American refrigerators are often full of sugary drinks. According to the Centers for Disease Control and Prevention (CDC), more than 60% of American adults drink one or more sugar-sweetened beverages a day.
Despite their sweet taste, sugary drinks pose significant health risks. Researchers have already linked the beverages to obesity, diabetes, and heart disease. Now, Mass General Brigham researchers have uncovered a potential new link to another serious condition: liver disease, the ninth leading cause of death in the United States.
Longgang Zhao, PhD, and Xuehong Zhang, MBBS, ScD, of Brigham and Women’s Hospital, found that postmenopausal women who drank one or more sugar-sweetened beverages per day had a higher risk of developing liver cancer and dying from chronic liver diseases than those who drank three or less sugar-sweetened beverages per month.
Drs. Zhang and Zhao made their findings from the Women’s Health Initiative study of nearly 100,000 postmenopausal women between the ages of 50 and 79. Post-menopause begins once a woman reaches menopause, 12 months after their last menstrual period. Their research is rare; few studies have ever examined associations of sugary drinks with liver cancer and liver disease.
“We can’t say sugary drinks cause liver disease,” says Dr. Zhao. “But if a causal link is established, the implications on global public health would be substantial.”
So how do sugary drinks affect the liver? Drs. Zhao and Zhang explain their ongoing research and how the liver functions.
Sugar-sweetened beverages are drinks flavored with added sugars. These sugary drinks include:
While ingredient labels can simply list “sugar,” people might not recognize the names of other sugars added to their beverage. Added sugars can appear listed as:
People need sugar to fuel cells throughout the body. Cells use this “fuel” to power specific functions.
“The cells in our hearts, brain, muscles — everywhere, really — need sugars to keep us breathing, thinking, and moving,” explains Dr. Zhao. “It’s the body’s version of gas powering a car.”
Unlike plants, which generate sugar from light and carbon dioxide, humans cannot produce sugar on their own. They must extract sugar from carbohydrates, or carbs, in the foods and beverages they eat and drink.
The digestive system breaks carbs into a special sugar called glucose. When glucose enters the bloodstream, a chemical produced by the pancreas called insulin helps deliver the sugar to cells.
Consuming too much sugar can lead to:
In its Dietary Guidelines for Americans, the U.S. Departments of Agriculture (USDA) and Health and Human Services (HHS) recommend limiting added sugar to less than 10% of daily calorie intake. A 2,000-calorie diet, for example, would consist of 200 calories, or 50 grams, of added sugar a day.
Since a typical 12-ounce can of soda contains about 39 grams of sugar, one and a half cans would far exceed the daily recommended amount.
“It’s essential to take precautions when selecting sugary drinks to prevent excessive sugar intakes,” says Dr. Zhao. “Check product labels for hidden sugars and opt for healthier alternatives like tea or water.”
Patients with existing liver conditions should seek dietary guidance from their health care provider.
The liver regulates sugar entering the bloodstream. It stores excess sugar by turning it into a substance called glycogen. When sugar levels fall too low, the liver releases its excess. The liver also cleans toxic substances, such as alcohol, and creates sugar from food sources other than carbs.
According to the American Cancer Society, liver cancer cases have tripled over the past 3 decades in America. Tens of thousands of people receive a liver disease diagnosis each year. The role sugar-sweetened beverages play in these conditions remains a mystery.
Dr. Zhao explains several leading explanations:
Drinking too many sugar-sweetened beverages can increase the likelihood of obesity, a strong risk factor for liver cancer and liver disease.
Sugar-sweetened beverages are a major source of fructose, an added sugar commonly found in fruits and fruit-flavored drinks. The liver rapidly stores fructose, but in an unusual way. Instead of storing fructose as glycogen, the liver tends to store excess fructose as fat.
Fatty liver disease is one of the most common chronic liver diseases. It can lead to liver cancer, as well as:
The body processes sugar from drinks much quicker than it does from foods. Frequent spikes in blood sugar from sugar-sweetened beverages can lead to liver problems.
Recently discovered chemicals in sugar-sweetened drinks might also play a role. Chemicals found in these drinks that can harm the body include: