Soda is not good for you. A single 12-ounce can of regular soda contains about 42 grams of added sugar, which is more than the entire daily limit of 25 grams recommended by the World Health Organization for adults. Whether regular or diet, soda offers zero nutritional benefit and carries a surprisingly long list of health consequences that go well beyond the sugar itself.
What Happens When You Drink Liquid Sugar
Your body processes liquid calories very differently from solid food. When you eat an apple, the chewing, the fiber, and the time it takes to finish all send signals to your brain that energy is coming in. Your body adjusts by dialing down hunger. Liquids skip most of that process. You can drink a soda at a rate of over 200 grams per minute, giving your mouth and throat almost no time to register what just passed through. The result: your brain never gets the memo that you just consumed 140 or more calories.
This has been tested directly. In a four-week crossover study, participants consumed the same number of carbohydrate calories in either solid or liquid form. When they ate the solid version, they naturally ate less food for the rest of the day to compensate. When they drank the liquid version, they didn’t reduce their intake at all. The calories from the drink simply stacked on top of everything else they ate. This is one reason soda consumption is so strongly linked to weight gain: the calories enter your body, as researchers have put it, essentially “undetected.”
How Sugar From Soda Affects Your Liver
Most sodas are sweetened with high-fructose corn syrup or sucrose, both of which deliver a large dose of fructose. Unlike glucose, which your cells throughout the body can use for energy, fructose gets processed almost entirely in the liver. And the liver handles fructose with no built-in braking system. There’s no immediate feedback mechanism to slow absorption or processing, so fructose keeps getting converted into fat-building blocks at a rapid, unrestricted pace.
Over time, this drives fat accumulation directly inside liver cells. Fructose also blocks the normal process of burning existing fat for fuel, so the fat that builds up has fewer ways to leave. This combination of increased fat production and decreased fat burning is a primary driver of non-alcoholic fatty liver disease, a condition that now affects roughly one in four adults globally. Fructose also triggers inflammation in the liver, which can push simple fat accumulation toward more serious scarring and damage.
Heart Disease Risk Goes Up With Every Serving
Research from Harvard’s T.H. Chan School of Public Health found that adding just one sugary drink per day was associated with an 18% increased risk of cardiovascular disease, regardless of how much a person exercised. That last part matters: you can’t outrun a soda habit. People who consumed two or more sugar-sweetened beverages daily but still met the recommended 150 minutes of weekly exercise had a 21% higher risk of developing cardiovascular disease compared to people who rarely drank them. Physical activity helps your heart in many ways, but it doesn’t neutralize the metabolic damage from regular soda consumption.
Soda Is Highly Acidic, and Your Teeth Pay the Price
Tooth enamel begins to dissolve at a pH of about 5.5. Most popular sodas are far more acidic than that. Coca-Cola has a pH of 2.48. Pepsi sits at 2.46. Mountain Dew comes in at 3.14, and even relatively mild options like Sprite measure 3.27. For context, water is neutral at 7.0. Every sip of soda bathes your teeth in acid strong enough to actively dissolve enamel.
Diet sodas aren’t much better on this front. Diet Coke has a pH of 3.22, and Diet Pepsi measures 2.94. The sugar in regular soda adds a second layer of damage by feeding bacteria that produce their own acid, but even without sugar, the acidity alone is enough to erode enamel over time. A&W root beer, at 4.80, is one of the least acidic options but still falls below the safety threshold.
Phosphoric Acid and Your Bones
Dark-colored sodas like cola contain phosphoric acid, which gives them their sharp, tangy bite. High phosphorus intake directly interferes with calcium metabolism in a dose-dependent way, meaning the more you consume, the worse the effect. Research published in the British Journal of Nutrition found that high phosphorus doses increased parathyroid hormone levels, decreased markers of bone formation, and simultaneously increased markers of bone resorption. In plain terms, your body builds less new bone and breaks down more existing bone.
This is especially concerning for younger women and postmenopausal women. Studies have found that cola consumption predicts a higher risk of fractures in girls, and in postmenopausal women, it can lead to elevated parathyroid hormone levels and lower blood calcium. Over the long term, regularly consuming high amounts of phosphorus with inadequate calcium intake could meaningfully lower bone mineral density.
Diet Soda Isn’t a Clean Alternative
Switching to diet soda eliminates the sugar and the calories, but it introduces a different set of concerns. Artificial sweeteners activate the same sweet taste receptors in your mouth and gut that sugar does. When those receptors fire, they can signal the pancreas to prepare for incoming carbohydrates, triggering a small insulin release even though no sugar ever arrives. This is called a cephalic phase insulin response, and while it doesn’t raise blood sugar, some research suggests it may slightly increase insulin levels in certain people.
The bigger concern is what artificial sweeteners do to the gut. A 2022 study published in Cell found that both sucralose and saccharin impaired glycemic responses in healthy volunteers who had not previously consumed artificial sweeteners. The researchers went a step further: they transplanted gut bacteria from the human participants into germ-free mice, and the mice developed glucose intolerance that mirrored what had happened in their human donors. This demonstrated a causal link between sweetener-altered gut bacteria and impaired blood sugar control. The effects were also highly individualized, meaning some people’s microbiomes were more disrupted than others.
As for cancer risk, the WHO’s International Agency for Research on Cancer classified aspartame as “possibly carcinogenic to humans” in 2023, placing it in Group 2B. That sounds alarming, but the same category includes things like aloe vera and pickled vegetables. The WHO’s food safety committee found no sufficient reason to change the acceptable daily intake of aspartame, which for a 150-pound person would mean drinking roughly 12 to 14 cans of diet soda per day to exceed the limit. The evidence is limited, not conclusive.
What About Caramel Coloring?
The brown color in colas comes from caramel coloring, which can contain a compound called 4-MEI. A two-year study by the National Toxicology Program found increased lung tumors in mice exposed to 4-MEI, but at doses far exceeding what any human would get from drinking soda. The FDA currently states it has no reason to believe there are immediate or short-term health risks from 4-MEI at the levels found in food, and is not recommending dietary changes based on current evidence. This is one of the lower-priority concerns on the list, but it’s worth noting that the brown color in your cola serves no purpose other than appearance.
The Bottom Line on Soda
Regular soda delivers a large dose of sugar in a form your body is poorly equipped to regulate, contributing to weight gain, fatty liver disease, cardiovascular risk, tooth erosion, and weakened bones. Diet soda avoids the sugar but may alter your gut bacteria and interfere with blood sugar regulation in ways researchers are still mapping out. Neither version provides anything your body needs. Water, unsweetened tea, or sparkling water with a squeeze of citrus will give you the hydration without any of the trade-offs.