Hashimoto's: Foods to Avoid in Your Daily Diet

Hashimoto's disease is an autoimmune form of hypothyroidism. The thyroid is a butterfly-shaped endocrine gland located in the neck, below the larynx. It produces two hormones, T3 (triiodothyronine) and T4 (thyroxine), which regulate many bodily functions such as metabolism, growth, body temperature, and heart rate. This condition is characterised by a deficiency of thyroid hormones, resulting in a slowing of certain bodily functions such as body temperature regulation and basal metabolism (the amount of energy consumed for the body's functioning at rest). The difference from classic hypothyroidism lies in the fact that it belongs to the category of autoimmune diseases, meaning those caused by a malfunction of the immune system that attacks its own cells, in this case, those of the thyroid. But autoimmune diseases can affect other systems, such as the intestines in the case of Crohn's disease or the joints in the case of rheumatoid arthritis. They all have an inflammatory nature, which is not necessarily the case with classic hypothyroidism. There is no specific treatment for Hashimoto's disease, but medical monitoring is essential to stabilise the thyroid through the use of thyroid hormones. The diagnosis is based on a blood test measuring TSH levels, which are abnormally high in cases of hypothyroidism. The autoimmune nature of the condition can be confirmed by testing for anti-thyroid antibodies and by a thyroid ultrasound.

The causes of Hashimoto's thyroiditis are not yet fully understood, but several factors, often in combination, may contribute to its development. As with many autoimmune diseases, a genetic predisposition likely plays a significant role, but other factors related to lifestyle or the environment may also be involved.

Genetic Predispositions

Some people may be genetically more susceptible to developing Hashimoto's, particularly those with a family history of autoimmune diseases (thyroiditis, lupus, polyarthritis, etc.). Women are also more commonly affected, particularly after age 40 or around menopause, likely due to hormonal fluctuations.

An Immune System Disorder

In Hashimoto's thyroiditis, the immune system malfunctions and produces antibodies directed against thyroid cells, gradually disrupting its function. This autoimmune process may be exacerbated by intestinal hyperpermeability, an imbalance in the microbiota, or chronic damage to the digestive mucosa, which could lead to repeated activation of the immune system.

Environmental and Lifestyle Factors

Environmental factors such as viral or bacterial infections, endocrine disruptors, or chronic exposure to stress may contribute to the onset of the disease.

The modern Western diet, rich in ultra-processed foods, refined sugars, gluten, or pro-inflammatory additives, is also implicated in some cases, as are nutritional deficiencies (in selenium, zinc, vitamin D, iron, or iodine). Regular consumption of alcohol, tobacco, or certain medications may also increase the risk of immune dysregulation, although the causal link has yet to be confirmed.

The symptoms of Hashimoto’s thyroiditis are most often those of progressive hypothyroidism, as chronic inflammation of the thyroid gland generally eventually impairs its ability to produce hormones. This hormonal deficiency leads to an overall slowing of metabolism, with various physical and psychological symptoms, some of which can be insidious.

• Persistent fatigue: A decrease in thyroid hormones reduces cellular energy production, which can cause chronic fatigue that is not relieved by rest or sleep. This fatigue is often one of the first symptoms experienced.

• Unusual sensitivity to cold: Thyroid hormones also regulate body temperature. A deficiency can lead to a constant feeling of cold, even in a temperate environment.

• Slowed bowel movement: Intestinal peristalsis—that is, the contractions that allow stool to move through the intestines—is stimulated by thyroxine. In cases of deficiency, constipation or persistent bloating is often observed.

• Unexplained weight gain: a slowed basal metabolic rate can result in moderate weight gain, even with a balanced diet. This does not apply to all cases, but can be a warning sign. It is therefore helpful to adjust your diet to support thyroid function (without referring to "forbidden foods," except in cases of specific intolerances).

• Hair loss: diffuse hair loss, sometimes accompanied by dry, brittle, or dull hair, is common. It is linked to slowed cell turnover and reduced blood flow to the scalp, two consequences of hypothyroidism.

• Muscle pain and stiffness: Some people with Hashimoto’s disease may experience diffuse pain, muscle stiffness, or cramps, often more pronounced in the morning. This could be linked to the underlying inflammation typical of autoimmune diseases.

• Goitre: A visible swelling at the base of the neck, known as a goiter, may appear. It results from an enlargement of the thyroid gland, sometimes in response to low hormone levels or chronic inflammation. This symptom is not universal but warrants medical attention when present.

The symptoms of Hashimoto's thyroiditis are closely linked to the slowing down of thyroid gland function. It is therefore essential to stabilise thyroid function through regular medical monitoring and, if necessary, hormone replacement therapy. At the same time, certain natural approaches can help improve overall well-being and alleviate certain symptoms in daily life.

A healthy, varied diet rich in essential nutrients can help support metabolism, reduce chronic inflammation, and improve digestion, which is often slowed in cases of hypothyroidism.

It is recommended to prioritise foods rich in omega-3s (small fatty fish, flax or chia seeds), lean proteins (fish, eggs, legumes), fresh fruits and vegetables (especially those rich in antioxidants), and sources of iron, zinc, selenium, and vitamin D, nutrients essential for thyroid function. Limit: ultra-processed, high-sugar, or high-fat foods. Processed meats, meat in sauce, cream, and other sources of saturated fats that are difficult to digest can slow digestion and worsen certain symptoms. In cases of digestive issues or intestinal sensitivity, personalised guidance can be helpful in identifying inflammatory foods to reduce (e.g., gluten, lactose, soy, etc., depending on the individual).

