Taro shoots: a light vegetable with an untested oxalate question

The question that hangs over taro shoots is oxalate, and we found no study that measured it in the shoots. The nearest human evidence is about oxalic acid in general. In a randomized crossover isotope study of 16 women in Zurich, adding 1.26 g of oxalic acid to a kale meal left iron absorption unchanged, 11.5% against 10.7%. In taro, oxalate sits in needle-shaped calcium oxalate crystals, and we found no test of how those affect absorption in people. What USDA does record is a very light vegetable. Raw shoots have 11 calories, 21 mg of vitamin C and 332 mg of potassium per 3.5 oz (100 g), from one legacy record with no measured spread. A cooked cup of sliced shoots is a 140 g reference portion with about 26 mg of vitamin C and 482 mg of potassium. Cooked shoots list 18.9 mg of vitamin C per 3.5 oz (100 g) against 21 mg raw, and the two records do not adjust for water, so this is no true retention figure.

The numbers, per 3.5 oz (100 g)

How much is actually in it

• USDA lists raw taro shoots at 11 calories per 3.5 oz (100 g) with 21 mg of vitamin C and 332 mg of potassium, about a quarter of the vitamin C Daily Value. — USDA SR Legacy record Taro shoots, raw, FDC 168489 (n = 1 record) Evidence E source
  Per 100 g raw: energy 11 calories, water 95.8 g, protein 0.92 g, vitamin C 21 mg (23% DV), potassium 332 mg (7% DV), copper 0.088 mg (10% DV), iron 0.6 mg, calcium 12 mg

What a real portion looks like

• USDA sizes a half cup of sliced raw taro shoots at 43 g and a cup of sliced cooked shoots at 140 g, which gives about 26 mg of vitamin C per cooked cup. — USDA SR Legacy portion weights for FDC 168489 and 169309 (n = 2 records) Evidence E source
  0.5 cup slices raw 43 g (about 9 mg vitamin C); 1 cup slices cooked 140 g (about 26 mg vitamin C, 482 mg potassium); no FNDDS survey food for taro shoots

What your body absorbs

• In a randomized crossover isotope study of 16 women, adding 1.26 g of oxalic acid to a kale meal did not change iron absorption (11.5% against 10.7%). — Sixteen apparently healthy women aged 18 to 45, under 132 lb (60 kg), Zurich; 13 completed both studies (n = 16) Evidence B source
  Geometric mean iron absorption 10.7% from kale meal against 11.5% with 1.26 g oxalic acid added as potassium oxalate, P=0.86
• In 19 Thai women, calcium from two local green vegetables was absorbed at 0.39 to 0.48 against 0.55 from milk, a gap the authors partly put down to phytate, oxalate and fiber. — 19 healthy adult women aged 20 to 45, Thailand, 100 mg calcium load with rice (n = 19) Evidence B source
  Fractional calcium absorption 0.391 +/- 0.128 winged bean, 0.476 +/- 0.109 ivy gourd, 0.552 +/- 0.119 milk; vegetables 71% to 86% of milk

What cooking and storage change

• USDA records list 18.9 mg of vitamin C per 3.5 oz (100 g) of cooked taro shoots against 21 mg raw, without adjusting for water, while the USDA retention table assigns 60 to 70% vitamin C retention to boiled or baked greens as a group. — USDA SR Legacy records Taro shoots, raw (FDC 168489) and Taro shoots, cooked, without salt (FDC 169309); USDA retention factors for the Vegetables and Vegetable Products group (n = 2 records) Evidence E source
  Per 100 g raw to cooked: vitamin C 21 to 18.9 mg, iron 0.6 to 0.41 mg, potassium 332 to 344 mg, copper 0.088 to 0.094 mg; USDA Retn_Code 3004 greens boiled in little water and drained keeps vitamin C 60%, potassium 90%, copper 95%; Retn_Code 3001 greens baked keeps vitamin C 70%
• Household soaking, blanching and 30 to 60 minute cooking cut oxalic acid in Colocasia leaves by 27 to 35% in a laboratory study. — Fresh Colocasia leaves from a household garden in Kapurthala, Punjab, India Evidence D source
  Oxalic acid down 27.07 to 35.32%, tannic acid down up to 96%, calcium up to 16.38% higher across treatments
• Steaming taro flowers for 2 hours shrank and blunted the needle-like calcium oxalate crystals that numb the mouth, while total calcium oxalate stayed the same. — Fresh taro flowers from Yunnan Province, China Evidence D source
  After 120 min of steaming crystals about 80% shorter and about 70% fewer (full text), calcium oxalate content unchanged at about 2.5% of dry weight (p > 0.05)

Safety, limits and interactions

• In Japan, the ornamental Alocasia odora is often eaten by mistake because its above-ground parts look like taro, and its calcium oxalate crystals can cause oral pain, vomiting and laryngeal edema. — Poisoning cases from one hospital in Shizuoka Prefecture and published reports, Japan Evidence D source
  Symptoms: oral pain, nausea, vomiting, laryngeal edema with near asphyxia, diarrhea, skin dermatitis

Who this works differently for

• A 2-year-old boy with pica developed drooling, trouble speaking and swallowing after eating a raw leaf of Colocasia esculenta grown as a houseplant. — One otherwise healthy 2-year-old boy with pica and iron deficiency anemia (n = 1) Evidence D source
  Acute sialorrhoea, difficulty speaking, dysphagia; uneventful 9-month follow-up

