Bone Health, Food / Nutrition

Selenium: Why Too Little or Too Much Can be Deadly

brazil nuts
Brazil nuts

Selenium is a trace mineral essential to your body’s ability to function normally. Despite its importance, relatively little selenium is needed; yet, failure to consume that minuscule quantity can lead to serious, even life-threatening, health problems. And the same holds true for consuming too much. To fully appreciate the importance of this mineral, we must first examine the consequences and symptoms of not getting enough selenium in our diets.

Symptoms of Selenium Deficiency

  • Fatigue
  • Muscle weakness
  • Muscle wasting
  • Heart problems
  • Catching a cold often and easily, despite taking care to avoid it
  • Longer healing/recovery periods

These signs are quite subtle, in that all of these things can be explained away or attributed to something else. And, sometimes, there are no obvious symptoms. Nothing that you can definitively point to and say, “This must be why!”

Illnesses Caused By Selenium Deficiency

Hypothyroidism – Without sufficient Selenium intake your thyroid cannot produce the T3 hormone, also known as triiodothyronine (and yes, that’s spelled correctly), our bodies need to function properly.

Keshan Disease – A form of congestive cardiomyopathy caused by both Selenium deficiency and the presence of a mutated strain of Coxsackievirus. This disease is mostly seen in children and women of childbearing age. Keshan causes enlarged heart and loss of heart tissues and arrhythmia and is often fatal.

Joint Problems – Joint pain, morning stiffness, some scientists have even linked Selenium deficiency to Kashin-Beck Osteoarthropathy/ Kashin Beck’s Disease (KBD), a chronic bone disease which causes deterioration of the joint tissue.

Immunity Issues – According to the American Society for Nutritional Sciences, “Selenium is essential for the efficient and effective operation of many aspects of the immune system in both animals and humans.”1 Consequently, a deficiency is a hindrance to effective immune function.

Growth Retardation – Selenium deficiency affects bone metabolism and growth, for example, KBD (mentioned above). It’s been proven scientifically, using lab rats, that selenium deficiency can result in a loss of more than 20% of the bone mineral density (BMD) that one should have when it reaches adulthood.

Myxedematous Endemic Cretinism – Some scientists now attribute this dreadful condition to thyroid atrophy (See Hypothyroidism above). Common signs of myxedematous endemic cretinism include a slowing of mental and physical activity, generalized fatigue, apathy, mental sluggishness, cold intolerance, constipation, decreased sweating and increased weight gain. It may also cause a broadening and coarsening of your facial features, enlargement of your tongue and deepening of your voice. The severity of mental impairment in cretinism is directly influenced by the time at which the deficiency occurs. That is why childhood and prenatal nutrition are so very crucial for proper human development.

How Much Selenium Do We Need?

The Recommended Dietary Allowance (RDA) for adults:

  • Adults need at least 55 mcg
  • Pregnant women need at least 60 mcg
  • Breastfeeding women need at least 70 mcg.

The Recommended Dietary Allowance (RDA) for Children:

  • Infants 0 to 6 months need 15 mcg
  • Infants 7 to 12 months need 20 mcg
  • Children 1 to 3 years need 20 mcg
  • Children 4 to 8 years need 30 mcg
  • Children 9 to 13 years need 40 mcg
  • Adolescents 14 to 18 years need 55 mcg

The maximum RDA for adults is 200 mcg, and this is from ALL sources – food and supplements. I couldn’t find a maximum for children, but to be safe, I recommend sticking with the RDA for each age group and not going more than 5 mcg above that number. Selenium is one of those nutrients that one must be very careful not to over ingest.

Best Selenium Sources

Brazil nuts – The most selenium dense food on Earth. The National Institutes of Health has said, “It is wise to eat Brazil nuts only occasionally because of their very high selenium content.”2 One serving – 1 ounce (6-8 nuts) contains 544 mcg, on average

Sunflower seed kernels, dry roasted – 1 ounce contains 23 mcg, on average

Fortified Oatmeal, instant – 1 cup cooked contains 12 mcg, on average

Whole wheat bread – 1 slice contains 11 mcg, on average

Brown rice, long-grain – ½ cup cooked contains 10 mcg, on average

Egg, hard-boiled – 1 large contains 15 mcg, on average

Tuna, canned in water – 3 ounces contains 68 mcg, on average

Cod, cooked – 3 ounces contains 32 mcg, on average

Turkey, roasted – 3 ounces contains 27 mcg, on average

Egg bagel – 4 inches in diameter, contains 27 mcg, on average

Chicken breast (lean), roasted – 3 ounces contains 24 mcg, on average

Beef chuck roast (lean), roasted – 3 ounces contain 23 mcg, on average

There are many more selenium-rich foods, but I won’t mention them all here, because I don’t want this article to turn into a book. Also, you need to be aware that the Selenium content of food can vary (sometimes widely), depending on the soil conditions where it was grown and, in the case of meats and fish, where it was raised and what it ate.

