What's the difference between selenium and selenomethionine?

While both are crucial for human health, a key difference is that selenomethionine is an organic, highly bioavailable form of selenium that the body absorbs more efficiently than inorganic forms. The form you choose for supplementation or get from your diet impacts its absorption and storage in the body.

Quick Summary

This article explains the core differences between elemental selenium and selenomethionine, focusing on their chemical forms, bioavailability, metabolic pathways, and applications for supplementation. It details how the body processes each form and their distinct benefits for supporting overall health.

Key Points

• Form: Selenomethionine is a specific organic form, while selenium is a general term covering both organic (like selenomethionine) and inorganic forms (like selenite).

• Absorption: The body absorbs selenomethionine more efficiently (up to 90%) than inorganic selenium forms (around 50%).

• Storage: Selenomethionine can be stored in body proteins as a selenium reservoir, which inorganic selenium cannot do effectively.

• Bioavailability: Due to its high absorption and storage, selenomethionine is considered a highly bioavailable source for increasing selenium levels in the body.

• Source: Selenomethionine is found naturally in many foods, including Brazil nuts and enriched yeast, and is a common supplement ingredient.

• Supplementation: For those needing to boost selenium levels, supplements containing selenomethionine are often recommended due to its superior absorption.

Selenium: The Essential Trace Mineral

Selenium is an essential trace mineral required for numerous bodily functions, including thyroid hormone metabolism, DNA synthesis, reproduction, and protecting the body from oxidative damage and infection. The body cannot produce selenium, so it must be obtained through diet or supplementation. The selenium content in plant-based foods, such as grains, legumes, and nuts, depends heavily on the soil's mineral levels where they are grown. In foods and supplements, selenium exists in various chemical forms, categorized as either organic or inorganic.

Inorganic vs. Organic Selenium

Inorganic forms, such as sodium selenite and sodium selenate, are produced from chemical compounds and are harder for the body to process, leading to decreased bioavailability. Conversely, organic forms, like selenomethionine and selenocysteine, are chemically similar to the selenium found in natural foods and the human body. Organic forms are generally better absorbed by the intestines.

Selenomethionine: The Bioavailable Organic Form

Selenomethionine is a specific organic form of selenium where the mineral replaces the sulfur atom in the amino acid methionine. It is the most common organic form of selenium found in foods like cereal grains, soybeans, and certain nuts, and is also widely used in supplements.

Superior Absorption and Storage

The primary advantage of selenomethionine is its superior bioavailability. The body absorbs up to 90% of the selenium from selenomethionine, while the absorption rate for inorganic forms like selenite is significantly lower, around 50%. This high absorption rate allows selenomethionine to effectively increase the body's selenium levels.

A Body Reservoir

Unlike inorganic selenium, selenomethionine can be nonspecifically incorporated into proteins in place of methionine. This provides a storage reservoir of selenium in the body, which can be drawn upon to synthesize vital selenoproteins during periods of low dietary intake. However, this storage ability means that long-term, high-dose intake can potentially lead to higher-than-desired accumulation, so monitoring intake is important.

A Role in Health

Selenomethionine's benefits are primarily linked to its role as a superior source of selenium for the body's vital functions. It acts as a powerful antioxidant, protecting cells from oxidative stress and contributing to the normal function of the immune system. Research has also focused on its positive effects on thyroid function, particularly in cases of autoimmune thyroiditis. For example, one study found that supplementing with selenomethionine significantly improved thyroid function in patients with Hashimoto's disease.

Comparison: Selenium vs. Selenomethionine

Feature	Selenium (General Term)	Selenomethionine (Specific Form)
Chemical Form	A mineral element that exists in multiple chemical forms, both inorganic and organic.	A specific, organic form of selenium where it replaces sulfur in the amino acid methionine.
Bioavailability	Varies widely by form. Inorganic selenite has lower absorption (~50%).	High, with absorption rates up to 90%, making it a highly effective supplemental form.
Metabolism	Utilized for selenoprotein synthesis and can also be excreted from the body.	Can be stored in body proteins as a reservoir, providing a long-term supply of selenium.
Body Reserves	Inorganic forms do not create a significant reserve and are more quickly excreted.	Creates a stored reservoir in body proteins, which the body can tap into later.
Source	Found naturally in the soil and, by extension, in foods and supplements.	The most common organic form found in nature, especially in nuts and enriched yeast.

