Persistent tiredness, constipation, dry skin, hair loss, greater sensitivity to cold, difficulty concentrating and weight gain can accompany hypothyroidism. These symptoms can also have other causes and deserve investigation.
In short
- Hashimoto's can be present even with normal TSH and free T4.
- Prioritize real food and avoid very restrictive diets.
- Excess iodine can worsen thyroid dysfunction: don't use Lugol's solution or iodine supplements on your own.
- Only remove gluten when indicated, and test for celiac disease first.
01
Hashimoto's can be present even with normal hormones
Hashimoto's thyroiditis is an autoimmune disease in which the immune system attacks the thyroid. In the early stages, antibodies may be high while TSH and free T4 remain normal. This is different from subclinical hypothyroidism, in which TSH is high and free T4 is still normal. Medical follow-up makes it possible to identify when hormone treatment is needed.
02
Where to start with food?
Prioritize real food: leafy greens, vegetables, fruit, beans, eggs, fish and other sources of protein, according to your tolerance. Vary your foods and cut back on sugary drinks, frequent sweets and ultra-processed foods. Very restrictive diets can make it harder to get the nutrients your body needs.
03
Nutrients that deserve attention
Iodine
Needed to produce thyroid hormones. Iodized salt in small amounts, eggs, fish and dairy can contribute. In Hashimoto's, excess iodine can worsen the dysfunction: avoid using Lugol's solution, iodine supplements or concentrated seaweed on your own.
Selenium
Involved in thyroid hormone metabolism and antioxidant protection. It is found in fish, eggs, meat and Brazil nuts. The amount in Brazil nuts varies a lot; supplementation requires assessment, and a drop in antibodies doesn't necessarily mean symptoms will improve.
Zinc
Contributes to immune function and hormone metabolism. Include meat, seafood, beans and seeds.
Manganese
Part of enzymes related to metabolism and antioxidant defense. It is found in whole grains, legumes and nuts. Deficiency is rare, and there is no established indication for supplementing it to treat Hashimoto's.
04
Gut health and gluten: individualized care
Constipation, diarrhea, bloating and discomfort after meals deserve attention. Caring for the gut involves investigating the cause, adjusting fiber and hydration and correcting nutritional deficiencies. Changes in intestinal permeability are being studied in autoimmune diseases, but it should not be assumed that everyone with Hashimoto's has this problem or that treating it reverses the disease.
Removing gluten is necessary when there is celiac disease. In people with Hashimoto's without celiac disease, studies have not yet shown a consistent benefit that would justify recommending exclusion to everyone.
If celiac disease is suspected, get tested before cutting out gluten, as the restriction can alter test results.
Throughout my clinical practice, I have seen symptoms improve in patients with Hashimoto's after individualized adjustments to diet and gut care, including removing gluten when indicated. This experience reinforces the importance of assessing each person: the response varies and cannot be attributed to a single change.
Your care needs to consider more than a single test
In the consultation, I assess your diet, symptoms, bowel function, history and tests to build a nutritional strategy suited to your needs, together with your medical follow-up. Food complements treatment and does not replace hormone replacement when it is needed.
Dra. Daniely Catharino TooleyClinical, functional and orthomolecular nutritionist · CRN3/6794
References (5)+
- American Thyroid Association. Hashimoto’s Thyroiditis.
- NIDDK. Hashimoto’s Disease; Diagnosis of Celiac Disease.
- American Thyroid Association. Selenium supplementation in Hashimoto’s thyroiditis (2024).
- NIH Office of Dietary Supplements. Manganese: Health Professional Fact Sheet.
- Effects of Gluten-Free Diet in Non-Celiac Hashimoto’s Thyroiditis. Nutrients, 2025;17:3437.
Educational content for adults. This guidance does not replace an individual consultation, diagnosis or treatment.