Phosphoric acid is not good for you in the amounts most people encounter it, though it’s not acutely dangerous either. It’s a food additive (E338) used almost exclusively to give cola beverages their sharp, tangy bite, and a single can of cola contains roughly 50 to 60 milligrams of it. In small, occasional doses, your body handles it fine. The problems start when intake becomes routine, because phosphoric acid affects your bones, kidneys, and teeth in ways that other common food acids do not.
What Phosphoric Acid Actually Does in Food
Phosphoric acid is the only inorganic acid widely used in food production, and it’s the cheapest acid available to manufacturers. Its primary job is acidifying cola and root beer to a pH around 2.5, which establishes proper carbonation and creates that characteristic “cola bite” no other acid quite replicates. Beyond sodas, its salts show up in processed cheese (to adjust pH), baked goods (as a leavening agent that helps dough rise), and cured meats like ham and corned beef (to help retain moisture). In jams and jellies, it acts as a buffering agent that strengthens the gel and prevents color from dulling.
It also has a small role in medicine. Combined with sugars, phosphoric acid is the active ingredient in over-the-counter anti-nausea products like Emetrol. Dentists use it as an etching solution to roughen tooth surfaces before placing fillings or brackets. These are controlled, targeted applications, very different from drinking it daily in soda.
How Your Body Absorbs It
This is where phosphoric acid diverges sharply from the phosphorus found naturally in meat, dairy, and grains. Natural (organic) phosphorus is bound to proteins and other molecules, requiring enzymatic digestion before your body can use it. That process is slow and incomplete, with absorption rates of 40% to 60%. Phosphoric acid, on the other hand, is an inorganic phosphate salt. It dissociates rapidly in stomach acid without needing any enzymatic help, and your body absorbs 80% to 100% of it.
That near-complete absorption means the phosphorus from a few cans of cola hits your bloodstream faster and more efficiently than the same amount of phosphorus from a chicken breast. Your body didn’t evolve to handle large, rapid spikes of inorganic phosphorus, and the downstream effects show up in several organ systems.
The Link to Weaker Bones
The most studied concern is bone health. The Framingham Osteoporosis Study, one of the largest long-running investigations into bone density, found that women who drank cola daily had 3.7% lower bone mineral density at the femoral neck (the most fracture-prone part of the hip) and 5.4% lower density at a nearby measurement site called Ward’s area, compared to women who drank less than one cola per month. Diet cola and decaffeinated cola showed similar patterns. Noncola carbonated beverages showed no significant effect on bone density at all.
The mechanism involves your body’s acid-buffering system. When blood becomes even slightly more acidic, bone mineral dissolves to neutralize the extra acid, releasing calcium and phosphate into the bloodstream. In the short term, this is a normal safety valve. Over months and years of regular cola consumption, it chips away at bone quality. Chronic low-grade acidosis also suppresses the cells that build new bone while activating the cells that break it down, and it increases how much calcium you lose through urine without a matching increase in calcium absorption from food.
Elevated blood phosphorus also suppresses the activation of vitamin D, the hormone your body needs to absorb calcium from your gut. Higher phosphate levels stimulate parathyroid hormone release, which further pulls calcium from bone to maintain blood levels. It’s a cascading effect: more phosphoric acid in, less calcium staying where it belongs.
Kidney Stone and Kidney Disease Risk
Cola beverages acidified with phosphoric acid have been linked to urinary changes that promote kidney stone formation. In a randomized trial among men who already had kidney stones, those who continued drinking phosphoric acid-containing soft drinks had higher stone recurrence than those who switched to beverages acidified with citric acid. Cola consumption specifically shifts urine composition in ways that favor calcium oxalate stones, the most common type.
The concern extends beyond stones. Case reports have linked high phosphate loads to calcium phosphate deposits in the kidney’s filtering tubes, a condition called nephrocalcinosis. While those cases involved concentrated medical preparations rather than soda, they illustrate what phosphorus overload can do to kidney tissue. For people with existing kidney disease, the risk is amplified because damaged kidneys are less able to excrete excess phosphorus.
Effects on Tooth Enamel
Any acid with a pH below about 5.5 can dissolve tooth enamel, and cola sits around 2.5. Interestingly, lab studies comparing phosphoric acid to citric acid (used in clear sodas and citrus drinks) found that citric acid causes significantly more enamel erosion across the same pH range. Phosphoric acid caused minimal erosion above pH 3 for enamel and above pH 4 for the softer tissue underneath. That said, “less erosive than citric acid” is not the same as safe. Regular contact with any strong acid wears down teeth over time, and sipping cola throughout the day keeps enamel bathed in acid for hours.
How Much Is Too Much
The European Food Safety Authority set the first group acceptable daily intake for phosphates at 40 milligrams per kilogram of body weight per day. For an average 70-kilogram (154-pound) adult, that works out to 2.8 grams of phosphorus daily from all sources combined, including food, drinks, and additives. A single can of cola contributes a modest amount on its own, but phosphoric acid and its salts are also in processed cheese, deli meats, flavored waters (some containing up to 85 mg of phosphorus per bottle), and baked goods. The total from a typical processed-food diet adds up quickly, especially given the near-complete absorption rate of inorganic phosphates.
People who drink several colas a day while also eating processed foods can easily approach or exceed that threshold without realizing it, since phosphorus content isn’t always listed on nutrition labels.
Cola vs. Other Carbonated Drinks
The clearest takeaway from the research is that cola is the problem, not carbonation itself. Noncola carbonated beverages, which use citric acid instead of phosphoric acid, showed no association with reduced bone density in the Framingham study and were linked to lower kidney stone recurrence in trials. Sparkling water with no added acid or sweetener carries none of these risks. If you enjoy fizzy drinks, choosing non-cola options sidesteps the specific harms tied to phosphoric acid while still giving you the carbonation.
Phosphoric acid in occasional, small amounts is something your body can handle without measurable harm. The issue is cumulative, daily exposure compounded by the fact that modern processed food already loads the diet with inorganic phosphates from dozens of other sources. For most people, the less phosphoric acid in your routine, the better off your bones, kidneys, and teeth will be over the long run.