Selenium Deficiency: Heart (Keshan Disease)

Of all the things a missing nutrient can do to the body, few are as dramatic as what severe selenium deficiency does to the heart. In the mountain belt of China where the soil holds almost no selenium, doctors documented a disease — Keshan disease — in which the heart muscle of children and young women slowly weakened, enlarged, and began to fail, sometimes over years and sometimes over a single frightening week. The medical name for what was happening is a dilated cardiomyopathy: a heart that stretches thin and pumps too weakly. This page explains what selenium-deficiency cardiomyopathy feels like, why a trace mineral your body needs in micrograms can decide whether heart muscle lives or dies, how honestly rare this is outside of selenium-poor regions and a few specific medical situations, and what is actually done about it. It is one of nutrition's clearest proofs that “just a trace” is not the same as “optional.”

Table of Contents

1. What Selenium-Deficiency Heart Disease Feels Like
2. The Mechanism: Why Heart Muscle Needs Selenium
3. An Honest Look: Cardiomyopathy Has Many Causes
4. Clues That Point Toward Selenium
5. What Causes Selenium to Fall This Low
6. The Virus Twist: Why Selenium and Infection Interact
7. Getting Tested and Diagnosed
8. Correcting Low Selenium Safely
9. When to Seek Care / Red Flags
10. Key Research Papers
11. Connections
12. Featured Videos

What Selenium-Deficiency Heart Disease Feels Like

Selenium-deficiency cardiomyopathy is, at its core, heart failure — the heart muscle becomes too weak to pump enough blood to meet the body's needs. The symptoms are the symptoms of a failing pump, and they tend to come on gradually unless an acute attack strikes. People with the chronic form describe a slow erosion of what their body can do:

• Breathlessness that builds over weeks — first only with exertion (climbing stairs, walking uphill), then with ordinary activity, and in severe cases even at rest or when lying flat. Lying down can bring on breathlessness because fluid shifts back toward the lungs; many people end up propping themselves on extra pillows.
• Fatigue and a feeling of being “winded” easily — a weak heart delivers less oxygen-rich blood to working muscles, so everything feels harder than it should.
• Swelling (edema) — puffiness in the ankles, feet, and legs, and sometimes a swollen, tender abdomen, as a weak right heart lets fluid back up into the body.
• Palpitations and an irregular pulse — a stretched, struggling heart is prone to abnormal rhythms (arrhythmias), felt as fluttering, pounding, or skipped beats.
• A heart that is visibly enlarged on a chest X-ray — the classic finding in Keshan disease was a big, globular heart with a weak, poorly contracting wall.

There is also an acute form that gave the disease its fearsome reputation. In acute Keshan disease, a person who had seemed only mildly ill could deteriorate within hours to days into cardiogenic shock — the heart suddenly unable to maintain blood pressure — with chest discomfort, nausea and vomiting, cold and clammy skin, and dangerous rhythm disturbances. Children were especially vulnerable. This sudden-collapse pattern is part of why the syndrome was studied so urgently, and why severe selenium deficiency is treated as a real medical danger rather than a vague “low level.”

It is worth being clear about who this affected. Keshan disease classically struck children and women of childbearing age living in a long, narrow band of selenium-poor land running from northeast to southwest China, named after Keshan County in Heilongjiang Province where it was first carefully described. It is a disease of geography and diet, not of personal failing — people simply ate food grown in soil with almost no selenium in it.

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The Mechanism: Why Heart Muscle Needs Selenium

Selenium does not act in the body as a lone atom. It is built into a small family of specialized proteins called selenoproteins, where it sits at the heart of the enzyme as an unusual amino acid, selenocysteine. Roughly 25 human selenoproteins are known, and several of them are, in effect, the body's antioxidant fire brigade. The most famous, glutathione peroxidase, was the very protein in which selenium's biochemical role was first discovered in 1973: it uses selenium to neutralize hydrogen peroxide and other reactive oxygen species — the corrosive byproducts that every hard-working cell generates.

