Nutrition Support for Thyroid Conditions

Patients with thyroid conditions are among the most motivated to change their diet, and among the most confused. They encounter advice to avoid broccoli, soy, gluten, dairy and coffee, to take iodine, selenium and thyroid support formulas, and to follow special protocols. Much of this advice is exaggerated or wrong, and some is harmful. This article sets out practical, evidence based nutrition support for the most common thyroid conditions.

Iodine: enough, not too much

Iodine is essential for thyroid hormone production. Deficiency causes goitre and hypothyroidism and, in pregnancy, can impair fetal brain development. Excess can also cause thyroid dysfunction, particularly in people with autoimmune thyroid disease or nodular goitre.

• Use iodised salt where it is the main source of iodine, within guidance for overall salt intake.
• Include dairy, eggs and seafood if these are part of the diet.
• Take an iodine containing supplement in pregnancy and breastfeeding where recommended.
• Avoid kelp, seaweed supplements and high dose iodine products, which can contain very large and variable amounts.
• Be cautious with large amounts of seaweed in food, particularly varieties such as kombu.

Selenium: food first

Selenium supports thyroid hormone metabolism and protects the gland. Good food sources include fish, eggs, meat, whole grains and Brazil nuts, although Brazil nut content varies enormously, and eating many daily can lead to excess. In autoimmune thyroiditis, selenium supplementation lowers antibody levels, but clinical benefit is uncertain and excess carries risk. A reasonable approach is to ensure adequate intake from food, and to consider supplementation mainly where intake is low or in specific situations such as mild Graves orbitopathy under specialist guidance.

Iron, vitamin D and B12

Iron deficiency is common in women with hypothyroidism, impairs thyroid hormone synthesis and causes symptoms that overlap with hypothyroidism. Vitamin D deficiency is common, and B12 deficiency is associated with autoimmune thyroid disease through autoimmune gastritis. Checking and correcting these deficiencies is one of the most useful nutritional steps in thyroid care.

Levothyroxine and food

Levothyroxine absorption is sensitive to what is taken with it.

Consistency is the key principle. If a patient changes their routine, their TSH may change, and their dose may need adjusting.

Goitrogens: a largely unnecessary worry

Cruciferous vegetables such as broccoli, cabbage and kale contain compounds that can interfere with iodine uptake by the thyroid at very high intakes, particularly when iodine intake is low. At normal dietary intakes, and especially when cooked, they are not a concern for people with adequate iodine intake, and their benefits outweigh any theoretical risk. Soy can affect levothyroxine absorption, but moderate dietary soy is not a cause of hypothyroidism in people with adequate iodine intake.

Gluten

Coeliac disease is more common in people with autoimmune thyroid disease, and in them a strict gluten free diet is essential and may improve levothyroxine absorption. For people without coeliac disease, evidence that a gluten free diet improves thyroid outcomes is limited. Coeliac serology should be checked, while eating gluten, before any decision to go gluten free.

Weight and hypothyroidism

Untreated hypothyroidism causes modest weight gain, much of it fluid. Treatment typically reverses only part of any weight gained, and most weight change in people with treated hypothyroidism reflects the same factors that affect everyone: diet, activity, sleep, age and life stage. Nutrition plans for weight in treated hypothyroidism follow general principles, without special restrictions.

Hyperthyroidism

• Energy and protein: untreated hyperthyroidism increases energy expenditure and can cause weight and muscle loss; adequate energy and protein help until treatment takes effect.
• Bone: hyperthyroidism accelerates bone loss; adequate calcium and vitamin D are important.
• Iodine: avoid iodine supplements and kelp, which can worsen some forms of hyperthyroidism.
• Low iodine diet: before radioactive iodine treatment or some scans, a temporary low iodine diet may be prescribed by the treating team, avoiding iodised salt, seafood, dairy and some other foods for a defined period.
• Caffeine and alcohol: may worsen palpitations and tremor.
• Weight after treatment: weight often increases after hyperthyroidism is treated; planning for this helps.

Thyroid support supplements

Many products marketed for thyroid support contain iodine, kelp, selenium, tyrosine, herbs and sometimes animal thyroid tissue. Analyses of some such products have found measurable thyroid hormone. They can cause excess iodine intake, interfere with tests, cause hyperthyroidism and interact with prescribed treatment. They are best avoided.

Practical plan for treated hypothyroidism

1. Take levothyroxine consistently, separated from food, coffee, calcium, iron and fibre supplements.
2. Ensure adequate iodine from iodised salt and food, without kelp or high dose supplements.
3. Obtain selenium from food.
4. Check and correct iron, vitamin D and B12.
5. Test for coeliac disease before considering gluten free diets.
6. Eat a varied, balanced diet including cooked cruciferous vegetables.
7. Pause biotin before thyroid tests.
8. Avoid thyroid support supplements.

An illustrative case

A 44 year old woman with Hashimoto thyroiditis on levothyroxine has stopped eating broccoli and soy, takes a thyroid support formula with kelp, eats 4 Brazil nuts a day and takes her levothyroxine with breakfast and coffee. Her TSH has been unstable and she feels tired. Her ferritin is low. Her plan: take levothyroxine an hour before breakfast and coffee, stop the thyroid formula and reduce Brazil nuts to 1 or 2 a few times a week, reintroduce cooked vegetables, and treat her iron deficiency. Her coeliac serology is negative. 3 months later her TSH is stable and her energy has improved. The changes were simple; the confusion had been the problem.

Simple, consistent, evidence based

Nutrition support for thyroid conditions is less about special diets than about getting a few things right: adequate iodine without excess, selenium from food, correction of common deficiencies, consistent levothyroxine timing and avoiding products that cause harm. Clear advice replaces fear with a plan.