For those who believe that supplementing is necessary for them, due to their diet, lifestyle and/or their environment, I refer you to the advice of Dr. Andrew Weil, who recommends using an organic form of selenium, like yeast bound selenium or selenomethionine. Inorganic forms of selenium, such as selenium selenite, do not play well with some vital nutrients – Vitamin C, is one example.

Personally, I do not believe that Selenium supplementation is necessary for most people; not even strict vegetarians. It’s just so easy to not only get the RDA of Selenium in your diet but exceed it, that I can’t help but think that supplementing puts one in unnecessary danger of overdosing.

Symptoms of Selenium Overdose

  • Brittle nails and hair, and also deformed nails
  • Nail and hair loss
  • Tooth discoloration and decay
  • Skin discoloration
  • Stomach issues – upset stomach, intestinal cramps, and diarrhea
  • Nausea and vomiting
  • Burps that leave a bitter, metallic taste in your mouth
  • Coughing for no apparent reason
  • Bad breath
  • Bronchitis or bronchial pneumonia
  • Shortness of breath, leading to pulmonary edema, leading to respiratory failure, hypoxia-induced cardiac arrest, and possibly death
  • Brain damage – the symptoms include (but are not limited to) fatigue, irritability, passivity, reduced mental alertness, emotional instability, hand tremors, tingling or loss of sensation in the arms or legs, reduced blood pressure and, eventually, unconsciousness and death. You may have noted that a couple of these symptoms can also indicate a Selenium deficiency.

The last two symptoms scare me the most because they are likely to result in death. But if you are experiencing any of these symptoms, you should get tested for selenium poisoning as soon as possible.

Also, and this isn’t a symptom… but, the University of Maryland Medical Center has stated, “When researchers examined whether selenium had any effect on skin cancer, they found something unexpected: People who took as little as 200 mcg of selenium per day for more than 7 years had a significantly higher risk of developing type 2 diabetes. More studies are needed to understand exactly what might be happening. In the meantime, you should not take more than the daily recommended allowance of selenium without your doctor’s supervision.”3 Good advice.

Despite the alarming consequences of getting either too much or too little Selenium, once you are aware of which foods contain this vital nutrient (and how much) it’s easy to plan your meals to ensure that you and your children get enough without getting too much.

Selenium Benefits

  • Selenium beautifies the skin – It’s antioxidant properties regenerate vitamins E and C, thereby decreasing the aging of the skin. And who doesn’t want that?
  • Fights dandruff – Shampoos containing Selenium are said to alleviate dandruff.
  • Fights off disease – Selenium isn’t just vital to immune function, it has been proven to specifically improve the immune system’s ability to fight off bacterial and viral infections, cancer cells, herpes virus, cold sores, and shingles.
  • Improves heart health – One of the primary nutritional benefits of selenium is increasing the HDL cholesterol to LDL cholesterol. This is believed to be crucial for good heart health.

I should also mention that your ability to absorb Selenium is dependent on your intake of Vitamin E and that gastrointestinal illnesses such as Crohn’s disease and Ulcerative Colitis inhibit Selenium absorption.

In addition, if you smoke cigarettes, regularly drink alcohol or take birth control pills you may need to consume more Selenium than you normally would. How much more will depend on the individual. If you are a smoker, alcohol drinker, and/or take the pill, it would be wise to have your Selenium levels tested every time you see your physician. It’s better to be safe than sorry.


1 JR Arthur, RC McKenzie and GJ Beckett. “Selenium in the Immune System”. The Journal of Nutrition, May 1, 2003. Web. February 9, 2016

2 Dr. Singerman. “Selenium”. The Unvarnished Truth About Nutrition <>, February 17, 2013. Web. February 9, 2016

3 “Selenium: Antioxidant and Heart Health”., June 6, 2015. Web. February 9, 2016

Higdon, Jane, PhD. “Selenium”. Linus Pauling Institute/Oregon State University, 2001. Web. February 9, 2016

Weil, Andrew, MD. “Selenium”. Dr. Weil, n.d. Web. February 9, 2016

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