Engage in gentle, regular physical activity

Physical activity, even moderate exercise, helps boost metabolism, limit weight gain associated with hormonal slowdown, improve mood through the release of endorphins, and promote bowel regularity, which is often sluggish in cases of hypothyroidism. Activities such as brisk walking, yoga, gentle swimming, or stretching are particularly recommended to prevent excessive fatigue while providing energy.

Learning to Manage Stress Better

Chronic stress is a recognised factor in worsening autoimmune diseases: it promotes inflammation and fatigue, and can disrupt hormonal balance. Regularly practising relaxation techniques such as cardiac coherence breathing, meditation, sophrology, or gentle yoga can have a positive effect on symptoms overall, as well as improving sleep and mood.

In cases of Hashimoto’s thyroiditis, certain food categories may exacerbate inflammation or interfere with thyroid function. Although there is no single, universal diet, certain dietary recommendations can help better manage symptoms, in addition to medical treatment. Here are the foods most commonly discouraged, which should be evaluated on a case-by-case basis depending on individual sensitivities.

Gluten-containing grains: Gluten, found particularly in rye, wheat, and barley, may promote inflammation of the intestinal lining in some people, especially in cases of leaky gut. This mechanism is sometimes cited as a trigger for autoimmune diseases. A supervised gluten-free trial may be considered for sensitive individuals. Rice, quinoa, amaranth, and millet are naturally gluten-free and well-tolerated.

Dairy products: Cow's milk, its derivatives (cheese, yoghurt), and casein may exacerbate intestinal inflammation in some people. In cases of proven intolerance or sensitivity, it may be advisable to opt for plant-based beverages (almond, rice, hazelnut, coconut, depending on individual tolerance), ensuring you choose versions without added sugars or additives. Oats generally contain gluten, unless specified as gluten-free.

Foods containing goitrogens: Soy (milk, yoghurt, tofu) and raw cruciferous vegetables such as cauliflower, broccoli, and turnips, kale or white cabbage contain goitrogens, substances that may inhibit the production of thyroid hormones. These foods do not necessarily need to be avoided, but should be limited, especially if consumed raw and in large quantities. Cooking significantly reduces their goitrogenic effect.

Alcohol: Alcohol, even in small doses, can exacerbate inflammation, disrupt the gut microbiota, and impair liver function, a key organ in the conversion of T4 (thyroxine) to T3 (the active form of the hormone). It is therefore advisable to limit or avoid alcohol consumption as part of a comprehensive management plan for Hashimoto's disease.

Processed foods: Prepared meals, store-bought biscuits, sugary cereals, ready-to-use sauces, and fizzy drinks often contain additives, refined sugars, and trans fats, all of which are known for their pro-inflammatory effects. They can also disrupt the gut microbiota and promote weight gain, two factors that worsen hypothyroidism.

Here are the main recommendations, based on the latest research, to reduce the risk of developing autoimmune diseases:

1. Make sure to stay adequately hydrated throughout the day, opting for filtered, purified water to limit the intake of unwanted substances and support all metabolic and immune functions.

2. Adopt an anti-inflammatory diet: Prioritise foods rich in omega-3 (small fatty fish like sardines and mackerel), antioxidants (red fruits, berries, colorful vegetables), fibre (vegetables, fruits, legumes), and healthy fats (extra virgin olive oil, nuts). Regularly include fermented foods (sauerkraut, kefir, kombucha) to support the diversity of the gut microbiome, a key factor in regulating the immune system. Eat leafy greens and mushrooms regularly for their anti-inflammatory properties and high vitamin and mineral content.

3. Meet your essential micronutrient needs: Ensure an adequate intake of vitamins A, D, and B, as well as minerals such as zinc, selenium, iron, and iodine, all of which play a role in modulating immunity. Choose natural sources: liver, eggs, fatty fish, seafood, organ meats, nuts, and a variety of vegetables. If you reduce your intake of dairy products, compensate for the loss of calcium with foods such as sardines, almonds, and leafy green vegetables.

4. Promote gut health: Protect the intestinal barrier with foods rich in fibre, probiotics, and bone broth, which provide amino acids and collagen beneficial for intestinal tissue and the intestinal lining. Avoid gut irritants (excess gluten, additives, alcohol, ultra-processed foods) to limit intestinal permeability, a risk factor for autoimmunity.

5. Adopt a generally balanced lifestyle: Engage in regular physical activity suited to your abilities, manage stress, get enough sleep, and avoid exposure to environmental toxins.

A healthy lifestyle can help limit Hashimoto’s symptoms but is not a substitute for medical care. 

The symptoms of Hashimoto’s hypothyroidism do not necessarily all appear at the same time and can be confused with those of other conditions because they are not specific to this disease. This is the case, for example, with chronic fatigue, which can have a multitude of causes (nutritional deficiencies, anemia, stress, depression, etc.). That is why, if in doubt, it is recommended to consult a doctor who can order a blood test to measure thyroid hormone levels in order to establish an accurate diagnosis.

After completing a Master’s degree in Management, followed by around twenty years working for renowned companies in the dietary supplements and natural cosmetics sectors, I decided to turn my passion – nature – into my profession.

I now practise naturopathy for both humans and animals, as well as sophrology. I also mentor trainee naturopaths and sophrologists at various schools.