Now consider what the heart actually is. It is a muscle that never rests, contracting roughly 100,000 times a day, every day, for a lifetime. To do that it burns an enormous amount of fuel, and burning fuel at that rate generates a constant spray of reactive oxygen species inside heart-muscle cells. In a selenium-replete person, glutathione peroxidase and its sibling selenoproteins mop up that spray continuously, protecting the delicate machinery — the contracting filaments, the energy-producing mitochondria, the membranes — from oxidative damage.

When selenium runs out, those antioxidant enzymes cannot be built in adequate amounts. The fire brigade is understaffed. Oxidative damage accumulates in the very tissue that can least afford it, and heart-muscle cells are injured and die. As cells are lost, the heart wall stretches and thins to try to keep up — like an overworked rubber band losing its snap — and pumps ever more weakly. That is the dilated cardiomyopathy of selenium deficiency: a heart slowly worn down from the inside by the very process (energy metabolism) that keeps it alive, because the protection that normally contains that process is missing.

An analogy. Picture an engine that runs day and night without ever switching off. Combustion inside it constantly throws off sparks and soot. Selenium-built enzymes are the engine's cooling and cleaning system — the part that quenches the sparks and clears the soot so the metal isn't slowly burned and pitted. Take that system away and the engine doesn't stop the next minute; it keeps running, but every hour of running now scars it a little, until one day it can no longer hold compression and simply won't deliver power. The heart in selenium deficiency fails the same way: not from a single dramatic break, but from protection quietly withdrawn from a part that can never stop working. Beyond the antioxidant role, selenoproteins also help regulate calcium handling and inflammation in heart tissue, which is why their loss disturbs both the strength and the rhythm of the beat.

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An Honest Look: Cardiomyopathy Has Many Causes

Here is the most important thing to understand, and it is easy to get wrong: a weak, enlarged heart is almost never caused by low selenium in well-nourished parts of the world. Dilated cardiomyopathy and heart failure are common conditions with a long list of far more frequent causes. If you develop breathlessness and ankle swelling, selenium deficiency is, statistically, near the bottom of the list of likely explanations — not the top.

The common, everyday causes of a dilated, weakened heart include:

• Coronary artery disease — previous heart attacks that scarred and weakened the muscle; this is the single most common cause in many countries.
• Long-standing high blood pressure — years of pumping against high pressure eventually tires and remodels the heart.
• Heart-valve disease — a leaky or narrowed valve forces the heart to work abnormally and enlarge.
• Viral myocarditis — a viral infection of the heart muscle (interestingly, this thread reconnects with selenium — see the virus section below).
• Alcohol and certain toxins — heavy alcohol use is a well-recognized, and often reversible, cause of cardiomyopathy.
• Chemotherapy drugs — some cancer treatments (such as anthracyclines) are cardiotoxic.
• Genetic (familial) cardiomyopathy — inherited forms run in families.
• Thyroid disease, pregnancy-related cardiomyopathy, and uncontrolled diabetes — each can weaken the heart.

So this page is not saying “if your heart is weak, you must be low in selenium.” The truthful framing is the reverse: selenium deficiency is a real and proven cause of cardiomyopathy, but it is a relatively uncommon one that mostly appears in specific, identifiable settings — selenium-poor regions, severe malnutrition, or people fed intravenously without selenium. In a typical well-fed adult with new heart failure, the workup looks for the common causes first, and a selenium level is checked only when the picture suggests it. Treating heart failure is never a matter of simply taking a selenium pill, and no one should delay proper cardiac evaluation on the assumption that a supplement will fix a failing heart.

