Study finds link between ‘free sugar’ intake and cardiovascular disease

By Kristen Rogers, CNN

Eating a lot of free sugars — also known as added sugars — might feel harmless in the moment, but it could increase your risk for getting cardiovascular disease, a new study has found.

Free sugars are those added during the processing of foods; packaged as table sugar and other sweeteners; and naturally occurring in syrups, honey, fruit juice, vegetable juice, purees, pastes and similar products in which the cellular structure of the food has been broken down, according to the United States Food and Drug Administration. They don’t include sugars naturally occurring in dairy or structurally whole fruits and vegetables.

Previous studies have reported that links between carbohydrate consumption and cardiovascular disease might depend on the quality, rather than the quantity, of carbohydrates consumed, according to the new study published Monday in the journal BMC Medicine. To test that theory, the authors behind the latest research assessed diet and health data from more than 110,000 people who participated in UK Biobank, a cohort study that collected data between 2006 and 2010 from more than 503,000 adults based in the United Kingdom.

People included in the new study participated in two to five 24-hour online dietary assessments, logging their food and beverage intake multiple times within each 24-hour period. After over nine years of follow-up, the researchers found total carbohydrate intake wasn’t associated with cardiovascular disease. But when they analyzed how outcomes differed depending on the types and sources of carbohydrates eaten, they found higher free sugar intake was associated with a higher risk for cardiovascular disease and greater waist circumference.

The more free sugars some participants consumed, the greater their risk of cardiovascular disease, heart disease and stroke was. All heart diseases are cardiovascular disease, but cardiovascular disease is the term for all types of diseases that affect the heart or blood vessels, such as stroke, congenital heart defects and peripheral artery disease, according to the US National Heart, Lung and Blood Institute (PDF).

Higher intake of free sugars was also linked with higher concentrations of triglycerides — a type of fat that comes from butter, oils and other fats people eat, plus extra calories their bodies don’t immediately need. Having high triglyceride levels — defined as more than 150 milligrams per deciliter — can increase risk for heart diseases such as coronary artery disease.

“This study provides much needed nuance to public health discussions about the health effects of dietary carbohydrates,” said Dr. Maya Adam, director of Health Media Innovation and clinical assistant professor of pediatrics at Stanford University School of Medicine, via email. Adam wasn’t involved in the study. “The main takeaways are that all carbs are not created equal.”

Free sugars vs. sugar in whole foods

The link between higher free sugar intake and cardiovascular disease risk lies in the differences between how the body metabolizes free sugar versus sugar in whole foods.

“Added sugar intake can promote inflammation in the body, and this can cause stress on the heart and blood vessels, which can lead to increased blood pressure,” said Brooke Aggarwal, assistant professor of medical sciences in the cardiology division at Columbia University Irving Medical Center. Aggarwal wasn’t involved in the study.

“Added sugars are often found in processed foods which have little nutritional value and may lead to overeating and excess calorie intake, which in turn leads to overweight/obesity, a well-established risk factor for heart disease,” Aggarwal said via email.

Based on their findings, the authors suggest replacing free sugars with non-free sugars naturally occurring in whole fruits and vegetables to lower your risk of developing cardiovascular disease — and experts in nutrition and cardiovascular health agree.

“Whole food carbohydrates take longer to break down into simple sugars, and a part of them — the fiber — can’t be broken down at all,” Adam added. “This means that whole, intact grains don’t cause the same spikes in blood sugar that we experience when we eat simple sugars. Blood sugar spikes trigger insulin spikes, which can destabilize our blood glucose and … be the underlying cause of health problems in the long run.”

Additionally, the fiber in whole food carbohydrates acts as an “internal scrub brush” when it passes through the digestive system, Adam added. “That’s why, generally speaking, we need a certain amount of these ‘good carbs’ in our diets to stay healthy.”

Total fiber intake should be at least 25 grams daily, according to the FDA.

Reducing free sugar intake

Awareness is the first step toward reducing your intake of free sugars, so look at nutrition labels when shopping, said CNN Medical Analyst Dr. Leana Wen, an emergency physician and public health professor at George Washington University. Wen wasn’t involved in the study.

“Many times, people think about cutting calories or not consuming fatty foods, but they may not be aware of the dangers of free sugars,” Wen said.

“When we buy packaged foods — even the ones we don’t think of as being sweet like bread, breakfast cereals, flavored yoghurts or condiments — these foods usually have plenty of added sugar, and it adds up,” Adam said.

Cut back on sugary drinks and go for water sweetened with fruit slices instead, Aggarwal suggested. Have fresh or frozen fruit for dessert instead of cakes, cookies or ice cream. Foods with higher fiber content can also help you stay fuller longer, she added.

Cooking and baking at home more often is one of the best ways to reduce sugar in your diet, Adam said.

“The American Heart Association recommends that added sugars make up less than 6% of calories per day, which works out to about 6 teaspoons of sugar per day for women, and 9 teaspoons per day for men,” Aggarwal said.

Lastly, efforts to change your diet shouldn’t only happen in the kitchen or grocery store. “Aim to get at least seven to eight hours of good quality sleep per night, as we tend to choose foods higher in sugar when we’re tired,” Aggarwal said.

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