Citric acid is the small organic acid that makes lemons and limes sour. Lemon fruit cells keep it in compartments called vacuoles, with a pH of about 2.5. That is three pH units more acidic than a typical plant vacuole, according to a 1996 study. Sweet, “acidless” citrus varieties have two of the genes for acid pumps switched down.
In a lab analysis of squeezed juice, lemons held 48.0 g of citric acid per liter and limes 45.8, against 9.10 for squeezed oranges.
You make and burn citrate yourself, too. It is the acid that gives the cell’s main energy cycle its name. Hans Krebs proposed the “citric acid cycle” in 1937 and shared the 1953 Nobel Prize in Physiology or Medicine for it. In his Nobel lecture, he judged that about two-thirds of the energy from food in higher organisms is set free along this common pathway.
Most of the citric acid sold for food today is made by feeding sugar to the black mold Aspergillus niger. It is the food additive E 330. Online you will read that this “manufactured” citric acid causes inflammation. That idea rests on four case reports from 2018, which this page weighs below, next to the stronger evidence on kidney stones, teeth and minerals.
Health benefits of citric acid
None of the studies below reaches strong evidence. The best-supported finding is about kidney stones, and it concerns a prescription form: potassium citrate and other citrate salts cut new stones in trials. Lemon juice and lemonade are a weaker story. The largest lemon juice trial missed its main goal, and one crossover trial found lemonade did not raise urinary citrate.
We found no trial that tested citric acid from food as a treatment for any other condition. The cards on minerals and teeth ask whether citrate helps or harms in other ways, and the results are mixed. Here is what 28 studies found, strongest evidence first, including the trials that found nothing.
Potassium citrate, a prescription drug, cut kidney stone recurrence by 79%
This umbrella review pulled together 9 systematic reviews covering 88 randomized trials and 27,286 people, across non-surgical stone treatments. Potassium citrate, a drug and not a food, was rated high certainty on the GRADE scale for preventing recurrence. The abstract gives no dose. The Cochrane review below rates the reporting of the citrate trials as moderate to poor.
Citrate salts cut new stones, but side effects made more people quit
This Cochrane review pooled 7 randomized trials with 477 people, mostly with calcium oxalate stones, treated for at least 6 months. The drugs were potassium citrate, potassium-sodium citrate and potassium-magnesium citrate, not food. New stones fell to 0.26 times the risk, but dropouts because of side effects, mainly upper gut upset, were 4.45 times as likely. The authors call the reporting moderate to poor and ask for a larger trial.
Fruit juice raised urinary citrate about 167 mg a day; results varied
This meta-analysis (a study that pools earlier studies) covered 13 controlled studies of diet changes with 358 people. Six of the studies were in people without stones. Commercial fruit juice raised urinary citrate by 167.2 mg a day, but results varied widely between studies (heterogeneity 88.1%). Soft drinks, mineral water, high-fiber diets, low-animal-protein diets and a plant extract showed no clear pooled change, and the authors call for larger trials.
Calcium citrate was absorbed 20 to 27% better than calcium carbonate
This meta-analysis pooled 15 studies with 184 people comparing two calcium supplements. Absorption from citrate was 20.0% higher in the whole set, 27.2% higher on an empty stomach and 21.6% higher with meals. Later trials below found a smaller gain or no difference.
Show 24 more studies
Potassium citrate did not slow bone loss in postmenopausal women
276 healthy postmenopausal women took high-dose potassium citrate (55.5 mEq a day), low-dose (18.5 mEq) or a placebo (dummy pill) for two years. A fourth group ate 300 g more fruit and vegetables a day. Bone turnover markers did not differ, apart from one marker that was lower at 4 to 6 weeks on the high dose. Spine bone loss was 1.8% on placebo and 2.1% on treatment. The authors conclude that alkali does not explain any long-term bone benefit of fruit and vegetables.
Potassium citrate lowered one bone-breakdown marker at one month, not others
This meta-analysis pooled 5 randomized trials with 401 postmenopausal women. The marker urinary NTX fell by 4.05 nmol BCE/mmol creatinine, a borderline result. Two other bone markers, CTX and P1NP, did not change clearly at 3, 6 or 12 months. The authors say the clinical relevance is uncertain.
