Can a poor diet cause hypothyroidism?

From the Guidelines

A poor diet, specifically one deficient in iodine, can contribute to the development of hypothyroidism, as iodine is crucial for thyroid hormone production. According to the espen micronutrient guideline published in Clinical Nutrition in 2022 1, severe iodine deficiency can cause goiter and hypothyroidism due to insufficient iodine concentrations for thyroid hormone production. Key points to consider include:

• Iodine deficiency disorders pose a significant global health threat, affecting individuals and societies, including those in affluent countries.
• Iodine deficiency can lead to an increased risk of developing autonomous thyroid nodules unresponsive to TSH control.
• During pregnancy and breastfeeding, iodine deficiency can adversely affect child development, including brain development, neurocognitive function, and IQ.
• A balanced diet rich in whole foods, adequate iodine (from sources like iodized salt, seafood, dairy), and other thyroid-supporting nutrients like selenium, zinc, iron, and vitamins A, D, and B12 is essential for maintaining thyroid health.
• While diet alone is unlikely to be the sole cause of hypothyroidism, with most cases resulting from autoimmune conditions, genetic factors, or medical treatments, a poor diet can exacerbate or contribute to thyroid dysfunction. If symptoms of hypothyroidism such as fatigue, weight gain, cold intolerance, or depression are experienced, consulting a healthcare provider for proper diagnosis and treatment, which typically involves thyroid hormone replacement medication, is crucial.

From the Research

Relationship Between Poor Diet and Hypothyroidism

• A poor diet can contribute to the development of hypothyroidism, as certain nutrient deficiencies can impair thyroid function 2, 3.
• Deficiencies in essential minerals and trace elements, such as iodine, iron, selenium, and zinc, can disrupt thyroid hormone metabolism and lead to hypothyroidism 2, 3, 4.
• A diet lacking in these essential nutrients can exacerbate thyroid disorders, particularly in individuals with autoimmune thyroid diseases (ATDs) 3.
• Malnutrition or the presence of numerous nutritional deficiencies can be a cause of thyroid disorders, including hypothyroidism 3.

Specific Nutrient Deficiencies and Hypothyroidism

• Iron deficiency can impair thyroid hormone synthesis by reducing the activity of heme-dependent thyroid peroxidase 2.
• Selenium deficiency can lead to impaired thyroid hormone synthesis and metabolism, and may increase the risk of hypothyroidism 2, 5.
• Zinc deficiency can also contribute to thyroid dysfunction, and supplementation with zinc, vitamin A, and magnesium may have beneficial effects in patients with hypothyroidism 4.
• Iodine deficiency is a well-established cause of hypothyroidism, particularly in regions with severe iodine deficiency 2, 6.

Dietary Approaches to Managing Hypothyroidism

• A balanced diet that includes essential nutrients can help reduce the symptoms of hypothyroidism and maintain a healthy weight 3.
• Avoidance of certain foods, such as gluten and dairy, may be beneficial for patients with concomitant sensitivities, but has little proven benefit for most patients with thyroid disorders 5.
• Supplementation with certain nutrients, such as selenium and zinc, may be beneficial in specific populations, but the evidence for other dietary approaches is limited or inconclusive 5.