Electrolyte research report

The Forum for Endurance Athletes

Electrolyte research report

Postby glenng » Fri Apr 01, 2011 11:11 am

I wondered if you had seen this report of a research study and how you think it squares up with your work with Endurolytes. Seems to be in conflict to me???? ... tion_25073
Posts: 1
Joined: Fri Apr 01, 2011 11:08 am

Re: Electrolyte research report

Postby steve-born » Sat Apr 02, 2011 12:59 pm

Hello Glenn -

I have just recently read this article, as has Dr. Bill Misner, and here are a couple comments I wanted to make on it, followed by some information from Dr. Bill that he sent me following our correspondence on this topic.

A portion of the article reads:

For his first study, which he completed with students at Point Loma Nazarene University in San Diego, Calif., he tested water versus an electrolyte solution with about three times the sodium of Gatorade Endurance. Subjects began the study fully hydrated then drank about 1.5 liters of either water or the sodium solution over 30 minutes.

He found that after three hours of monitoring, the subjects who had consumed water had actually "dehydrated"---on average, they had lost 22 percent more water than they drank. But the subjects who drank the high-sodium solution retained 35 percent of the fluid---they became hyper-hydrated.

For his second study, Goforth compared the hydration effects of three different solutions: one with a sodium level equivalent to Gatorade Endurance, one with twice the sodium of Gatorade Endurance, and one that was three times saltier. He tested against Gatorade Endurance because of its high sodium level for a sports drink.

After three hours, the subjects who consumed the Gatorade Endurance equivalent were dehydrated---on average, they had lost 6 percent more water than they had consumed. But the subjects who drank the mid-range sodium solution retained 25 percent of the water they drank, and the subjects who drank the saltiest solution retained 35 percent.

--- END ---

My thoughts, which again, I discussed with Dr. Misner, are as follows:

#1 - Drinking 1.5 liters of water in 30 minutes, after one is already "fully hydrated" to begin with (as indicated in the study), is an awful lot of fluid to consume in a very short time (even if one is not fully hydrated to begin with), enough to potentially cause the body to lose fluids and sodium via urination.

#2 - Drinking 1.5 liters of a high-sodium fluid solution in 30 minutes is also a lot of fluid (and now sodium) in a short period of time, especially when one is already "fully hydrated."

What caught my interest is the use of the word "retained." Now, to me, retaining fluid as a result of high-sodium intake means that the recirculating/conservation properties of aldosterone have been shut down, with vasopressin (the "anti-diuretic" hormone) now predominating. This, in my opinion, is what is causing the fluid retention and my hypothesis is that this additional fluid is NOT inside the cells (such as what glycerol loading would do), but rather in distal areas outside the cell - the hands, feet, and face. In other words, this additional fluid wouldn't be a beneficial hyper-hydration but rather non-beneficial edema-like symptoms.

#3 - If #1 and #2 are accurate, and I believe that they are, then the increased percentage of water retention from an even more higher sodium intake (the second study) would be expected.

#4 - In my opinion, to say that the "water only" subjects were dehydrated is not really the proper use of the word "dehydrated."

-- END --

Dr. Bill replied to me stating, "I tend to agree with your assessment. No doubt that there are a few individuals who can adapt to the loading dose effects by forcing their body to adapt. Emergency medicine treatment for dehydrated athletes or normal people exposed to hyperthermia treats the individual according their level of water intoxication, dehydration, or sodium dilution state. Noakes and Speedy have answered this in a paper, one in 2006 and a more recent one in 2008. Here is a link to the full text earlier version of this paper: ... ool=pubmed

Dr. Bill then responded with another email to me in which he provided some specific research:

Only modest fluid intake causes hyponatremia during prolonged events

Speedy-Noakes concluded that Subjects who developed hyponatremia had evidence of fluid overload despite modest fluid intakes:

1. Clin J Sport Med. 2001 Jan;11(1):44-50.
Fluid balance during and after an ironman triathlon.

Speedy DB, Noakes TD, Kimber NE, Rogers IR, Thompson JM, Boswell DR, Ross JJ, Campbell RG, Gallagher PG, Kuttner JA.
Department of General Practice and Primary Care, University of Auckland, New Zealand.

OBJECTIVE: To record weight changes, fluid intake and changes in serum sodium concentration in ultradistance triathletes.

DESIGN: Descriptive research.

SETTING: Ironman triathlon (3.8 km swim, 180 km cycle, 42.2 km run). Air temperature at 1200 h was 21 degrees C, (relative humidity 91%). Water temperature was 20.7 degrees C.

18 triathletes.


MAIN OUTCOME MEASURES: Subjects were weighed and had blood drawn for serum sodium concentration [Na], hemoglobin, and hematocrit, pre-race, post-race, and at 0800 h on the morning following the race ("recovery"); subjects were also weighed at transitions. Fluid intake during the race was estimated by athlete recall.

