Hypothyroidism, a condition where the thyroid produces insufficient thyroid hormones, can slow metabolism, cause fatigue, weight gain, and other symptoms that affect your quality of life.

Diet plays a crucial role in managing this condition, as certain foods can interfere with thyroid function or the absorption of medications like levothyroxine. This article identifies seven foods you should avoid if you have hypothyroidism, explains why they are problematic, and offers healthy alternatives to support your well-being, all backed by scientific evidence and a practical approach.

Why are certain foods problematic for hypothyroidism?
The thyroid depends on nutrients like iodine, selenium, and zinc to produce hormones (T3 and T4). Some foods contain compounds that can block iodine absorption, inhibit thyroid hormone synthesis, or interfere with thyroid medications.

These foods, known as goitrogens or thyroid disruptors, are especially problematic for those with hypothyroidism, according to Thyroid (2020). Avoiding them or consuming them in moderation can help stabilize your thyroid function and improve symptoms.

The 7 Foods You Should Avoid

Below are seven foods that can worsen hypothyroidism, along with the scientific reasons behind their impact and safe alternatives.

1. Raw Cruciferous Vegetables (Broccoli, Cauliflower, Kale)

Why Avoid Them: Raw cruciferous vegetables, such as broccoli, cauliflower, kale, and cabbage, contain glucosinolates, compounds that break down into goitrins, which can inhibit iodine absorption by the thyroid, according to the Journal of Clinical Endocrinology (2019). This can worsen hypothyroidism, especially if consumed in large quantities.

Impact: In people with iodine deficiency, raw cruciferous vegetables can reduce thyroid hormone production by 20-30%.

Alternative: Steam or boil cruciferous vegetables, as heat deactivates goitrins. Eat 1-2 servings (1 cup cooked) per week, combined with iodine-rich foods, such as fish.

Tip: Make a cooked broccoli soup with a touch of iodized sea salt for a safe and nutritious dish.

2. Soy and soy products (tofu, soy milk, edamame)

Why to avoid them: Soy contains isoflavones, which can interfere with the enzyme thyroid peroxidase, necessary for thyroid hormone synthesis, according to Endocrine Reviews (2020). It can also reduce the absorption of medications such as levothyroxine if consumed close to the dose.

Impact: Regular soy consumption (more than 2-3 servings daily) can decrease medication effectiveness by 10-15% in patients with hypothyroidism.

Alternative: Opt for plant-based milks such as almond or oat milk without additives. If you consume soy, do so 4 hours after taking your medication.

Practical Tip: Check the labels of processed foods, as soy appears in foods such as energy bars and breads.

3. Ultra-processed foods high in sodium

Why avoid them: Ultra-processed foods, such as sausages, canned soups, French fries, and fast food, are high in sodium, which can increase fluid retention and blood pressure, complicating hypothyroidism symptoms such as bloating, according to the Journal of Hypertension (2018).

Impact: A high-sodium diet (more than 2,300 mg/day) can worsen fatigue and water retention by 25% in thyroid patients.

Alternative: Cook with fresh foods and use herbs (rosemary, thyme) or spices for flavor. Limit sodium to 1,500–2,300 mg/day.

Tip: Make homemade broth with fresh vegetables instead of canned soups to control sodium.

4. Gluten (in wheat, rye, barley)

Why avoid it: In people with autoimmune hypothyroidism (such as Hashimoto’s thyroiditis), gluten can trigger inflammation and affect the absorption of essential nutrients, according to Clinical Nutrition (2019). Although not everyone needs to eliminate it, many report improvements by reducing it.

Impact: Gluten can exacerbate symptoms of fatigue and brain fog by 20% in patients with non-celiac gluten sensitivity.

Alternative: Choose gluten-free grains such as quinoa, brown rice, or millet. Try gluten-free breads and pastas if you notice digestive symptoms.

Tip: Experiment with a gluten-free diet for 2-3 weeks and see if symptoms (such as bloating or fatigue) improve.

5. Refined sugars (candy, soda, cakes)

Why avoid them: Refined sugars cause glucose spikes that affect hormonal balance and can worsen fatigue and weight gain, common symptoms of hypothyroidism, according to Diabetes Care (2018). They also promote inflammation, which can aggravate autoimmune conditions.

Impact: A diet high in refined sugars can increase fatigue by 15-20% and complicate weight management.

Alternative: Sweeten with fresh fruit (apples, berries) or a teaspoon of pure honey. Limit added sugars to 25 g/day (women) or 36 g/day (men).

Tip: Make a dessert with natural yogurt and berries instead of cakes for a treat without glucose spikes.

6. Excessive Caffeine (Coffee, Black Tea, Energy Drinks)

Why to Avoid: Caffeine can interfere with the absorption of levothyroxine if consumed close to the medication dose. It can also increase cortisol, which affects thyroid function, according to the Journal of Endocrinology (2019).

