Summary
Following a request from the European Commission, the EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA) was asked to deliver a Scientific Opinion on Dietary Reference Values (DRVs) for the European population, including phosphorus.
Phosphorus is involved in many physiological processes, such as in the cell’s energy cycle, in regulation of the body’s acid–base balance, as a component of the cell structure, in cell regulation and signalling, and in the mineralisation of bones and teeth. About 85 % of the body’s phosphorus is in bones and teeth, 14 % is in soft tissues, including muscle, liver, heart and kidney, and only 1 % is present in extracellular fluids. Phosphorus homeostasis is intricately linked to that of calcium because of the actions of calcium-regulating hormones, such as parathyroid hormone (PTH) and 1,25-dihydroxy-vitamin D (1,25(OH)2D), at the level of the bone, the gut and the kidneys.
Phosphorus absorption occurs through passive diffusion and sodium-dependent active transport and via paracellular and cellular pathways. In adults, limited data suggest that net phosphorus absorption ranges from 55 to 80 % of intake. Phosphorus absorption is affected by the total amount of phosphorus in the diet and also by the type of phosphorus (organic versus inorganic), the food origin (animal- versus plant-derived) and the ratio of phosphorus to other dietary components. Absorption is regulated by 1,25(OH)2D and PTH.
Hypophosphataemia, defined by a serum inorganic phosphorus concentration of < 0.80 mmol/L (2.48 mg/dL), only rarely occurs because of inadequate dietary phosphorus intake, and is generally due to metabolic disorders.
The major dietary contributors to phosphorus intake are foods high in protein content, i.e. milk and milk products followed by meat, poultry and fish, grain products and legumes. Based on data from 13 dietary surveys in nine European Union countries, mean phosphorus intakes range from 265 to 531 mg/day in infants, from 641 to 973 mg/day in children aged 1 to < 3 years, from 750 to 1 202 mg/day in children aged 3 to < 10 years, from 990 to 1 601 mg/day in children aged 10 to < 18 years and from 1 000 to 1 767 mg/day in adults (≥ 18 years).
Balance studies in adults were considered to be heterogeneous and to have many limitations. Overall, balance studies, including those in children and pregnant women, could not be used for setting DRVs for phosphorus. In addition, it was considered that estimations of phosphorus absorption from the diet, as well as losses of phosphorus via urine and faeces, vary over a wide range, so that the factorial approach cannot be used for deriving the requirement for phosphorus.
Evidence from human studies on the relationship between phosphorus intake and various health outcomes was also reviewed. It was considered that data on measures of bone health, cancer-related outcomes and evidence related to all-cause mortality and cardiovascular outcomes could not be used to derive DRVs for phosphorus.
Data on the molar ratio of calcium to phosphorus in intact bone of healthy adults suggest a range of approximately 1.6:1 to 1.8:1. Using the calcium to phosphorus molar ratio in bone of 1.6:1 to 1.8:1 and adjusting for the proportion of calcium and phosphorus found outside bone, a molar ratio of calcium to phosphorus in the adult body of about 1.37:1 to 1.55:1 is estimated. In addition, data from measurements of whole-body calcium and phosphorus contents in Caucasian men and women indicate that the calcium to phosphorus molar ratio in the whole body ranges from 1.48:1 to 1.69:1 in women and from 1.57:1 to 1.89:1 in men. The Panel thus considered that the ratio of calcium to phosphorus in the whole body ranges from about 1.4:1 to 1.9:1 and proposed, in the absence of other consistent evidence, that DRVs for phosphorus be set based on the approximate molar ratio of calcium to phosphorus in the body. The fractional absorption of phosphorus is higher than that of calcium. However, as phosphorus absorption has been reported to vary over a wide range, it was considered that the actual amounts of calcium to phosphorus that are available for absorption from the diet and that may be retained in the body cannot be determined. In the absence of this information, the Panel proposed to set DRVs for phosphorus based solely on the range of the molar ratio of calcium to phosphorus in the whole body. The Panel considered that the data are insufficient to derive Average Requirements and Population Reference Intakes (PRIs) for phosphorus and proposed to set Adequate Intakes (AIs) for all population groups. Based on the AI (for infants aged 7–11 months) and the PRIs (for all other ages) for calcium and considering a molar calcium to phosphorus ratio of 1.4:1 to 1.9:1, adequate quantities of phosphorus were calculated in mg/day. The Panel chose the lower bound of this range (i.e. a ratio of 1.4:1 which results in the higher phosphorus intake value) for setting an AI for phosphorus, taking into account estimated phosphorus intakes in Western countries which are considerably higher than the calculated values.
The AI is 160 mg/day for infants aged 7–11 months and between 250 mg/day and 640 mg/day for children. For adults, the AI is 550 mg/day. Taking into consideration adaptive changes in phosphorus metabolism that may occur during pregnancy and lactation, it was considered that the AI for adults also applies to pregnant and lactating women.
Keywords
phosphorus, calcium, molar ratio, Adequate Intake, Dietary Reference Value
Source: European Food Safety Authority