Nuts and Thyroid Cancer: Safety, Timing, and Practical Tips

Most people with thyroid cancer can safely eat nuts as part of a balanced diet. Unsalted nuts are allowed on low‑iodine diets used before radioactive iodine treatment, and they are generally encouraged for protein and healthy fats during and after treatment. ^[1] A healthy, varied diet including fruits, vegetables, and balanced protein and fats is recommended for those living with thyroid cancer, and nuts can fit well into this guidance. ^[2]

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When Nuts Are Especially Relevant

• Before radioactive iodine (RAI) therapy: Many care teams prescribe a temporary low‑iodine diet to help the treatment work better. On this diet, you should choose unsalted nuts and nut butters, and avoid salted nuts and salted seeds. ^[1] The purpose is to reduce iodine from food so cancer cells take up the radioactive iodine more effectively. ^[3]

• Routine survivorship and general nutrition: Outside of the RAI prep period, there are typically no foods that must be avoided specifically for thyroid cancer, and balanced eating is encouraged. ^[4] Nuts provide protein and energy, which can be helpful during head and neck cancer care to maintain weight and strength. ^[5]

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Levothyroxine Timing: Don’t Take Pills With Nuts

If you take thyroid hormone replacement (levothyroxine), avoid taking it at the same time as walnuts (and other known binding foods/supplements). ^[6] Walnuts and high‑fiber foods can reduce levothyroxine absorption, potentially altering your thyroid levels, so take levothyroxine on an empty stomach and wait several hours before eating nuts. ^{[7] [8] [9] [10]}

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Iodine and Salt Considerations

• Unsalted vs salted nuts: During a low‑iodine diet, unsalted nuts are allowed, while salted nuts should be avoided because iodized salt can add iodine. ^[1] This distinction matters only during the RAI preparation period; outside of it, standard salted nuts are generally fine if you’re not otherwise limiting sodium. ^{[3] [4]}

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Selenium in Nuts (Brazil Nuts)

Nuts especially Brazil nuts contain selenium, a trace mineral involved in antioxidant defenses and thyroid hormone regulation. Dietary selenium from foods like nuts is normal and generally safe in typical portions, but high‑dose selenium supplements are not proven to prevent cancer and can be harmful at excessive doses. ^{[11] [12]} No clear link has been found between normal dietary selenium intake and thyroid cancer incidence. ^[13] If you consider selenium supplements, it’s best to discuss them with your clinician, as long‑term high doses can raise risks. ^[14]

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Practical Tips

• If you’re preparing for RAI:

  • Choose unsalted nuts or nut butters (peanut, almond, cashew). ^[1]
  • Avoid salted nuts/seeds and foods with soy oil on low‑iodine diet days. ^[1]

• If you take levothyroxine:

  • Take your pill on an empty stomach with water.
  • Wait at least 4 hours before eating walnuts or taking calcium/iron, which can reduce absorption. ^{[6] [7]}

• For overall health:

  • Include nuts as part of a balanced, protein‑rich diet to support energy and recovery. ^[5]
  • Aim for diet variety and overall healthy lifestyle habits during and after treatment. ^[2]

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Summary Table: Nuts and Thyroid Cancer

Situation	Can you eat nuts?	Key caveats
General thyroid cancer care	Yes	Choose balanced portions as part of a varied diet. [2]
Low‑iodine diet before RAI	Yes, if unsalted	Avoid salted nuts/seeds; keep iodine intake low. [1] [3]
Taking levothyroxine	Yes	Do not take levothyroxine with walnuts; separate by several hours. [6] [7]
Considering selenium	Food sources OK	Avoid high‑dose supplements unless clinician‑guided; no proven cancer prevention. [13] [14] [12]

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Bottom Line

Nuts are generally safe for people with thyroid cancer and can be part of a healthy diet. ^[2] Use unsalted nuts during low‑iodine diet periods before radioactive iodine therapy, and separate walnuts and similar binding foods from your levothyroxine dose to keep your medication working properly. ^{[1] [3] [6] [7]} Normal dietary selenium from nuts is fine, but high‑dose supplements aren’t recommended for cancer prevention. ^{[13] [14] [12]}