A large, fast growing leafy perennial shrub that is believed to have originated in the Yucatan Peninsula of Mexico and through Central America. The specific epithet, "aconitifolius", means Aconitum-like leaves. It has succulent stems which exude a milky sap when cut. It can grow to be 6 meters tall, but is usually pruned to about 2 m for easier leaf harvest. It is a popular leaf vegetable in Mexican and Central American cuisines, similar to spinach. The leaves must be cooked before being eaten, as the raw leaves are toxic.
The young shoots and tender leaves of chaya are cooked and eaten like spinach. They comprise part of the staple diet and are the main dietary source of leafy vegetable for the indigenous people of Yucatan peninsula of Mexico and Kekchi people of Alta Verapaz in Guatemala (Harris and Munsell 1950; Booth et al. 1992). There are many underexploited native leafy plants with potential as a traditional food source (NAS 1975). With current renewal of interest in household gardens, attention is being focused on promoting some of these plants as leafy green vegetables among populations in the developing countries (FAO 1987). The edible parts of chaya plant, which taste like spinach when cooked, provide important nutritional sources for protein, vitamins (A and C), minerals (calcium, iron, phosphorus), niacin, riboflavin, and thiamine among populations that cannot afford expensive foods rich in these nutrients (Yang 1979). The plant may also constitute a potentially valuable leafy green vegetable here in the United States and elsewhere.
Nutritional Properties of Chaya:
For this test, young leaves and shoots of C. chayamansa were collected from
greenhouse-grown plants. Raw and cooked (in microwave oven for 5 min) samples
of the leaves and shoot were analyzed for their moisture content, crude fiber,
fat, and ß-carotene using the AOAC standard methods (1984), for the
protein content (N2 content multiplied by 6.25) using modified semi
micro-kjeldahl method of Searle (1974), for mineral contents using an atomic
absorption spectrohotometer and for total carbohydrate using gas
chromatography. All samples were analyzed in triplicate. Nutritional
components and average nutritive value (ANV) of chaya leaves were compared to
spinach leaves.
The nutritional analysis of chaya (C. chayamansa) leaves and spinach (Spinacia oleracea L.) are presented in the table above for comparison. Chaya leaves were found to contain substantially greater amounts of nutrients than the spinach leaves. The chaya leaf is especially high in protein (5.7%), crude fiber (1.9%), calcium (199.4 mg/100 g), potassium (217.2 mg/100 g), iron (11.4 mg/100 g), vitamin C (164.7 mg/100 g), and carotene (0.085 mg/100 g). The levels of chaya leaf nutrients, in this study, agree with published reports (Martin and Ruberte 1978; Munsell et al. 1949; Booth et al. 1992) and are two to threefold greater than most edible leafy green vegetables. In terms of the average nutritive value, chaya leaves [14.9] is by far superior to other leafy green vegetables such as spinach [6.4], amaranth [11.3], Chinese cabbage [7.0], and lettuce [5.4] (Grubben 1978). While some edible leafy green vegetables are usually good sources of mineral macronutrients (Levander 1990), chaya leaf furnishes appreciable quantities of several of the essential mineral macronutrients necessary for human health maintenance. For example, potassium has been shown to be an important mineral nutrient in the control of hypertension and in the reduction of risks of stroke (NRC 1989), calcium is important for ossification and iron is necessary for normal hematopoiesis. Brise and Hallberg (1962) reported that vegetables, such as chaya, with high vitamin C content may enhance absorption of nonheme iron.
Traditionally leaves are immersed and simmered for 20 minutes and then served with oil or butter. Cooking for 20 minutes or more will render the leaves safe to eat. The stock or liquid the leaves are cooked in can also safely be consumed as the cyanide is volatilized as hydrogen cyanide (HCN) during cooking. Cooking in aluminum cookware can result in a toxic reaction, causing diarrhea.
Possible Antidiabetic Effect
The experimental animals (rabbits) for this study were supplied by Dr. Steven
Lukefahr of the Department of Animal and Wildlife Sciences, Texas A&M
University-Kingsville. All animals were housed and maintained in compliance
with Texas A&M University-Kingsville IACUC policy on animal care and use.
The rabbits were fed with standard rabbit chow and given water ad
libitum. Diabetes was induced by a single subcuteanous injection of 60
mg/kg streptozotocin (STZ), after fasting for 18 h, according to the method
described by Bonner-Weir et al. (1981). The rabbits exhibited post-STZ blood
glucose levels that were at least double that of the pre-STZ levels one week
after diabetes had been induced.
The leaves of C. chayamansa were collected from plants grown in
the greenhouse. About 10 g of the leaves was extracted with boiling water
(1000 mL) for 30 min until the volume of the water had been reduced to 90% of
the original. The tea (900 mL) was filtered and used in the subsequent
experiments. Two groups of 8 rabbits each were used. The first group of 8
rabbits were normoglycemic (non-diabetic). Four of the normoglycemic rabbits
recieved water (control) only and the remaining 4 received chaya tea treatment
only. The second group of 8 rabbits were hyperglycemic (diabetic). Four of
the diabetic rabbits received water only and the remaining 4 received chaya tea
only.
Before administering the tea or water (control), blood samples were obtained
from the ears of 18 h fasted nondiabetic and diabetic rabbits using a capillary
tube. Then the tea or water was administered orally through drinking water
bottles ad libitum. Blood sampling was repeated at hourly intervals for
6 h after the oral administration. Blood glucose was determined using a blood
glucometer (Miles Inc., Diagnostic Division, Elkhart, IN, U.S.). The mean
blood glucose values ±SE were determined and the significance of the
difference between the means of treated and control groups was established by
Student's t-test.
Distribution and ecology
Chaya is easy to grow, a tender perennial in the US, and suffers little insect damage. It is tolerant of heavy rain and has some drought tolerance. Propagation is normally by woody stem cuttings about 6-12 inches long, as seeds are produced only rarely. Early growth is slow as roots are slow to develop on the cuttings, so leaves are not harvested until the second year. Chaya leaves can be harvested continuously as long as no more than 50% of the leaves are removed from the plant, which guarantees healthy new plant growth.
