An observation study evaluating the effect of a high phosphorus density diet on chronic kidney disease (CKD) development found that diabetic patients are at an increased risk of CKD.
Proper renal function is critically important for maintaining healthy homeostasis of waste management, minerals/water reabsorption and more. Impaired kidney function is associated with an increased risk of morbidity and mortality and should be closely monitored. Increased serum phosphorus levels were previously linked to renal failure in a population of CKD patients. The effect of serum phosphorus level on the development of CKD in populations with proper renal function (both diabetic and non-diabetic) are yet to be determined.
Phosphorus, like carbon, nitrogen, hydrogen, oxygen and sulfur, is a cellular building block used to build proteins, nucleic acids and cellular energy (ATP) units. Serum phosphorus comes from dietary consumption, renal excretion and reabsorption and exchanges from bone tissue (main phosphorus concentration). Dietary sources include meat, fish, milk, cheese and phosphorus enriched products such as processed meat.
A recent study published in the American Journal of Clinical Nutrition analyzed data collected between 2001 and 2014 from adults aged 40 to 69 participating in the Korean Genome and Epidemiology Study. A total of 873 subjects with diabetes mellitus (DM) and 5846 subjects without DM were included in the final analysis. The primary outcome of the study was the incidence of CKD defined by glomerulus filtration parameters (<60ml.min-1.1.73 m-2) and protein appearance in the urine. To obtain dietary data on phosphorus (in milligrams), and protein (in grams) intakes for single day, the participants were asked to fill a semi quantitative dietary food-frequency questionnaire (FFQ). The survey was conducted twice by trained interviewers. The FFQ was previously validated and used to calculate daily calories based on Korean Nutrition Society guidelines. Dietary phosphorus density was defined as the ratio of phosphorus consumed during single day to the total daily calorie intake.
Baseline measurements were collected from an approximately equal number of men and woman between 51 and 55 years of age. Basic physical health measurements such as glucose blood levels and renal function parameters were obtained from each group. Baseline glomerular filtration rates were in normal range (<90 ml.min-1.1.73 m-2) for both DM and non-DM groups.
During the follow-up period of approximately 100-115 months, CKD had developed in 283 (32.4%) DM participants and 792 (13.5%) non-DM participants. After adjusting for dietary phosphorus density, the results demonstrate a significant association between high phosphorus uptake and the development of CKD in DM individuals with previously normal renal function. The relation was not found in non-DM subjects. It is important to note that the correlation was found only with the highest phosphorus-density diet, suggesting that phosphate is not toxic unless very high amounts are consumed.
A limitation of the observational nature of the study is that no standardized intervention is considered. The amount of phosphorus uptake may have varied throughout the course of the study, affecting the accuracy of the final conclusion. Additional research is needed to evaluate the effect of high versus low phosphorous uptake on renal function.
Written By: Bella Groisman, PhD