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  • Dr. Kali MacIsaac

Thyroid Series Part 3: Nutrients and Your Thyroid

In parts 1 and 2 of this thyroid series, we’ve seen that the thyroid gland is often touted as the most important hormonal gland because thyroid hormone affects literally every cell in the human body. It can either make you feel healthy, vital, and fertile, or it can make you feel like your body is falling apart.

We’ve learned that there is more to thyroid hormone testing than getting a TSH and calling it a day, and now it’s time to shift focus onto how you can support proper thyroid hormone production.

The first thing we need to discuss is exactly how the body produces thyroid hormones.

To make thyroid hormones (T4 and T3), this is what basically happens:

In the thyroid, through the action of the enzyme thyroperoxidase (TPO), iodine is bound to tyrosine residues within thyroglobulin proteins (Tg) to make T4 and T3. The combination of Tg + 4 iodine molecules makes T4, and the combination of Tg + 3 iodine molecules makes T3. Another enzyme called lysosomal protease severs T4 and T3 from the Tg proteins, and the hormones are released into circulation. As we discussed earlier, the vast majority of hormone released from the thyroid is in the form of T4; most of it gets converted in the peripheral organs and tissues to T3, the active version of thyroid hormone that binds to receptors and causes cellular change (more on this in Thyroid Series Part 1).

There are several important nutrients that are needed throughout this process, and in particular these nutrients are needed in the right amounts in order to convert T4 into active T3, and not into reverse T3 (read Thyroid Series Part 2 if you have no idea what I’m talking about).

Here are some of the important nutrients for thyroid function and why you should be concerned about getting enough of them:

1. iodine

Often the first nutrient my patients will ask about when they are told they have a thyroid problem, iodine is the trickiest of nutrients to prescribe. Classically, synthetic T4 (like Synthroid) and potassium iodide were used to treat thyroid disorders, because they’ve been shown to inhibit benign thyroid nodule growth in about 2/3 of patients. However, give too much iodine to someone who has a hidden hot nodule – and you can cause a thyroid strorm (it’s just as bad as it sounds).

As a crucial component of T4 and T3, iodine is necessary for thyroid hormone production. The highest prevalence of thyroid disorders is seen in iodine-deficient areas. And goiters (thyroid enlargement) are extremely common in iodine-deficient populations. You need iodine, just not too much – iodine supplementation in areas of iodine-deficiency has resulted in higher prevalence of autoimmune thyroid disorders, and too much iodine can shut down T4 production.

In North America, iodine deficiency has become less common due to iodized salt being introduced starting in 1924 – but iodine intake started to decline in the 70s and is now becoming more common. Recent estimates state that 16-50% of pregnant women may be iodine deficient.

My recommendation typically starts with increasing iodine intake from food sources; sea life is the predominant source – so sea vegetables (seaweed) and seafood (fish and shellfish) have the highest quantities. Other foods like beans, nuts, seeds, and some vegetables (peppers, spinach, chard, squash, turnip, onion and garlic) are good sources of iodine as long as they’re grown in good quality soil. Dairy and eggs also have fairly good iodine content, the higher the welfare the better. The RDA for iodine is 150ug for an adult male (that’s 150 micrograms) – for comparison, 1 gram of iodized salt contains 76ug of iodine. Having sea vegetables, and seafood high in iodine, 3-4 times per week is a good starting recommendation. You should be monitored by an integrative MD or ND with experience dosing iodine before taking any supplemental iodine.

If I do supplement with iodine, I do so in a low-and-slow way, always being sure to pair iodine with selenium to prevent a negative side effect (especially in any patient with autoimmune thyroid).

2. selenium

Selenium is an incredibly necessary nutrient for many aspects of thyroid health – first, it is an essential component of glutathione peroxidase, an enzyme that reduces oxidative stress damage by sequestering free radicals that could damage the thyroid. It is also an essential component of all three deiodinase enzymes (the enzymes that produce active free T3 from T4 in peripheral tissues). Selenium supplementation has been shown to increase glutathione levels by about 20%, reduce TPO antibodies by up to 76%, and prevents oxidation damage to thyroid cells. For most patients with thyroid disease (and especially all patients with autoimmune thyroid disease), selenium supplementation of 200mcg per day is a common recommendation.

3. zinc

An important nutrient for many body processes, zinc is important for maintaining normal thyroid hormone balance. It is involved in thyroid hormone synthesis as well as the proper expression of gene expression within the thyroid. If a patient is zinc deficient, I’ll often supplement with a Zinc and Copper supplement until levels return to normal. We diagnose zinc deficiency with an in-office test, or a more involved micronutrient test, here at the clinic.

4. iron

The last incredibly important nutrient for proper thyroid hormone production is iron. Research shows that iron-deficiency anemia patients have impaired thyroid hormone metabolism. If your ferritin is below 50, it may be interfering with your thyroid – patients with ferritin below 70 have shown to have reduced total T4 and T3 concentrations, reduction in conversion between T4 and T3, increased rT3 levels, and increased TSH. Iron deficiency may also affect thyroid hormone production by reducing activity of the TPO enzyme in the thyroid gland. I only dose iron once I’ve seen a patient’s ferritin – and the type and amount of iron that works for one patient may not work for the next! It’s helpful to chat with an integrative MD or ND about your iron test results in order to figure out the right supplementation for you, but you want that ferritin value above 50 to be sure it’s not hindering your thyroid.

If you’re curious about nutritional deficiencies that may be affecting your thyroid, feel free to ask me during a free-15 consult, or at your next appointment. We run comprehensive nutritional testing at Acubalance that helps our thyroid patients get to the root of their imbalances.

In health,

Dr. Kali MacIsaac HBSc, ND

Naturopathic Doctor

Previously in this series:

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