Selenium isn’t as widely spoken about as other well-known nutrients like vitamin C, iron, and calcium – in fact, you might not have come across it before. But, while it’s only needed in very small amounts, this mighty nutrient is essential for your health.
With this in mind, we’ll explore exactly what selenium is, why we need it, and how you can make sure you’re getting enough.
What is selenium?
Selenium is an essential mineral that’s needed for healthy body function.
Although it’s only needed in small amounts, selenium has strong antioxidant properties and plays an important role in a number of bodily processes – including metabolism, thyroid health, and immune system function.
The body can’t produce selenium on its own so we have to get it through our diet. Luckily, selenium occurs naturally in a number of different foods.
What are some of the health benefits of selenium?
We’ll cover some of the various health benefits of selenium below…
1. Selenium is a powerful antioxidant and can protect against cell damage
Selenium has powerful antioxidant properties. Antioxidants are compounds found in foods that help to prevent damage to cells caused by free radicals.
Free radicals are formed in the body every day – they’re natural byproducts of processes such as the metabolism. Our bodies need free radicals to perform important functions, however, things like stress, smoking, and excessive alcohol use can cause an excess of free radicals to build up.
In time, this buildup can lead to oxidative stress – which research has linked to a number of chronic health conditions like heart disease, cancer, Alzheimer’s, and strokes.
Antioxidants, such as those found in selenium, play an important role in maintaining a healthy balance of free radicals in the body and reducing the impact of oxidative stress.
2. Selenium may reduce the risk of certain cancers
Research has suggested that selenium may help to lower the risk of certain cancers.
This is largely down to its ability to destroy cancer cells, boost the immune system, and reduce oxidative stress and DNA damage.
For example, this scientific review of over 350,000 people found that having high levels of selenium in the blood was linked with a lower risk of certain types of cancer, including breast, colon, lung, and prostate cancers.
It’s important to note that this effect was linked only with selenium consumed through foods, rather than supplements.
3. Selenium can give your immune system a boost
Selenium plays an important role in the healthy functioning of the immune system.
This is largely due to its antioxidant properties, which help to lower levels of oxidative stress, reduce inflammation, and boost immunity. Studies have also noted that selenium can increase white blood cell count and improve the function of T-cells – these are a specific type of white blood cell that protect against foreign particles.
Therefore, experts have linked having higher levels of selenium in the blood with increased immunity. By the same token, selenium deficiency has been found to harm immune cells and weaken immune response.
These benefits have also been seen in people with health conditions that can weaken the immune system, like tuberculosis, hepatitis C, influenza, and HIV. For example, this study reported that selenium supplementation improved symptoms and reduced hospitalisations in people with HIV.
4. Selenium may boost heart health and reduce the risk of heart disease
Studies have linked low selenium levels with an increased risk of heart disease, which suggests that eating a diet rich in selenium is important for keeping your heart healthy.
For example, in this scientific review, a 50% increase in selenium levels in the blood was found to reduce the risk of heart disease by 24%.
Due to its antioxidant properties, selenium may also help to lower inflammatory markers in the body, which is another key risk factor for heart disease.
In this collection of studies, when people with heart disease took selenium supplements, levels of the inflammatory marker C-reactive protein (CRP) reduced, while levels of glutathione peroxidase (a powerful antioxidant) increased.
These results suggest that selenium may help to lower the risk of heart disease by reducing inflammation and oxidative stress in the body. High levels of inflammation and oxidative stress have both been linked to atherosclerosis (the buildup of plaque in arteries), which can lead to life-threatening conditions like stroke, heart attacks, and heart disease.
5. Selenium is important for healthy thyroid function
The thyroid gland is responsible for growth, development, and regulating metabolism.
Thyroid tissue contains a higher amount of selenium than any other organ in the body, and the mineral plays an important role in its function. This includes protecting the thyroid against oxidative stress and supporting the production of thyroid hormones.
This means that a lack of selenium has been linked with thyroid conditions, such as Hashimoto’s thyroiditis – a type of hypothyroidism that causes the immune system to attack the thyroid gland.
A well-functioning thyroid is also important for healthy hair and nail growth.
6. Selenium may help prevent cognitive decline and reduce the risk of Alzheimer’s
Oxidative stress is thought to play a role in both the onset and development of neurological diseases such as multiple sclerosis, Parkinson’s, and Alzheimer’s.
