Consumption of dairy foods, cereals, and grain products with inorganic phosphate additives raises phosphorus in the blood, a new study finds. Eating dairy products with naturally-occurring organic phosphorus also has an effect, albeit smaller.
For the study, Linda W. Moore, RD, and colleagues from Houston Methodist Hospital in Texas, analyzed the impact of diet on serum phosphorus concentrations in 7,895 adults who participated in the National Health and Nutrition Examination Survey 2003–2006. Participants underwent fasting blood and urine testing and provided a detailed history of the foods, drinks, and supplements they consumed in the prior 24 hours.
According to results published in the American Journal of Clinical Nutrition, dairy foods significantly increased serum phosphorus. Milk and dairy products with inorganic phosphate additives (e.g., processed cheese) elevated serum phosphorus concentration by 0.07 mg/dL for each additional serving. Cereal and grain products (e.g., ready-to-eat cereals and pancakes) also increased phosphorus concentration to a lesser extent by 0.005 mg/dL per serving.
Some phosphate additives are 100% absorbed, whereas only 40%–60% of organic phosphorus in foods is absorbed from a meal, according to the investigators. “It seems prudent for the FDA to consider adding phosphorus to the Nutrient Facts Label but also for food manufacturers to consider alternatives to phosphate additives,” the authors wrote.
The results explain only 2.7% of the variance in serum phosphorus but have important implications. “This indicates that other factors (e.g., parathyroid hormone, vitamin D, fibroblast growth factor 23, and others) should be evaluated, if possible, to improve our understanding of the intra- and interindividual variation in serum phosphorus concentration,” the researchers stated. Serum phosphorus, including in the normal range, has been linked with cardiovascular events and mortality.
For their analyses, the researchers examined and controlled for estimated glomerular filtration rate (eGFR), albumin-to-creatinine ratio, and body mass index (BMI). Serum phosphorus concentrations were significantly higher among participants with an eGFR below 30 mL/min/1.73 m2 compared with an eGFR of 30–44 and 45–60 mL/min/1.73 m2. Having an eGFR below 30 was linked with a 0.244 mg/dL increase in serum phosphorus. However, the researchers made no assumptions about chronic kidney disease based on these single measurements. Underweight adults (BMI less than 18.5 kg/m2) also had higher serum phosphorus compared with obese individuals, warranting further study.