Sodium phosphates
A group of sodium salts of phosphoric acid used to preserve processed meats, stabilise dairy products and retain moisture in meat.
High intake of phosphate additives is linked to accelerated kidney function decline, raised blood phosphorus levels and increased cardiovascular risk, particularly for people with kidney disease. EFSA's 2019 re-evaluation set a group ADI and noted the limit does not protect people with moderate to severe kidney impairment.
What is it?
E339 covers three forms of sodium phosphate: monosodium phosphate (NaH2PO4), disodium phosphate (Na2HPO4) and trisodium phosphate (Na3PO4). They are the sodium salts of phosphoric acid. Unlike naturally occurring phosphorus in whole foods (which is bound to protein and partly unabsorbed), phosphate additives are inorganic salts that are absorbed almost completely in the gut.
What does it do?
Sodium phosphates act as acidity regulators, emulsifiers, stabilisers and sequestrants depending on which form is used and in what food. In processed meats they bind water into the protein matrix, increasing yield and improving texture. In processed cheese they act as emulsifying salts, preventing fat separation during melting. In baked goods they function as leavening agents (reacting with bicarbonate to produce CO2). They can also chelate metal ions that would otherwise accelerate rancidity.
Where you will see it
Found in sliced processed ham and cooked meats, reformed chicken products, hot dogs, fish fingers, processed cheese slices, spreadable cheese, instant noodles, some baked goods and ready meals. On the label it may appear as 'sodium phosphates', 'disodium phosphate', 'trisodium phosphate', or simply 'E339'.
What the science says
Kidney function and high phosphate intake
Phosphate additives in processed food are absorbed far more efficiently than the phosphorus naturally present in whole foods. Observational studies have associated high dietary phosphate intake with faster progression of chronic kidney disease and raised serum phosphorus levels. EFSA's 2019 expert panel consulted nephrologists who confirmed that its group ADI does not protect people with moderate to severe kidney impairment, because their kidneys cannot excrete the extra load.
EFSA derived a group ADI for phosphates (E338-341, E450-452) of 40mg phosphorus per kg body weight per day, and stated explicitly that this ADI does not apply to individuals with moderate to severe renal impairment.
Nephrology experts consulted by EFSA confirmed that high phosphate additive intake is a clinically relevant concern for patients with chronic kidney disease, because inorganic phosphates from additives are almost completely absorbed, unlike organic phosphate from protein-bound food sources.
Cardiovascular signals from observational research
Several large observational studies have found associations between high serum phosphorus levels and increased risk of cardiovascular events and mortality, including in people without kidney disease. These are associations, not proven cause and effect, and the relative contribution of phosphate additives versus dietary phosphorus from whole foods is difficult to isolate in population data.
Higher serum phosphorus levels were associated with increased cardiovascular mortality in the general population in a large US cohort study, independent of kidney function.
A systematic review of studies found that elevated serum phosphorus is associated with cardiovascular risk even within the normal reference range, leading authors to suggest dietary phosphate additives may contribute to risk at a population level.
Additive phosphate versus natural phosphate: absorption difference
Phosphorus in whole foods such as meat, fish, nuts and pulses is attached to protein molecules and absorbed at roughly 40-60% efficiency. Inorganic phosphate salts used as food additives are absorbed at around 80-100% efficiency. This means that additive-derived phosphorus has a greater effect on blood phosphorus per gram consumed, which matters most for people with impaired kidney clearance.
Inorganic phosphate additives have a bioavailability of approximately 80-100%, compared to approximately 40-60% for organic phosphate from protein-rich whole foods, giving additive sources a disproportionately larger effect on serum phosphorus.
Dietary exposure and children
Because phosphate additives appear across a wide range of processed foods, children eating a heavily processed diet can reach high cumulative daily intakes. EFSA's dietary exposure modelling found that high consumers (95th percentile) across some age groups approach or reach the group ADI when additive intake alone is considered, before natural dietary phosphorus is added on top.
EFSA's 2019 exposure assessment found that high consumers of phosphate additives (95th percentile), particularly adolescents, could approach or exceed the group ADI from additive sources alone, independently of background dietary phosphorus.
Where it stands with the regulators
Who should be careful
People with chronic kidney disease should discuss phosphate additive intake with their renal dietitian: the kidneys cannot clear the extra phosphorus load and blood phosphate levels rise, accelerating disease progression. Look for 'sodium phosphate', 'disodium phosphate', 'trisodium phosphate', or 'E339' on the ingredients list, particularly on processed meats, cooked ham, spreadable cheese and ready meals.
The honest read
The phosphate additive question divides opinion in nutrition science. Phosphorus is an essential nutrient and the body needs it. The controversy is specific to additive-derived inorganic phosphates, which are absorbed almost in full, unlike phosphorus in whole foods. EFSA set a formal group ADI in 2019 precisely because the evidence base had grown enough to need one, and high consumers, particularly adolescents eating heavily processed diets, can approach it from additives alone before their natural dietary phosphorus is counted. The cardiovascular signals from population studies are associations and do not prove that additive phosphate causes heart disease. What is not disputed is the renal picture: for anyone whose kidneys already struggle to excrete phosphorus, the additive load is a clinical concern, not a theoretical one.
Related additives
Common questions
Is E339 banned in the UK?
No. E339 is an approved food additive in the UK under the assimilated EU Regulation 1333/2008. It is permitted across a range of processed food categories including processed meat, cheese and baked goods.
Should people with kidney disease avoid E339?
Yes. EFSA's 2019 scientific review stated explicitly that the group ADI for phosphate additives does not protect people with moderate to severe kidney impairment. Renal dietitians routinely advise kidney disease patients to minimise foods containing phosphate additives, because inorganic phosphate is absorbed almost completely and the kidneys cannot clear the excess.
What foods contain E339?
Sodium phosphates are most commonly found in sliced cooked meats and processed ham, hot dogs, reformed chicken products, processed cheese slices, spreadable cheese, fish fingers, instant noodles, some baked goods and ready meals. Check the ingredients list for 'sodium phosphates', 'disodium phosphate', 'trisodium phosphate', or 'E339'.
Is E339 vegan?
Yes. Sodium phosphates are mineral salts and contain no animal-derived ingredients. They are suitable for vegans and vegetarians.
Sources
- EFSA ANS Panel re-evaluation of phosphoric acid and phosphates (E338-341, E343, E450-452), EFSA Journal 2019;17(6):5674
- EFSA press release: EFSA issues new advice on phosphates (June 2019)
- EFSA Supporting Publications EN-1624: Outcome of nephrology expert consultation on phosphate food additives re-evaluation
- UK FSA: Sodium phosphates (E339) approved additive entry
- UK FSA: Approved additives and E numbers
- Calvo MS and Uribarri J: Contributions to total phosphorus intake: all sources considered. American Journal of Kidney Diseases 2013
- Tonelli M et al.: Relation between serum phosphate level and cardiovascular event rate in people with coronary disease. Archives of Internal Medicine 2005
- Kalantar-Zadeh K et al.: Understanding sources of dietary phosphorus in the treatment of patients with chronic kidney disease. Clinical Journal of the American Society of Nephrology 2010
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