Nezam El-Tayebat Fact CheckA scientific assessment of the “نظام الطيبات” nutrition system
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Mostly false Certainty of evidence: low provisional C-VEG-10

Raw cruciferous greens such as bok choy suppress the thyroid (glucosinolates) and can cause myxedema coma.

Conclusion: One extreme case does not show that crucifers harm the thyroid at normal intake.
  1. Original statement
  2. Scientific assessment
  3. In plain language
  4. Studies on this claim
  5. Regional context
  6. What applies in my country?
  7. References

Original statement

No Arabic original wording available.

Translation

Raw cruciferous greens such as bok choy suppress the thyroid (glucosinolates) and can cause myxedema coma.

Origin

Source status
Archive editors
Attribution
Archive editors
Origin
https://eltayebat.com/rule/leafy-greens-cucurbits/
Attribution uncertainty
Archive editorial text and study selection written by the archive operators, not necessarily by Elawady.
Claimed mechanism

Glucosinolate breakdown products inhibit iodine uptake.

Claimed health effect

Hypothyroidism, myxedema coma.

Population concerned

Everyone eating raw crucifers

Geographic restriction by Elawady

none found

Scientific assessment

Mostly false – Essential parts of the statement are not supported by the evidence or are strongly exaggerated.

Certainty of evidence: low – Further research is likely to change the assessment considerably.

1. What was claimed?

Raw crucifers cause severe hypothyroidism.

2. What is demonstrably correct?

A case of myxedema coma attributed to very high raw bok choy intake was published (Chu & Seltzer 2010).

3. What is wrong or exaggerated?

A single case at extreme intake cannot be generalised; cooking reduces glucosinolate activity (general knowledge, not verified here).

4. What remains unclear?

Threshold intake is unknown.

5. Which studies support it?

Chu & Seltzer 2010 (case).

6. Which studies contradict it?

Aune 2017 (cruciferous vegetables inversely associated with CVD, mortality and cancer).

7. What applies to Germany and Europe?

Not specific.

8. What is known about Egypt?

Not specific.

9. What practical conclusion is appropriate?

Normal intake of cruciferous vegetables is not a thyroid risk for people with adequate iodine.

Assessment details

Rationale for certainty of evidence

The evidence is a single case (NEJM letter) involving an 88-year-old woman; the archive's card states 'large quantities' daily. A single extreme case does not show a risk at normal intake; goitrogenic effects are mainly relevant with iodine deficiency (as Doerge 2002 notes for soy).

Source quality

Single case report; no PubMed abstract available, details taken from the archive card were not verifiable.

Regional transferability

Iodine status matters; Germany has iodised salt; Egypt has a salt iodisation programme (not reviewed).

Individual exceptions

People with iodine deficiency or existing hypothyroidism consuming very large raw amounts.

Regional scope of the claim
general (biological/medical)
Last reviewed
25 October 2026 provisional

In plain language

The archive cites one elderly woman who fell into a severe thyroid crisis after eating large amounts of raw bok choy every day. This is a single extreme case. Eating normal amounts of cabbage-family vegetables is not known to harm the thyroid in people who get enough iodine, and these vegetables are linked to lower disease risk in large studies.

Studies on this claim

Studies supporting the claim (1)

  • Thyroid crisis after raw bok choy

    Chu M, Seltzer TF. N Engl J Med 2010 · PMID 20484407 · DOI 10.1056/NEJMc0911005
    Case series / case reportcited by the Tayebat archiveabstract only checked★ key study

    One elderly woman with extreme raw bok choy intake; no generalisation possible.

    Does the study support the specific claim? Partly · Methodological quality: very low · Certainty of evidence: see overall assessment of the claim

    Original publication · Scientific details

    Study explained simply
    What did the researchers want to find out?

    Report case

    How was the study done?

    Case letter

    How many people, animals or samples were studied?

    1

    What was actually found?

    Myxedema coma

    How large was the observed effect?

    Not applicable

    What do the results mean in everyday life?

    Extreme intakes can matter.

    What are the study's limitations?

    Single case

    What does it say about Elawady's specific claim?

    Very weak

    Do the results apply to Germany and Europe?

    Moderate

    What can explicitly not be concluded from this study?

    Cannot show risk at normal intake.

    Scientific details →

Studies contradicting or limiting the claim (1)

  • Fruit, vegetables and death rates

    Aune D et al.. Int J Epidemiol 2017 · PMID 28338764 · DOI 10.1093/ije/dyw319
    Meta-analysisindependent cross-checkfull text checked★ key study

    Each extra 200 g of fruit and vegetables a day was linked to 10% lower death risk; green leafy vegetables and salads were also protective.

    Does the study support the specific claim? No · Methodological quality: high · Certainty of evidence: see overall assessment of the claim

    Original publication · Scientific details

    Study explained simply
    What did the researchers want to find out?

    F&V and outcomes

    How was the study done?

    Meta-analysis

    How many people, animals or samples were studied?

    95 studies

    What was actually found?

    Lower CVD, cancer, mortality

    How large was the observed effect?

    RR 0.90 per 200 g

    What do the results mean in everyday life?

    Eat plenty of vegetables.

    What are the study's limitations?

    Observational

    What does it say about Elawady's specific claim?

    Contradicts avoidance

    Do the results apply to Germany and Europe?

    High

    What can explicitly not be concluded from this study?

    Cannot prove causation.

    Scientific details →

Studies with mixed or unclear results (0)

No studies in this group.

Regional context

Germany / EU

Not specific.

Egypt

Not specific.

What applies in my country?

General scientific assessment

Mostly false One extreme case does not show that crucifers harm the thyroid at normal intake.

The following areas of food safety are relevant to this statement:

  • Pesticides and pesticide residues
  • Contaminants (heavy metals, PFAS, PCBs, dioxins, nitrate)
  • Pathogens (Salmonella, Campylobacter, etc.)

Fruit and vegetables

Choose a country to see the checked information for it.

Limits: legal rules describe what is allowed, not what every single food contains. Measurement data come from samples and are meaningful only together with their method details.

Country of residence or purchase Compare with another country

References

  1. Myxedema coma induced by ingestion of raw bok choy.. Chu M, Seltzer TF. N Engl J Med 2010 · PMID 20484407 · DOI 10.1056/NEJMc0911005
  2. Fruit and vegetable intake and the risk of cardiovascular disease, total cancer and all-cause mortality-a systematic review and dose-response meta-analysis of prospective studies.. Aune D et al.. Int J Epidemiol 2017 · PMID 28338764 · DOI 10.1093/ije/dyw319

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