Phosphorus Additives in Processed Foods May Increase CKD

WASHINGTONProcessed and fast foods enriched with phosphorus additives may play a role in health disparities in chronic kidney disease, according to a study appearing online Sept. 16 in the Journal of the American Society of Nephrology (JASN).

Phosphorus, a mineral found naturally in foods such as milk, cheese, beans and peanut butter, is vital for the formation of bones and teeth, as well as energy production and the formation of cell membranes. Since the kidneys excrete excess phosphate, patients with CKD may develop increased blood levels of phosphate, or hyperphosphatemia.

Manufacturers add phosphates to foods to give them a longer shelf life and make them more appealing.

Researchers analyzed phosphate levels in the blood of patients participating in the Chronic Renal Insufficiency Cohort Study (CRIC), a prospective cohort study established by the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) to examine risk factors for kidney disease progression and cardiovascular disease in patients with CKD.

Many studies have demonstrated that an elevated level of phosphate in the blood is associated with adverse outcomes in patients with chronic kidney disease and that blacks have higher phosphate levels than whites but we did not understand why levels are higher in blacks," they wrote. Our earlier work in the general population suggested that poverty was linked to a higher phosphate level, so we decided to delve deeper into that connection in the setting of chronic kidney disease."

Previously, genetics was considered the leading reason blacks are four times more likely to progress to end-stage renal disease than Caucasians and have much higher rates of cardiovascular disease and mortality in early chronic kidney disease (CKD).

Among the 3,612 racially and ethnically diverse participants, those with the lowest incomes and those who were unemployed had higher phosphate concentrations in their blood than participants with higher income and rates of employment. There was no difference in phosphate levels by race when only blacks and Caucasians in the lowest income group were compared. The researchers concluded that the known racial difference in phosphate levels is largely driven by differences in socioeconomic status.

For low-income patients, access to healthy food choices is limited, so their diet tends to consist of processed and fast foods heavily enriched with highly-absorbable phosphorus additives," they wrote. The amount of phosphorus additives in food is not always listed, so people unknowingly ingest more phosphorus than they probably should."