Best Supplements for Thyroid Support: Selenium, Myo-Inositol, Ashwagandha, and Iodine Evidence Review

Here’s a head-scratcher: more and more people feel tired, foggy, and out of balance—then land in the endocrinologist’s office to find out their thyroid needs help. The twist? Half the people I talk to in Melbourne don’t even know what their thyroid does until things go haywire. If you’re one of those folks trawling the internet for a fix beyond prescription meds, you’re not alone. There’s a wild mix of natural supplements out there claiming to work wonders for thyroid health—selenium, myo-inositol, ashwagandha, and iodine seem to take the spotlight. People swear by them, but how much of that is hype, and what’s actually backed by science?

Let me cut through the confusion with straight talk—no fluffy nonsense. In this deep-dive, you’ll find out exactly what these supplements can do, what risks you might be ignoring, who should stay far away, and how you can tell if they’re worth your money. Ready to ditch the guesswork? Let’s get into the facts (and some surprises) about keeping your thyroid running like it should.

Selenium: The Antioxidant Micronutrient With Big Thyroid Benefits

Selenium gets championed a lot for thyroid health, and for good reason. Your thyroid needs selenium to churn out hormones and keep itself from freaking out under stress. Basically, without decent selenium levels, your thyroid struggles to protect itself—especially when you’re fighting things like autoimmune attacks.

Some of the hardest-hitting evidence on selenium comes from studies on Hashimoto’s thyroiditis, which is the most common autoimmune thyroid problem. Back in 2010, a randomized controlled trial from Germany gave participants with Hashimoto’s 200 micrograms of selenium per day. After 3 months, their thyroid antibodies (TPOAbs) dropped by up to 40%. That’s a big deal—you want those antibodies low because they cause a lot of the inflammation and damage in Hashimoto’s.

But you can overdo selenium, which is where some people mess up. The sweet spot for most adults is between 55 and 200 micrograms per day. Go above 400 micrograms and you risk selenium toxicity—think nail changes, hair loss, stomach upsets, and even neurological problems in severe cases. It’s surprisingly easy for those living in Australia, since our soils (especially here in Victoria) are often selenium-poor, making deficiencies more common.

Selenium supplements come in different forms, usually selenomethionine or sodium selenite. Experts tend to prefer selenomethionine because it’s absorbed better. If your food choices are on point (lots of eggs, Brazil nuts, seafood), you might not need a supplement. But if your diet’s lacking, a modest supplement can help fill the gap. A word of warning—if you’re already taking a multi with selenium, don’t double up or you might go over the safe range. Always get your levels checked if you’re unsure.

For anyone juggling Hashimoto’s or even Graves’ disease, selenium can be a smart addition, but it’s not a magic pill. Don’t expect it to replace proper thyroid hormone replacement if you need it. Always worth a chat with your GP or an endocrinologist to check if a supplement makes sense for your specific case.

Myo-Inositol: The Unsung Hero for TSH Regulation

Myo-inositol is way less famous than selenium or iodine, which is a shame considering how much research is stacking up behind it. This sugar-like compound is naturally present in the body and helps with things like cell signaling. Over the past few years, some sharp clinical trials have shown that pairing myo-inositol with selenium can have game-changing effects for thyroid patients.

The big win? Myo-inositol seems to smooth out TSH (thyroid-stimulating hormone) levels, especially in folks with subclinical hypothyroidism. In a 2017 study out of Italy, women with subclinical hypothyroidism (that’s when your thyroid’s still chugging along, but not quite at full throttle) took 600 mg of myo-inositol plus 83 mcg of selenium each day. After just 6 months, over 60% saw their TSH drift back toward normal, and many noticed symptoms (like sluggishness and brain-fog) ease up. There’s growing buzz about using this combo early on, to potentially keep people off full-blown thyroid meds.

Myo-inositol seems safe for most people at recommended doses—generally around 600–2000 mg per day. Rare side effects include mild nausea or digestive stuff, but those are usually short-lived. Unlike iodine, going a bit overboard isn’t going to tip your thyroid into dangerous territory. Fun fact—myo-inositol is also popular for PCOS management, so if you’re dealing with both thyroid issues and irregular cycles, it may pull double duty.

There isn’t a massive set of warnings attached to myo-inositol, but take it with a grain of salt if you’re on any meds that change hormone levels, or if you’ve got blood sugar problems. Myo-inositol helps with insulin sensitivity, so it could nudge your blood sugar downward if you’re already prone to lows.

Something even seasoned thyroid patients might not know: clinical evidence suggests *combining* myo-inositol with selenium boosts the benefits for thyroid antibodies and TSH much more than either on its own. That said, research is mostly focused on women, so blokes might not see the exact same effects—though chances are still good it’ll help.

To sum it up: myo-inositol is one of the most promising, low-risk options for early thyroid support, especially if you don’t want to be shackled to prescriptions straight away.

Ashwagandha: Ancient Herb with Modern Promise (and Caution)

Ashwagandha, also called Indian ginseng, has exploded in popularity. If you’ve wandered through a Melbourne health food shop, you’ve seen it—capsules, powders, teas lining the shelves. People say it helps everything from stress and sleep to energy. But its link to thyroid health is where things get interesting—and a bit complicated.