2026 review: alkali treatment may reduce stone recurrence, only low-certainty evidence
This systematic review covered 31 studies (26 randomized trials and 5 non-randomized) on preventing repeat kidney stones. For calcium oxalate or phosphate stones, several steps may each reduce recurrence, all rated low certainty. They are more water, a diet with normal to high calcium, low protein and low sodium, thiazides, alkali treatment and allopurinol. Lemon juice brought more minor side effects, and US government agencies (PCORI and AHRQ) funded the review.
Fresh lemon juice for 2 years did not clearly cut stone recurrence
203 people with recurrent calcium oxalate stones, all on a standard diet, took 60 mL of lemon juice twice a day or not. Stones came back in 21 of 100 on lemon juice against 32 of 103 controls (0.62 times the risk, a gap that could be chance). Adherence fell from 68% at one year to 48% at two, and gut problems were more frequent with lemon juice. In an exploratory one-year analysis, 10 people on lemon juice and 22 controls had a recurrence (hazard ratio 0.43); the trial had no funding.
A lime-based mix cut stone recurrence from 45% to 14% against placebo
In a double-blind trial, 173 people from six Thai hospitals took it after stone removal, and 151 finished. Recurrence was counted over 2 years. The product, called LPR, is a lime-based preparation holding citrate and flavonoids, so the result cannot be credited to citric acid alone. Stone risk was 0.24 times that on placebo, and urinary IL-8 (an inflammation marker) and urinary protein also fell; the abstract gives no dose.
Lemon juice raised urinary citrate 2.5-fold, potassium citrate 3.5-fold
30 people with calcium stones and low urinary citrate were split into three equal groups in a randomized trial. They took fresh lemon juice (about 85 mL a day, 60 mEq), potassium citrate (60 mEq) or diet advice only. Urine was tested at 3 months, and urinary calcium fell in the lemon juice and potassium citrate groups only. The trial was small and short, and it measured urine chemistry, not stones.
Lemonade did not improve urinary citrate or pH; potassium citrate did
This crossover trial compared lemonade therapy with potassium citrate in 21 people who form stones, using 24-hour urine tests. Urine volume was higher on lemonade than on potassium citrate. Neither treatment changed uric acid clearly. The abstract does not give the lemonade recipe or amount.
Orange juice, not lemonade, raised urinary citrate and pH
13 volunteers (9 healthy, 4 stone formers) on a fixed diet drank water, orange juice or lemonade in turn, in random order. The juices had similar citrate content, but orange juice supplied alkali and lemonade did not. Orange juice also raised urinary oxalate and the calculated supersaturation of brushite, a calcium phosphate, while calcium oxalate supersaturation fell. It was a short-term study.
Long-term lemonade raised urinary citrate 383 mg a day in 11 people
This look back compared 11 people on lemonade therapy, for a mean of 44.4 months, with 11 matched people on slow-release potassium citrate. Citrate on the drug rose by 482 mg, and 10 of the 11 had higher urinary citrate on lemonade. Stones fell from 1.00 to 0.13 per person per year, but that change could be chance. The authors call for a randomized trial.
Citrus juices raised urinary citrate, but grapefruit juice went with more stones
This systematic review covered 13 articles. Ten small studies found that all three juices, orange, grapefruit and lemon, raised urinary citrate. Three large population studies found grapefruit juice a risk factor for stones, while orange juice did not raise the risk. Only orange and grapefruit juice made urine more alkaline, both raised urinary oxalate, and the authors say more and better data are needed.
In a mouth test, citric acid sped up early enamel softening
Twelve volunteers wore enamel and root dentine slabs in the mouth. The slabs met solutions of pH 2.5 or 3.5 with 0, 25 or 100 mM citric acid. Adding citric acid raised early enamel softening 2.5 to 3 times and dentine softening at least 5 times. The lowest pH with the most citric acid did the most harm. In 20 participants, saliva took longer to recover its pH after solutions with more citric acid. These were simulated drinks, and the test measured early erosion only.
