Benefits of Selenium (Food Sources, Deficiency & Side Effects)

Selenium is a trace mineral that plays a vital role in human health. It is needed only in small amounts; selenium supports everything from your immune system to thyroid function, as well as cancer protection. In this article, we’ll explore the scientifically proven benefits of selenium, the best food sources, and what happens when your body has too little or too much of this essential nutrient.

What is Selenium?

Selenium is an essential trace element. It cannot be made in the body. It is a key component of important antioxidant enzymes like glutathione peroxidase, which help fight free radical damage and support healthy metabolism.

Health Benefits of Selenium

1. Powerful Antioxidant & Anti-Inflammatory

Selenium protects cells from oxidative stress by neutralizing harmful free radicals. This reduces chronic inflammation and lowers the risk of diseases like heart disease and cancer. It is a key component of enzymes like glutathione peroxidases and thioredoxin reductases, which protect cells from damage caused by free radicals and oxidative stress.

By neutralizing harmful reactive oxygen species (ROS), selenium helps:

• Prevent cellular damage to DNA, proteins, and lipids

• Lower the risk of chronic inflammation

• Support protection against cancer, heart disease, and neurodegenerative disorders.  Study1 

• Enhance the body’s ability to cope with environmental stress and toxins

2. Boosts Immune Function

Adequate selenium strengthens immune defenses, helping fight infections and viruses by supporting the production and activity of white blood cells. Hence, it enhances the body’s ability to fight infections. Research states that selenium also helps regulate inflammation and boosts the response to viruses, making the immune system more resilient.

The thyroid has the highest concentration of selenium in the body. It helps convert thyroxine (T4) into its active form, tri-iodothyronine (T3), essential for metabolism and energy regulation. Studies state that selenium supplementation was found to improve thyroid autoimmunity and mood in patients with Hashimoto’s thyroiditis. Adequate selenium may also reduce the risk of thyroid disorders such as Hashimoto’s thyroiditis and hypothyroidism.

4. May Reduce Cancer Risk

Some studies suggest selenium lowers the risk of cancers, including prostate, lung, and colorectal cancers, due to its antioxidant and DNA-protective roles. Research has shown that selenium supplementation reduces cancer incidence in selenium-deficient individuals.

5. Heart & Brain Protection

Low selenium levels are associated with increased cardiovascular disease risk. Its deficiency weakens antioxidant defenses, leading to oxidative stress, inflammation, and damage to blood vessels that can promote atherosclerosis. In the brain, inadequate selenium impairs protective enzymes that guard neurons against oxidative damage, which may accelerate cognitive decline and raise the risk of conditions like Alzheimer’s disease. A meta-analysis found that selenium may protect against Alzheimer’s disease and improve brain function.

Selenium is important for male fertility (sperm motility and quality) and female reproductive health. Selenium plays an important role in reproductive health by protecting sperm and egg cells from oxidative damage. In women, adequate selenium levels are linked to healthy pregnancy outcomes and may reduce the risk of complications such as miscarriage or preeclampsia. Research has found that low selenium has been associated with infertility and adverse pregnancy outcomes.

️ Food Sources of Selenium

The best way to get selenium is through a balanced diet.

• Brazil nuts (richest natural source—just 1–2 nuts can meet daily needs)

• Seafood & fish (tuna, sardines, salmon, shrimp)

• Meat & poultry (beef, chicken, turkey)

• Eggs

• Whole grains (brown rice, whole wheat bread, oats)

• Legumes & seeds (lentils, sunflower seeds, chia seeds)

• Dairy products

Symptoms of Selenium Deficiency

Deficiency is rare but can occur in people with poor diet, gastrointestinal diseases, or living in low-selenium soil regions.

• Weak immune function

• Fatigue & brain fog

• Hair loss & brittle nails

• Hypothyroidism symptoms (weight gain, cold intolerance)

• Infertility in men and women

• Increased risk of infections

Side Effects of Too Much Selenium (Toxicity)

Excess selenium (above 400 µg/day) can be toxic, especially from supplements.

Symptoms of Selenium Toxicity (Selenosis):

• Garlic-like breath odor

• Nausea, vomiting, stomach upset

• Hair loss & brittle nails

• Skin rashes

• Nervous system problems

• In severe cases: kidney failure or death

EndNote

The benefits of selenium are many. Selenium is an essential mineral with powerful antioxidant, thyroid, immune, and fertility benefits. Best obtained through whole foods like Brazil nuts, fish, eggs, and whole grains. Both deficiency and excess are harmful. Balance is the key. Supplements should only be taken under medical advice, especially during cancer treatment or thyroid conditions.