Research · Observational study
Thyroid abnormalities associated with long-term spirulina consumption
Mazokopakis et al. · 2008 · Journal of Herbal Pharmacotherapy
Key finding
Case series and review found that prolonged high-dose spirulina supplementation (> 10 g/day for > 6 months) was associated with thyroid abnormalities in some individuals, potentially linked to spirulina's iodine content and immune-modulating properties. No such association was observed at typical consumer doses.
Why this matters for consumers
Relevant context for people with pre-existing thyroid conditions or autoimmune disorders. The risk appears confined to very high doses — not 1–3 g/day consumer use — but the caution to consult a physician before supplementing is clinically sound for anyone with thyroid or autoimmune history.
Study limitations
Case series methodology; confounding from other dietary iodine sources not controlled; causality not established.
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Enhancement of immunity by dietary spirulina
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Activation of the human innate immune system by spirulina
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