The Chinese cabbage, cousins of our European cabbages, are in the process of conquering Western restaurants thanks to their crunch, their delicate flavour, both raw and cooked, and their ease of cultivation.
The Chinese cabbage holds both white cabbage and salad. Its pale green leaves are tender and fine, and its white ribs are crispy. Its fine and slightly sweet taste, less strong than that of the classic cabbage, makes it appreciate raw. It is indeed much more digestible than the other cabbages.
History of Chinese cabbage
“Chinese cabbage” is a general term which can refer to several subspecies of Brassica which are grown and consumed in Asia as well as in the Asian communities of the Western world. However, the subspecies pekinensis generally refers to the Chinese elongated apple cabbage, type Chihli or Napa type, which can be found in grocery stores. Brassica Rapa has recently replaced Brassica campestris as a scientific name, as this species is not botanically different from turnips. To summarize, the Chinese cabbage is a leafy turnip.
Brassica rapa may be the first plant of the genus Brassica having been domesticated. This species probably came from two completely independent lineages: one of Western origin (Europe, Central Asia and India) including turnip and rapeseed, and the other, of Eastern origin (East Asia), including leafy vegetables (many variants of Chinese cabbage). It is from the province of Anhui, in southern China, that this second line would came and spreaded in other parts of the world. Although there is no mention of Chinese cabbage in the writings before the 5th century A.D., researchers believe it is quite possible that it was cultivated some 7 000 years ago.
Introduced in the West in the late nineteenth century, Chinese cabbage has recently gained an excellent reputation throughout the Western world because of its nutritional value, yields and the fact that its production period is relatively short (50 to 60 days for early varieties).
It will arrived on the markets of the Chinese cabbage with a beautiful yellow or a bright orange color, fruit of the selection carried out by Chinese researchers for about ten years. In addition to being five times richer in beta-carotene, they would contain 60% more vitamin C.
There are more than 30 different varieties of Chinese cabbage. Most of them are commonly consumed in Asian countries and in Asiatic communities of Western countries. The Beijing cabbage (Pe-tsai) and the Pak-choi (bok choy) are varieties that are gaining popularity in North America. They are now found in most food markets. The Chinese cabbage, which is part of the big family of crucifers, contains a multitude of vitamins and minerals as well as active compounds whose properties on health are well demonstrated.
Active principles and properties
Several prospective and epidemiological studies have shown high consumption of fruits and vegetables reduces the risk of cardiovascular diseases, certain cancers and other chronic diseases. Some mechanisms of action have been proposed to explain this protective effect; the presence of antioxidants in fruits and vegetables could play a role in it.
With respect to the Brassica family’s vegetables (broccoli, cauliflower, cabbage, Chinese cabbage, etc.), research argues regular consumption could help prevent several cancers such as lung, pancreas, ovaries and kidney. However, it appears this protective effect would not be the same among all individuals due to genetic factors. In addition, a study showed a link between frequent consumption of brassicas (more than 30 times per month) and a lower blood concentration of homocysteine. Elevated levels of homocysteine in the blood were associated with increased risk of cardiovascular disease. Finally, a study exploring the cognitive function among the elderly showed women often consuming brassica vegetables showed a slower cognitive decline than older women who rarely consumed them, a result for the time being is still prelliminary.
Cancer. Studies have shown a link between the consumption of Chinese cabbage and the reduction of the risk of certain cancers. In a recent study in China, subjects consuming the largest quantities of Chinese cabbage (which means more than 27 kg per year) had 50% less risk of lung cancer than those who consumed the least (which means less than 18 kg per year). It should be noted in this study the same type of association was obtained with other vegetables such as carrot, celery and chives. In a major study (more than 100 000 subjects), individuals consuming Chinese cabbage almost every day ran 50% less 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 Chinese cabbage and the incidence of different types of cancer (prostate, gastrointestinal, brain). As these results only come from observational studies and they target different types of cancers, it is not possible to establish a causal relationship. In addition, the quantities of Chinese cabbage consumed in these studies are difficult to reach in a North American context.
Different active compounds of Chinese cabbage would play a role in the preventive effect against cancer:
Glucosinolates. These compounds are mainly found in the brassicas. Glucosinolates are biologically inactive, but when the food undergoes physical transformations (for example, when chopping or chewing), they come into contact with an enzyme called myrosinase. Glucosinolates are then transformed into active molecules such as isothiocyanates as well as indoles. Isothiocyanates, in particular, would help to limit the development of cancer among humain. Cooking reduces the activity of myrosinase, which in theory would diminish the possibility of transforming glucosinolates into active compounds. However, intestinal bacterial flora can also transform glucosinolates, which would partially compensate for the loss of myrosinase of cooked foods. The Chinese cabbage contains glucosinolates, in smaller quantities than most other crucifers. In addition, the Pak-choi (bok choy) variety would contain about twice as much as the Beijing cabbage (PE-tsai). Boiling some brassica vegetables (Chinese cabbage has not been accurately evaluated) may also result in a significant loss of glucosinolates in cooking water. The ideal would be to consume it raw, lightly baked in little water or skipped.
