Italian researchers have developed a phosphorus pyramid, a type of food pyramid to help health care providers teach chronic kidney disease (CKD) patients how to reduce their dietary phosphorus load and stave off mineral and bone disorders (MBD).
“The phosphorus pyramid herein proposed is an original, visual, user-friendly tool for nutritional education. It can support patients and caregivers in making the right food choices by encouraging adherence to dietary prescriptions, which is a crucial component for CKD-MBD,” Adamasco Cupisti, MD, of the University of Pisa in Italy, and colleagues wrote in BMC Nephrology (2015;16:9).
Phosphorus is a concern at all stages of CKD, the researchers noted. The pyramid can help both CKD and dialysis patients understand what to eat and what to avoid, with appropriate tailoring. Here are some basic nutrition strategies:
- In non-dialysis patients, consider restricting protein intake. (Those on dialysis require extra protein.) In a mixed diet, each gram of protein is usually accompanied by 12–14 mg of phosphorus.
- Shift from phosphorus-rich foods to low phosphorus foods. Take into consideration bioavailability. Plant foods contain phosphorus but less than half of the mineral content is absorbed by the body. The phosphoric acid in soft drinks, by comparison, is almost completely absorbed.
- Boil foods to reduce their mineral content, including phosphorus (then discard the water). According to one study, boiling reduces phosphorus by 51% for vegetables, 48% for legumes, and 38% for meats.
- Try to identify and avoid phosphate additives. Processed foods contain considerable amounts of added phosphorus, including from preservatives.
The Phosphorus Pyramid
The food pyramid color codes food items similar to a traffic light: greens for go, yellows for slow, and reds for stop.
It consists of 6 levels with foods arranged by their phosphorus content, phosphorus to protein ratio (no more than 12 mg/g is favorable) and phosphorus bioavailability. Here’s an overview of each level from 1 (low phosphorus) to 6 (high phosphorus):
- Green: Foods with a very low phosphorus content include protein-free foods, fruit, vegetables, egg white, olive oil, and sugar. These items are not limited, unless a patient is overweight, diabetic,
- Light green: Foods with phytate, a less absorbable form of phosphorus, include cereal, rice, pasta, white bread, and legumes. 2–3 servings per day.
- Yellow: Among meats, choose lamb, rabbit, ham, or fish (e.g., trout, tuna, cod, hake, and sole). Avoid farmed fish because it has been fed with phosphorus to promote growth. Also choose milk and yogurt. No more than 1 serving per day.
- Orange: Foods with a higher phosphorus to protein ratio include turkey, offal, shrimp, squid, salmon, and soft cheeses. No more than 1 serving per week.
- Orange-Red: Foods with a very high phosphorus content include nuts, egg yolk, and hard cheeses. No more than 2-3 servings per month.
- Red: Processed foods with phosphorus-containing additives include colas, processed meat, and processed cheese. Avoid as much as possible.
Renal dietitians can help patients understand and use the pyramid. “How the dietitian interacts with the patients is as important as the dietary prescription: an understanding and nonjudging relationship is crucial for the patient to successfully adhere to the suggestions…” the researchers noted.