Dietary Recommendations for Hyperthyroidism
For adults with hyperthyroidism, the primary dietary intervention is limiting iodine intake—particularly avoiding high-iodine foods like seaweed, kelp, shellfish, and iodized salt—while maintaining a nutrient-rich diet with fresh fruits, vegetables, whole grains, and lean proteins. 1, 2
Core Dietary Principles
Iodine Restriction (Most Critical)
The cornerstone of dietary management for hyperthyroidism is moderating iodine intake, as excess iodine can worsen thyroid overactivity:
Foods to Avoid or Strictly Limit:
- Seaweed and kelp products contain extremely high iodine concentrations and should be eliminated 2
- Shellfish and seafood have naturally high iodine levels and should be consumed sparingly 1, 2
- Iodized salt and high-salt processed foods must be avoided 2
- Dairy products should not be consumed in excess, as they provide significant dietary iodine 2
- Iodine-containing supplements (including multivitamins) can interfere with treatment 2
Important caveat: Avoid extreme iodine restriction, as some iodine remains necessary for normal bodily functions—aim for moderation rather than complete elimination 1
Foods to Emphasize
Nutrient-Dense, Low-Iodine Options:
- Fresh fruits and vegetables (especially those low in iodine) provide antioxidants that combat oxidative stress associated with hyperthyroidism 1, 2
- Whole grains provide sustained energy and help maintain stable blood sugar during the hypermetabolic state 1, 2
- Lean proteins support muscle maintenance during the catabolic state of hyperthyroidism 1, 2
- High-fiber foods support overall metabolic health 1
Additional Dietary Modifications
Foods and Substances to Limit
Beyond iodine restriction, several other dietary factors warrant attention:
- Processed foods often contain high levels of iodized salt and should be limited 2
- Simple sugars can exacerbate metabolic issues associated with hyperthyroidism 2
- Caffeinated beverages may worsen symptoms like tachycardia, anxiety, and tremors—consume in moderation 2
- Alcohol can interfere with medication metabolism and worsen symptoms—limit or avoid 2
Hydration
- Adequate water intake is essential due to increased metabolism and potential dehydration associated with hyperthyroidism 2
Special Considerations for Patients on Antithyroid Medication
If you are taking carbimazole or other antithyroid drugs, iodine restriction becomes even more critical, as excessive iodine can directly interfere with medication effectiveness 2. All the above iodine-avoidance recommendations apply with particular emphasis 2.
Common Pitfalls to Avoid
Do not confuse hyperthyroidism dietary recommendations with hypothyroidism guidance—the iodine recommendations are opposite. Hypothyroidism requires adequate iodine intake 3, while hyperthyroidism requires iodine restriction 1, 2.
Avoid "thyroid-supporting" supplements marketed for general thyroid health, as these often contain high iodine levels that will worsen hyperthyroidism 2, 4.
Do not eliminate cruciferous vegetables or soy based on internet advice—these restrictions have little proven benefit in hyperthyroidism and may unnecessarily limit nutritious foods 4.
Monitoring and Follow-Up
Work closely with your healthcare provider when implementing dietary changes, as thyroid function should be monitored regularly 5, 6. Dietary modifications complement but do not replace medical treatment with antithyroid drugs, radioactive iodine, or surgery 5, 6.