Why Sugary Drinks May Be the Unhealthiest Food Out There

6 min read

June 11, 2024 – You know that sugary drinks are bad for you, so you limit them – just a couple of sodas a week. Plus, you exercise regularly, so you’re fine, right? 

Maybe not. Sugar-sweetened beverages – the kind with added sugars, like soda, lemonade, fruit punch, and sports drinks – can harm your health, even in moderation, said Lorena Pacheco, PhD, a registered dietitian and nutrition research scientist at Harvard’s T.H. Chan School of Public Health.

“Being a dietitian myself, I agree with the fact that we should strive for moderation,” said Pacheco – but not when it comes to sugar-sweetened drinks. “These beverages are liquid candy and are noxious to one’s health.” They should be avoided, not moderated, she said. 

In an eye-opening 2024 study of more than 100,000 people, Pacheco found that those who exercised regularly and consumed just two sugary beverages per week had a 15% higher risk of heart disease than active folks who abstained from sugary drinks. Participants who drank two sugary drinks per week and did not exercise were at even greater risk: nearly 50% more likely to develop heart disease. 

“Marketing campaigns highlight that sugar-sweetened beverages will not have a negative effect on people’s health [as long as you exercise],” Pacheco said. “Based on our findings, this is not true. For this reason, it is best to reduce one’s intake of sugar-sweetened beverages as much as possible and replace these beverages with water.”

Why Is Liquid Sugar So Bad for You?

It’s no secret that getting too much added sugar – in any form – can lead to poor health, but accumulating evidence suggests that liquid sugar is particularly problematic. 

For one thing, sugar-sweetened drinks tend to lack other nutrients – like fiber, protein, and fats – that slow the digestion of sugar and delay its absorption into the blood, said nutrition scientist Jonathan Clinthorne, PhD, director of nutrition at the Denver-based Simply Good Foods Company. Liquids also have a shorter gastric emptying time than solid foods – they move out of the stomach into the small intestine much faster. That forces your body to metabolize large amounts of sugar all at once, quickly raising blood sugar and overloading the vital organs. 

“The extreme doses of sugar found in sugar-sweetened beverages seem to overwhelm much of the body’s carbohydrate metabolism mechanisms,” Clinthorne said. “This results in a lot of negative downstream impacts.”

Most of the sugar from these beverages is processed in the small intestine and “enters the portal vein, which takes the sugar to the liver,” Clinthorne said. 

Two types of sugar commonly found in sugar-sweetened drinks are sucrose and high-fructose corn syrup. Both contain glucose and fructose. While your liver absorbs the fructose, the glucose is transported directly to the bloodstream, spiking blood sugar levels and wreaking havoc along the way. “If sugar is not removed quickly from the bloodstream, it can react with proteins, creating advanced glycation end products, which are inflammatory,” Clinthorne said. These harmful compounds have been linked to heart disease. 

As blood sugar levels rise, the pancreas also makes insulin, a hormone that moves sugar out of the blood and into your body’s cells to be stored or used for energy. Over time, cells may stop responding to insulin, becoming insulin resistant. The pancreas responds by churning out even more insulin, but eventually it can’t keep up and blood sugar rises to dangerous levels. 

“High glucose levels and high insulin levels lead to blood vessel damage, diabetes, and its complications,” said Jeff Stanley, MD, an internal medicine doctor and medical director at Virta Health, a telehealth company that specializes in type 2 diabetes reversal. “Insulin resistance is a huge risk factor for cardiovascular disease.” People can be insulin resistant long before they develop symptoms, he added. 

And what about all that fructose accumulating in your liver? That can cause damage as well. 

Natural foods like fruit also contain fructose, but there’s a difference, Clinthorne said. The amount of fructose in a piece of fruit is relatively small and easily metabolized – plus, the fruit’s fiber slows down fructose absorption. 

Sugar-sweetened drinks tend to have a large amount of fructose. “While there may be a few grams of fructose in a banana, there might be 10 times that much in a sugary drink,” Clinthorne said. The liver converts excess fructose into fat, which over time can lead to the development of metabolic dysfunction-associated steatotic liver disease (a condition formerly known as non-alcoholic fatty liver disease). 

Indeed: Research has linked excessive consumption of fructose to oxidative stress, inflammation, high blood pressure, insulin resistance, and high triglycerides – all factors associated with heart disease. 

Research also suggests that your brain does not register liquid calories as it does calories from solid food. In studies, people who eat sugar in solid form (like candy) tend to compensate by eating fewer calories from other sources. By contrast, people who drink liquid sugar (soda) end up increasing their total calorie intake, leading to weight gain. 

As if all that wasn’t enough, sugar-sweetened drinks may also have detrimental effects on your gut microbiome, Clinthorne said. Different sugars are absorbed and transported through different pathways in the intestines. 

“The pathway that absorbs fructose isn’t believed to be one of the most rapidly transported,” Clinthorne said. “This means the gut’s ability to absorb fructose can be overwhelmed, resulting in excess fructose making its way to the colon where it can feed microbes, resulting in bacterial overgrowth.” 

In animal studies, this bacterial imbalance has led to inflammation and intestinal permeability, or leaky gut, he said, though more research is needed to confirm the effect in humans.

The Problem With Moderation

Though cutting out sugary beverages completely may seem extreme, for some it’s actually easier than practicing moderation, Stanley said. 

For some patients, “moderation is difficult because you’re triggering cravings,” Stanley said. 

Of course, that’s not the case for everyone, Stanley warns. “We see some patients where if something is forbidden, it becomes really difficult for them to not feel deprived.” 

He recommended at least trying to give them up. “It might be difficult initially, but once you’re past that point of craving them” – which typically takes a few days, he said – “and can find good alternatives, that can actually be easier than just sticking with one or two sodas per week.” 

Finding an enjoyable alternative is key, Stanley said. “Water is best,” Stanley said, but unsweetened coffee or tea (iced or hot) can help add variety. Carolyn Newberry, MD, a gastroenterologist at Weill Cornell Medicine, suggested adding skim milk to coffee or tea. For soda drinkers, sparkling water may slake carbonation cravings, and you can add flavor with a splash of fruit juice or fresh citrus. (Try this recipe for sparkling iced tea with lemon, cucumber, and mint from the Harvard School of Public Health website.)

You can also try adding sugar-free flavorings to still or sparkling water, Stanley said. “We recommend xylitol, sucralose, stevia, monk fruit, and allulose. These have been studied extensively and appear to be safe in moderation,” he said. 

Artificial sweeteners can be controversial, as research on their health effects is mixed. But for those who drink sugary drinks regularly, sugar-free or diet options “seem to be quite a bit healthier,” Stanley said. “So for people who really miss the flavor or want something similar, that can be an option.”

Be warned that diet soda may trigger cravings, said Newberry. “There is some literature that diet sodas can induce increased hunger due to delivery of taste without associated calories,” Newberry explained. 

And if you just can’t stay away from sugary drinks? Try to limit them as much as you can. Remember: Even though just two drinks a week raised the risk of heart disease in the study, that amount is still better than drinking more. 

“The damage [sugary drinks] inflict on someone's health is going to be based on the amount that they consume and their other personal risk factors,” said Newberry. “The best approach is both realistic and able to be adhered to.”