained with some other vegetables like carrots, celery and chives.
Bok Choy and Prostate Cancer
In a large study (more than 100 000 subjects), individuals consuming Chinese cabbage almost daily running 50% lower risk of urinary tract cancer than those who consumed less than one to two times per month. A similar trend is observed in other studies evaluating the consumption of Bok Choy and the impact of different types of cancer: prostate, gastrointestinal, brain. As these results only come from observational studies and that they target different types of cancers, it is not possible to establish cause and effect. In addition, the quantities of Bok Choy consumed in these studies were difficult to determine accurately.
Bok Choy Cancer Prevention
Several epidemiological studies have shown that high consumption of fruits and vegetables decreased the risk of certain cancers and other chronic diseases. Although many mechanisms of action have been proposed to explain this preventive effect, the main factor remains the presence of antioxidants in the fruits and vegetables. Regarding cruciferous vegetables (broccoli, cauliflower, cabbage, Chinese cabbage, etc.), research argue that regular consumption could help prevent many cancers such as lung, pancreas, ovary and kidney. It seems however that this preventive effect is not the same in all individuals. It may be due to genetic factors or just lifestyle.
Different active compounds in Bok Choy play a role in cancer prevention, among them include glucosinolates and antioxidants.
Glucosinolates. These compounds are found primarily in cruciferous. They are biologically inactive, but when the food undergoes physical transformations (chewing), glucosinolates come into contact with an enzyme called myrosinase. They are then transformed into active molecules such as isothiocyanates and indoles. Isothiocyanates, in particular, help to limit the development of cancer in humans. However, cooking reduces the activity of myrosinase, which in theory would reduce the possibility of transforming the glucosinolate active compounds. However, the intestinal bacterial flora may also convert glucosinolates, which partially offset the loss of myrosinase in cooked food. So ideally, eating the vegetable raw, lightly cooked in little water or jumped, is better.
Antioxidants. Antioxidants are compounds that protect the cells of body from damage caused by free radicals, highly reactive molecules that are involved in the development of cardiovascular disease, certain cancers and other diseases related to aging. Bok Choy contains phenolic compounds as well as carotenoids. The amounts of total phenolics in the vegetable are comparable to those of pepper, parsley and parsnips, but lower than the carrot, eggplant, red cabbage and some lettuce. The main phenolic compounds in all Chinese cabbage varieties are various types of flavonoids and sinapinic acid (or sinapic acid). Studies show that although Chinese cabbage contains less phenolic its antioxidant capacity seems to be more resistant in the body to certain treatments that tend to damage the health cells.
In addition, all Chinese cabbages, including Bok Choy, contain significant amounts of carotenoids, particularly in the form of beta carotene. Carotenoids are compounds which also possess antioxidant properties. In general, consumption of foods rich in carotenoids is linked to a lower risk of developing certain cancers. A 100g serving of Chinese cabbage contains 1400 mcg to 2600 mcg of beta-carotene. In comparison, carrot, recognized as one of the best sources of beta carotene, contains more than 4000 micrograms.
When Chinese cabbage is cooked in water it loses up to 7% of its content in beta carotene. In the body, beta carotene has the ability to turn into vitamin A. It is observed that carotenoids, including beta-carotene, are better absorbed in the organism when a small amount of lipids (fats) is consumed at the same time. It is therefore appropriate to consume, for example, Chinese cabbage with a hint of healthy oil such as olive oil or hempseed oil.
- Brennan P, Hsu CC,et al.Effect of cruciferous vegetables on lung cancer in patients stratified by genetic status: a mendelian randomisation approach. Lancet 2005 October 29;366(9496):1558-60.
2. Chan JM, Wang F, Holly EA. Vegetable and fruit intake and pancreatic cancer in a population-based case-control study in the San Francisco bay area. Cancer Epidemiol Biomarkers Prev 2005 September;14(9):2093-7.
3. Hu J, Mao Y, White K. Diet and vitamin or mineral supplements and risk of renal cell carcinoma in Canada. Cancer Causes Control 2003 October;14(8):705-14.
4. Pan SY, Ugnat AM, et al. A case-control study of diet and the risk of ovarian cancer. Cancer Epidemiol Biomarkers Prev 2004 September;13(9):1521-7.
5. Wang LI, Giovannucci EL, et al. Dietary intake of Cruciferous vegetables, Glutathione S-transferase (GST) polymorphisms and lung cancer risk in a Caucasian population. Cancer Causes Control 2004 December;15(10):977-85.
6. Lampe JW, Peterson S. Brassica, biotransformation and cancer risk: genetic polymorphisms alter the preventive effects of cruciferous vegetables. J Nutr 2002 October;132(10):2991-4.
7. Galeone C, Negri E, et al. Dietary intake of fruit and vegetable and lung cancer risk: a case-control study in Harbin, northeast China. Ann Oncol 2007 February;18(2):388-92.
8. Sakauchi F, Mori M, et al. Dietary habits and risk of urothelial cancer incidence in the JACC Study. J Epidemiol 2005 June;15 Suppl 2:S190-S195.
9. Kristal AR, Lampe JW. Brassica vegetables and prostate cancer risk: a review of the epidemiological evidence. Nutr Cancer 2002;42(1):1-9.
10. Hara M, Hanaoka T, et al. Cruciferous vegetables, mushrooms, and gastrointestinal cancer risks in a multicenter, hospital-based case-control study in Japan. Nutr Cancer 2003;46(2):138-47.
11. Hu J, La VC, et al. Diet and brain cancer in adults: a case-control study in northeast China. Int J Cancer 1999 March 31;81(1):20-3.
12. Zhang Y. Cancer-preventive isothiocyanates: measurement of human exposure and mechanism of action. Mutat Res 2004 November 2;555(1-2):173-90.
13. Conaway CC, Yang YM, Chung FL. Isothiocyanates as cancer chemopreventive agents: their biological activities and metabolism in rodents and humans. Curr Drug Metab 2002 June;3(3):233-55.
14. Lund E. Non-nutritive bioactive constituents of plants: dietary sources and health benefits of glucosinolates. Int J Vitam Nutr Res 2003 March;73(2):135-43.
15. Song L, Thornalley PJ. Effect of storage, processing and cooking on glucosinolate content of Brassica vegetables. Food Chem Toxicol 2007 February;45(2):216-24.
16. Willcox JK, Ash SL, Catignani GL. Antioxidants and prevention of chronic disease. Crit Rev Food SciNutr 2004;44(4):275-95.
17. Roy MK, Takenaka M, et al. Antioxidant potential, anti-proliferative activities, and phenolic content in water-soluble fractions of some commonly consumed vegetables: Effects of thermal treatment. Food Chemistry 2006; Article in press.