RESULTS: Median weight change during the race = -2.5 kg (p < 0.0006). Subjects lost weight during recovery (median = -1.0 kg) (p < 0.03). Median hourly fluid intake = 716 ml/h (range 421-970). Fluid intakes were higher on the bike than on the run (median 889 versus 632 ml/h, p = 0.03). Median calculated fluid losses cycling were 808 ml/h and running were 1,021 ml/h. No significant difference existed between pre-race and post-race [Na] (median 140 versus 138 mmol/L) or between post-race and recovery [Na] (median 138 versus 137 mmol/L). Plasma volume increased during the race, median + 10.8% (p = 0.0005). There was an inverse relationship between change in [Na] pre-race to post-race and relative weight change (r = -0.68, p = 0.0029). Five subjects developed hyponatremia ([Na] 128-133 mmol/L).

CONCLUSIONS: Athletes lose 2.5 kg of weight during an ultradistance triathlon. most likely from sources other than fluid loss. Fluid intakes during this event are more modest than that recommended for shorter duration exercise. Plasma volume increases during the ultradistance triathlon. Subjects who developed hyponatremia had evidence of fluid overload despite modest fluid intakes.

Too much sodium is not a preventative for hyponatremia.

Speedy et al., concluded: "Sodium ingestion was associated with a decrease in the extent of weight loss during the race. There was no evidence that sodium ingestion significantly influenced changes in [Na] or PV more than fluid replacement alone in the Ironman triathletes in this study. Sodium supplementation was not necessary to prevent the development of hyponatremia in these athletes who lost weight, indicating that they had only partially replaced their fluid and other losses during the Ironman triathlon."

1. Clin J Sport Med. 2002 Sep;12(5):279-84.
Oral salt supplementation during ultradistance exercise.
Speedy DB, Thompson JM, Rodgers I, Collins M, Sharwood K, Noakes TD.
Department of General Practice and Primary Care, University of Auckland, New Zealand.
Erratum in: Clin J Sport Med. 2003 Jan;13(1):67.

OBJECTIVE: The objective of this study was to determine whether sodium supplementation 1) influences changes in body weight, serum sodium [Na], and plasma volume (PV), and 2) prevents hyponatremia in Ironman triathletes.

SETTING: The study was carried out at the South African Ironman triathlon.

PARTICIPANTS: Thirty-eight athletes competing in the triathlon were given salt tablets to ingest during the race. Data collected from these athletes [salt intake group (SI)] were compared with data from athletes not given salt [no salt group (NS)].

INTERVENTIONS: Salt tablets were given to the SI group to provide approximately 700 mg/h of sodium.

MAIN OUTCOME MEASUREMENTS: Serum sodium, hemoglobin, and hematocrit were measured at race registration and after the race. Weights were measured before and after the race. Members of SI were retrospectively matched to subjects in NS for 1) weight change and 2) pre-race [Na].

RESULTS: The SI group developed a 3.3-kg weight loss (p < 0.0001) and significantly increased their [Na] (delta[Na] 1.52 mmol/L; p = 0.005). When matched for weight change during the race, SI increased their [Na] compared with NS (mean 1.52 versus 0.04 mmol/L), but this did not reach statistical significance (p = 0.08). When matched for pre-race [Na], SI had a significantly smaller percent body weight loss than NS (-4.3% versus -5.1%; p = 0.04). There was no significant difference in the increase of [Na] in both groups (1.57 versus 0.84 mmol/L). PV increased equally in both groups. None of the subjects finished the race with [Na] < 135 mmol/L.

--- END ---

In a section of the article, "Electrolyte Replenishment - Why It’s So Important and How to Do It Right" ( ... .1274.html), I paraphrase Dr. Bill in writing:

Aldosterone is a hormone that controls the rate of sodium circulated in the human body. When sodium levels dip too low, via loss in perspiration or urine, aldosterone is released, stimulating the kidney tubule cells to increase re-absorption of sodium back into the blood. In basic terms, the body has a very complex and effective way of monitoring, recirculating, and thus conserving its stores of sodium.

High sodium intake will suppress serum aldosterone, whereas low sodium intake will elevate serum aldosterone. In other words, too much sodium—be it via diet and/or during exercise—will suppress and neutralize aldosterone’s sodium recirculation (and thus sparing) effects, causing more sodium to be lost. Conversely, a low-sodium diet and a more conservative sodium intake—in tandem with other depleting electrolytes—during a workout or race creates an environment where lower amounts of sodium are lost in sweat and urine.

--- END ---

I also like what Dr. Bill states regarding sodium and fluid intake, and this statement remains our position on the topic: "The human body is constructed to be sensitive to monitor homeostatic electrolyte balance, suggesting consistent intake of small amounts of fluid and electrolyte volume prevent severe deficits of fluid and electrolyte loss."

I hope you will find this information useful and helpful.

Sincerely -

Steve Born
Fueling Expert
Event Sponsorship Coordinator
User avatar
Posts: 300
Joined: Mon Mar 08, 2010 11:16 pm

Return to Endurance Forum

Who is online

Users browsing this forum: No registered users and 4 guests