Moderate carb intake may lower cardiovascular risk

But there is a controversy behind this multi-billion-dollar wellness phenomenon: The research is divided regarding carbohydrate-restricted diets.

While high-carb diets are known to increase the risk of clogged arteries, heart disease and stroke, the benefits of low-carb diets are not as clear cut. Some studies have found that low-carb diets can improve these health markers, while others have found no such benefits or even that they increase heart disease risk.

Now, a study led by researchers with the Texas A&M University School of Public Health at Texas A&M Health adds a piece to the puzzle of why a diet that works for one person’s metabolism might send another person’s cholesterol levels skyrocketing.

The team’s analysis of studies involving nearly 11,500 adults in 27 countries found that moderate carb intake may offer the best long-term health outcomes.

“Cutting carbs can be a powerful tool for losing weight, lowering blood pressure and reducing triglycerides, but it requires monitoring lipid profiles,” said doctoral student Shuo Feng, the study’s first author. “Ketogenic and low-carb diets showed the biggest improvements in a few specific health markers, but moderate-carb diets improved a wider variety of health markers overall.”

Both the very low-carb, high-fat keto diet and low-carb diets were associated with increases in LDL — the “bad” cholesterol — but whether this affects heart health is unknown. More importantly, lipid rates, which are considered more reliable indicators of heart health than LDL cholesterol alone, showed similar improvements in all three diets.

For their meta-analysis, published in The American Journal of Clinical Nutrition, the team reviewed 174 high-quality journal articles involving 11,481 adults across 27 countries.

They compared the results of adults who ate low-carb diets (where carbohydrates made up 45 percent or less of daily calories) and higher-carb diets and used statistical software to measure changes in participants’ cholesterol, blood pressure and other cardiovascular markers, as well as changes in weight, body fat and waist size.

They also broke down the data into smaller categories to see if results changed based on certain details, including carbohydrate levels, foods consumed to replace carbohydrates, participant traits, how each study was done and results of diets over time.

Other findings included the following:

• Best results: The benefits were most notable in women and individuals who were overweight or obese.
• Time factor: Following the diet for at least six months had stronger positive effects on triglyceride ratios and inflammation.
• Best combination: Replacing carbohydrates with a mix of healthy fats and proteins provided the most comprehensive health improvements.

Feng noted that the study had several limitations. Most of the studies were from North America and Europe, so the results might not apply elsewhere. In addition, the quality of the food was not assessed and some analysis groups had too few studies to be statistically reliable.

Still, he believes this new knowledge sheds important light on a global health priority.

“In an era when cardiovascular diseases are the leading cause of death worldwide — accounting for nearly one out of every three deaths — narrowing the gap in our understanding of how low-carb diets work could save lives,” he said.

Others from Texas A&M involved in the research were Brian Colwell, Sunghyun Chung, Adam Barry and Huishan Wang with the Department of Health Behavior, Christopher Thompson with the Department of Educational Psychology and a colleague with Baylor University.