Phosphorus Intake Levels and Phosphate Additives in Processed Foods

Kidney disease changes the picture

Healthy kidneys remove extra phosphorus. In chronic kidney disease (CKD) they cannot, and phosphorus can build up in the blood, which can harm blood vessels and thin the bones. [1] MedlinePlus says high blood phosphorus occurs only with severe kidney disease or severe problems of calcium regulation, and that dietary deficiency is rare. [2] If you have kidney disease, a kidney dietitian and doctor set your phosphorus plan. Do not rely on the general figures below.

Official intake figures

Phosphorus figures are in milligrams (mg) of phosphorus per day. The amounts here are for healthy people eating food; they are reference values, not advice for an individual.

Upper limits

Health Canada's table lists a Tolerable Upper Intake Level of 4,000 mg a day for ages 9 to 70 (3,500 mg in pregnancy, and 3,000 mg for ages 1 to 8 and over 70). [3] The table shows no upper level for infants. [3] The NHS says taking 250 mg or less a day of phosphorus supplements on top of food is unlikely to cause harm, and that high supplement doses for a short time can cause diarrhea or stomach pain. [5] Note the different bases: the Canadian limit covers total intake, the NHS statement covers supplements only.

Natural phosphorus and phosphate additives

Phosphorus occurs naturally in protein foods such as meat, poultry, fish, nuts, beans and dairy. [7] It is also added to foods as phosphate additives, including phosphoric acid, disodium phosphate, sodium tripolyphosphate and others. [7] MedlinePlus lists processed foods that contain sodium phosphate as a main food source alongside meat and milk. [2]

The sources describe how well each kind is absorbed:

• Animal-food phosphorus is absorbed more easily than plant-food phosphorus. [7]
• Whole grains contain phosphorus stored in a form humans do not absorb. [2]
• The National Kidney Foundation (NKF) says phosphorus from food additives is completely absorbed. [7]
• NIDDK says additives may raise blood phosphorus more than naturally occurring phosphorus, and are the primary source of phosphorus for many people. [1]

These absorption statements come from kidney-disease patient pages. They do not tell us how much additive phosphorus the average healthy person eats.

Is extra phosphorus harmful in healthy people?

Proper evidence not found for a harm threshold from additives in people with normal kidneys. We searched PubMed for dietary phosphorus and phosphate additives in healthy adults and for cardiovascular outcomes. A systematic review of 10 cross-sectional studies in healthy adults found that 8 linked higher blood phosphorus to vascular calcification, but there were no randomized trials, and the authors say a cause-and-effect link has not been shown. [8] Blood phosphorus is not the same as diet intake, so this does not prove that additives cause harm. Biomarker association is not a clinical outcome.

Reading labels

NIDDK says to check the ingredient list for "phosphorus" or words containing "PHOS", such as phosphoric acid, disodium phosphate and monosodium phosphate. [1] Some packaged meats and poultry have added phosphorus, and a meat department worker can say which do not. [1] Phosphorus supplements and multimineral products: see quality testing, and ask a clinician or pharmacist about interactions (Medication Interactions).

Testing

NKF gives a normal blood phosphorus of 2.5 to 4.5 mg/dL; laboratory ranges can differ, so use your own lab's range and your clinician's reading. [7] A health professional can check it with a blood test. [1]

Related

Phosphorus, Foods high in phosphorus, Minerals and kidney disease.