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Can Onions Induce Arrhythmia in Some Patients and Prevent it in Others?

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It’s easy to diagnose an arrhythmia.  Simply wear a Holter monitor or a 2 week loop monitor and it is likely the physician will catch it.    Treating arrhythmias are also doable with an EP study that involves placing EP Catheters in the heart and destroying the pathway that is causing it arrhythmia.   But what about preventing an arrhythmia or limiting the triggers that induce it?  This article will discuss the effects onions can have on inducing  arrhythmias.


Onions come with a mixed reputation.  On one hand, many physicians recommend eating onions for heart health.   On the other, some people get arrhythmias just from eating onions.   Though the amount of publications corroborating the idea that onions can cause irregular heart rhythm is limited, the anecdotal evidence is everywhere.


Despite this anecdotal evidence many doctors and publications recommend eating onions and garlic as part of a heart healthy diet to prevent arrhythmias.   PBS reports that to reduce the likelihood of an arrhythmia people should eat foods with antioxidants like Quericetin, which is commonly found in onions.   The book Medical Botany says onions are a food that reduces oxidative stress.   There’s an inverse relationship between your odds of getting heart disease and the amount of onion antioxidants in your system.   Further, onions reduce the chance of stomach cancer and pancreatic cancer.

So why is it that people claim that onions cause their arrhythmias when so much research points to onions being heart and arrhythmia friendly?  There is evidence that onions can kill dogs and cattle can develop tachycardia from eating onions.   Despite this you won’t find a reference indicating a direct link between irregular heart rhythms and onions.

The secret may likely lie in the vagus nerve.   The vagus nerve is a complex and very long pair of cranial nerves that conveys information to the brain about the body’s internal organs.   Heart parasympathetic innervation is mediated by the vagus nerve.   In other words, there are parts of the nervous system that there are no conscious control over that can excite the heart (ie. the vagus nerve acts to lower the heart rate).  You can witness your vagus nerve at work when you breath.  Your heart rate slows down when you exhale and sleeps up when you inhale.   During each respiratory cycle, the degree that your heart rate changes is the measure of your vagal tone. The greater control your vagus nerve has over the heart rate, the better it’s supposed to be for one’s health.

vagus nerve

However, while vagal tone extends refractory periods in ventricular muscle, making it anti-fibrillatory, the opposite is true for atrial muscle.  Vagal tone shrinks the refractory period of atrial muscle, promoting the formation of re-entrant electrical wavelets; thereby, creating an environment where supraventricular arrhythmias (SVTs) can develop.    A Swedish study showed that 5% of paroxysmal atrial fibrillation patients had their arrhythmia triggered by onions.

Further, because the vagus nerve innervates the stomach as well, it is possible that a sensitized vagus nerve with gastric distress due to spicy foods (like onions) or distension (bloating) from a large meal and/or retained gas, would exert it’s influence on the heart, exciting the muscles in the atrium while calming those in the ventricles, creating a ready environment for palpitations.

The best approach to solving this riddle for yourself, after seeing your physician, is to keep a food diary.   Tracking your food intake by quantity and type along with any corresponding appearance of arrhythmia may give you insight to target those foods triggering your arrhythmia and then eliminated or reducing them.

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