The trick with ashwagandha is how it interacts with thyroid hormones. Small studies out of India (including a 2018 double-blind placebo trial) show that 600 mg of ashwagandha root extract each day may gently boost T4 and T3 hormone levels, especially in people with mild hypothyroidism. Participants in the trial saw their TSH nudge downward, which usually means their thyroid was working more efficiently. The study also reported that people felt more energetic and less tired, which is a huge deal if you’re used to dragging through the day.

But there’s a catch: if your thyroid is already running fast (think Graves’ disease or hyperthyroidism), ashwagandha could make things worse—it may increase hormone production even more and tip you into dangerous territory. People on thyroid medication need to approach ashwagandha with caution too. Since it can change T4 and T3 production, mixing it with meds like levothyroxine could send your hormone levels into overdrive or, on the flip side, cause swings that leave you feeling unsteady.

Dose-wise, aim for 300–600 mg a day if you want to try it. Side effects are usually mild (upset stomach or sleepiness), but some people get a racing heartbeat, anxiety, or even severe liver issues in rare cases.

The key takeaway: ashwagandha holds promise for people with slow thyroids and high stress, but it’s not for everyone. If you’re dealing with autoimmunity or on thyroid meds, check with your doctor before diving in. It’s an herb, not candy. The research is promising but still young—don’t throw away your other management strategies just yet.

Iodine: Double-Edged Sword for Thyroid Health

This is where things start getting heated. People think iodine is always good for your thyroid, but that’s not the whole story. Yes, your thyroid needs iodine to make hormones. But “the more, the better” is the fastest way to mess up your thyroid if you’re not careful.

Australia isn’t plagued by the iodine deficiencies seen in some parts of the world; most of us get enough from iodized salt, dairy, seafood, and a handful of everyday foods. But there’s been a weird uptick in people overdosing on iodine—especially with the popularity of kelp supplements and high-dose drops from overseas. Too much iodine ramps up the risk for thyroiditis, worsens Hashimoto’s, and can even speed up autoimmunity in people with a family history. I’ve seen folks who thought they were helping themselves actually make things worse—like kickstarting an underactive thyroid into being overactive, or vice versa.

The sweet spot is surprisingly slim: the recommended daily intake for adults hangs around 150 micrograms. If you’re pregnant or breastfeeding, you need a bit more, but still nowhere near mega-doses. One kelp tablet can pack over 1000 micrograms, which is way more than your body needs or can handle.

A 2014 study in New Zealand showed that supplementing iodine in adults who already had enough actually increased thyroid antibodies—the direct opposite of what you want. If you have Hashimoto’s, graves, or a history of thyroid autoimmunity, high iodine can rapidly worsen your symptoms. On the flip side, if you live somewhere remote, don’t eat iodized salt, and avoid dairy and seafood, a modest supplement might help—just don’t guess. Ask your GP for a urinary iodine test.

Signs you’re getting too much? Swelling in the neck (goiter), anxiety, palpitations, or sudden weight changes. If you already take a multivitamin, check the label. Overlapping supplements add up fast.

So while iodine might be a lifesaver for some, it’s poison for others. Don’t start supplementing “just because.” Get checked, and work with a doctor who actually understands the nuances here (there are plenty good ones in Melbourne, trust me).

How to Choose and Use Thyroid Supplements Wisely

Anyone can walk into a chemist and buy a handful of bottles, but that doesn’t mean they’re making smart choices. If you’re serious about supporting your thyroid, you’ve got to get fussy about quality, dosage, and how each supplement fits with your own health picture.

First off, don’t combine all these supplements without a solid reason—more isn’t better. Think about what your tests actually show: low selenium? Go for a quality selenomethionine. Off-balance TSH? Myo-inositol might smooth things out, especially in the early stages. Super stressed and sluggish? If ashwagandha fits, trial a low dose and monitor how you feel (and maybe get a professional’s input if you’re on meds).

If you’re shopping for supplements, look for brands that actually test for purity—Australian standards are decent, but there’s heaps of junk online. Avoid wild claims about permanent “thyroid cures”—nothing replaces real medical advice or proper thyroid hormone replacement when you need it.

Timing matters too. Some minerals, like selenium, are best taken with food to cut down your risk of nausea. Spacing out supplements and meds by at least an hour can also help prevent weird interactions.

People sometimes ask if these supplements are enough to ditch thyroid medication altogether. Here’s where a reality check comes in: if your thyroid has fizzled out completely (total hypothyroidism), supplements alone won’t bring it back from the dead. But if you’re in the gray area—borderline sluggishness, autoimmunity just getting started, or post-pregnancy thyroid swings—these tools might give you an edge and slow down progression.

Curious about other natural alternatives to synthroid? That link digs into some options worth considering if you’re on thyroid meds but want another route.

Just keep this in mind: test, don’t guess. Regular blood work is key—TSH, free T4, free T3, and even antibody levels to track progress. If anything feels off—especially your heart rate, mood, or weight—pull back and talk to your doc. Melbourne has some of the most up-to-date endocrinologists in the country, so tap their brains. Get your nutrition right (protein helps thyroid hormone travel in your blood), keep your stress managed, and get decent sleep. Supplements might play a solid supporting role—but you’re still the main player in your thyroid story.