Why Your Blood Needs Selenium (Know The Benefits)

Why Your Blood Needs Selenium

A selenium deficiency can lead to health problems like nerve damage and mental retardation. Your blood needs selenium to function properly.

Selenium helps to protect your body from free radicals and oxidative stress, which can cause it to age and weaken before it’s time.

Selenium supports the immune system, making it harder for viruses to spread, and easier for antibodies to be created.

Some foods contain selenium in small amounts, including seafood, meat, eggs, dairy and grain products. Selenium can be found in dietary supplements as well.

In this blog post, we will talk about the importance of selenium, why your blood needs this mineral nutrient, and what happens if you don’t get enough in your diet. Ready? Let’s jump right in!

What is Selenium and What Does it Do in Your Blood?

Selenium is a trace mineral that is vital for reproduction, thyroid gland function, DNA synthesis, protecting your body against infections, and damage caused by free radicals.

Getting enough selenium is important for good health because it helps in:

  • Regulating selenium transport
  • Redox homeostasis
  • DNA production
  • Thyroid hormone metabolism
  • Immunity

Selenium goes through series of reaction mechanisms in the blood to combine with proteins, forming selenoproteins.

This type of protein carries out DNA synthesis and protects the cells against damage in the body.

Why Your Blood Needs Selenium (Know The Reasons)

Researchers are studying selenium to understand how it affects our overall
health. Here are some of the reasons why your blood needs selenium:


Studies suggest that people who take lower amounts of selenium could have an increased risk of developing cancers of the colon and rectum, prostate, lung, bladder, skin, esophagus, and stomach.

A study published in BMC Cancer looked at selenium levels and colorectal cancer risk across 27 countries.

This was a large observational study examining the link between the intake of dietary selenium and colorectal cancer rates across various countries.

Data was collected from 27 different countries, representing a diverse range of populations.

Specific amounts weren’t provided for each country, but the study looked at national dietary selenium intake levels.

The study found that, countries with lower average selenium intake had higher rates of colorectal cancer. [1, 2]

Another relevant study also investigated the relationship between selenium supplementation and cancer prevention, this was a randomized, double-blind, placebo-controlled trial. [3] Participants were assigned either a selenium supplement or a placebo.

A population of 13,000 men with a history of prostate cancer were involved in the study. The intervention group received a daily dose of 200 mcg (micrograms) of selenium yeast. [4]

The study showed a significant reduction in total cancer diagnoses and prostate cancer specifically in the selenium group compared to the placebo. [5]

Cardiovascular Disease

Scientists are studying whether selenium helps reduce the risk of cardiovascular diseases. Some studies show that people with lower blood levels of selenium have a higher risk of heart disease, but other studies do not.

There is an evidence to support the connection between low selenium levels and increased risk of heart disease.

A large analysis of 25 observational studies found a link between a 50 percent increase in blood selenium levels and a 24% decrease in the risk of heart disease.

Here’s one observational study on selenium and heart disease:

Selenium status and risk of cardiovascular mortality among US adults [6]

  • This study, published in 2009, examined the association between blood selenium levels and cardiovascular mortality (death from heart disease) in a large sample of US adults.
  • Over 8,500 adults aged 45 and over were involved in the study. Researchers tracked their health over a 17-year period.
  • Direct selenium intake wasn’t measured. Blood selenium levels were used as an indicator of dietary intake over time.
  • The study found that participants with the lowest blood selenium levels had a higher risk of cardiovascular mortality compared to those with higher levels.
  • This suggests a potential link between low selenium levels and increased risk of death from heart disease.

A different study also looked at the connection between selenium deficiency and cardiomyopathy. [7]

Studies have shown that severe selenium deficiency can be a risk factor for a rare form of heart disease called Keshan Disease. This disease is uncommon in most areas of the world due to sufficient selenium intake through diet.

Evidence for the relationship between selenium and heart disease, comes from observing populations with different selenium levels and their risk of heart problems.