Antioxidants. Antioxidants are compounds protecting the body’s cells from damage caused by free radicals. The latter are highly reactive molecules would be involved in the development of cardiovascular diseases, certain cancers and other diseases related to aging. The Chinese cabbage contains phénolic compounds as well as carotenoids. The quantities of total phenolic compounds in Chinese cabbage are comparable to those of peppers, parsnips and parsley, but less than those of carrot, eggplant, red cabbage and some lettuce. The main phenolic compounds of Chinese cabbage would be various types of flavonoids as well as sinapinic acid. Studies show that although Chinese cabbage contains fewer phenolic compounds than some vegetables (white cabbage, spinach and some green vegetables consumed in Japan), its antioxidant capacity seems to be better “resisting” the thermal treatments.
The Chinese cabbage contains considerable amounts of carotenoids, especially in the form of beta-carotene. Carotenoids are compounds which also possess antioxidants properties. In general, the consumption of carotenoid-rich foods would be linked to a lower risk suffering from certain cancers. A portion of 100 g of Chinese cabbage contains 1 400 μg to 2 600 μg beta-carotene. As a comparison, the carrot, recognized as one of the best sources of beta-carotene, contains more than 4 000 μg of this precious carotenoid. The cooking of Chinese cabbage in water results in a minimal loss (5% to 7%) of its content in beta-carotene. In the body, beta-carotene has the ability to turn into vitamin A. It should be noted carotenoids, including beta-carotene, are better absorbed in the organism when a small amount of fat is consumed in the same moment. It is therefore appropriate to consume, for example, Chinese cabbage with a hint of olive oil or vinaigrette.
Is there calcium in Chinese cabbage?
The Chinese cabbage is one of the vegetables containing the most bio-available calcium, in other words calcium which the body can absorb and use. The bioavailability of calcium contained in some vegetables (mainly leafy greens) is variable. The presence of compounds such as oxalates and phytate decreases the absorption of this mineral in body. Bok choy contains a significant amount of calcium (84 mg per 125 ml serving) and is highly bio-available (absorption rate of 54%). As a comparison, milk calcium is absorbed only at 32%, while spinach is only 5%. Milk remains the main source of calcium in the diet since a portion of 250 ml contains 315 mg. The addition of Chinese cabbage in a balanced diet is an interesting way to increase the daily intake of this precious mineral.
Crucifers and thyroid cancer: a myth
The crucifers contain thioglucosides, substances related to the onset of thyroid gland cancer among animals. Scientists questioned the possibility the use of cabbage and other vegetables from the same family would have the same impact among humans. They carried out a meta-analysis of studies from many countries and brought together thousands of persons. As a result, high consumption of brassicas was not associated with a higher risk of thyroid cancer. On the contrary, in several cases it was associated with a lower risk.
Irritable bowel syndrome
Irritable bowel syndrome is characterized by various disorders of the digestive system, including abdominal pain, flatulence and changes in defecation habits. This disorder may also be manifested by gastro-esophageal reflux or dyspepsia. Some people with this syndrome may feel intolerant to various foods, including vegetables from the cabbage family. By limiting or avoiding these foods, people who suffer from this syndrome can alleviate their symptoms (abdominal pain, bloating, diarrhea, etc.). When symptoms are mild or during periods of “remission”, it is sometimes possible to gradually reintegrate these foods, always respecting individual tolerance. To learn more about this functional disorder, see the irritable bowel syndrome.
The interaction between crucifers and certain medications
Indoles, compounds present in the brassica vegetables, may include reducing the action of certain analgesics such as products containing acetaminophen (Tylenol, Atasol, Tempur, etc.) and other medications combining a mixture of active ingredients (Benylin, Contac, Robaxacet, etc.). People who consume a large amount of crucifers vegetables must take this aspect into consideration.
Choice and conservation
Choose heavy apples in the hand, well firm and healthy leaves, with no sign of browning.
Refrigerator: two weeks. For salads, it is best to eat it within four or five days of purchase.
Freezer: Blanch two or three minutes, cut into thin strips and cool in icy water before putting it in a freezer bag.
For its maturation, Chinese cabbage prefers autumn, when the days shorten and where the temperatures are fresh. The optimum temperatures for its good growth range from 15 °C to 20 ° C. Paradoxically; it does not support cold spring temperatures. Exposed to temperatures of 10 °C or less for one week, the young plant may rise to seed. Therefore, under temperate climates, it is better to sow or transplant it between 10 and 30 July. Despite these precautions, and given the climatic aberrations that have been known over the past few years, it is recommended to choose varieties that are resistant for growth.
Ecology and environment
Every year, the damage caused to the vegetables by the slugs results in losses of several million dollars: the sight of a field of Chinese cabbages completely defoliated by these voraciouss has enough to discourage the most valiant producers. In addition, the molluscicides used to destroy them are costly, in addition to being toxic to other creatures living in the ground, as well as for birds and mammals such as shrew and field mice.
Moreover, these substances are not very effective, the slugs being perfectly adapted to their environment. In fact, they hide underground, and the mucus layer in their bodies gives them relative protection. However, in September 2003, researchers at the University of Newcastle Upon Tyne discovered a purified extract of garlic could severely limit the damage caused by these creatures, destroying not only the adults, but also the eggs deposited on the ground, which is quite extraordinary. After treatment, the damage to the leaves was measured to seethey were minimal. According to the researchers, if, in large crops, it is preferable to use a purified extract, in the family vegetable garden, a preparation based on crushed garlic and water will do the trick.