Juice: no erosion link in children, enamel loss in small adult tests
This systematic review of 100% fruit juice and teeth covered 5 prospective cohorts in children and teens and 9 randomized trials in adults. The adult trials used mouth devices without normal plaque or saliva, in conditions unlike everyday juice drinking. The authors call the evidence not conclusive. The Juice Products Association partly funded the review, and the authors consult for industry.
After weight-loss surgery, calcium citrate lowered parathyroid hormone more than carbonate
150 people took both supplements in turn, double-blind, 6 months after one of three kinds of weight-loss surgery (50 each). Citrate gave a small gain in absorption. Peak blood calcium was 9.8 against 9.5 mg/dL, and the 8-hour area under the curve was 76.1 against 74.7 mg/dL per hour. The differences are small and apply to people whose gut was changed by surgery.
In 24 postmenopausal women, calcium citrate was absorbed as well as carbonate
The women took single doses of a marketed calcium carbonate, an encapsulated calcium carbonate and a marketed calcium citrate, in random order. Blood calcium was followed for 24 hours, and the three gave identical time courses. Urine calcium rose slightly more with citrate, but the gap could be chance. The authors say cost favors the cheaper carbonate.
Zinc citrate was absorbed as well as gluconate, better than oxide
15 healthy adults took each of three supplements (10 mg of zinc) without food, in random order, double-masked. Median absorption was 61.3% from citrate, 60.9% from gluconate and 49.9% from oxide. Three people absorbed little or no zinc from oxide.
Magnesium citrate gave the highest blood magnesium of three forms
46 healthy adults took 300 mg of magnesium a day for 60 days as amino-acid chelate, citrate, oxide or a placebo, double-blind. 24-hour urine tests showed the two organic forms were absorbed better than oxide, and oxide did not differ from placebo. Red cell magnesium did not differ between groups.
Citric acid in a meal cut iron absorption to about a third
The study in 49 people compared ways to change iron absorption from a simple Latin American-type meal of maize, rice and beans. Adding 1 g of citric acid lowered non-heme iron absorption to 0.06 mg, while 75 g of meat raised it from 0.17 to 0.45 mg. This is a single meal type, tested in 1984.
Citric acid in an oat drink raised iron absorption by 54%, borderline
42 healthy adults drank an oat-based drink made for toddlers, with labeled iron as ferric ammonium citrate. 60 mg of citric acid raised absorption from 3.9% to 6.0%, a result that just missed statistical significance. Removing phytate with the enzyme phytase raised it more, by 78%. The drink combined several treatments, and the authors judged the combination useful against iron deficiency.
With an antacid, calcium citrate raised aluminum absorption 5 to 11 times
8 healthy men took 950 mg of calcium citrate four times a day, or placebo, during 3 days of aluminum hydroxide (2.4 g a day). Urinary aluminum was 11.1, 8.8 and 5.3 times higher on days 1, 2 and 3 with calcium citrate. Plasma aluminum did not differ. The authors say the two must not be prescribed together in kidney failure.
Calcium citrate raised aluminum absorption from ordinary food in 30 healthy women
The women took 800 mg of calcium a day as calcium citrate. Urinary and plasma aluminum rose during treatment, while lead levels did not change. Animal studies had suggested that citrate raises aluminum absorption. The authors say more studies are needed to learn whether long-term use leads to aluminum buildup.
Citrus fruit over twice daily: 37 times the odds of erosion
This case-control study compared 106 people with erosion and 100 without. After adjustment, citrus fruit more than twice a day went with 37 times the odds. Daily soft drinks went with 4 times, weekly apple vinegar 10 and weekly sports drinks 4. Vomiting (31) and stomach symptoms (10) also stood out. It is a small 1991 study, and citrus fruit holds other acids and sugars besides citric acid.
Acidic foods went with 2.4 times the odds of tooth wear
This systematic review and meta-analysis covered observational studies in permanent teeth (87 publications on 71 studies). Acidic foods went with 2.40 times the odds of erosive tooth wear, carbonated drinks with 1.43 times and regurgitation with 2.27 times. Most studies had a low risk of bias. “Acidic foods” is a broad group, not citric acid alone.