Although these studies show a positive correlation, more research is needed to determine if selenium supplementation directly reduces the risk of heart disease.

Thyroid Disease

The thyroid gland stores a mineral called selenium, it helps the thyroid to function properly.

Studies suggest that women who have low blood selenium levels might develop problems with their thyroid.

Three relevant studies looked into the connection between low blood selenium levels and thyroid function:

1. The Correlation Between Selenium Levels and Autoimmune Thyroid Disease: A Systematic Review and Meta-Analysis [8, 9, 10]

  • This review analyzed existing research on selenium levels and autoimmune thyroid disease (AITD).
  • Data from various studies involving thousands of participants with AITD were included.
  • The studies reviewed didn’t necessarily involve administering selenium, but rather compared selenium levels in people with and without AITD.
  • The analysis found a correlation between low selenium levels and increased levels of thyroid antibodies, suggesting a potential role for selenium in AITD.

2. Selenium Supplementation and Autoimmune Thyroid Diseases [11, 12, 13]

  • This research reviewed studies on selenium supplementation and autoimmune thyroid diseases.
  • One particular study highlighted involved women with positive thyroid peroxidase antibodies (TPOAb) but normal thyroid function.
  • The study group received 200 mcg of sodium selenite daily for a year, while the control group received a placebo.
  • Selenium supplementation showed potential benefits in lowering TPOAb levels and improving thyroid ultrasound results compared to the placebo group.

3. Selenium and the Thyroid: A Close-Knit Connection [14, 15]

  • This study explores the role of selenium in thyroid function.
  • 16 healthy volunteers were used as participants for this study.
  • Participants received different amounts of selenium (0, 50, 100, or 200 mcg/day) for 7 weeks.
  • The study found that low selenium intake (0 mcg/day) impaired the conversion of T4 (inactive) to T3 (active) thyroid hormone.

All these multiple studies show a good connection between selenium and thyroid function, and the results are promising, but more research is needed to confirm if selenium plays a key role in thyroid function.

What Foods Provide Selenium?

Selenium is found naturally or they exist in many foods. The amount of selenium in some plant foods depends on the amount of selenium in the soil where they were grown.

The amount of selenium found in some animal products depends on the selenium content in certain foods the animals eat.

You can get recommended amounts of selenium by eating different varieties of foods, including Brazilian nuts, Halibut, Shrimps, Oysters, Beef, and Pork.

What About Selenium Supplements?

Selenium is available in multivitamin-mineral supplements and other dietary supplements. Selenium supplements are in different forms, like selenomethionine and sodium selenate.

If you want to buy selenium supplements, we’ve selected the best ones for you:

  • Selen-L-Monomethionin – High dose as selenium methionine
    • High dose with 200mcg per capsule
    • Very high bioavailability
    • Free from unwanted additives
  • Nutricost Selenium (100 mcg, 240 Capsules) – Selenium is a vital component of glutathione. Nutricost’s yeast-free selenium is a 100% natural, premium chelated form of selenium. It is non-GMO and gluten-free.
  • Codeage Liposomal Selenium+ (180 Capsules) – Codeage Liposomal Selenium+ offers a modern blend of 200 mcg of L-Selenomethionine per serving, encased in a phospholipid matrix from non-GMO sunflower oil and lecithin to help support absorption.

Remember not take too much of these supplements, they can be toxic if you don’t follow or stick to the recommended dosage.

Are There any Interactions with Selenium that You Should Know?

Yes, some of the medications you take may interact with selenium.

For example, cisplatin, used to treat cancer can lower selenium levels, but the effect this has on the body is not clear.

The following medications may interfere with selenium:

  • Cisplatin
  • Clozapine
  • Prednisone
  • Valproic acid
  • Anticoagulants and antiplatelet drugs like warfarin, clopidogrel, heparin, and aspirin.

If you are taking any of these drugs, talk to your doctor first before you start with selenium supplements.

In addition to medications, there are a few other things that can also interfere with selenium absorption, such as high doses of vitamin C, iron, or zinc, kidney disease or HIV/AIDS.