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Clues That Point Toward Selenium

If selenium-related heart disease is uncommon, when should anyone — patient or doctor — actually think of it? A handful of features raise the suspicion:

• Geography and diet. Living in (or having grown up in) a known selenium-poor region, or eating an extremely restricted diet made entirely from food grown in such soil, is the classic setting. Keshan disease tracked the map of low-selenium land almost exactly.
• Long-term intravenous (parenteral) nutrition. People kept alive on IV feeding for months or years — for example, after major bowel surgery or with severe intestinal disease — can become profoundly selenium-deficient if selenium isn't added to the formula. Cardiomyopathy in this setting is a recognized and reversible complication, and it is one of the main reasons selenium is now routinely included in long-term IV nutrition.
• Severe malabsorption or very restrictive diets. Conditions like short-bowel syndrome, or extreme elimination diets followed for years, can drive selenium low enough to matter.
• A cardiomyopathy with no other explanation — when the common causes (coronary disease, hypertension, valve disease, alcohol, genetics) have been excluded, a nutritional cause including selenium becomes worth checking.
• Other signs of selenium deficiency together. Selenium also matters to the thyroid, the immune system, and skeletal muscle (low selenium can contribute to muscle weakness and aching). When several of these appear in the same person, a single low selenium level can tie the story together.

Notice that none of these clues is the heart problem itself — they are the context around it. That is the honest reality of nutritional cardiomyopathy: the symptom looks like ordinary heart failure, and only the surrounding situation tells you to reach for a selenium test.

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What Causes Selenium to Fall This Low

The amount of selenium in food is decided not by the food itself but by the soil it grew in. Plants take up selenium from the ground; animals get it from the plants. Where soil selenium is abundant, ordinary food is rich in it; where the soil is depleted, the same crops carry almost none. This is why selenium status varies so dramatically by region — far more than for most nutrients. The causes of true deficiency follow from that fact:

• Living on food from selenium-poor soil. Large parts of China, and patches elsewhere in the world, have soil so low in selenium that a locally-grown, subsistence diet cannot supply enough. This was the root cause of Keshan disease, confirmed when selenium supplementation programs dramatically cut its incidence.
• Long-term intravenous feeding without added selenium — as described above, a now-preventable medical cause.
• Severe malabsorption — short-bowel syndrome, severe inflammatory bowel disease, and similar conditions that prevent the gut from absorbing the selenium that is eaten.
• Extremely restrictive long-term diets — very limited diets, especially those built around foods from low-selenium areas, can fall short over time.
• Dialysis and some chronic illnesses — can lower selenium status, though rarely to the depths that cause cardiomyopathy on their own.

For most people eating a varied diet from mixed sources, selenium deficiency simply does not happen, because the food supply pools selenium from many regions. A handful of selenium-rich foods — Brazil nuts are famously concentrated, along with seafood, organ meats, eggs, and grains — supply far more than enough. The mineral is needed only in micrograms; the adult requirement is on the order of 55 micrograms a day. That tiny number is exactly why geography, not appetite, is what usually determines whether someone is deficient.

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The Virus Twist: Why Selenium and Infection Interact

One of the most fascinating findings to come out of Keshan disease research is that low selenium does not act entirely alone — it appears to cooperate with a virus. Researchers noticed that Keshan disease had seasonal and year-to-year swings that pure soil chemistry could not explain; soil selenium does not change from one season to the next, but the disease did. That pointed to an infectious co-factor, and suspicion fell on coxsackievirus, a common virus that can infect heart muscle (causing myocarditis).

Laboratory work then revealed something remarkable. In selenium-deficient hosts, a normally mild coxsackievirus strain could mutate into a more virulent, heart-damaging form — and, strikingly, that newly aggressive virus stayed aggressive even when later grown in selenium-normal hosts. In other words, the nutritional deficiency in the host was driving a permanent genetic change in the virus itself. The leading explanation ties back to the same mechanism described above: without enough selenoprotein antioxidant defense, the extra oxidative stress in the host's tissues accelerates viral mutation. This is widely cited as one of the clearest demonstrations that the nutritional state of the host can shape the genetics of a pathogen.

For understanding Keshan disease, this two-hit model — low selenium plus a viral trigger — helps explain why not everyone in a selenium-poor region fell ill, and why outbreaks waxed and waned. It also connects this heart page to selenium's broader role in immune defense: the same antioxidant selenoproteins that protect heart muscle also help the immune system fight infection cleanly, without collateral oxidative damage. (This is a window into the biology — it is not a claim that selenium treats any specific infection.)

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Getting Tested and Diagnosed

Two separate questions have to be answered: is the heart weak? and is selenium low? They are tested in different ways.