Acidic drinks and sweets went with more erosion in children and teens
This meta-analysis covered 13 observational studies in people aged 8 to 19. Acidic fruit juices, carbonated drinks and acid sweets went with more erosion, while milk and yogurt went with less. Results varied between studies for soft drinks, sweets and acidic juices, and the way diet was measured differed. The studies could not separate citric acid from the other acids and sugars in these products.
Four case reports blamed manufactured citric acid, but cannot show cause
Four adults described repeated inflammatory reactions after foods, drinks or vitamins with added citric acid: joint pain, muscle pain, breathing symptoms, bowel symptoms or fatigue. They had no symptoms with citric acid from lemons and limes. The authors traced the link from ingredient labels, could not give amounts, and suggest mold fragments may trigger a reaction in susceptible people. We found no blinded challenge or test of the products for mold residue in the report, and the authors call for safety studies.
Foods high in citric acid
Lemons and limes are the richest everyday sources. In one lab analysis, squeezed lemon juice held 48.0 g of citric acid per liter and lime juice 45.8. A ready-to-drink grapefruit juice held 25.0, and two bottled orange juices 16.7 to 16.9. Orange juice squeezed from the fruit held 9.10.
Ready-to-drink lemonades and limeades held only 4.4 to 7.3. The authors note that they are generally made with 15% real juice or less.
The ranking below comes from a Danish food composition database and lists only three foods. So the table adds published measurements of juices and drinks, per liter of drink, not per 100 g. A second lab measured citrate by a different method and in other units (mmol/L, millimoles per liter). Its figures are listed after the first and should not be compared with them directly.
Citric acid is also added to many foods as E 330, and we found no measured amounts for those foods.
Per serving. No daily amount is set, so bars compare each food with the top food.
Per 100 g. No daily amount is set, so bars compare each food with the top food.
Per 100 kcal: the same calories of each food, for a fair comparison. Bars compare each food with the top food.
Food labels have no Daily Value or Reference Intake for citric acid, so the % compares each food with the top food.
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| Food or drink | Citric acid as published | Source |
|---|---|---|
| Lemon juice, squeezed from fruit | 48.0 g/L | 1 |
| Lime juice, squeezed from fruit | 45.8 g/L | 1 |
| Lemon or lime juice from concentrate (3 products) | 34.1 to 39.2 g/L | 1 |
| Grapefruit juice, ready to drink (1 product) | 25.0 g/L | 1 |
| Orange juice, ready to drink (2 products) | 16.7 to 16.9 g/L | 1 |
| Orange juice, squeezed from fruit | 9.10 g/L | 1 |
| Lemonade and limeade, ready to drink (9 products) | 4.4 to 7.3 g/L | 1 |
| Lemonade drink mixes, made up as directed (6 products) | 0.92 to 4.2 g/L | 1 |
| Grapefruit juice | 64.7 mmol/L citrate | 2 |
| Pineapple juice | 41.57 mmol/L citrate | 2 |
| Cranberry juice | 19.87 mmol/L citrate | 2 |
| Lemon-flavored Gatorade | 19.82 mmol/L citrate | 2 |
| Mountain Dew | 8.84 mmol/L citrate | 2 |
| Diet 7Up | 7.98 mmol/L citrate | 2 |
Sources
- Penniston KL, Nakada SY, Holmes RP, Assimos DG. Quantitative assessment of citric acid in lemon juice, lime juice, and commercially-available fruit juice products. J Endourol. 2008. Ion chromatography; values from Table 1 of the paper (g/L).
- Haleblian GE, Leitao VA, Pierre SA, et al. Assessment of citrate concentrations in citrus fruit-based juices and beverages: implications for management of hypocitraturic nephrolithiasis. J Endourol. 2008. Proton NMR spectroscopy (mmol/L).
- Frida, Danish Food Composition Database, version 5.5 (2025). National Food Institute, Technical University of Denmark. Source of the ranking above.
How citric acid works
Most of what we know about how citric acid acts comes from biochemistry, urine chemistry and lab tests on teeth, not from trials. Four ideas matter. It is a link in the cell’s energy cycle, and it holds on to calcium in urine. It also dissolves tooth mineral and changes how some minerals and metals are absorbed.
Here is each one, and what has been seen in people.
