A Controlled Increase in Dietary Phosphate Elevates BP in Healthy Human Subjects

Area of Science:

• Cardiovascular Physiology
• Nutritional Science
• Endocrinology

Background:

• Epidemiologic studies link high dietary and serum phosphate to cardiovascular issues in healthy adults.
• Vitamin D, while beneficial for cardiovascular health, enhances phosphate absorption.
• Controlled studies on phosphate's hemodynamic effects in humans with normal renal function were lacking.

Purpose of the Study:

• To investigate the impact of controlled high dietary phosphate intake on systemic hemodynamics in adults with normal renal function.
• To assess the influence of vitamin D supplementation on these hemodynamic parameters.

Main Methods:

• A 11-week prospective, randomized, blinded outpatient study involving 20 young adults with normal renal function.
• Participants were assigned to either a high-phosphate diet or a low-phosphate diet (using lanthanum to inhibit absorption).
• All subjects received a high-dose intramuscular vitamin D3 injection after 6 weeks; 24-hour ambulatory blood pressure, pulse rate, and biomarkers were measured.

Main Results:

• The high-phosphate group showed significant increases in fasting plasma phosphate, 24-hour systolic and diastolic blood pressure, and pulse rate compared to the low-phosphate group.
• Elevated urinary metanephrine and normetanephrine excretion was observed in the high-phosphate group, suggesting increased sympathoadrenergic activity.
• Vitamin D supplementation did not alter any measured hemodynamic parameters, endothelial function, or arterial elasticity.

Conclusions:

• Increased dietary phosphate intake, independent of sodium, significantly elevates blood pressure and pulse rate in individuals with normal renal function.
• The observed hemodynamic changes are, at least partly, mediated by an increase in sympathoadrenergic activity.
• Vitamin D supplementation did not mitigate or exacerbate the effects of phosphate on cardiovascular parameters in this study.