Natural Factors SelenoExcell® Selenium 200mg 90 Capsules

Selenium is one of those minerals that works quietly in the background, supporting antioxidant defenses, thyroid function, and immune health, but the form you take it in makes a real difference to how much of it your body can actually use. Natural Factors SelenoExcell® is organically bound selenium yeast, chosen specifically because of how well it’s absorbed, retained and put to work.

Why selenium matters

Selenium is an essential trace mineral, meaning your body needs it in small amounts but can’t make it, it has to come from food or supplementation. Once absorbed, selenium becomes part of selenoproteins, a family of specialised proteins that carry out some of the body’s most important protective and regulatory work:

• Antioxidant defense: Selenium is a core component of glutathione peroxidase, one of the body’s primary antioxidant enzymes. It helps neutralise reactive oxygen species generated during normal metabolism, protecting cells from oxidative stress.
• Immune system support: Selenoproteins play a role in modulating immune cell function, which is why selenium is consistently associated with healthy immune system activity.
• Thyroid hormone regulation: More on this below, selenium is essential to how the thyroid actually uses iodine.

Why choose organically bound selenium yeast

Not all selenium supplements are created equal, and the form matters as much as the dose.

Selenium supplements generally come in two forms: inorganic (sodium selenite or selenate) and organic (selenium yeast, in which selenium is bound into amino acids, primarily as selenomethionine, through natural fermentation).

Here’s why the organic, yeast-bound form is the better choice-

• Better absorbed and retained. Because selenomethionine is chemically similar to the amino acid methionine, the body absorbs and incorporates it efficiently including storing it in body proteins for later use, something inorganic selenite doesn’t do as effectively. Animal studies comparing the two forms have found selenium yeast to be substantially more bioavailable than sodium selenite.
• Gentler on the body. Inorganic selenite is more chemically reactive, which is part of why it carries a narrower margin between an effective dose and an excessive one. The organic, protein-bound form of selenium in yeast is considerably better tolerated at nutritionally relevant doses. The European Food Safety Authority has noted that the higher bioavailability of organic selenium is offset by its lower toxicity relative to inorganic forms.
• Closer to how selenium occurs naturally. In food, selenium is largely present in this same organically bound, protein-incorporated form, so selenium yeast mirrors the way your body is designed to encounter and process it, rather than presenting it as an isolated salt.

SelenoExcell® is a proprietary, well-researched selenium yeast, standardized to deliver selenium primarily as selenomethionine, giving you a form the body recognizes and uses efficiently.

A note on the yeast itself: the Saccharomyces cerevisiae yeast used to produce SelenoExcell® is inactivated during manufacturing. It’s used as a fermentation medium to bind selenium into its organic form, not as a living culture. The yeast cells can’t grow or reproduce in the body, so this isn’t a live-yeast or probiotic product, and it shouldn’t feed or aggravate a yeast or fungal infection.

Why selenium and iodine work as a pair

Selenium and iodine are often talked about separately, but for thyroid health, neither one does its job properly without the other.

Iodine builds the hormone. Selenium activates it. Iodine is the raw material the thyroid uses to construct thyroid hormones, T4 and T3. But T4 is the inactive form, it has to be converted into T3, the form your cells can actually use. That conversion is carried out by a family of selenium-dependent enzymes called deiodinases. Without adequate selenium, this conversion is impaired, even when iodine intake is perfectly adequate.

Selenium also protects the thyroid while it works. Producing thyroid hormone is an oxidative process, the thyroid generates hydrogen peroxide as part of the process of attaching iodine to the hormone precursor. Left unmanaged that byproduct can damage thyroid tissue. Selenium-dependent glutathione peroxidase enzymes neutralize this oxidative byproduct, which is part of why the thyroid gland holds one of the highest concentrations of selenium of any tissue in the body.

In short: iodine without enough selenium can leave you unable to fully activate the hormone you’re producing, and thyroid hormone production without enough selenium leaves the gland more exposed to oxidative stress. The two minerals are a package deal, physiologically speaking.

Selenium and respiratory health

Lung tissue is under constant oxidative pressure – every breath brings in oxygen the body has to manage, alongside whatever’s riding on it: pollution, smoke, and everyday airborne irritants. That oxidative load is part of why selenium-dependent enzymes are so concentrated in lung tissue.

Glutathione peroxidase and thioredoxin reductase (both selenium-dependent enzymes) are key parts of the lung’s own antioxidant defence system, helping to neutralise the reactive oxygen species generated by normal breathing and by exposure to airborne irritants. Animal studies on selenium deficiency consistently show reduced activity of these lung-based antioxidant enzymes, alongside a reduced capacity to cope with oxidative challenges to lung tissue which underscores how central selenium is to the lung’s own defence system.

Human studies in this area are mostly observational rather than interventional but they are noteworthy. We’ve seen firsthand the positive impact selenium has made to chronic respiratory issues. Several observational studies have found lower selenium and glutathione peroxidase levels in people with chronic respiratory conditions compared to those without. This kind of research shows an association worth noting and one that hopefully we’ve have validated in good time via proper trials.

What’s in each capsule

Each capsule provides 200 mcg of selenium (364% Daily Value) as SelenoExcell® selenium yeast (Saccharomyces cerevisiae). One capsule daily, or as directed by your health professional.

As with any supplement, check with your health professional before use if you’re pregnant, breastfeeding, trying to conceive, taking medication, managing a medical condition, or preparing for surgery.

Always read the label and follow the directions for use. If symptoms persist, talk to your health professional.

We suggest pairing with Nascent Iodine or Molecular Iodine as well as Wild C, Magnesium, Trace Minerals and Vitamin E if you are seeking a comprehensive approach to iodine repletion. This approach is outlined in our Iodine Digital Guide.

FAQ

What’s the difference between selenium yeast and other forms of selenium, like selenite? Selenium supplements are either inorganic (sodium selenite or selenate) or organic (selenium bound into yeast, mainly as selenomethionine). The organic, yeast-bound form is absorbed and retained by the body more efficiently, and it’s better tolerated at nutritionally relevant doses than the inorganic salts. SelenoExcell® is a well-researched selenium yeast standardised to deliver selenium predominantly as selenomethionine.

Why is selenium often mentioned alongside iodine? Because the two work as a pair in the thyroid. Iodine supplies the raw material for thyroid hormone; selenium-dependent enzymes then convert the hormone (T4) into its active form (T3), and selenium-dependent antioxidant enzymes protect the thyroid gland from the oxidative by-products generated during hormone production. Adequate iodine without adequate selenium can leave that conversion step under-supported.

Who might need to be careful with selenium supplementation? Selenium is needed in small amounts, and more isn’t automatically better, very high intakes over time can cause selenium toxicity. If you eat a lot of Brazil nuts, seafood, or organ meats, or you’re already taking a multivitamin or other supplement containing selenium, it’s worth checking your total intake with a health professional before adding this in.

Is the yeast in this product alive? Could it be an issue if I have a yeast or fungal infection? No. The Saccharomyces cerevisiae yeast used to produce SelenoExcell® is inactivated during manufacturing. It’s used purely as a growth medium to bind selenium into an organic, food-like form; the yeast cells themselves cannot grow, reproduce, or colonise in the body. This is not a probiotic or live-culture product, so it isn’t expected to feed or worsen a candida or other fungal infection. That said, if you have a diagnosed yeast or fungal infection or a known yeast sensitivity, it’s still worth mentioning this product to your health professional before starting it.

Is this suitable to take with a multivitamin? Many multivitamins already contain some selenium, so it’s worth checking your label and total daily intake before combining. Your pharmacist or healthcare professional can help you work out the right total dose for you.