Sodium Risks in Hydration During Exercise and the Value of Trial Dosing

In the recent weeks, there's been some commentary on David Roche, a high-profile runner in Colorado, quitting in a spectacular way at the Western States 100-mile endurance race. In a YouTube tell-all after the event, he goes into what I can only term as a "near death" experience despite leading a third of the way at this race. What can we make of this drama?

I know very little about Western States. The race this year was "hot" and Roche being a bit of a showman went into his own head and self-sabotaged himself (by his own admission). What interested me more was his account of vomiting and blurred vision during the race, and his attempts to correct his condition by dialing back his sodium intake. That is quite interesting as it sounds like the symptoms of hyponatremia. Was he clinically diagnosed for it?

Could those odd and rare cases of people collapsing in our communities during outdoor endurance exercise be related to hydration and sodium imbalances, rather than cardiac pre-conditions? We can prevent a fatality from happening near us by spreading awareness about these risks.

With the recent explosion in high carb and high sodium sports products, it is time to explore the topic of exercise related water poisoning, sodium risks and market choices of a variety of electrolyte brands categorized by the amount of sodium and potassium they contain. 

SODIUM RISKS IN HYDRATION DURING EXERCISE 
AND THE VALUE OF TRIAL DOSING

1. Introduction

Normal range of blood plasma sodium concentration is 135–145 mmol/L. Under heat stress, both overconsumption of plain water and excessive sodium intake can invite negative effects by changing the plasma sodium concentration.

"Hydrate," they say. But if you’ve ever finished a hot run with a dull headache after gulping tons of water, you’ve just poisoned yourself.

In fact, we know a lot about water intoxication from early marathons.  At the 2002 Boston Marathon, around 1,900 of nearly 15,000 finishers - more women than men - developed some level of a condition called “hyponatremia”. In this condition, plasma sodium concentration fell to alarming levels <135 mEq/l.

About 90 runners experienced critical cases and one runner died. These individuals had, unintentionally, diluted their blood sodium to dangerous levels by overconsuming plain fluids.

“Hypernatremia” is the opposite condition, when plasma sodium concentration rises above 145 mEq/l. A publication from the Australian Institute of Sport noted that athletes can experience mild hypernatremia during exercise because sweat losses deplete fluid stores at a higher rate than sodium/electrolyte losses.

Being aware of the effects of low sodium and high sodium concentration is an important aspect of heat training for all endurance athletes in our community.

2. What’s an electrolyte?

Electrolytes are mineral salts that conduct electricity in the body. Like a car battery generates electrical energy from ion flow, nerve transmission and muscle contraction rely on the movement of ions such as sodium, potassium, and calcium across your cell membranes. Potassium helps set the electrical resting state, sodium and potassium drive electrical impulses, and calcium triggers neurotransmitter release and muscle contraction.

Under mild conditions of exercise, the body has a mechanism to reduce sodium losses in sweat by retaining sodium through the kidneys. This process is regulated by hormones like aldosterone. However, under prolonged exercise in hot and humid conditions, sodium losses in sweat can outpace the body’s conservation mechanics.

Simply drinking lots of plain water would just dilute the sodium levels in the body and lead to water intoxication. Another "additive" effect along with hyperhydration seems to be increased sodium loss in sweat and loss of anti-diuretic hormone (ADH) suppression. 

The clinical sign that differentiates hyponatremia from other conditions is vomiting. According to Veniamakis et. al (2022), vomiting is related to reflex action in response to the increasing distension of large and unnecessary amounts of fluid within the gastrointestinal tract or may be caused by the central nervous system. Muscle cramps, hypoglycemia, heat stroke, weariness and headache can be outward signs of hyponatremia. In severe cases, coma or death is the result. 

3. What about too much sodium?

Clinical hypernatremia is diagnosed when plasma sodium concentration rises above 145 mEq/l. Water shifts out of the cells into the extra-cellular space, which can cause cell shrinkage.  