How Much Selenium Do You Need?

The amount of selenium you need each day depends on your age, and the average daily recommended amounts below are in micrograms:

  • Birth to 6months: 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
  • Men 19–50 years: 55 mcg
  • Women 51–70 years: 45 mcg
  • Pregnant women: 60 mcg
  • Breastfeeding women: 70 mcg

The daily upper limits for selenium from foods and dietary supplements are below:

  • Birth to 6 months: 45 mcg
  • Infants 7–12 months: 60 mcg
  • Children 1–3 years: 90 mcg
  • Children 4–8 years: 150 mcg
  • Children 9–13 years: 280 mcg
  • Teens 14–18 years: 400 mcg
  • Adults: 400 mcg

What Happens if You Have Low Levels of Selenium?

Selenium deficiency (low selenium) is rare. The dysregulation of selenoproteins and selenium deficiency results in several disorders such as:

  • Colorectal Cancer
  • Keshan disease
  • Osteoarthritis
  • Liver disease
  • Arthropathy
  • Male infertility
  • A defective immune system against viral infections

Certain groups of people are likely than others to have trouble getting enough selenium, including people undergoing kidney dialysis, people living with HIV, people who eat only local foods grown in soils that are low in selenium.

Side Effects of Selenium

Is selenium harmful? Yes, if you take too much. Brazil nuts, for example, contains high amounts of selenium and can cause you to go over the upper limit if you eat too much.

Having too much selenium in your body over a long period of time can cause a range of symptoms, affecting different parts of your body. Here are some of the signs to watch out for:

  • Garlic breath and metallic taste: This is one of the first signs of selenium toxicity.
  • Gastrointestinal problems: Nausea, vomiting, and diarrhea.
  • Hair and nail changes: Hair loss, brittle nails, and nail discoloration can occur.
  • Skin problems: Rashes and skin irritation are possible.
  • Neurological problems: Fatigue, weakness, tingling, numbness, and difficulty walking can be signs of nerve damage.
  • In severe cases: Respiratory problems, muscle weakness, and even coma.

Extreme high intakes of selenium causes severe problems like, difficulty breathing, tremors, heart attacks, and even diabetes.


Selenium in your blood is vital for DNA production, metabolic processes, and protecting cells from oxidative damage.

Dietary intakes of selenium prevents cardiovascular diseases, cancer, and thyroid disease.

Although studies have not clearly shown that low intakes of selenium increases your risks of developing certain diseases further research is still on going to study the effects and impacts of selenium on humans.


