- What is Selenium
- Metabolic Benefits
- Effect on Thyroid
- Antiviral effects
Selenium is a nutrient that the body needs to stay healthy. Selenium is important for reproduction, thyroid gland function, DNA production, and protecting the body from damage caused by free radicals and from infection.
How much selenium do I need?
The amount of selenium that you need each day depends on your age. Average daily recommended amounts are listed below in micrograms (mcg).
|Life Stage||Recommended Amount|
|Birth to 6 months||15 mcg|
|Infants 7–12 months||20 mcg|
|Children 1–3 years||20 mcg|
|Children 4–8 years||30 mcg|
|Children 9–13 years||40 mcg|
|Teens 14–18 years||55 mcg|
|Adults 19–50 years||55 mcg|
|Adults 51–70 years||55 mcg|
|Adults 71 years and older||55 mcg|
|Pregnant teens and women||60 mcg|
|Breastfeeding teens and women||70 mcg|
What foods provide selenium?
Selenium is found naturally in many foods. The amount of selenium in plant foods depends on the amount of selenium in the soil where they were grown. The amount of selenium in animal products depends on the selenium content of the foods that the animals ate. You can get recommended amounts of selenium by eating a variety of foods, including the following:
Can selenium be harmful?
Yes, if you get too much. Brazil nuts, for example, contain very high amounts of selenium (68–91 mcg per nut) and can cause you to go over the upper limit if you eat too many. Getting too much selenium over time can cause the following:
- Garlic breath
- Skin rashes
- Metallic taste in the mouth
- Brittle hair or nails
- Loss of hair or nails
- Discolored teeth
- Nervous system problems
A study from 2015 assessed the effect of long-term selenium supplementation on the regression of cervical tissues and metabolic profiles of patients with cervical intraepithelial neoplasia CIN1: (elevated risk for cervical cancer).
Patients were randomly assigned to two groups to receive either 200 μg Se supplements (n 28) or placebo (n 28) daily for 6 months.
Outcome after 6 months
- A greater percentage of women in the Se group had regressed CIN1 (88·0 v. 56·0 %; P=0·01) compared with those in the placebo group.
- significant decreases in fasting plasma glucose levels and serum insulin levels
- Increased insulin sensitivity
- decreased serum triglycerides and increased HDL-cholesterol levels
- significant rises in plasma total antioxidant capacity and Glutathione (an antioxidant) levels
- significant decrease in malondialdehyde levels (an oxidative stress marker in diabetics)
Source: Karamali, M., Nourgostar, S., Zamani, A., Vahedpoor, Z., & Asemi, Z. (2015). The favourable effects of long-term selenium supplementation on regression of cervical tissues and metabolic profiles of patients with cervical intraepithelial neoplasia: A randomised, double-blind, placebo-controlled trial. British Journal of Nutrition, 114(12), 2039-2045. doi:10.1017/S0007114515003852
The thyroid gland is the organ with the highest amount of selenium per gram of tissue. Selenium contributes to the antioxidant defense in the thyroid.
Selenium deficiency decreases the synthesis of thyroid hormones, as it decreases the function of selenoproteins, in particular iodothyronine deiodinases (DIOs), which are responsible for the conversion of T4 to T3.
This decreased production of thyroid hormones leads to the stimulation of the hypothalamic-pituitary axis increasing TSH production. TSH stimulates the DIOs to convert T4 to T3 with consequent production of hydrogen peroxide, which is not adequately removed by less active glutathione peroxidases (GPx) and accumulates itself in the thyroid tissue causing thyrocyte damage with subsequent fibrosis.
200 μg Selenium supplementation in the presence of antithyroid peroxidase and antithyroglobulin antibodies (TPOAb and TgAb, resp.) in patients with autoimmune thyroiditis showed a decrease of TPO antibodies by 40% in the group treated with selenium (versus 10% in the placebo group) and in 9 of 36 patients (25%), TPOAb completely normalized; during this period, thyroid echogenicity also improved. In this trial, patients receiving selenium supplementation reported better well-being compared with the placebo group.
One study demonstrated that the oral administration of 200 μg/day of selenomethionine reduces effectively serum levels of TPOAb and even patients with selenium intake above the recommended levels may benefit from treatment with this dose.
Selenium has shown several antiviral effects, working on all relevant levels:
- Reduces viral mutations
- Inhibits viral replication
- Antioxidant effect - Immunonutrition
- Cell system support: improves lymphatic flow
Recently, selenium status was reported to positively correlate with the survival of patients with COVID-19 compared with non-survivors.