Ingestion of high amounts of phosphates, known as phosphate loading, as a
method used by some endurance athletes to improve performance. This article
will briefly discuss this method of performance enhancement, as well as the
possibility of phosphate supplementation to enhance weight loss.
Phosphate loading is based on the fact that in vitro studies have found that
higher concentrations of phosphate lead to an increase in 2,3-biphosphoglycerate
(2,3-BPG) in red blood cells. 2,3-BPG is one of the various factors that
leads to a rightward shift in the oxygen dissociation curve, which can in
turn allow for greater muscle oxygen utilization. Studies attempting to determine
if phosphate loading increases 2,3-BPG and performance in endurance athletes
have been contradictory. However, a wide variety of protocols have been used
– for example, 22.2 g of calcium phosphate acutely, 4 g of potassium phosphate
for 4 days, or 4 g sodium phosphate for 3 or 6 days. A conclusion that can
be drawn from the research is that at least 2-3 days of phosphate loading
seems to be required to increase plasma phosphate enough to increase 2,3-BPG
to the level required for performance enhancement. If these conditions are
met, phosphate loading can increase blood cell 2,3-BPG levels by as much
as 25%. Whether or not this leads to an increase in endurance performance
is not well established, but it is likely that the change does improve maximal
oxygen consumption and peripheral oxygen delivery [1]. Additionally, in one
study, phosphate supplementation of 4 g for two days decreased the rating
of perceived exertion from endurance exercise [2].
Some older research indicates that phosphate ingestion may also facilitate
weight loss. In two placebo-controlled studies on obese women on weight reduction
programs, one found that phosphates prevented the decrease in T3 levels and
increased metabolic rate, while the other found that phosphate supplementation
increased resting metabolic rate but did not cause a statistically significant
increase in weight loss [3-4]. Two studies also found that acute phosphate
addition to a meal increased thermogenesis in obese women, while one additionally
found that there was no effect in lean women [5-6]. Therefore, while it is
likely that phosphate supplemenation is useful for weight loss programs in
the obese, it is less likely that it is beneficial to those who are already
relatively lean.
In conclusion, phosphate supplemenation may be useful to endurance athletes
and for weight loss in the obese. The suggested dosing schedule is 4 g of
sodium, calcium and/or potassium phosphate daily, although smaller doses
may still be of benefit.
If you have any questions or comments regarding this article, please email
dvdtlsn@bulknutrition.com.
No part of this article may be reproduced in any form without the permission of David Tolson or Mike McCandless.
