Controlled dietary phosphate loading in healthy young men elevates plasma phosphate and FGF23 levels

Area of Science:

• Nephrology
• Endocrinology
• Mineral Metabolism

Background:

• Dietary inorganic phosphate (P_i) intake influences renal P_i excretion via hormones like PTH and FGF23.
• Previous human studies on dietary P_i effects are limited by short durations or varied calcium intake.
• The impact of controlled, isolated dietary P_i changes over short periods remains unclear.

Purpose of the Study:

• To investigate the effects of controlled high dietary P_i intake on mineral metabolism in healthy young men.
• To determine the impact of isolated dietary P_i changes on key hormonal and metabolic parameters.

Main Methods:

• A randomized cross-over trial involving 10 healthy young men.
• Participants consumed a low P_i diet (with phosphate binder) or a high P_i diet (supplemented with phosphate capsules) for 5 days each, with a 7-day washout period.
• Measurements included plasma P_i, urinary P_i and calcium, intact FGF23 (iFGF23), and other hormonal markers.

Main Results:

• High P_i intake significantly increased plasma P_i levels and 24-hour urinary P_i excretion.
• Urinary calcium excretion decreased, while plasma iFGF23 increased and plasma Klotho decreased.
• No significant changes were observed in PTH, calcidiol, calcitriol, Fetuin-A, dopamine, or aldosterone levels.

Conclusions:

• Elevated dietary P_i intake increases plasma P_i and renal P_i excretion in healthy young men.
• The hormone iFGF23 plays a role in P_i homeostasis and calcitriol reduction during high dietary P_i intake.
• Sustained high P_i intake may represent a cardiovascular health risk due to elevated serum P_i levels.