Assessing the heart is done first and is the same regardless of the suspected cause. The central test is an echocardiogram — an ultrasound of the heart — which shows whether the heart is enlarged and measures how strongly it is pumping (the ejection fraction). A chest X-ray may show an enlarged heart and fluid in the lungs; an electrocardiogram (ECG) looks for rhythm disturbances and strain; and blood tests for natriuretic peptides (BNP or NT-proBNP) help confirm heart failure. Because a failing heart is a serious matter, this cardiac evaluation should not wait on nutrition testing — it is the priority.

Assessing selenium status is done when the context (geography, IV nutrition, malabsorption, an otherwise-unexplained cardiomyopathy) raises the question. Selenium is measured by a blood test — serum or plasma selenium — and, for a longer-term picture, sometimes by red-cell selenium or even toenail selenium, which reflect intake over the preceding months. Glutathione peroxidase activity can also be measured as a functional readout of whether there is enough selenium to do its job. These are specialized tests, not part of a routine panel.

It is worth noting what selenium testing is not: a standard Comprehensive Metabolic Panel does not include selenium. Selenium has to be ordered specifically. So a normal routine blood panel does not rule out selenium deficiency — the mineral simply isn't on it. Because selenium also interacts with the thyroid, a clinician investigating possible selenium deficiency may also check thyroid function (see selenium and thyroid problems).

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Correcting Low Selenium Safely

If a genuine selenium deficiency is found, correcting it is generally straightforward — but it must be done with awareness that selenium has a narrow safe window. The gap between “too little” and “too much” is smaller for selenium than for most nutrients, and excess selenium is itself harmful (see the selenium toxicity hub). More is emphatically not better.

• Food first, where appropriate. Most people who are not in a deficient region get plenty from a varied diet. Selenium-rich foods include Brazil nuts (extraordinarily concentrated — a couple of nuts can exceed a day's requirement, so they should not be eaten by the handful), seafood, organ meats such as liver, eggs, poultry, and grains. For most well-nourished people, no supplement is needed at all.
• Supplemental selenium — when a true deficiency is confirmed, modest supplementation (commonly as selenomethionine or sodium selenite) restores levels. Doses are kept sensible: the adult requirement is about 55 micrograms a day, and the tolerable upper intake limit for adults is around 400 micrograms a day from all sources. Routine high-dose selenium for the general population is not recommended and has shown no benefit — and some harm — in well-nourished people.
• In the medical setting — for someone on long-term IV nutrition, selenium is simply added to the formula, which prevents the deficiency in the first place. Established deficiency may be corrected with carefully dosed intravenous or oral selenium under medical supervision.
• Treat the heart in parallel. If a cardiomyopathy has developed, standard heart-failure care (medications that unload and protect the heart, management of fluid and rhythm) is given alongside selenium repletion. Importantly, in the original Keshan-disease populations, preventing the deficiency with selenium supplementation dramatically reduced new cases — selenium's clearest proven role here is prevention in deficient populations, not as a stand-alone cure for an already-failing heart.

A reasonable rule of thumb for individuals: do not take high-dose selenium supplements on a hunch about your heart. If you have reason to think your intake is genuinely low — a very restricted diet, a malabsorption condition, or life in a known low-selenium area — ask a clinician to check a level and guide repletion. For nearly everyone else, food covers it.

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When to Seek Care / Red Flags

The symptoms of a failing heart are serious in their own right, whatever the cause. Some warrant emergency care right away — call emergency services, do not wait for a routine appointment:

• Severe or sudden shortness of breath, breathlessness at rest, or breathlessness so bad you cannot lie flat or are waking gasping at night.
• Chest pain or pressure, especially with sweating, nausea, or breathlessness.
• Fainting or near-fainting, or a racing, pounding, or wildly irregular heartbeat (possible dangerous arrhythmia).
• Cold, clammy, pale or bluish skin with confusion or extreme weakness — possible signs of cardiogenic shock, the dangerous acute pattern of Keshan disease. This is a life-threatening emergency.
• Rapid weight gain with worsening swelling of the legs or abdomen over a few days — a sign of fluid building up from a failing heart.

