Vegan Diets: Hypothyroidism Friend Or Foe?

A vegan diet may not necessarily lead to hypothyroidism. In fact, a 2013 study found that the prevalence of hypothyroidism among vegans was 11% lower than among non-vegetarians. However, vegans may be at a higher risk of developing iodine deficiency since animal products are typically rich sources of iodine, which is essential for thyroid hormone production. Additionally, soy products, often used as a natural protein replacement for meat, may adversely affect thyroid function.

Vegan diets may also result in nutrient deficiencies, such as protein, calcium, omega-3s, zinc, and vitamin B12. However, these deficiencies can be avoided by consuming a well-planned and balanced vegan diet that includes nutrient-rich whole foods and fortified foods.

Iodine deficiency and hypothyroidism

Iodine is a crucial mineral for the body. Cells require iodine to convert food into energy. The thyroid gland, which controls the body's metabolism, or how cells use energy from food, uses iodine to produce thyroid hormones. These hormones regulate the body's heartbeat, digestion, and other functions.

Iodine deficiency occurs when the body does not get enough iodine. This can cause the thyroid gland to work harder, leading to swelling or enlargement, known as a goiter. In some cases, the gland may not be able to produce enough thyroid hormones, resulting in a condition called hypothyroidism. Iodine deficiency is more common in women and can increase the risk of thyroid autoimmune disease, thyroid or other cancers, pregnancy-related high blood pressure, and learning disabilities in children born to iodine-deficient mothers.

A vegan diet may be associated with a lower risk of iodine deficiency since animal products tend to be rich in iodine. However, it is important for vegans to ensure adequate iodine intake as a deficiency can lead to hypothyroidism. This can be achieved through the use of iodized salt, which is recommended over natural sea salt for this purpose. Seaweed, while delicious, is not a reliable source of iodine due to variability in manufacturing processes.

In summary, while a vegan diet may offer protection against hypothyroidism, it is crucial for individuals following this diet to monitor their iodine intake and ensure they are getting sufficient amounts through the use of iodized salt or other sources.

The pros and cons of soy products

Soy products have been linked to both positive and negative health effects.

Pros

• Soy is a nutrient-dense source of protein, B vitamins, fiber, potassium, magnesium, and high-quality protein.
• Soy may help lower cholesterol levels, especially when eaten in place of animal protein.
• Soy may help protect heart health by reducing inflammation in blood vessels and improving their elasticity.
• Soy may help lower blood pressure, especially in people with high blood pressure.
• Soy may help lower blood sugar and insulin levels, especially in menopausal women and people with type 2 diabetes or metabolic syndrome.
• Soy may improve fertility in women.
• Soy may reduce menopause symptoms, such as fatigue, joint pain, depression, irritability, anxiety, and vaginal dryness.
• Soy may improve bone health in menopausal women.
• Soy may reduce the risk of certain cancers, especially breast cancer.
• Soy may reduce the risk of other types of cancer, including digestive tract, colon, colorectal, and prostate cancer.

Cons

• Soy may have a long-term influence on growth, digestion, sexual maturation, thyroid health, and breast cancer risk.
• Soy may have feminizing effects in men.
• Soy may be dangerous to babies.
• Soy may be harmful if it is genetically modified (GMO).
• Soy contains antinutrients that may lower the body's ability to absorb the vitamins and minerals they contain.
• Soy may cause digestive issues.

The importance of selenium

Selenium is a crucial mineral for thyroid health, and it plays a vital role in the metabolism of thyroid hormones. The mineral is essential for the conversion of the thyroid hormone T4 into the more active form, T3. A deficiency in selenium has been linked to autoimmune thyroid disease, which can cause hypothyroidism.

Brazil nuts are an excellent source of selenium, and just a few nuts a day can help meet the recommended daily intake. However, it is important not to overindulge in Brazil nuts, as excessive consumption can lead to selenosis. For those who are not fond of Brazil nuts, selenium can also be found in sunflower seeds, whole-wheat bread, and tofu.

Selenium is just one of several essential nutrients that support thyroid health. Iodine, for example, is vital for thyroid hormone production, and a deficiency can lead to hypothyroidism. Iodine is typically found in animal products, so vegans should be mindful of their iodine intake and consider using iodized salt.

Iron is another key component of thyroid health, as it is involved in thyroid hormone production. Iron-rich plant foods, such as spinach, contain non-heme iron, which is not as readily absorbed by the body as the heme iron found in animal products. Therefore, vegans may need to be mindful of their iron intake and pair iron-rich plant foods with vitamin C-rich foods to enhance absorption.

Vitamin B12 is also important for thyroid health, and a deficiency can lead to fatigue, a common symptom of hypothyroidism. As vitamin B12 is naturally found in animal products, vegans may need to supplement their diet with B12 or consume fortified foods such as plant-based milk and nutritional yeast.

Zinc plays a role in thyroid hormone metabolism, and a zinc deficiency can contribute to the development of hypothyroidism. Plant sources of zinc include pumpkin seeds, cashews, chickpeas, and whole grains. However, the zinc from these sources may be less bioavailable due to the presence of phytic acid, which hinders absorption.

In conclusion, maintaining optimal thyroid health on a vegan diet requires a mindful approach to ensure sufficient intake of specific nutrients like iodine, selenium, iron, vitamin B12, and zinc. Consulting with a healthcare professional or registered dietitian can provide personalized guidance to meet individual nutritional needs.

