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7 Supplements With Hidden Dangers To Your Heart, Experts Warn: Arrhythmias, More

October 10, 2025 by Mariam Qayum
shefinds | Food
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Many people take dietary supplements thinking they’re doing something healthy for their body—but not all supplements are harmless. In fact, some popular vitamins and herbal remedies may pose serious risks to your heart, increasing the likelihood of heart attack, stroke, or irregular heart rhythms. We spoke to health experts to uncover seven supplements that could be silently harming your cardiovascular health. Read on to learn more!

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1. Fish oil without antioxidants

Fish oil is one of the more popular supplements due to its great benefits, such as reducing inflammation and lowering triglycerides. However, experts say that if you’re taking fish oil and it doesn’t contain antioxidants, it can be pretty risky for your cardiovascular health.

"While fish oil is very beneficial for cardiovascular health, it can be harmful," Robert Iafelice, MS, RDN, says. Fish oil that isn't preserved with antioxidants like Vitamin C, E, or astanxanthin poses a risk, as "fish oil is extremely susceptible to rancidity and the production of toxic byproducts." Yikes!

For this reason, Iafelice says, you should "always be sure that your fish oil has antioxidants in it to protect it from rancidity."

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2. Ephedra

Ephedra has actually been banned in dietary supplements since 2004 by the FDA. This ingredient is known to increase your heart rate, blood pressure, and other cardiovascular complications.

But Ramit Singh Sambyal, MD, warns, “Despite this ban, some products may still have ephedra or its derivatives, like ma-huang in traditional Chinese medicine.”

He further adds that "this stimulant can increase blood pressure, heart rate, and metabolism. Ephedra can interact with blood pressure medications and other drugs such as caffeine and decongestants."

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3. Calcium without magnesium

This is a lesser-known supplement fact that isn’t talked about often, but calcium and magnesium supplements need to be taken in balance. Magnesium aids in regulating calcium in the body and helps support heart functions, so taking these two together is best.

"Calcium and magnesium need to be in balance," Iafelice says. "Many people take calcium supplements that do not contain magnesium; this can result in a relative deficiency of magnesium, especially if the person is also eating a lot of dairy foods."

Iafelice adds that magnesium is also "essential for keeping the heart pumping with a normal heart rhythm" and "a lack of magnesium can lead to arrhythmias or Afib."

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4. Licorice Root

Licorice root is usually taken for digestion issues and sore throats, but if you’re not getting enough magnesium along with it, it could end up harming your heart health.

Registered nurse Lauren Thayer also adds that “licorice root can be dangerous as it can also cause high blood pressure and decrease potassium levels, which can lead to life-threatening arrhythmias."

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5. High-Dose Vitamin E

While vitamin E is an essential nutrient with antioxidant properties, excessive intake, particularly from supplements, can pose risks. High doses of vitamin E have been associated with an increased risk of bleeding and may interfere with blood clotting mechanisms. Additionally, some studies suggest that high-dose vitamin E supplementation could elevate the risk of all-cause mortality. It's advisable to obtain vitamin E through a balanced diet and consult with a healthcare provider before considering supplementation.

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6. Red Yeast Rice

Red yeast rice is a traditional supplement used to lower cholesterol levels. However, it contains monacolin K, which is chemically identical to the active ingredient in the prescription drug lovastatin. This poses a risk of unintentional overdose, especially if one is already taking statin medications. Overconsumption can lead to muscle pain, liver damage, and other serious side effects. Due to variability in monacolin K content and potential contaminants like citrinin, which can cause kidney failure, the use of red yeast rice supplements is not recommended without medical supervision.

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7. Bitter Orange (Synephrine)

Bitter orange extract, often marketed as a weight-loss aid, contains synephrine, a compound similar to ephedrine. Synephrine can constrict blood vessels, elevate blood pressure, and increase heart rate, leading to an increased risk of cardiovascular events such as strokes, heart attacks, and angina. Despite being marketed as a safer alternative to ephedra, bitter orange has been associated with serious health complications and should be avoided, especially by individuals with heart conditions.

Author:

Editorial Assistant

Mariam is an Editorial Assistant and writer at SheFinds, covering everything from style and beauty to health and wellness. Splitting her time between New York and Philadelphia, she brings a sharp eye for trends and a passion for storytelling to the digital space. With a strong editorial background, she’s always exploring the latest in fashion, skincare, and wellness. When she’s not writing or pitching, you’ll find her in the kitchen experimenting with new recipes or planning her next travel adventure. You can reach Mariam at mariam@shefinds.com.

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Woman taking magnesium supplement for health benefits.
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Drinking spearmint tea for potential skin benefits.
Variety of bread types displayed on a rustic surface.
Costco bakery showcasing an assortment of fresh pastries.
Woman holding her head in frustration or stress.
Woman experiencing discomfort from joint pain.
Shutterstock image related to beauty and skincare.
Popular coffee and fast food brands displayed together.
Woman adding sugar to a steaming cup of aromatic coffee.
Wooden board with bagels, blueberries, and butter arrangement.
Comparison of cooking spray and olive oil for cooking.
Brazilian dish featuring rice, beans, and chicken top view.
Checking time on a watch while enjoying breakfast.
Grocery store display of deli meats and sandwich products.
Cooked salmon served with rice, avocado, and greens.
Inside view of a Costco store displaying various products.
Woman taking magnesium supplement for health benefits.
Selection of s'mores brownies and baked goods from Aldi.
Grilled chicken breast with fries, salad, and dipping sauces.
Frozen pizza selection available in grocery store aisle.
Plate of fried fish served with crispy fries.