Peer reviewed by Dr. Heather Maddox, MD
The thyroid is sensitive. By the time you reach 50, subtle shifts in nutrition, hormones, and metabolism start adding up—and the thyroid often takes the hit. It’s no surprise that thyroid dysfunction becomes increasingly common with age, especially among women, with hypothyroidism affecting up to 20% of women over 60.
Part of the problem? Subclinical nutrient deficiencies that fly under the radar. Even if your bloodwork is “normal,” low levels of iodine, selenium, zinc, and iron can impair thyroid hormone conversion, affect energy, and contribute to symptoms like fatigue, weight gain, constipation, and mood shifts.
"Many of the thyroid patients I see in midlife have borderline labs—not quite hypothyroid, but not optimal either," says Dr. Heather Maddox, MD. "And more often than not, they're low in at least one or two key nutrients that the thyroid absolutely depends on."
Let’s take a closer look at the most important thyroid-supporting nutrients, why they matter, and how to get more of them.
Iodine: Necessary—but Not a Free-for-All
Iodine is essential for the production of thyroxine (T4) and triiodothyronine (T3), the two major thyroid hormones. Without enough iodine, the thyroid can’t manufacture hormones at all—leading to hypothyroidism or, in severe cases, goiter.
While iodine deficiency is rare in developed countries, it’s making a quiet comeback, particularly among older adults, vegans, and people avoiding iodized salt.
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The World Health Organization estimates that nearly 2 billion people globally are iodine deficient, including populations in the U.S. where iodized salt use has declined.
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Iodine requirements increase with age due to reduced absorption and changes in gut health.
But more isn’t better.
"Iodine is a Goldilocks nutrient," says Dr. Maddox. "Too little causes hypothyroidism. But too much—especially from kelp-based supplements—can actually trigger or worsen autoimmune thyroid disease in susceptible individuals."
Smart Sources of Iodine:
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Seaweed, in moderation (wakame, dulse and nori are milder options)
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Dairy products like milk and yogurt
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Eggs and iodized salt, used regularly but not excessively
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White fish such as cod and haddock
If you suspect low iodine, ask your provider about serum and urinary iodine testing, especially if you eat a mostly plant-based or low-sodium diet.
Selenium: Converts T4 Into Active T3
Selenium is required to convert the inactive hormone T4 into T3, the form your body actually uses. It also protects the thyroid from oxidative stress, which is elevated in autoimmune conditions like Hashimoto’s.
One clinical trial published in Thyroid found that supplementing with selenium (200 mcg/day) for three months significantly reduced thyroid peroxidase antibodies (TPOAb) in women with Hashimoto’s, indicating less autoimmune activity.
Selenium deficiency is more common in areas with low-selenium soils, and in older adults with poor dietary variety or absorption issues.
Best Food Sources of Selenium:
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Brazil nuts: Just 2–3 per day meet your full requirement
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Canned tuna, sardines, and halibut
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Sunflower seeds, eggs, and brown rice
“Selenium is a non-negotiable if you're supporting thyroid conversion or managing Hashimoto’s,” says Dr. Maddox. “But keep the dose reasonable. Going above 400 mcg daily can backfire.”
Zinc: The Underestimated Mineral
Zinc plays a crucial role in thyroid function, including helping convert the storage form of thyroid hormone (T4) into its active form (T3). It also supports the pituitary gland, which signals the thyroid to produce hormones, and is essential for T3 receptor sensitivity—without enough zinc, your cells may not respond properly to thyroid signals, even if hormone levels appear normal.
As we age, zinc absorption declines, and medications like proton-pump inhibitors (PPIs) can worsen this effect. Older adults are at higher risk for marginal zinc deficiency, which often presents with:
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Thinning hair
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Weakened immunity
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Loss of taste or smell
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Fatigue and slow wound healing
A 2013 study in Biological Trace Element Research found that people with hypothyroidism had significantly lower zinc levels than controls—and supplementation improved symptoms like fatigue and dry skin.
Where to Get Zinc:
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Oysters (the richest food source by far)
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Beef, chicken, and turkey
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Pumpkin seeds, cashews, and chickpeas
“Zinc is easy to overlook, but it’s involved in hundreds of cellular reactions—including thyroid hormone signaling,” Dr. Maddox explains. “It's one of the first minerals I test in patients with unexplained fatigue or thyroid resistance.”
Iron: The Thyroid’s Oxygen Supply Line
Iron deficiency, even without anemia, can disrupt thyroid function. Iron is required for the activity of thyroid peroxidase, the enzyme responsible for converting iodide into thyroid hormone.
Low iron can also mimic thyroid symptoms: fatigue, hair shedding, cold intolerance, brain fog, and low exercise tolerance.
In a 2017 study, women with subclinical hypothyroidism and iron deficiency saw improved thyroid function and symptom relief after iron supplementation, even without thyroid medication.
Older adults, especially women post-menopause, often develop low iron from poor absorption, chronic inflammation, or digestive conditions.
Best Iron Sources:
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Red meat and organ meats like liver
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Shellfish (clams, mussels, oysters)
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Lentils, spinach, and blackstrap molasses
“Ferritin, your iron storage marker, should ideally be above 80 and 100 ng/mL for thyroid support,” notes Dr. Maddox. “Below that, I often see energy and hair issues—even if hemoglobin looks fine.”
Quick Note on Labs
Standard thyroid tests (TSH and T4) often miss suboptimal function. Ask your doctor about:
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Free T3 and Free T4
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Reverse T3
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Thyroid antibodies (TPOAb, TgAb)
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T3 uptake, serum iron, zinc, selenium, and vitamin D
“Testing gives us the full picture,” says Dr. Maddox. “Especially for women over 50, these labs can guide targeted nutrition and avoid unnecessary medication.”
Final Thoughts
Thyroid health doesn’t run on hormones alone—it runs on nutrients. And after age 50, deficiencies in iodine, selenium, zinc, and iron become more common due to absorption changes, medication use, and dietary patterns.
Supporting your thyroid with nutrient-dense foods and targeted testing is one of the most impactful ways to maintain energy, metabolism, mood, and cognitive clarity as you age.
“You don’t always need medication first,” Dr. Maddox emphasizes. “Sometimes, optimizing the basics—nutrients, sleep, movement—gets people feeling better than they have in years.”
