Low-carb diets linked to atrial fibrillation

Low-carb diets are all the rage, but can cutting carbohydrates spell trouble for your heart? People getting a low proportion of their daily calories from carbohydrates such as grains, fruits and starchy vegetables are significantly more likely to develop atrial fibrillation (AFib), the most common heart rhythm disorder, according to a study being presented at the American College of Cardiology's 68th Annual Scientific Session.

Atrial Fibrillation - Image Credit: Joshya / Shutterstock
Atrial Fibrillation - Image Credit: Joshya / Shutterstock

The study, which analyzed the health records of nearly 14,000 people spanning more than two decades, is the first and largest to assess the relationship between carbohydrate intake and AFib. With AFib, a type of arrhythmia, the heart doesn't always beat or keep pace the way it should, which can lead to palpitations, dizziness and fatigue. People with AFib are five times more likely to have a stroke than people without the condition. It can also lead to heart failure.

Restricting carbohydrates has become a popular weight loss strategy in recent years. While there are many different low-carbohydrate diets including the ketogenic, paleo and Atkins diets, most emphasize proteins while limiting intake of sugars, grains, legumes, fruits and starchy vegetables.

"The long-term effect of carbohydrate restriction is still controversial, especially with regard to its influence on cardiovascular disease," said Xiaodong Zhuang, MD, PhD, a cardiologist at the hospital affiliated with Sun Yat-Sen University in Guangzhou, China, and the study's lead author. "Considering the potential influence on arrhythmia, our study suggests this popular weight control method should be recommended cautiously."

The findings complement previous studies, several of which have associated both low-carbohydrate and high-carbohydrate diets with an increased risk of death. However, while previous studies suggested the nature of the non-carbohydrate component of the diet influenced the overall pattern observed, the new study did not.

"Low carbohydrate diets were associated with increased risk of incident AFib regardless of the type of protein or fat used to replace the carbohydrate," Zhuang said.

Researchers drew data from Atherosclerosis Risk in Communities (ARIC), a study overseen by the National Institutes of Health that ran from 1985-2016. Of the nearly 14,000 people who did not have AFib when they enrolled in the study, researchers identified nearly 1,900 participants who were subsequently diagnosed with AFib during an average of 22 years of follow-up.

Study participants were asked to report their daily intake of 66 different food items in a questionnaire. The researchers used this information along with the Harvard Nutrient Database to estimate each participant's daily carbohydrate intake and the proportion of daily calories that came from carbohydrates. On average, carbohydrates comprised about half of calories consumed. The Dietary Guidelines for Americans recommend that carbohydrates make up 45 to 65 percent of total daily calorie intake.

Researchers then divided participants into three groups representing low, moderate and high carbohydrate intake, reflecting diets in which carbohydrates comprised less than 44.8 percent of daily calories, 44.8 to 52.4 percent of calories, and more than 52.4 percent of calories, respectively.

Participants reporting low carbohydrate intake were the most likely to develop AFib. These participants were 18 percent more likely to develop AFib than those with moderate carbohydrate intake and 16 percent more likely to develop AFib than those with high carbohydrate intake.

Several potential mechanisms could explain why restricting carbohydrates might lead to AFib, Zhuang said. One is that people eating a low-carbohydrate diet tend to eat fewer vegetables, fruits and grains--foods that are known to reduce inflammation. Without these foods people may experience more inflammation, which has been linked with AFib. Another possible explanation is that eating more protein and fat in lieu of carbohydrate-rich foods may lead to oxidative stress, which has also been associated with AFib. Finally, the effect could be related to an increased risk of other forms of cardiovascular disease.

Zhuang said that while the research shows an association, it cannot prove cause and effect. A randomized controlled trial would be needed to confirm the relationship between carbohydrate intake and AFib and assess the effect in a more ethnically diverse population. In addition, the study did not track participants with asymptomatic AFib or those who had AFib but were never admitted to a hospital, nor did it investigate different subtypes of AFib, so it is unknown whether patients were more likely to have occasional episodes of arrhythmia or persistent AFib. The study did not account for any changes in diet that participants may have experienced after completing the questionnaire.


  1. S S S S United States says:

    My wife and I went on the keto diet about 2 years ago and she lost 50 lbs and her heart atrial fibrillation went way completely...I read all kinds of negative so-called studies on the keto diet but we have experienced nothing but great health improvements!

    • Keemoy Mitchell Keemoy Mitchell United States says:

      My diabetes went away and so did my high blood pressure. They're always trying to trick us into going back to the pill farm 🤦🏿

    • Erika Shaffer Erika Shaffer United States says:

      Their source doesn't go to the study they are referencing. How do they expect anyone to actually take this seriously. 2/5 indeed.

    • Mau Jathey Mau Jathey United States says:

      The problem with nutritional studies and their results is there insane number of variables and medical researchers are doing their best to interpret and disclose these findings.  So long as they are acting in good faith, it's good to get more research and then later develop a meta-analysis of all these findings to help us best fuel and maintain our bodies.

      The biggest problem with the standard American diet (SAD) is that is quite possible the worst diet on the planet.  We were lied to by advocates in the sugar and processed food industries about the harm of ingredients like high fructose syrup and preservatives like sodium nitrate while vilifying fats and pushing trans fats.

