The importance of selenium supplementation for metabolic health

The body’s metabolism encompasses all processes that convert food into energy, as well as those that maintain stable blood sugar levels, normal lipid balance, and normal blood pressure. Metabolic health is therefore crucial in the prevention and management of a range of lifestyle-related diseases. Selenium plays a key role through various enzymatic processes and as a protective antioxidant. Since selenium deficiency is widespread, a team of researchers has reviewed a number of studies examining how selenium supplementation may be relevant in metabolic disorders, including insulin resistance and metabolic syndrome, which is a precursor to type 2 diabetes. Selenium supplementation may also be relevant in connection with various thyroid disorders.

Selenium is an essential trace element and is incorporated into approximately 25–30 different selenoproteins that function as vital enzymes. Overall, these selenoproteins are important for:

• Thyroid function and metabolism
• Cellular energy turnover and ATP production
• Fertility
• The immune system and regulation of inflammation
• Various antioxidant functions

In a recent review article published in Nutrition Reviews, researchers examined a number of studies to clarify the therapeutic effects of selenium supplementation on different metabolic disorders in adults. The researchers focused particularly on conditions such as chronic inflammation, oxidative stress, and disturbances in carbohydrate and lipid metabolism. These metabolic disturbances are commonly seen in conditions such as insulin resistance, type 2 diabetes, and PCOS (polycystic ovary syndrome).
Using scientific databases, the researchers identified a number of relevant studies and observed that selenium supplementation taken for 12 weeks or longer had the following positive effects on various markers:

• Improvement in insulin resistance of up to 26%, measured by HOMA-IR (Homeostatic Model Assessment of Insulin Resistance). Insulin resistance is a condition in which the cells’ ability to absorb glucose from the bloodstream is impaired. It is also a component of metabolic syndrome, a precursor to type 2 diabetes
• Reduction in inflammation, including reductions in CRP (C-reactive protein) of up to 62%
• Improvement in the body’s antioxidant defenses, which help protect cells and tissues from damage caused by free radicals and oxidative stress

The researchers also found that supplementary intake of probiotics and other antioxidants could enhance the effects in some studies. With regard to PCOS, the results of selenium supplementation were mixed. The researchers therefore conclude that selenium supplementation may be particularly relevant in adults with insulin resistance and diabetes. In addition, supplementation may be relevant for preventing deficiencies and related conditions.

Selenium’s importance for thyroid function

As described, the new review article primarily focused on blood sugar and related metabolic disturbances. However, metabolic disorders may also involve thyroid function.
The thyroid gland produces the metabolic hormones T4 (containing four iodine atoms), which is inactive, and T3 (containing three iodine atoms), which is active. The T3 hormone enables oxygen to enter cells, allowing them to convert calories from food into energy.
Metabolism must always be carefully regulated according to the body’s needs, and selenium-containing enzymes (deiodinases) are responsible for removing an iodine atom from T4, thereby converting it into active T3.
Nonetheless, an increasing number of people appear to be unable to convert sufficient T3 from T4, which may be a significant factor behind the rising prevalence of thyroid disorders.
According to another review article from 2025, several studies have shown that selenium supplementation may benefit patients with Hashimoto’s disease, which leads to hypothyroidism, and Graves’ disease, which leads to hyperthyroidism. This is partly because selenium plays a role in regulating thyroid hormones and partly because it helps protect the thyroid gland from damage caused by oxidative stress and chronic inflammation.

• In these studies, daily selenium supplementation has typically ranged from 100–200 micrograms.

Sources of selenium, widespread deficiencies, and relevant supplementation

Selenium is found in organ meats, meat, fish, shellfish, eggs, and Brazil nuts. The selenium content of grains and other crops depends on soil conditions, and because European soils are low in selenium, this contributes to widespread deficiency throughout the food chain. Daily selenium intake in Europe often ranges between 20–35 micrograms, which is too low and increases the risk of metabolic disturbances and other disorders.
According to research from recent decades, an intake of approximately 100–200 micrograms of selenium per day may be needed for various metabolic processes, antioxidant defenses, and other functions. Many researchers also recommend supplementation in the form of organic selenium yeast, which generally provides better bioavailability. Since excessive selenium intake should be avoided, EFSA (the European Food Safety Authority) has established an upper daily limit of 300 micrograms.

References:

Linda Morales-Juàrez et al. Current Insights and Research Gap in Selenium Supplementation for Metabolic Health: A Scoping Review. Nutrition Review, 2026

Luciana Sant´Ana Leone de Souza et al. Selenium nutritional status and thyroid function. Archives of Endocrinology and Metabolism, 2025