Added phosphorus inversely tied to kidney function

A negative association exists between added phosphorus (P) and kidney function, reveals a study, which also raises concern regarding P additives in the food supply.

A team of researchers assessed 3,962 African-American participants of the Jackson Heart Study, aged 21‒84 years, with urine albumin:creatinine ratio <30 mg/g, and eGFR ≥60 mL · min⁻¹ · 1.73 m⁻², and without self-reported kidney disease. They evaluated diet via food-frequency questionnaires.

P in foods was categorized as naturally occurring or added. The researchers weighted intake by P bioavailability, based on published literature, and analysed the associations between P variable and estimated glomerular filtration rate (eGFR) using multivariable regression.

In participants with eGFR 60‒89 and ≥90 mL · min⁻¹ · 1.73 m⁻², the respective mean intakes were 1,178 and 1,168 mg for total P, 296 and 291 mg for bioavailable added P, and 444 and 443 mg for bioavailable natural P. Major sources of total P were fish, milk, eggs, cheese, poultry, and beef, while those for added P included fish, beef, poultry, processed meat, and soft drinks.

P intakes, including total (β, ‒0.32; p=0.03), added (β, ‒0.73; p=0.01), bioavailable total (β, ‒0.62; p=0.01), and bioavailable added (β, ‒0.77; p=0.01) significantly correlated with lower eGFR after adjusting for confounders. On the other hand, both total and bioavailable P from natural sources were not associated with eGFR.