It is a link in the cell’s energy cycle
Citrate is the first acid formed in the cycle that burns food for energy. Pyruvate or acetate from carbohydrate joins oxaloacetate to make citrate, and a chain of other acids then rebuilds the oxaloacetate. Krebs named it the citric acid cycle in 1937, after one of its typical acids. Fats and many amino acids feed the same cycle, and he judged that it runs in all respiring animal tissues.
The cycle runs clockwise, one acid after another. Simplified from the scheme in Krebs’s Nobel lecture; the steps are not to scale.
This is the body’s own citrate, made from food of every kind. It does not mean that swallowing citric acid feeds the cycle. In people, ingested citrate is rapidly metabolized and blood citrate varies little, according to a 2010 review.
It holds on to calcium in urine
In urine, citrate binds calcium into soluble complexes. Two reviews say this stops calcium crystals from starting, clumping and growing. Low urinary citrate, called hypocitraturia, is found in 20 to 60% of people who form stones. One common cutoff is 320 mg of citrate in a 24-hour urine sample.
A schematic, not to scale. Real citrate-calcium complexes are not hexagons; the drawing only shows the idea.
What raises urinary citrate is alkali more than the acid itself. After an acid load the body makes less urinary citrate, and after an alkaline load it makes more, according to the 2010 review. This may explain a crossover study in which orange juice raised urinary citrate and pH but lemonade did not. Both had similar citrate content, but orange juice supplied alkali and lemonade did not.
It dissolves tooth mineral
Enamel dissolves in acid. In an in situ test, worn in the mouth, two properties of a drink mattered. Its pH etches the surface at once. Its titratable acidity, the amount of acid there is to be neutralized, slows the return of saliva to a normal pH.
Adding citric acid raised early enamel softening 2.5 to 3 times. The test used simulated drinks in 12 volunteers.
A schematic of the two effects, not to scale. The curves show the direction reported: saliva recovers more slowly after a solution with more citric acid.
Real-life harm is harder to pin on citric acid. A review of 100% fruit juice, partly funded by the juice industry, found no link with erosion in prospective cohorts of children. Small adult trials with mouth devices did show enamel loss. Population studies cannot separate citric acid from the other acids and sugars in the same foods.
It changes how some minerals and metals are absorbed
Citrate binds metals, and the results in people differ by mineral. Calcium citrate was absorbed 20 to 27% better than calcium carbonate in a pooled analysis, but no better in a 24-woman trial. Citric acid cut iron absorption from a maize, rice and bean meal to about a third in one study. In another, it raised iron absorption from an oat drink by 54%, a borderline result.
With aluminum the effect is clearer and unwanted. Calcium citrate raised aluminum absorption in healthy women, and 5 to 11 times when taken with an aluminum antacid. Animal studies had pointed to this.
What has been seen in people
These effects are easier to show in a dish than in a person. The calcium idea has the best human support: citrate drugs cut new stones (0.26 times the risk). But lemon juice and lemonade gave mixed results, and the one large lemon juice trial missed its main goal.
The tooth effects come from small in situ tests and from observational studies that cannot isolate citric acid. For minerals, the answer depends on the mineral and the study. All of these are among the cards above.
Sources
- Krebs HA. The citric acid cycle. Nobel Lecture, December 11, 1953. NobelPrize.org.
- Hans Krebs: facts. NobelPrize.org. Prize motivation: “for his discovery of the citric acid cycle.”
- Arnold PK, Finley LWS. Regulation and function of the mammalian tricarboxylic acid cycle. J Biol Chem. 2023.
- Zacchia M, Preisig P. Low urinary citrate: an overview. J Nephrol. 2010.
- Zuckerman JM, Assimos DG. Hypocitraturia: pathophysiology and medical management. Rev Urol. 2009.
- Penniston KL, Nakada SY, Holmes RP, Assimos DG. Quantitative assessment of citric acid in lemon juice, lime juice, and commercially-available fruit juice products. J Endourol. 2008. The 320 mg cutoff is quoted in the discussion.
- Odvina CV. Comparative value of orange juice versus lemonade in reducing stone-forming risk. Clin J Am Soc Nephrol. 2006.
- Fernández CE, Brandao ACS, Bícego-Pereira EC, et al. Effect of pH and titratable acidity on enamel and dentine erosion. Clin Oral Investig. 2022.
