When timed correctly, carbohydrates can become powerful muscle-building fat-burning weapons for athletes. But carbs can have a dark side—and not just for your gut.
Downing too many simple carbs in one go can have a serious and detrimental effect on your heart, according to research from Vanderbilt University Medical Center.
In the study, published in the Journal of the American College of Cardiology, researchers recruited 33 men and women. Before testing began, participants were placed on a standard diet for a couple of days to remove any dietary variability. After, researchers analyzed them after they ingested a 294-calorie glucose drink consisting of 75.9g carbs (all from sugar), .01g fat, and 2.1g protein. Sure, that sounds like an insane amount of sugar, but this 20 oz smoothie has 98 grams of sugar and this one has 105 grams! So, it's totally possible to down that much sugar in one sitting all while thinking you're drinking something healthy.
Subjects’ blood levels were monitored for six hours. Specifically, researchers were looking for a change in the heart's production of atrial natriuretic peptide (ANP)—a hormone that eliminates excess salt and reduces blood pressure in the body. The high-carb shake led to a 25 percent drop in ANP in participants in just a few short hours.
Here's why that matters: Researchers already know from past research that obese people make less ANP, predisposing them to salt retention and high blood pressure; so, if a high dietary carb load lowers circulating ANP levels even further, these consequences could be dangerous for your heart health. Lead study author Thomas Wang, M.D., told us that while they zeroed in on obese individuals, they also studied a group of lean people and found the same relative decrease in ANP after carb-loading.
The researchers also looked into why and how ANP levels decreased. The principal driver for the drop in ANP seems to be the increase in blood sugar thanks to those simple carbs, the researchers say.
That doesn't mean you should cut all carbs, though. The researchers only studied simple carbs. "Because the rise in blood sugar occurs much more rapidly with simple carbohydrates, it's possible the more gradual rise in blood sugar seen with complex carbohydrates might reduce the negative effects [a.k.a. the drop in ANP], but this hasn't been tested yet," Wang told us.