  • Can selenium levels act as a marker of colorectal cancer risk? [read]
    • Authors: Marcin R Lener, Satish Gupta, Rodney J Scott, Martin Tootsi, Maria Kulp, Mari-Liis Tammesoo, Anu Viitak, Anders Metspalu, Pablo Serrano-Fernández, Józef Kładny, Katarzyna Jaworska-Bieniek, Katarzyna Durda, Magdalena Muszyńska, Grzegorz Sukiennicki, Anna Jakubowska & Jan Lubiński.
    • Published in: BMC Cancer volume 13, Article number: 214 (2013)
  • Selenium and the Prevention of Prostate and Colorectal Cancer [read]
    • Authors: Ulrike Peters and Yumie Takata
    • Published in: Mol Nutr Food Res. 2008 Nov; 52(11): 1261–1272. doi: 10.1002/mnfr.200800103
  • Baseline Characteristics and the Effect of Selenium Supplementation on Cancer Incidence in a Randomized Clinical Trial: A Summary Report of the Nutritional Prevention of Cancer Trial [read]
    • Authors: Anna J. Duffield-Lillico; Mary E. Reid; Bruce W. Turnbull; Gerald F. Combs, Jr.; Elizabeth H. Slate; Lori A. Fischbach; James R. Marshall; Larry C. Clark;
    • Published in: Cancer Epidemiol Biomarkers Prev (2002) 11 (7): 630–639
  • The Nutritional Prevention of Cancer: 400 mcg per day Selenium Treatment [read]
    • Authors: Mary E Reid 1, Anna J Duffield-Lillico, Elizabeth Slate, Nachimuthu Natarajan, Bruce Turnbull, Elizabeth Jacobs, Gerald F Combs Jr, David S Alberts, Larry C Clark, James R Marshall
    • Published in: Nutr Cancer
      . 2008;60(2):155-63.
      doi: 10.1080/01635580701684856.
  • Selenium for Preventing Cancer [read]
    • Authors: Marco Vinceti, Tommaso Filippini, Cinzia Del Giovane, Gabriele Dennert, Marcel Zwahlen, Maree Brinkman, Maurice PA Zeegers, Markus Horneber, Roberto D’Amico, Catherine M Crespi, and Cochrane Gynaecological, Neuro‐oncology and Orphan Cancer Group.
    • Published in: Cochrane Database Syst Rev. 2018; 2018(1): CD005195. Published online 2018 Jan 29. doi: 10.1002/14651858.CD005195.pub4
  • Selenium Status and Risk of Cardiovascular Mortality Among US Adults [read]
    • Authors: Joachim Bleys 1, Ana Navas-Acien, Eliseo Guallar
    • Published in: Arch Intern Med
      .2008 Feb 25;168(4):404-10.
      doi: 10.1001/archinternmed.2007.74
  • An Original Discovery: Selenium Deficiency and Keshan Disease (an endemic heart disease) [read]
    • Author: Junshi Chen
    • Published in: Asia Pac J Clin Nutr
      . 2012;21(3):320-6
  • The Correlation Between Selenium Levels and Autoimmune Thyroid Disease: A Systematic Review and Meta-Analysis [read]
    • Authors: Ying Zuo, Yaling Li, Xiaoqin Gu, Zhen Lei.
    • Published in: Ann Palliat Med
      . 2021 Apr;10(4):4398-4408.
      doi: 10.21037/apm-21-449. Epub 2021 Apr 16
  • Selenium Supplementation for Autoimmune Thyroiditis: A Systematic Review and Meta-Analysis [read]
    • Authors: Yaofu Fan, Shuhang Xu, Huifeng Zhang, Wen Cao, Kun Wang, Guofang Chen, Hongjie Di, Meng Cao, and Chao Liu.
    • Published in: Int J Endocrinol. 2014; 2014: 904573. Published online 2014 Dec 11. doi: 10.1155/2014/904573
  • Selenium and Thyroid Diseases [read]
    • Authors: Fei Wang , Chunyu Li, Shaoxin Li, Lili Cui, Junyu Zhao, and Lin Liao
    • Published in: Front Endocrinol (Lausanne). 2023; 14: 1133000. Published online 2023 Mar 24. doi: 10.3389/fendo.2023.1133000
  • The Effects of Selenium Supplementation in the Treatment of Autoimmune Thyroiditis: An Overview of Systematic Reviews [read]
    • Authors: Yong-Sheng Wang, Shan-Shan Liang, Jun-Jie Ren, Zi-Yi Wang, Xin-Xin Deng, Wen-Di Liu, Yi-Long Yan, Gui-Hang Song and Xiu-Xia Li.
    • Published in: Nutrients 2023, 15(14), 3194; https://doi.org/10.3390/nu15143194
  • Selenium and the Thyroid: A Close-Knit Connection [read]
    • Authors: Leonidas H. Duntas
    • Published in: The Journal of Clinical Endocrinology & Metabolism, Volume 95, Issue 12, 1 December 2010, Pages 5180–5188, https://doi.org/10.1210/jc.2010-0191
  • Selenium and Thyroid Disease: From Pathophysiology to Treatment [read]
    • Authors: Mara Ventura, Miguel Melo, and Francisco Carrilho.
    • Published in: Int J Endocrinol. 2017; 2017: 1297658. Published online 2017 Jan 31. doi: 10.1155/2017/1297658

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