Chaya (tree spinach): easy and heat-loving, never raw, boil 15-20 min uncovered

Chaya (tree spinach, ผักไชยา in Thai) is a leafy shrub from Mexico with lobed leaves a bit like papaya leaves. It is easy to grow, a tropical vegetable that dislikes cold, and it pushes out new leaves quickly after cutting. But raw leaves release cyanide, so they must be boiled long enough, and the water poured away, every time.

This lesson uses research from Mahidol University, ECHO and UF/IFAS to show how long to boil, what boiling costs in nutrients, and how to grow it.

Why never raw

Chaya leaves contain cyanogenic glycosides, mainly linamarin. In an intact leaf, this compound and the enzyme that breaks it down sit in different parts of the cell. Cut, crush, chew or blend the leaf and the two meet, releasing hydrogen cyanide (HCN). Gut bacteria can also release HCN from the compound.

The FAO/WHO expert committee set a provisional maximum long-term intake of 0.02 mg HCN per kg of body weight per day:

• about 1.4 mg/day for a 70 kg adult
• about 0.24 mg/day for a 12 kg child

ECHO notes the risk is higher for young children and for people eating little protein, because the body uses sulfur-containing amino acids to clear HCN.

How much is left after boiling: worked example

HCN measured in raw chaya varies widely between studies. ECHO’s table runs from 0.08-1.48 mg up to 27-42 mg per 100 g of raw leaves, and the Mahidol study measured more still.

Take the case most generous to raw leaves, the lowest set of figures:

1. 100 g of raw leaves at 1.48 mg HCN (the top of the lowest range).
2. Against a 70 kg adult’s 1.4 mg/day, 100 g of raw leaves is already over.
3. Against a 12 kg child’s 0.24 mg/day, it is about 6 times over.

Now after boiling. The Mahidol team boiled leaves for 15 minutes and measured 0.67 mg/kg of HCN left.

1. 0.67 mg/kg equals 0.067 mg per 100 g of boiled leaves.
2. Against the adult’s 1.4 mg, that is about 5% of the limit.
3. Against the child’s 0.24 mg, that is about 28% of the limit.

One 100 g handful of raw leaves can exceed the limit; properly boiled leaves fall far below it. That is why you boil every time, with no exceptions.

How to boil it

Sources give different times. In ECHO’s test, 5-10 minutes was enough, but ECHO advises boiling longer as a safety margin because HCN levels vary so much between plants. The Mahidol study used 15 minutes; UF/IFAS says simmer 20 minutes. This lesson uses 15-20 minutes.

1. Cut young leaves and tips wearing gloves, and rinse them.
2. Cut large leaves into bite-size pieces.
3. Bring the water to a boil first, then add the leaves, fully covered by water.
4. Leave the lid off. HCN leaves with the steam and dissolves into the cooking water. Open a window or run the extractor fan, and don’t lean over the pot breathing the steam.
5. Time 15-20 minutes from when the water returns to the boil.
6. Pour the cooking water away. Never use it as stock.
7. Then stir-fry the leaves, add them to an omelette, or put them in a curry.

Step 4 is a cautious practice: the research explains that HCN leaves by evaporation and by leaching into water, so an open pot and good ventilation help get it out of the kitchen.

Method	Safe?
Raw, in a salad	No
Blended fresh into a green drink	No; blending breaks the cells and releases HCN
Freezing raw leaves to eat later	No; ECHO cites work finding freezing increased the HCN released
Quick stir-fry with no boiling first	No; far too short
Boil 15-20 min, lid off, pour water away	Yes

What boiling costs

The Mahidol study measured nutrients in 100 g of leaves before and after a 15-minute boil:

Nutrient (per 100 g)	Fresh	Boiled
Protein	7.74 g	4.54 g
Total vitamin A	1,579 µg	945 µg
Vitamin B1 (thiamine)	0.11 mg	0.001 mg
Vitamin B2 (riboflavin)	0.24 mg	0.04 mg
Calcium	232 mg	119 mg
Iron	3.85 mg	1.31 mg
Potassium	334 mg	83 mg

Beta-carotene kept 95.8% because it doesn’t dissolve in water; the water-soluble nutrients went largely into the cooking water. The researchers call it a trade-off between safety and nutrition and still treat boiling as essential. For the B vitamins, pair chaya with other vegetables cooked to keep more nutrients.

Growing chaya

From UF/IFAS:

• Dislikes cold. It is a vegetable of the drier tropics; start it at the beginning of a warm spell.
• Cuttings. Use thick woody stems about 15-30 cm long. Chaya rarely sets seed. The cuttings root slowly, so be patient.
• Soil must drain well. Young stems are soft and rot easily in soggy ground.
• First year growth is slow. After that, prune and harvest and it regrows quickly.
• Harvest up to about 60% of the leaves and still leave enough for healthy regrowth. One plant is enough for a household.
• Size. It becomes a shrub about 1.8-2.4 m tall; keeping it pruned low makes picking easier.

Wear gloves every time you cut. Young stems usually carry stinging hairs, and broken stems ooze white latex. Varieties differ in how hairy they are. The Mahidol study used the top 3-5 pairs of dark green leaves on each shoot.

Common mistakes

• Blanching for a couple of minutes like other greens. Far too short; it needs 15-20 minutes.
• Lid on, kitchen closed. Steam is one way HCN leaves. Lid off and ventilate.
• Using the cooking water for soup. Part of the HCN is dissolved in it.
• Blending raw leaves into a “health” drink. The most dangerous option of all.
• Cutting without gloves. The hairs sting and the white sap irritates skin.

Sources

• For How Long Should Chaya Leaves be Boiled? (EDN 141) — ECHO
• Impact of Boiling on Cyanogenic Detoxification and Nutrient Retention in Cnidoscolus aconitifolius (Chaya) Leaves — Foods (MDPI), 2026, Mahidol University
• Chaya, Cnidoscolus chayamansa (HS578) — UF/IFAS Extension (archived copy)
• Cnidoscolus aconitifolius seed fact sheet — ECHO Asia