CHAMGAP
APPROVEDReviewed and approved by the Chamgap Editorial Team (2026-08-03). The draft was written by AI, the existence of all 2 cited sources was verified at the original page, and the verdict passed blind grading and adversarial audit. Methodology v0.6.
Verdict No. 2033 · Search date 2026-08-03 · Methodology v0.6

Kombu-powder cookies boiled for 60 minutes to reduce iodine,
does it really help with Lower blood pressure in adults with overweight?

30-Second Summary
C
Evidence Grade C · 48 · Safety caution
A blood-pressure signal appeared with kombu-powder cookies boiled for 60 minutes to reduce iodine, but the registered primary endpoint was null
The measured 420 micrograms/day iodine was below the adult upper level, but total intake matters in thyroid disease or with other iodine-rich foods or medicines. Ordinary kombu can contain far more iodine.
What the
research shows
The grade is C with 48 points. A 12-week trial randomized 44 adults and 41 completed; the per-protocol analysis included 21 receiving kombu-powder cookies boiled for 60 minutes to reduce iodine and 20 controls. Blood pressure was lower at selected visits. The registered primary visceral-fat endpoint did not improve, and blood pressure was not even a registered secondary endpoint but an exploratory result from a general measurement item.
What the
ads claim
This result cannot be transferred to ordinary kombu intake. The test food was kombu-powder cookies boiled for 60 minutes to reduce iodine, with measured iodine of 70 micrograms per cookie and 420 micrograms/day. General kombu values are much higher and variable. Verdict 091 is C with 50 points for fucoidan, and verdict 308 is C with 48 points for fermented kelp extract; both differ in form and claim.
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Useful facts when choosing a product

  • The paper dose was 0.98 g per cookie times six, 5.88 g/day, whereas the registry specified 1 g times six, 6 g/day.
  • The 70 micrograms per cookie and 420 micrograms/day iodine values belong to this iodine-reduced test product, not ordinary kombu.
  • The finding cannot be generalized to ordinary kombu intake. Product sodium was not reported.
Gap Measurement · Verdict 2033 · C 48
What advertising claims
What independent, higher-quality research supports
△ GAP
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What the research actually shows

Forty-four adults were randomized and 41 completed; the per-protocol analysis included 21 receiving kombu-powder cookies boiled for 60 minutes to reduce iodine and 20 controls. The paper dose was 0.98 g per cookie times six, 5.88 g/day, versus the registry's 1 g times six, 6 g/day. Registered primary visceral fat was null overall, and blood pressure was a general measurement rather than a registered secondary endpoint. Support came from the Hokkaido Federation of Fisheries Cooperative Associations and Otsuma grant N2301; authors were affiliated with Maruyanagi Oguraya and the contracted research organization CPCC. The authors declared no conflicts of interest.

02

Why this is classified as C (48)

A surrogate blood-pressure endpoint, one 44-person industry-linked trial, a 41-person completer analysis, a null registered primary endpoint, and uninterpretable clinical effect size give C with 48 points.

Counterpoint. This verdict applies to kombu-powder cookies boiled for 60 minutes to reduce iodine and cannot be generalized to ordinary kombu intake.

Rejudgment record. Editor ruling applied — The registered primary visceral-fat endpoint was null and blood pressure was not a registered secondary endpoint; exploratory status, specialized product, per-protocol analysis, and unrecoverable effect interval were reflected

Scoring profile behind this grade
EndpointSSurrogate marker - laboratory or imaging measures
ReplicationR1Single confirmatory trial
IndependenceI0Evidence comes only from manufacturer studies
Effect sizeEXThe clinical size of the effect could not be judged

The scoring table and the verdict agree (C).

Sub-claim grades by effect

This ingredient is marketed for several effects. A single overall grade blends strong and weak claims together, so each effect is graded separately here. The overall grade reflects the strongest disconfirming or core claim.

Effect (sub-claim)GradeBasis
Lower blood pressure from kombu-powder cookies boiled for 60 minutes to reduce iodineCThe registered primary was null; blood pressure was not a registered secondary endpoint, and its treatment-effect CI could not be recovered.

Cross-check — Codex and Claude

This verdict was drafted by Codex through literature review and source-existence checks, cross-checked through blind grading and adversarial audit, and settled by reapplying the methodology boundary rules. Cases with split grades were resolved through rejudgment.
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Evidence Table

StudyDesignSampleFundingEndpointResultWeight
Study 1Twelve-week randomized double-blind cellulose-cookie-controlled trial20Hokkaido fisheries cooperative federation and Otsuma N2301 support; Maruyanagi Oguraya and CPCC affiliations; authors declared no conflictsRegistered primary visceral fat null; blood pressure was an unregistered general measurementBlood-pressure differences at selected visits; absent numeric labels prevented recovery of the ANCOVA treatment-effect CIUnregistered exploratory signal for a specialized product
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Receipt — 2 References

All 2 cited sources were verified for existence at the original page (as of 2026-08-03).

Aoe S, Ohtoshi H, Nakamura F. Effects of Daily Kombu (Laminaria japonica) Intake on Body Composition, Blood Pressure, and Fecal Microbiota in Healthy Adult Japanese: A Randomized, Double-Blind Study. Food Sci Nutr. 2025;13:e70298. PMID: 40390848. PMCID: PMC12086367.
checked
Zava TT, Zava DT. Assessment of Japanese iodine intake based on seaweed consumption in Japan: A literature-based analysis. Thyroid Res. 2011;4:14. PMCID: PMC3204293.
checked
Draft and rewrite: Codex (AI) · Verification: Codex blind grading and adversarial audit · Final adjudication: Claude
Reviewed and approved: Chamgap Editorial Team · Approval date: 2026-08-03 · Corrections: none

Cite this verdict

Kombu-powder cookies boiled for 60 minutes to reduce iodine x lower blood pressure Evidence Grade C card
[Chamgap] Kombu-powder cookies boiled for 60 minutes to reduce iodine x lower blood pressure — Evidence Grade C·48. 2 cited sources checked. Source: https://chamgap.com/en/verdicts/heart/deiodized-kombu-cookie-blood-pressure/ · CC BY 4.0

CC BY 4.0 — free to use with attribution; do not distort grades, numbers, or verdict meaning.

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