The role of iron in thyroid health

Iron is an essential nutrient, required for various physiological functions. Iron deficiency (ID) is a common nutritional disorder, affecting about two billion people worldwide, particularly pregnant women and women of childbearing age. ID occurs when the body lacks adequate amounts of iron, which is a key component of hemoglobin, a protein present in red blood cells that carries oxygen from the lungs to different tissues and organs in the body.

Iron is also crucial for enzymes and proteins involved in energy production and cell function, including thyroid peroxidase, an enzyme that catalyzes the iodination of tyrosine residues in thyroglobulin, a precursor protein for thyroid hormone synthesis. A deficiency in iron can therefore lead to adverse effects on the thyroid gland and its functioning.

A growing body of evidence suggests that ID may play a significant role in the pathogenesis of thyroid dysfunction, particularly hypothyroidism. Several studies have reported a high prevalence of ID in patients with thyroid diseases, which can impair the synthesis and function of thyroid hormones. The production of thyroid hormones is negatively affected by ID, and their deficiency reduces the proliferation of erythrocyte precursors, both directly and through reduced secretion of erythropoietin by the kidneys. ID can also affect the hypothalamic-pituitary-thyroid axis, leading to altered thyroid hormone levels and a decreased response to thyroid-stimulating hormones.

Research has shown that thyroid hormones stimulate erythropoiesis, and iron is essential for the activity of thyroid peroxidase. Correlation between ID and hypothyroidism is likely due to impaired thyroperoxidase (TPO) hemoprotein biosynthesis. Furthermore, animal studies have shown that ID can interfere with thyroxine deiodinase activity by reducing the conversion of thyroxine (T4) to triiodothyronine (T3) and with the regulation of thyroid metabolism at the central level.

The Link Between Iron and Thyroid Disorders

The relationship between iron and thyroid disorders is complex and not yet fully understood. Studies have found that ID is associated with an increased risk of thyroid dysfunction, while others have found no significant association. A 2013 review showed that the prevalence of overt and subclinical hypothyroidism is higher in pregnant women and women of childbearing age with ID, who had higher thyroid-stimulating hormone (TSH) values and reduced free thyroxine (FT4) values, with a possible increase in the risk of autoantibody positivity.

A 2020 study of Chinese pregnant women with ID or ID anemia observed that serum FT3 and FT4 values had a significant downward trend in the ID and ID anemia groups, with lower levels in the second group compared to the control group. Significantly higher TSH values were also reported in pregnant women with ID or ID anemia, and the rate of hypothyroidism was higher in these groups of patients.

Another study of Chinese women in the first trimester of pregnancy showed that serum TSH levels in women with ID were significantly higher than in the control group, while blood FT4 levels were significantly lower. A 2015 study of pregnant and non-pregnant women in China found that ID was an independent risk factor for isolated hypothyroxinemia, with no significant differences in serum TSH levels.

A 2018 study on a large sample of subjects without thyroid diseases, representative of the Spanish adult population, showed that subjects with low ferritin levels were more likely to have low FT4 and FT3 levels than subjects with higher ferritin levels, confirming a possible association between ID and hypothyroxinemia.

Treating Iron Deficiency

ID can be corrected by taking supplemental iron or increasing iron-rich foods in one's diet. People with thyroid disease and iron deficiency usually need to take iron supplements twice daily, with a dose ranging between 60 mg to 120 mg depending on lab results and symptom severity. People taking thyroid hormone medication like levothyroxine should separate their thyroid medication from their iron supplement, as iron interferes with thyroid medication absorption in the gut, lowering the thyroid hormone in the body.

To maximize iron absorption, some people take it with vitamin C, which makes it easier to absorb and boosts its bioavailability. Red meats contain the highest sources of iron, as do organ meats like liver. Other iron-rich foods include oysters, mollusks, clams, pumpkin seeds, sesame seeds, and iron-fortified foods.

The impact of a vegan diet on Hashimoto's disease

Hashimoto's disease is an autoimmune disorder that affects the thyroid gland, causing hypothyroidism. A vegan diet can have both positive and negative impacts on this condition.

Positive impacts

• A vegan diet can provide anti-inflammatory benefits, which can help reduce pain associated with autoimmune diseases.
• A vegan diet is typically rich in fruits, vegetables, and fibre, which are associated with a lower BMI and can help with weight management.
• A vegan diet can have a positive impact on the gut microbiome, reducing inflammation and pain in patients with autoimmune diseases.

Negative impacts

• Vegans may be at a higher risk of iodine deficiency since animal products tend to be rich in iodine, and it is essential for thyroid hormone production.
• A vegan diet may exacerbate blood sugar imbalances in those with Hashimoto's.
• A vegan diet may prevent the healing of intestinal permeability (leaky gut).
• A vegan diet may contribute to nutrient deficiencies, including iron, which is essential for thyroid hormone production.

Tips for a vegan diet with Hashimoto's

• Focus on including a variety of nutrient-rich, whole foods and fortified foods to ensure adequate nutrient levels.
• Include foods rich in selenium, such as Brazil nuts, sunflower seeds, whole-wheat bread, and tofu, as selenium is involved in thyroid hormone metabolism.
• Pair plant-based iron-rich foods with vitamin C-rich foods, such as citrus fruits, bell peppers, and broccoli, to enhance iron absorption.
• Consult a healthcare professional, such as a registered dietitian or nutritionist, to ensure your nutritional needs are being met and to monitor any deficiencies.

Frequently asked questions