Arrange a prompt (non-emergency) medical visit if you have gradually worsening breathlessness on exertion, new ankle swelling, unusual fatigue, or palpitations — these deserve evaluation with an examination, ECG, and likely an echocardiogram. And remember the framing of this page: heart failure has many causes, most of them more common than selenium deficiency, so the goal of seeing a clinician is a proper diagnosis — not to self-treat with a supplement. If you are on long-term IV nutrition or have a severe malabsorption condition, make sure selenium is part of your care plan, and mention any new breathlessness or palpitations to your team without delay.

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Key Research Papers

1. Keshan Disease Research Group (1979). Observations on effect of sodium selenite in prevention of Keshan disease. Chinese Medical Journal;92(7):471-476. — PubMed
2. Rotruck JT, Pope AL, Ganther HE, Swanson AB, Hafeman DG, Hoekstra WG (1973). Selenium: Biochemical Role as a Component of Glutathione Peroxidase. Science;179(4073):588-590. — DOI: 10.1126/science.179.4073.588
3. Ge K, Yang G (1993). The epidemiology of selenium deficiency in the etiological study of endemic diseases in China. The American Journal of Clinical Nutrition;57(2):259S-263S. — DOI: 10.1093/ajcn/57.2.259S
4. Rayman MP (2000). The importance of selenium to human health. The Lancet;356(9225):233-241. — DOI: 10.1016/S0140-6736(00)02490-9
5. Beck MA, Levander OA, Handy J (2003). Selenium Deficiency and Viral Infection. The Journal of Nutrition;133(5):1463S-1467S. — DOI: 10.1093/jn/133.5.1463S
6. Fairweather-Tait SJ, Bao Y, Broadley MR, Collings R, Ford D, Hesketh JE, et al. (2011). Selenium in Human Health and Disease. Antioxidants & Redox Signaling;14(7):1337-1383. — DOI: 10.1089/ars.2010.3275
7. Schomburg L (2011). Selenium, selenoproteins and the thyroid gland: interactions in health and disease. Nature Reviews Endocrinology;8(3):160-171. — DOI: 10.1038/nrendo.2011.174
8. Rayman MP (2012). Selenium and human health. The Lancet;379(9822):1256-1268. — DOI: 10.1016/S0140-6736(11)61452-9
9. Labunskyy VM, Hatfield DL, Gladyshev VN (2014). Selenoproteins: Molecular Pathways and Physiological Roles. Physiological Reviews;94(3):739-777. — DOI: 10.1152/physrev.00039.2013
10. Benstoem C, Goetzenich A, Kraemer S, Borosch S, Manzanares W, Hardy G, et al. (2015). Selenium and Its Supplementation in Cardiovascular Disease — What do We Know? Nutrients;7(5):3094-3118. — DOI: 10.3390/nu7053094
11. Gunes S, Sahinturk V, Karasati P, Sahin IK, Ayhanci A (2016). Cardioprotective Effect of Selenium Against Cyclophosphamide-Induced Cardiotoxicity in Rats. Biological Trace Element Research;177(1):107-114. — DOI: 10.1007/s12011-016-0858-1

PubMed Topic Searches

• PubMed — Keshan disease, selenium, and cardiomyopathy
• PubMed — Selenium deficiency and dilated cardiomyopathy
• PubMed — Selenium deficiency in parenteral nutrition and the heart
• PubMed — Coxsackievirus, selenium deficiency, and viral virulence
• PubMed — Glutathione peroxidase, selenoproteins, and the heart

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Connections

• Selenium Deficiency Hub
• Selenium Deficiency and Thyroid Problems
• Selenium Deficiency and Weakened Immunity
• Selenium Deficiency and Muscle Weakness
• Selenium Toxicity
• Selenium Overview
• Selenium and Antioxidant Defense
• Selenium-Rich Foods
• Cardiomyopathy
• Heart Failure
• Arrhythmia
• Cardiology
• Iodine
• Vitamin E
• Comprehensive Metabolic Panel
• History of Selenium

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