Atrial fibrillation is a type of arrhythmia, or irregular heart rhythm, that is caused by an abnormal electrical activity in the atria of the heart. Vitamin deficiencies have been linked to atrial fibrillation, with some of the most common deficiencies being low levels of thiamine (vitamin B1), magnesium, and potassium. Low levels of thiamine can lead to a condition called beriberi, which is associated with atrial fibrillation. Magnesium is important for helping regulate the electrical activity in the heart muscle, and low levels of magnesium have been linked to an increased risk of atrial fibrillation. Low levels of potassium can also lead to an abnormal heart rhythm. In addition, there is some evidence that deficiencies of vitamins B6, B12, and folate may also play a role in atrial fibrillation.