- Liska D, Kelley M, Mah E. 100% fruit juice and dental health: a systematic review of the literature. Front Public Health. 2019. Partly funded by the Juice Products Association.
- Sakhaee K, Bhuket T, Adams-Huet B, Rao DS. Meta-analysis of calcium bioavailability: a comparison of calcium citrate with calcium carbonate. Am J Ther. 1999.
- Heaney RP, Dowell MS, Bierman J, Hale CA, Bendich A. Absorbability and cost effectiveness in calcium supplementation. J Am Coll Nutr. 2001.
- Hallberg L, Rossander L. Improvement of iron nutrition in developing countries: comparison of adding meat, soy protein, ascorbic acid, citric acid, and ferrous sulphate on iron absorption from a simple Latin American-type of meal. Am J Clin Nutr. 1984.
- Zhang H, Onning G, Oste R, Gramatkovski E, Hulthén L. Improved iron bioavailability in an oat-based beverage: the combined effect of citric acid addition, dephytinization and iron supplementation. Eur J Nutr. 2007.
- Coburn JW, Mischel MG, Goodman WG, Salusky IB. Calcium citrate markedly enhances aluminum absorption from aluminum hydroxide. Am J Kidney Dis. 1991.
- Nolan CR, DeGoes JJ, Alfrey AC. Aluminum and lead absorption from dietary sources in women ingesting calcium citrate. South Med J. 1994.
Is citric acid safe? Supplements, dose and interactions
At food amounts, the official reviews we found raise no safety concern. The Joint FAO/WHO Expert Committee on Food Additives (JECFA) lists an acceptable daily intake (ADI) of “not limited” for citric acid. That covers its calcium, potassium, sodium and ammonium salts as a group, and the latest evaluation was in 1973.
In the EU, EFSA (the EU’s food safety agency) reviewed citric acid esters in 2020. Its opinion notes an ADI of “not specified” for citric acid (E 330), set by the Scientific Committee on Food in 1991. EFSA will re-evaluate it, and we found no EFSA opinion on E 330 itself.
In the US, the FDA lists citric acid as generally recognized as safe (GRAS) for direct addition to food under 21 CFR 184.1033. There is no limit other than current good manufacturing practice. The concerns below come from specific forms and uses.
- Teeth. Acid softens enamel. In a 1991 case-control study, citrus fruit more than twice a day went with 37 times the odds of erosion. Vomiting and stomach symptoms went with 31 and 10 times. Prospective cohorts of children found no link with 100% fruit juice.
- Potassium citrate for stones. It is a prescription drug, not a food. In the Cochrane review, people on citrate salts were 4.45 times as likely to stop because of side effects, mostly upper gut upset. The trials above used 18.5 to 60 mEq a day. The lemon juice trial used 60 mL twice a day, which caused more gut problems. Ask your doctor before treating stones yourself.
- Aluminum antacids and kidney failure. With 2.4 g a day of aluminum hydroxide, calcium citrate raised aluminum absorption 5 to 11 times. The authors say the two must not be prescribed together in kidney failure. In 30 healthy women, calcium citrate alone also raised aluminum absorption from food. Whether long-term use leads to buildup is unknown.
- The inflammation claim. The 2018 report describes four people with symptoms after products with added citric acid. It cannot show that citric acid, and not another ingredient or mold residue, was to blame. Doses were unknown and nothing was tested blind. We found no controlled study of the claim, so if a product seems to make you ill, tell your doctor.
How to get more citric acid
- Best food. Squeezed lemon and lime juice hold 48.0 and 45.8 g/L, about five times the 9.10 in squeezed orange juice. Sixty milliliters of lemon juice, the amount in the large stone trial, holds about 2.9 g by that figure (our arithmetic).
- Juice or drug. In a 30-person trial, lemon juice raised urinary citrate 2.5-fold, against 3.5-fold for potassium citrate. But in a crossover trial of 21 people, lemonade did not raise urinary citrate or pH. Lemonade is not a stand-in for the drug.
- Food or supplement form. Calcium citrate was absorbed 20 to 27% better than calcium carbonate in a pooled analysis. But a 24-woman trial found no difference, and its authors said cost favors carbonate.