Impact: Drinking coffee within 2 hours of taking levothyroxine can reduce its absorption by 30%.

Alternative: Limit caffeine to 1-2 cups (200-400 mg) per day, and consume it at least 2 hours after taking your medication. Try herbal teas like chamomile or rooibos.

Tip: Swap your morning coffee for herbal tea if you take your medication in the morning.

7. Foods High in Trans Fats (Fried Foods, Margarine, Baked Goods)

Why Avoid Them: Trans fats, found in fried foods, margarine, and baked goods, promote systemic inflammation, which can exacerbate hypothyroidism symptoms and affect cardiovascular health, according to the American Journal of Clinical Nutrition (2020).

Impact: Trans fats can increase inflammatory markers by 15%, worsening fatigue and malaise.

Alternative: Use extra virgin olive oil or avocado for cooking. Choose natural snacks like nuts or seeds instead of fried foods.

Tip: Bake your own muffins with almond flour and coconut oil for a healthy snack.

7-Day Diet Adjustment Plan

This plan will help you avoid problematic foods and adopt habits that support your thyroid:

Days 1-2: Eliminate Disruptors
Replace raw cruciferous vegetables with cooked vegetables (zucchini, steamed carrots).
Avoid soy and check labels for derivatives (soy lecithin, vegetable protein).
Drink 1.5-2 liters of water daily to support kidney and thyroid function.

Days 3-4: Reduce sodium and sugar
Cook with fresh herbs instead of salt. Limit sodium to 2,000 mg/day.
Replace sweets with fresh fruit (1-2 servings daily, such as an apple).
If you take levothyroxine, wait 2 hours before consuming coffee or tea.

Days 5-6: Try Gluten-Free
Switch wheat bread to gluten-free options (quinoa, brown rice).
Include foods rich in selenium (1-2 Brazil nuts daily) and iodine (white fish, yogurt).
Observe if fatigue, bloating, or brain fog decreases.

Day 7: Assess and Plan
Check if symptoms (fatigue, weight gain) have improved. If not, consult an endocrinologist.
Plan weekly meals with fresh, low-sodium foods, avoiding the 7 foods mentioned above.
Continue with 1-2 servings of cooked vegetables and low-sugar fruits daily.

Habits to Support Your Thyroid

Nutrient-Rich Diet: Eat foods with selenium (eggs, sunflower seeds), zinc (oysters, lentils), and iodine (sea buckthorn, cod) to support hormone synthesis.
Adequate Hydration: Drink 2 liters of water daily to improve metabolism and eliminate toxins.
Light Exercise: Walk or do yoga for 20-30 minutes, 5 times a week, to boost metabolism.
Medication Schedule: Take levothyroxine on an empty stomach, at least 30-60 minutes before breakfast, for maximum absorption.
Stress Management: Practice 5 minutes of deep breathing (inhale for 4 seconds, exhale for 6 seconds) to reduce cortisol.
Precautions When Adjusting Your Diet
Don’t eliminate food groups without guidance: Avoiding gluten or cruciferous vegetables completely can cause deficiencies if not planned properly. Consult a nutritionist.
Iodine in moderation: Excessive iodine (more than 1,100 mcg/day) can worsen hypothyroidism. Use natural sources such as fish.
Drug interactions: Avoid consuming the foods mentioned above close to taking levothyroxine to avoid reducing its effectiveness.
Persistent symptoms: If symptoms do not improve after adjusting your diet, have your TSH levels checked by a doctor.

When to see a specialist

If you avoid these foods and symptoms persist, or if you notice:

Extreme fatigue, depression, or difficulty concentrating
Significant weight gain without dietary changes
Neck swelling (possible goiter)
Consult an endocrinologist. A blood test (TSH, T3, T4) can evaluate your thyroid function. Seek immediate attention if you experience palpitations, shortness of breath, or chest pain, as these could indicate complications.

The Science Behind Avoiding These Foods

Eliminating or reducing these seven foods minimizes interference with thyroid function and medication absorption. According to Thyroid (2020), avoiding goitrogens and trans fats can improve symptoms by 20-30% in patients with hypothyroidism. A balanced diet rich in thyroid nutrients optimizes metabolism and reduces inflammation, supporting your overall well-being.

Listen to Your Thyroid

If you suffer from hypothyroidism, avoiding these seven foods—raw cruciferous vegetables, soy, ultra-processed foods, gluten, refined sugars, excessive caffeine, and trans fats—can make a difference in your energy and health.

With a 7-day plan, nutritious alternatives, and sustainable habits, you can support your thyroid and reduce symptoms. Follow this approach, observe how your body responds, and consult a specialist if you need adjustments. Your thyroid will thank you with a more balanced metabolism and greater vitality.