Celeriac: a potassium root, and an allergen that cooking does not always tame

Most of what is known about celeriac concerns two groups of people: small children learning to eat vegetables, and adults allergic to celery. In a randomized experiment with 161 children aged 4 and 5, those allowed to pick their own cup of raw celeriac rated it 4.7 on a 6-point scale, against 4.0 for children simply handed one, after a single tasting. In 12 UK preschools, 337 children aged 2 to 5 who spent two weeks with a storybook about celeriac had higher odds of eating it than those given a carrot storybook, though the abstract gives no size for that effect. For nutrients, UK composition tables list 460 mg of potassium per 3.5 oz (100 g) of raw celeriac and 330 mg per 3.5 oz (100 g) boiled in unsalted water. Phosphorus goes from 63 to 52 mg on the same basis. For people allergic to celery, cooking does not reliably help: in a small challenge study, 6 of 11 allergic patients still reacted to cooked celery.

The numbers, per 3.5 oz (100 g)

How much is actually in it

• UK composition tables list raw celeriac at 460 mg potassium, 63 mg phosphorus and 0.08 mg vitamin B6 per 3.5 oz (100 g), falling to 330, 52 and 0.06 mg after boiling. — Celeriac sold in the UK, raw (13-219) and boiled in unsalted water (13-585) Evidence C source
  Potassium 460 to 330 mg, phosphorus 63 to 52 mg, vitamin B6 0.08 to 0.06 mg per 3.5 oz (100 g)

What cooking and storage change

• Cooking does not make celery safe for everyone with celery allergy: 6 of 11 patients still reacted to cooked celery in a double-blind challenge. — 12 patients with allergic reactions to raw or cooked celery (n = 12) Evidence C source
  Positive challenge to cooked celery 6/11, to celery spice 5/5; allergenicity kept in 4 patients after 76 min at 100 C equivalent
• A systematic review of pollen-related food allergy found that heating removed symptoms completely in 46% of celery-allergic individuals. — Adults with pollen-related food allergy, 4 heat-processing studies with 116 participants (n = 116) Evidence C source
  Heating eradicated symptoms in 46% of celery-allergic individuals
• By the USDA retention table for root vegetables boiled in covering water and drained, about 90% of vitamin B6, phosphorus and potassium and 65% of folate stay in the food. — Vegetables and Vegetable Products, roots, boiled, drained, water covering (applied to celeriac by group) Evidence C source
  Retention: vitamin B6 90%, phosphorus 90%, potassium 90%, folate 65%

Safety, limits and interactions

• In 16 celery-allergic patients confirmed by double-blind challenge, the celeriac cultivar Anita gave smaller skin reactions than Prinz (5.0 vs 7.0 mm) and fewer symptoms on oral challenge. — 16 celery-allergic patients confirmed by DBPCFC, 14 orally challenged (n = 16) Evidence C source
  Skin prick 5.0 mm (Anita) vs 7.0 mm (Prinz), P = .047; fewer symptoms with Anita (P < .001)
• In 32 people with a history of reactions to celery, 22 had allergy confirmed by double-blind placebo-controlled challenge. — 32 patients with a history of allergic reaction to celery (n = 32) Evidence C source
  22 of 32 positive; prick-to-prick with crude celery 96% sensitive

Who this works differently for

• In an RCT of 161 children aged 4-5, letting them pick a cup of raw celeriac raised acceptance to 4.7 vs 4.0 on a 6-point scale compared with no choice. — 161 children aged 4-5 years, single tasting session (n = 161) Evidence B source
  Acceptance 4.7 +/- 1.7 with choice vs 4.0 +/- 1.9 without choice; picky eaters accepted less
• In a cluster RCT of 337 preschoolers in 12 UK preschools, two weeks of a celeriac storybook raised the odds of eating celeriac versus a carrot storybook. — 337 children aged 2-5 years in 12 UK preschools, 2-week intervention (n = 337) Evidence B source
  Higher odds of eating celeriac with congruent storybook; sensory play raised odds in 85 baseline non-eaters

The bottom line

Celery allergy is the caution that matters here, and the studies below tested celery and celery root. Among 32 people who said celery had given them a reaction, 22 reacted again in a double-blind placebo-controlled challenge. Cooking helps some allergic people and not others. In a small challenge study, 6 of 11 allergic patients still reacted to cooked celery. A systematic review found heating removed symptoms completely in 46 percent of celery-allergic people, from studies its own authors call low-level evidence. If celery gives you a reaction, do not assume a cooked celeriac mash is safe. Varieties may differ as well. In 16 allergic patients, in a comparison that was not a randomized trial, the cultivar Anita produced smaller skin-prick reactions than Prinz, 5.0 against 7.0 mm, and fewer symptoms when 14 of them ate it under supervision. That is one small study, and it has not been repeated. Boiling costs some minerals. The USDA factor for boiled and drained root vegetables in general, from a table dated 1975, keeps about 90 percent of potassium, phosphorus and vitamin B6 and 65 percent of folate.

Sources

1. clrc-daily-r6-07 · food composition data
   13-219 Celeriac, raw: Phosphorus (mg) 63; Potassium (mg) 460; Vitamin B6 (mg) 0.08 ... 13-585 Celeriac, boiled in unsalted water: Phosphorus (mg) 52; Potassium (mg) 330; Vitamin B6 (mg) 0.06
   CoFID 2021, Public Health England, codes 13-219 and 13-585 · checked 2026-09-29
2. clrc-daily-r6-04 · food challenge study
   Six out of 11 patients showed a positive DBPCFC to cooked celery and five out of five patients to celery spice. Allergenicity of celery was preserved in four patients with a positive DBPCFC to cooked celery even if celery was treated at a Co-value of 76.07.
   Allergy, 2002 · checked 2026-09-29
3. clrc-daily-r6-06 · systematic review
   Heating was found to completely eradicate symptoms in 15⁻71% of hazelnut allergic and 46% of celery allergic individuals.
   Nutrients, 2018 · checked 2026-09-29
4. clrc-daily-r6-08 · nutrient retention data
   Retn_Code 3455 VEG,ROOTS,ETC,BLD,DRAIND,WTR COVER: folate_total_ug 65%; phosphorus_mg 90%; potassium_mg 90%; vitamin_b6_mg 90%
   USDA Table of Nutrient Retention Factors, Release 6 (2007), code 3455 · checked 2026-09-29
5. clrc-daily-r6-03 · food challenge study
   From the 10 investigated celeriac cultivars, two cultivars elicited significantly different skin reactivity ("Anita": 5.0 [2.0-12.0] mm vs "Prinz": 7.0 [3.0-9.5] mm; P = .047). Moreover, "Anita" induced fewer symptoms after a controlled oral-celeriac challenge in 14 patient (P < .001).
   Clin Exp Allergy, 2018 · checked 2026-09-29
6. clrc-daily-r6-05 · food challenge study
   Twenty-two of 32 patients had a positive DBPCFC result.
   J Allergy Clin Immunol, 2000 · checked 2026-09-29
7. clrc-daily-r6-01 · randomized controlled trial
   The results demonstrated that choice indeed significantly increased vegetable acceptance (4.7 ± 1.7 versus 4.0 ± 1.9 on a 6-point scale), irrespective of pickiness in eating.
   Appetite, 2023 · checked 2026-09-29
8. clrc-daily-r6-02 · cluster randomized trial
   Children receiving the congruent (celeriac) storybook had higher odds of eating celeriac compared to children who received the incongruent (carrot) storybook.
   J Acad Nutr Diet, 2019 · checked 2026-09-29