Choosing the Right Selenium Source

For most individuals obtaining selenium from a balanced diet is sufficient. However, those living in selenium-deficient soil regions or with certain health conditions may require supplementation. In supplementation, the choice between different forms is a common consideration.

Considerations for Supplementation

• Bioavailability: Given its high absorption rate, selenomethionine is often the preferred choice for those seeking to effectively boost their selenium levels.
• Storage vs. Immediate Use: If a patient needs to build up a body reserve of selenium, selenomethionine's storage property makes it a suitable option. Other forms, like selenite, provide a more immediate but less sustained source.
• Health Conditions: For specific conditions, such as certain thyroid issues, research has demonstrated positive outcomes with selenomethionine supplementation. Always consult a healthcare provider for personalized advice.
• Yeast-based vs. Yeast-free: Selenomethionine is often found in selenium-enriched yeast. Yeast-free options are available for those with yeast sensitivities. It is worth noting that some studies suggest selenium-enriched yeast may have different effects than pure selenomethionine, possibly due to other elements present in the yeast.

Final Guidance

As always, discussing your supplementation plan with a healthcare professional is crucial. They can assess your individual needs and help you determine the most appropriate form and dosage of selenium for your health goals. For individuals in areas with sufficient soil selenium, a varied diet is typically enough. For others, particularly those with diagnosed deficiencies or specific medical needs, a targeted supplement like selenomethionine can offer significant advantages due to its superior absorption and storage capabilities.

Conclusion

In summary, the key difference between general selenium and selenomethionine lies in their form, bioavailability, and metabolic fate. Selenomethionine is a specific, highly absorbable organic form that can be stored in the body's proteins, creating a reserve of the essential mineral. In contrast, general selenium can refer to both organic and less-absorbed inorganic forms. For those looking to optimize their selenium status, particularly through supplementation, selenomethionine's superior bioavailability makes it a compelling option for effectively raising and maintaining the body's mineral levels. Understanding this distinction is essential for making informed decisions about dietary intake and supplementation.

NIH Office of Dietary Supplements

Frequently Asked Questions

Which form of selenium is best for absorption?

Selenomethionine is considered the most bioavailable form of selenium, with studies showing the human body absorbs up to 90% of it, compared to around 50% for inorganic forms like selenite.

Can I get enough selenomethionine from my diet?

For most people, a balanced diet that includes selenium-rich foods like Brazil nuts, seafood, and meat provides sufficient selenium. The amount varies based on the soil quality where foods are grown.

Is selenomethionine better for thyroid health than other forms?

Research has shown positive results for selenomethionine supplementation in individuals with certain thyroid conditions, particularly autoimmune thyroiditis. It is often recommended as a supplement for thyroid support.

What are the benefits of selenomethionine?

As a highly absorbable form of selenium, selenomethionine offers antioxidant benefits, supports the immune system, promotes thyroid function, and helps protect cells from oxidative stress.

Can I take too much selenomethionine?

Yes, excessive intake of selenium, including selenomethionine, can be toxic and lead to selenosis. It is important to adhere to recommended daily allowances and consult a healthcare provider before taking high doses.

How does selenomethionine create a selenium reserve in the body?

Because selenomethionine's structure is similar to the amino acid methionine, the body can incorporate it into body proteins. This creates a stored reservoir of selenium that the body can use when dietary intake is insufficient.

Should I choose a yeast-based or yeast-free selenomethionine supplement?

The choice depends on individual sensitivity to yeast. Both forms provide highly absorbable selenomethionine, but some studies indicate that yeast-based sources may have slightly different effects due to other elements present. Consult your doctor for the best option.