Phosphorus additives are common in best-selling processed groceries and contribute significantly to their phosphorus content, according to researchers.

Additionally, foods containing phosphorus additives are less expensive than foods free of phosphorus additives, so patients with chronic kidney disease (CKD) may buy these popular low-cost groceries and unknowingly increase their intake of highly bioavailable phosphorus, the researchers reported in the Journal of Renal Nutrition (2013;23:265-270).

“Because phosphorus additives are highly bioavailable, patients eating these commonly purchased foods may have difficulty maintaining serum phosphorus within the normal range,” the authors noted. “These findings suggest that emphasis on label reading to avoid phosphorus additives is an appropriate strategy to manage serum phosphorus in persons with kidney disease in the absence of phosphorus content on labels.”

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Janeen B. León, MS, RD, LD, of MetroHealth Medical Center and Case Western Reserve University in Cleveland, and colleagues examined the labels of 2,394 top-selling branded grocery products in northeast Ohio for phosphorus additives. Phosphorus additives were present in 72% of prepared frozen foods, 70% of dry food mixes, and 65% of packaged meat.

Dietary phosphorus loads have been shown to increase serum phosphorus in CKD patients and to increase fibroblast growth factor-23 in healthy individuals and those with CKD. Consequently, CKD patients are advised to limit dietary phosphorus to 800-1,000 mg/day and to avoid foods containing phosphorus additives because of their high bioavailability. Phosphorus additives have long been added to convenience and processed foods for various reasons.

León’s team matched 56 of the five top-selling grocery items containing phosphorus additives with similar products without phosphorus additives. Foods with phosphorus additives contained an average of 67 mg phosphorus per 100 grams more than the matched foods without phosphorus additives.

The investigators also developed matched sample meals with and without phosphorus additives. The additive-containing meals were $2 per day cheaper than meals not containing additives. The authors pointed out that although $2 a day may seem insignificant, the average household supplemental food assistance benefits (SNAP) average only $287 per months, or $4.30 per person per day. Families eligible for SNAP are unlikely to afford $240 per month additional food costs to avoid phosphorus additives, they noted.