Various studies have revealed that patients with Alzheimer’s disease often have lower levels of selenium in their blood. Other research has also found that selenium-rich foods and supplements may help to improve patients’ memories.
For example, this small study found that supplementing with one selenium-rich Brazil nut each day led to improved cognitive functions and speech in people with mild cognitive decline.
Plus, the Mediterranean diet, which is high in selenium-rich foods such as nuts and seafood, has also been linked with a lower risk of developing Alzheimer’s disease.
7. Selenium may help to reduce asthma symptoms
Asthma is a chronic disease that affects the airways by causing them to narrow and become inflamed, leading to symptoms such as wheezing, chest tightness, shortness of breath, and coughing.
Research has suggested that people with asthma often have lower levels of selenium in their blood. And this study concluded that when people with asthma upped their selenium intake, they had better lung function than those with lower levels.
Asthma is another condition that’s been linked to increased inflammation and oxidative stress in the body. However, due to its antioxidant properties, studies have suggested that selenium may help to ease asthma-related symptoms.
For example, this study found that when people with asthma took 200μg of selenium per day, it reduced their need to use steroid medications to control and manage symptoms.
That being said, further research is still needed to confirm selenium’s role in the treatment of asthma.
How much selenium do I need and what are the best food sources?
According to the NHS, men need 75μg (micrograms) of selenium a day, and women need 60μg a day.
Some top sources of selenium include…
- Brazil nuts (544μg per 28g) – though, make sure you eat a serving of Brazil nuts no more than a few times a week to avoid selenium toxicity.
- Tuna (92μg per 85g)
- Oysters, sardines, halibut, salmon, prawns, and crab (between 40μg and 65μg per 85g)
- Pork (33μg per 85g)
- Beef steak (33μg per 85g)
- Turkey (31μg per 85g)
- Eggs (20μg per one hard-boiled egg)
Other sources of selenium include brown rice, baked beans, tofu, porridge oats, mushrooms, spinach, lentils, and cashews.
If you eat meat, fish, or nuts, you should be able to get enough selenium through your daily diet.
For inspiration on how to eat more selenium-rich foods, why not try one of these high-selenium recipes from Eat This Much? Or one of these 15 plant-based selenium-rich recipes from One Green Planet? You’ll find everything from baked halibut with orzo to cashew alfredo pasta sauce.
What are the symptoms of selenium deficiency and toxicity, and who’s at risk?
Our bodies may only need selenium in small amounts, but getting too much or too little can still be harmful.
We’ll cover some of the signs and risks of both selenium deficiency and toxicity below.
Selenium deficiency
The amount of selenium found in food sources largely depends on the quality of the soil that the food’s grown in. Rainfall, evaporation, and pH levels are all factors that can affect selenium concentration in soil. For this reason, selenium deficiency is more common in some parts of the world than others.
In the UK, selenium deficiency has historically been quite rare. However, due to extreme weather conditions caused by climate change, soil in Europe has lost a lot of its selenium content. As a result of this, research suggests that selenium consumption in the UK has dropped over the past 50 years, with people consuming an average of 30μg to 40μg per day – well below the recommended amount.
There are also certain factors that can make it more difficult for the body to absorb selenium. People affected include those who smoke, drink a lot of alcohol, have intestinal diseases such as Crohn’s disease, or are on dialysis, and women who are breastfeeding.
Symptoms of selenium deficiency can include fatigue, muscle weakness, joint pain, anxiety, mood swings, a weakened immune system, and impaired sperm production.
Selenium toxicity
Selenium toxicity is fairly rare in the UK.
However, a recent survey found that around one in four people in the UK currently take selenium supplements. Since toxicity is more likely to occur when taking supplements, it’s important to always follow the recommended dosage. According to the NHS, taking 350μg or less a day of selenium supplements is unlikely to cause any harm.
It’s also worth keeping an eye on your consumption of foods that are particularly high in selenium – for example, Brazil nuts – as eating too many could also lead to toxicity.
Signs of selenium toxicity include hair loss, nausea, dizziness, tremors, muscle soreness, and vomiting.
If you’re concerned about your selenium intake or are considering adding supplements to your diet, it’s important to seek advice from your GP.
Final thoughts…
Selenium may not be as well-known or widely spoken about as other essential vitamins and minerals – but due to its antioxidant properties and role in immune system function, getting the right amount is important for health.
For further health tips, head over to the diet and nutrition section of our website. Here you’ll find other essential vitamins and mineral guides, as well as a range of healthy recipes and diet tips.