If you’re thinking of riding the low-carb wave as a fast-track to wellness and a slim physique, you might want to think again, as a study suggests that eating a diet that skimps on the carbs could be linked to atrial fibrillation ( AFib) – a common heart-rhythm disorder. The study, which is set to be presented at the American College of Cardiology’s 68th Annual Scientific Session at the end of this week, adds to the controversy surrounding those diets and their potential effects on heart health.
What is AFib?
AFib is a condition that affects the rhythm of the heart and causes it to not beat the way it should or keep a proper pace. This can cause problems like palpitations, exhaustion and dizziness. In the long term, having AFib increases your risk of life-threatening conditions like heart failure and stroke.
Researchers analysed over 20 years worth of health records of nearly 14,000 people to study the link between carb intake and AFib. This study is considered to be the first and largest of its kind.
To get information on the participants’ diets, the researchers asked them to fill out a questionnaire that tracked their daily consumption of 66 different foods. With the help of the Harvard Nutrition Database, the answers were used to estimate the daily carb consumption of each participant as well as the percentage of their daily calories that come from carbs. On average, half the participants’ calories come from carbs. This falls within the range recommended by the Dietary Guidelines for Americans that recommends we get 45 to 65 per cent of our daily calories from carbs.
After this, the participants were split into three groups. Those who got less than 44.8 per cent of their daily calories from carbs were assigned to the low intake group. Those who got 44.8 to 52.4 per cent of their daily calories from carbs were assigned to the moderate intake group, and those who got more than that were put in the high intake group.
The participants in the low intake group were the most likely to develop AFib. They were found to be18 and 16 per cent more likely than the moderate and high intake groups respectively to develop the condition. These results support past study findings that linked both low and high carbohydrate consumption to a higher risk of death. Those past studies seemed to suggest that the non-carbohydrate parts of people’s diets affected the results, but this study doesn’t.
From the original 14,000 or so people who did not have AFib at the beginning of the study, 1,900 were diagnosed with the condition after being followed-up for an average of 22 years.
The study’s lead author, Xiaodong Zhuang, MD, PhD, a cardiologist at the hospital affiliated with Sun Yat-Sen University in Guangzhou, China, said that there could be several biological explanations for why low-carb diets increase the risk of AFib. One explanation, he says, could be that people who eat low-carb diets are less likely to eat fruits, vegetables and grains. These foods are known to reduce inflammation in the body, and inflammation increases the risk of AFib. Another explanation he offers is that replacing carbs with fats and proteins could cause oxidative stress in the body and this increases the risk of AFib and other cardiovascular diseases.
But, Dr Zhuang emphasises that this study doesn’t prove that low-carb diets cause AFib and that it simply shows a link that needs to be studied more.
He also adds that the study has limitations. Examples of these include the limited ethnic diversity of the participants and the fact that it didn’t account for participants who might have had asymptomatic AFib or had the condition in the past but had never gone to the hospital for it (so this information never made it to their health records). He also says that the study didn’t investigate different subtypes of AFib, so it wasn’t known whether the people who developed it were more at risk for continuous AFib or occasional bouts of arrhythmia instead. Another limitation, he adds, is that the study didn’t include information on whether the participants’ diets changed after filling out the questionnaire.
But as more studies come out in favour of dietary moderation, perhaps it is finally time to put restrictive approaches to bed. As the saying goes, a bit of what we fancy does us good!
Written by: Tesneem Ayoub
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