The bottom line

In 19 Thai women, calcium from two local green vegetables, winged bean and ivy gourd, was absorbed at 0.39 to 0.48 against 0.55 from milk, and the authors put part of the gap down to phytate, oxalate and fiber. We found no calcium absorption data for any part of taro in people. Cooking helps in the laboratory. Soaking, blanching and 30 to 60 minutes of cooking cut oxalic acid in Colocasia leaves by 27 to 35%, in leaves from one garden, and two thirds of the oxalate remained after the best treatment. Steaming taro flowers for 2 hours made the needle-shaped calcium oxalate crystals that sting the mouth shorter and fewer. Total calcium oxalate stayed the same, so long steaming eases the sting and leaves the oxalate load where it was. Two cautions come from case reports. A 2-year-old boy with pica and iron deficiency anemia developed drooling and trouble speaking and swallowing after eating a raw leaf from a Colocasia houseplant, and he had no further problems over 9 months. In Japan, the ornamental Alocasia odora is often eaten by mistake because its stems and leaves look like taro, and its oxalate crystals can cause mouth pain, vomiting and swelling of the larynx with near suffocation. Both reports concern raw leaves or a look-alike plant, not cooked shoots, and they matter most to anyone who forages or grows taro. We found no study of eating raw taro shoots, so the raw USDA figures above describe composition, not a tested way to eat them.

Sources

1. tsh-r4-01 · USDA FoodData Central SR Legacy, dataset
   Taro shoots, raw (FDC 168489, SR Legacy, Vegetables and Vegetable Products): energy 11 kcal, water 95.82 g, protein 0.92 g, vitamin C 21 mg, potassium 332 mg, copper 0.088 mg, iron 0.6 mg, calcium 12 mg per 100 g; Foundation samples 0
   USDA FoodData Central, SR Legacy, FDC 168489 · checked 2026-10-02
2. tsh-r4-03 · USDA SR Legacy portions, dataset
   Taro shoots, raw (FDC 168489): portion 0.5 cup slices = 43 g; Taro shoots, cooked, without salt (FDC 169309): portion 1 cup slices = 140 g; vitamin C 18.9 mg and potassium 344 mg per 100 g cooked; FNDDS search taro shoots: 0 of 5432 foods
   USDA FoodData Central, SR Legacy, FDC 168489 and 169309, portions · checked 2026-10-02
3. tsh-r4-04 · randomized crossover trial
   After normalization for the spinach reference meal absorption, geometric mean iron absorption from wheat bread rolls with kale (10.7%) did not differ significantly from wheat rolls with kale plus 1.26 g OA added as potassium oxalate (11.5%, P=0.86).
   Eur J Clin Nutr, 2008 · checked 2026-10-02
4. tsh-r4-05 · randomized crossover trial
   Fractional calcium absorption (X+/- SD) was 0.391 +/- 0.128 from winged beans, 0.476 +/- 0.109 from ivy gourd, and 0.552 +/- 0.119 from milk. ... The difference was partly accounted for by the phytate, oxalate, and dietary fiber content of the vegetables.
   J Food Sci, 2008 · checked 2026-10-02
5. tsh-r4-02 · USDA SR Legacy and USDA Retention Factors, dataset
   Taro shoots, raw (FDC 168489): vitamin C 21 mg, iron 0.6 mg, potassium 332 mg, copper 0.088 mg per 100 g; Taro shoots, cooked, without salt (FDC 169309): vitamin C 18.9 mg, iron 0.41 mg, potassium 344 mg, copper 0.094 mg per 100 g; USDA-RETN-R6:3004 VEG,GREENS,BOILD,LITTLE WATER DRAIN: vitamin_c_mg 60% retained, potassium_mg 90%, copper_mg 95%; USDA-RETN-R6:3001 VEG,GREENS,BAKED: vitamin_c_mg 70%
   USDA FoodData Central SR Legacy FDC 168489 and 169309; USDA Table of Nutrient Retention Factors, Release 6, 2007, Retn_Code 3004 and 3001 · checked 2026-10-02
6. tsh-r4-06 · laboratory study
   A significant decrease in fat (5.7–31.4%), ash (20.34–28.22%), oxalic acid (27.07–35.32%), and tannic acid (up to 96%) was also found in various treatments.
   Effect of household processing on nutritional and antinutritional composition, mineral-mineral ratios, and functional properties of Colocasia leaves. Heliyon, 2023 · checked 2026-10-02
7. tsh-r4-07 · laboratory study
   This study confirms the presence of needle-like calcium oxalate crystals in taro flowers and shows that prolonged steaming reduces their quantity, size, and sharpness, making them safer to eat.
   Impact of Cooking Duration on Calcium Oxalate Needle-like Crystals in Plants: A Case Study of Vegetable Taro Flowers in Yunnan. Foods, 2024 · checked 2026-10-02
8. tsh-r4-08 · case series
   A. odora is frequently associated with food poisoning because its aboveground parts resemble those of Satoimo (Colocasia esculenta). Moreover, A. odora contains insoluble calcium oxalate crystals, which cause poisoning symptoms, such as oral pain, nausea, vomiting, and laryngeal edema.
   Alocasia odora poisoning due to calcium oxalate needle crystals in Japan. Journal of Rural Medicine, 2024 · checked 2026-10-02
9. tsh-r4-09 · case report
   In addition, the history revealed that the child had earlier ingested a leaf from a poisonous houseplant called Colocasia esculenta, also known as "elephant's ear."
   J Child Neurol, 2002 · checked 2026-10-02