Yesterday, I attended a conference at the University of Colorado Medical Center that focused on the relationship between dietary phosphate, renal (kidney) disease and heart disease; the presenter was Dr. Myles Wolf from Northwestern University.
As reported by Dr. Wolf, our serum phosphate level is maintained within a narrow range, balancing intake through the GI tract and excretion through the kidneys; elevation of our serum phosphate may result from a high dietary load or from defective clearance due to renal disease. Most foods contain a large amount of phosphate; however, phosphate in meats, dairy products and processed foods is readily absorbed while that in legumes, vegetables and fruits is not nearly as bioavailable. Researchers have discovered that FGF23, a hormone, is secreted in response to high serum phosphate levels; released from bone cells, it acts on the kidneys to increase excretion of phosphate in the urine (assuming the kidneys are not diseased). In rat studies at Northwestern, FGF23 was also found to act on the heart, increasing the size of heart muscle cells, leading to thickening of the left ventricle. This latter development, which is common in patients with end stage kidney disease, leads to heart failure and ventricular arrhythmias.
It thus follows that a diet high in bioavailable phosphate (meats, dairy products, processed foods) may increase the risk of heart failure; indeed, the higher rate of congestive heart failure in African Americans may reflect socioeconomic factors that lead to a high phosphate diet. No doubt, other factors play a role as well (uncontrolled hypertension, high sodium intake and obesity to name a few) but the action of FGF23 is intriguing and appears to offer evidence that a vegetarian diet may help to prevent left ventricular thickening and secondary heart failure. In addition, the potential development of drugs that block the effects of FGF23 on heart muscle may provide new tools in the management of this common and often fatal disease. My thanks to Dr. Wolf for a fascinating presentation.