Nitrate supplements, claiming to improve the efficiency at which muscles use oxygen, have been popular for years, but do they work?
A new study says they may increase performance--they decrease the viscosity of blood, aiding in blood flow, while at the same time ensuring that tissue oxygen requirements are not compromised.
Researchers investigated the effects of nitrate supplementation on hemoglobin in four groups of rats, which were housed in either normoxic or hypoxic (low oxygen) conditions and supplemented with sodium nitrate (or sodium chloride, ordinary table salt, as a control). Intake of nitrate via diet and drinking water was carefully monitored. Hypoxia is known to elevate hemoglobin levels, but nitrate supplementation at a moderate dose largely suppressed this effect.
Unexpectedly, nitrate also lowered hemoglobin levels in normoxic animals. They found that at higher doses of nitrate, hemoglobin levels began to rise again. Researchers investigated the mechanisms underlying these effects and found that the suppression of hemoglobin was due to nitrate enhancing liver oxygenation and suppressing its expression of the hormone, erythropoietin. Conversely, as hemoglobin levels fell, the kidney became less well supplied with oxygen and at higher doses of nitrate it expressed more erythropoietin, reversing the effect.
"Our research sheds new light on how oxygen delivery to bodily tissues is controlled to support mammalian life, and what role the kidneys and the liver play in achieving this," said Andrew Murray, Ph.D., a researcher involved in the work from the Department of Physiology, Development and Neuroscience at the University of Cambridge in Cambridge. "These findings offer potential therapeutic avenues for dietary intervention in polycythemia and other conditions that warrant a reduction in red cell mass, but may have broader implications related to the way that supply and demand of oxygen are matched."
"This doesn't mean that taking a nitrate supplement will transform you into the next Marshawn Lynch," said Gerald Weissmann, M.D., Editor-in-Chief of The FASEB Journal. "What it does mean, however, is that we're beginning to understand the science behind why some people feel they turn into the Seahawk's 'Beast Mode' when taking these supplements."
Citation: Tom Ashmore, Bernadette O. Fernandez, Colin E. Evans, Yun Huang, Cristina Branco-Price, Julian L. Griffin, Randall S. Johnson, Martin Feelisch, and Andrew J. Murray. Suppression of erythropoiesis by dietary nitrate. FASEB J. March 2015 29:1102-1112; doi:10.1096/fj.14-263004