Sources
- Summary of evaluations performed by JECFA: citric acid (INS 330). IPCS INCHEM. Latest evaluation 1973; ADI “not limited”; group ADI with its calcium, potassium, sodium and ammonium salts.
- EFSA Panel on Food Additives and Flavourings (FAF). Re-evaluation of acetic acid, lactic acid, citric acid, tartaric acid, mono- and diacetyltartaric acid, mixed acetic and tartaric acid esters of mono- and diglycerides of fatty acids (E 472a-f) as food additives. EFSA J. 2020. Mentions the SCF ADI for E 330 and the planned re-evaluation.
- 21 CFR 184.1033: Citric acid. Code of Federal Regulations, US Food and Drug Administration. Read on the Cornell Legal Information Institute copy.
- Sweis IE, Cressey BC. Potential role of the common food additive manufactured citric acid in eliciting significant inflammatory reactions contributing to serious disease states: a series of four case reports. Toxicol Rep. 2018.
- Järvinen VK, Rytömaa II, Heinonen OP. Risk factors in dental erosion. J Dent Res. 1991.
- Liska D, Kelley M, Mah E. 100% fruit juice and dental health: a systematic review of the literature. Front Public Health. 2019.
- Phillips R, Hanchanale VS, Myatt A, et al. Citrate salts for preventing and treating calcium containing kidney stones in adults. Cochrane Database Syst Rev. 2015.
- Ruggenenti P, Caruso MR, Cortinovis M, et al. Fresh lemon juice supplementation for the prevention of recurrent stones in calcium oxalate nephrolithiasis. EClinicalMedicine. 2022.
- Aras B, Kalfazade N, Tuğcu V, et al. Can lemon juice be an alternative to potassium citrate in the treatment of urinary calcium stones in patients with hypocitraturia? Urol Res. 2008.
- Koff SG, Paquette EL, Cullen J, et al. Comparison between lemonade and potassium citrate and impact on urine pH and 24-hour urine parameters in patients with kidney stone formation. Urology. 2007.
- Macdonald HM, Black AJ, Aucott L, et al. Effect of potassium citrate supplementation or increased fruit and vegetable intake on bone metabolism in healthy postmenopausal women. Am J Clin Nutr. 2008.
- Coburn JW, Mischel MG, Goodman WG, Salusky IB. Calcium citrate markedly enhances aluminum absorption from aluminum hydroxide. Am J Kidney Dis. 1991.
- Nolan CR, DeGoes JJ, Alfrey AC. Aluminum and lead absorption from dietary sources in women ingesting calcium citrate. South Med J. 1994.
- Sakhaee K, Bhuket T, Adams-Huet B, Rao DS. Meta-analysis of calcium bioavailability: a comparison of calcium citrate with calcium carbonate. Am J Ther. 1999.
- Heaney RP, Dowell MS, Bierman J, Hale CA, Bendich A. Absorbability and cost effectiveness in calcium supplementation. J Am Coll Nutr. 2001.
- Penniston KL, Nakada SY, Holmes RP, Assimos DG. Quantitative assessment of citric acid in lemon juice, lime juice, and commercially-available fruit juice products. J Endourol. 2008.
History of citric acid
Citric acid was first isolated from lemon juice in 1784 by Carl Scheele, who added lime to the juice and obtained calcium citrate. For the next century or so it came from citrus. From 1860 it was made from lemons in the United Kingdom, France and Germany. In 1893 the German botanist Wehmer noticed that a mold, Penicillium glaucum, formed citric acid as a by-product.
In 1917 the American food chemist James Currie found that strains of Aspergillus niger give high yields of citric acid from cheap molasses. Pfizer began producing it this way in 1919, and the method is still used worldwide, especially in China. A 2023 review puts the world citric acid market at 2.8 million tons in 2022.
The acid has a second history in biochemistry. Between 1906 and 1920 Thunberg showed that animal tissues rapidly oxidize citrate and a number of other acids. In March 1937 Martius and Knoop worked out what happens to citrate when it is oxidized. Krebs then assembled the pieces into a cycle and named it after citric acid that same year.