      With that said, no matter what diet you're on, one needs to take the necessary measures to properly take care of one's self.  That includes speaking with your doctor or a nutritionist to see what diet scheme may work best for you and then learn from the results.

      I'm glad to hear you and your wife had a positive change and the keto diet worked for you both.

  2. Gordon Wagner Gordon Wagner United States says:

    Another day, another shady anti-keto story. Ho-hum. Could it be that big corporations that sell carb-laden food products are panicking over the popularity of the keto diet? Are they worried that people will stop eating their nutritionless food products?

  3. Douglas Fuller Douglas Fuller United States says:

    When I was on keto, I carefully recorded everything I ate and I found that I was getting almost no potassium. Potassium levels, either high or low, can cause a wide range of heart related issues.

  4. Joaquín Guisado Román Joaquín Guisado Román Lithuania says:

    1st - Everybody in the study was consuming a high carb diet, less than 44% is still high, keto is 5-10%. The only conclusion from this "study" is that possibly high carb diets cause AFib (1900/14000 = 13.5%), as there are no participants in a low carb diet.
    2nd - What kind of carbs were they consuming? How can they remember what they ate during 22 years?
    3rd - This is an observational study, the weakest type of study, it that does not prove anything. There is a observational study correlating number of Nicolas Cage movies every year with people who drowned by falling into a swimming-pool, same value as this study.

  5. Andrew McAvinew Andrew McAvinew United States says:

    Wow. This is science?

    First off, the ranges. 44.8% would likely not be considered low-carb on any of these low-carb diets. The middle range for moderate carb intake has a range of 8% before being considered high-carb. These seem like very cherry picked ranges in order to meet a pre-determined result.

    Also, it doesn't state anything about total caloric intake. Percentages are given but a person could be in the low-carb % range but still be eating 5000 calories a day. If you broke their diet into grams of carbohydrates, they could be WAY over what is considered "low-carb".

  6. Owen Kelchner Owen Kelchner United States says:

    First off this is a questionnaire study (horribly inaccurate) and low carb is anything under 45% of calories from carbohydrates. A ketogenic diet is at most 10% of energy from carbs. A couple weeks ago there was a google headline that low carb/ketogenic diets increased risk for all cause mortality. I looked up the actual study and the low carb group received 37% of their energy from carbs (way to high for ketogenic or even Paleo for that matter), had more smokers, more type 2 diabetics, and were less likely to engage in exercise then the other groups. This again was a questionnaire study. Ironically the article never mentioned all the other factors (smoking, diabetics, and less likely to exercise) that were in the low carb group (37% of calories from carbs IS NOT LOW CARB PEOPLE). The one thing I will say in regards to diet is if your carbs are relatively high 37% you're more than likely eating a significant amount of fat too (probably crappy vegetable oils) and its definitely worse to combine high fat and carbs. That's definitely the worse diet possible. I believe that ketogenic diet is extremely safe and beneficial if done correctly and I also believe a low fat high carb diet is healthy. I prefer keto and I think it's easier to maintain than a low fat diet but to each their own. Dont let these headlines deter you. Do some real research and see why many major universities are trialing a low carb diet and reporting completely opposite effects in regard to heart health. Ketones are a preferred fuel source for the heart and kidneys if you follow actual clinical studies. Ironically ketogenic diets are WAY more anti-inflammatory than a high carb diet in clinical studies (look at Virta health clinical study to get started).

  7. Baba Afrika Baba Afrika United States says:

    This is silly. People used to naturally eat low carb diet because cold drinks, candy, potato chips, pizza, etc wasn't in abundance like it is now. And heart related diseases were much fewer back then. Instead of focusing on the restriction of carbs, emphasize the correct way to do low carb diets such as plenty of raw veggies, fruits with low glycemic indexes and meat that has a healthier fat content.

  8. Amy Pruitt Amy Pruitt United States says:

    They don't tell you that these people are also suffering from lack of potassium and magnesium and salt.  Just another ploy to get people to stop doing Keto.

  9. Y A Talldog Y A Talldog United States says:

    1. Low carb diets can lead to low electrolyte levels (which every low carb person should know).
    2. Low electrolytes are associated with triggering an aFib event (which every person with aFib should know).

    It's no more complicated than that.

    Taking extra electrolytes (potassium, salt, magnesium) takes care of the risk.

    Exercising and sweating contributes to aFib too, because it depletes your electrolytes. My doctor warned me about getting getting hot and sweaty in the summer; he said I needed to supplement my electrolytes, or the low electrolyte levels could trigger an aFib event.

    Keep your electrolyte levels up. That's all you need to worry about.

  10. George Henderson George Henderson New Zealand says:

    No clinician who gives low-carb diet advice would recommend amounts of carbohydrate anything like these. So why isn't there a low carb clinician or researcher providing their perspective in this article?

  11. Lori Rainery Lori Rainery United States says:

    Fake. I have two holes in my heart and funny while eating carbs /sugars I would go into atachacardia more than once a month (freaky and terrifying). I've been strict keto for 9 months, down 50lbs, no joint pain, and no episodes of fluttering!! Don't believe this crazy!

  12. Mark Williams Mark Williams United States says:

    A low carb diet got me off of all diabetes medication.

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