The Nobel Foundation says Krebs presented a complete picture in 1937, building on work by Albert Szent-Györgyi. Krebs shared the 1953 Nobel Prize in Physiology or Medicine with Fritz Lipmann, who was honored for coenzyme A.
Sources
- Książek E. Citric acid: properties, microbial production, and applications in industries. Molecules. 2023.
- Sweis IE, Cressey BC. Potential role of the common food additive manufactured citric acid in eliciting significant inflammatory reactions contributing to serious disease states: a series of four case reports. Toxicol Rep. 2018. The Pfizer date and the 99% figure are the authors’ statements.
- Behera BC. Citric acid from Aspergillus niger: a comprehensive overview. Crit Rev Microbiol. 2020.
- Krebs HA. The citric acid cycle. Nobel Lecture, December 11, 1953. NobelPrize.org.
- Hans Krebs: facts. NobelPrize.org.
- Müller M, Irkens-Kiesecker U, Rubinstein B, Taiz L. On the mechanism of hyperacidification in lemon. Comparison of the vacuolar H(+)-ATPase activities of fruits and epicotyls. J Biol Chem. 1996.
- Strazzer P, Spelt CE, Li S, et al. Hyperacidification of Citrus fruits by a vacuolar proton-pumping P-ATPase complex. Nat Commun. 2019.
- Citric acid. Wikipedia.
Frequently asked questions about citric acid
What does citric acid do for the body?
It is a link in the energy cycle inside every cell, and your body makes it itself. As a treatment, the best-supported use is a prescription. Citrate salts cut new kidney stones in a Cochrane review of 7 trials (0.26 times the risk). We found no trial showing that citric acid from food treats any condition. In a 203-person trial, lemon juice did not clearly cut stone recurrence.
Is citric acid bad for you?
At food amounts, the official reviews we found raise no safety concern. JECFA lists an ADI of “not limited”, and the FDA lists it as GRAS with no limit other than good manufacturing practice. The clearest harm is to teeth, since acid softens enamel. People with kidney failure should not take calcium citrate with aluminum antacids.
Does manufactured citric acid cause inflammation?
No study has shown that. The claim comes from a 2018 report of four people who felt ill after products with added citric acid. Case reports cannot show cause, doses were unknown, and we found no blinded test or analysis for mold residue. Anyone who reacts to a product should tell a doctor.
Is citric acid made from mold?
Mostly, yes. Industry feeds sugar to the black mold Aspergillus niger and then separates the acid from the broth. James Currie found the method in 1917, and Pfizer used it from 1919. The FDA rule also lists recovery from lemon or pineapple juice, and it describes a solvent extraction process for the acid from A. niger liquor. The 2018 case report puts the share made with the mold at about 99%.
Does lemon juice prevent kidney stones?
Possibly, but less reliably than potassium citrate. In 203 people, 60 mL of lemon juice twice a day gave 21 recurrences against 32 in controls. That is 0.62 times the risk, a gap that could be chance, and adherence fell to 48% by year two. In 30 people it raised urinary citrate 2.5-fold, against 3.5-fold for potassium citrate, but a 21-person crossover trial found lemonade did not. Ask your doctor before swapping a prescription.
Does citric acid ruin your teeth?
It can soften enamel. In an in situ test, adding citric acid raised early enamel softening 2.5 to 3 times. In a review of 71 studies, acidic foods went with 2.4 times the odds of erosive tooth wear. Prospective cohorts of children found no link with 100% fruit juice, and none of these studies can separate citric acid from other acids and sugars.
Is calcium citrate better absorbed than calcium carbonate?
Somewhat, in some studies. A pooled analysis of 15 studies found 20 to 27% better absorption. In 150 people after weight-loss surgery, citrate lowered parathyroid hormone more. A 24-woman trial found identical blood calcium curves, and its authors said cost favors carbonate.
Which foods are highest in citric acid?
Lemons and limes. In one lab analysis, squeezed lemon juice held 48.0 g/L and lime juice 45.8. That compares with 25.0 for ready-to-drink grapefruit juice, 16.7 to 16.9 for bottled orange juice and 9.10 for squeezed orange juice. Ready-to-drink lemonades held 4.4 to 7.3.