A concentrated urine upon returning from a run is a common sign that fluid balance has been disrupted, indicating the body is conserving water. This can be a marker of dehydration and an altered salt-water balance.

The root cause of hypernatremia is sweat loss. This might seem counterintuitive because sweat loss is associated with sodium loss. But sweat is hypotonic (less salty) compared to blood (20-60 mmol/L vs 135-145 mmol/L) so in relative terms, sweat loss means more fluid loss than sodium loss (if you’ve ever tasted blood in your mouth, you might recall the salty taste).

With the sodium concentration now elevated, adding more sodium without proper dilution in water promotes conditions for hypernatremia. But the cause of the initial rise in sodium is fluid loss from the body!

A careless move might involve drinking fluids with high concentrated sodium. How? 

Consider oral rehydration packets based on the WHO formula.  One sachet, properly diluted in 1L of water, delivers 75 mmol/L of sodium, which falls within the range of a high sodium sweater (sweat has 60-90+ mEq/L or 1380-2070mg/L of sodium). This is the correct dilution level as per the instructions on the packet. But if someone mixed it into just 250mL of water with the hope of hydrating, they would have consumed a 300 mmol/L solution which is a fourfold increase in the formula!

For a 60 kg runner - say, a short woman with about 50% body water - it doesn't take much concentrated sodium intake to push the blood levels high. Depending on pre-conditions, such as hypertension, high sodium levels can bring about negative effects.

Stay tuned to signs like excessive thirst, concentrated urine, general fatigue, muscle twitching and confusion. These are signs you’re losing fluid and concentrating the sodium levels in the body.

4. What do we do about it?

This is why we train in distance running. Training involves understanding how your body reacts to dosing levels of water-electrolyte solutions in various conditions in the heat to get the right fluid balance. Bear in mind that the body also has a cunning way of conserving sweat losses over time with heat acclimation.

Both too little and too much sodium bring negative effects to the body. For those medically inclined, Braun et al. (2015) offer excellent guidance on managing hypo and hypernatremia through clinical decision trees.

Can commercial sweat tests help athletes get an idea about their sodium needs? That’s a debate in of itself.

Commercial sweat tests that recommend sodium replacement strategies often don’t reflect real-world needs. There’s a big difference between:

• Lab vs. field sweat
• Early vs. late sweat composition
• Localized patch sampling vs. full-body sweat

Baker et al. (2016) found regional patch tests (like those on the forearm) can differ by 10–20% from gold-standard whole-body wash-downs. Variables like electrolyte leaching or water absorption inside the patch can skew results. Dziedzic et al. (2014) reported 15–25% variability depending on patch placement and sweat rate. Even a high-sodium meal before a test can elevate sweat sodium levels for hours (Campbell et al., 2020).

In other words, your sweat test is probably telling you what you just ate, not what your physiology truly needs.

Having a sweat test is not a bad place to start. But before committing to one, understand the experience level of the lab and test protocol employed.   

Hydration strategies before, during and after exercise as documented in Veniamakis et.al

5. What's the best way to estimate fluid losses?

A practical, simple method to estimate whole body hourly fluid loss is the mass-balance approach.

Just weigh yourself accurately before and after a training run in the heat. Make sure to use a calibrated weighing scale. A known weight like a 5kg dumbbell can be used for calibration.

The change in body mass gives you a good ballpark estimate of sweat loss. Divide that number over the duration you exercised to get the fluid loss rate.

An easy online calculator from the Gatorade Institute can do all the math for you. Please access this at this link.

Combine this with an understanding of your own thirst and effort levels, and you have a field-ready strategy to manage hydration intelligently.

 

6. What electrolyte should I use?

For the reasons stated before, there is no simple answer other than to “trial dose” and find out what works for your biochemistry.

The market for sports electrolytes has a bizarre array of choices. A lot of things in sports nutrition is based on opinions of people, behavioral science and psychology. People have different tastes. Some like it sugary, some like it salty. Some don’t like sugar, some don’t like fruit, some don’t like aftertastes.

For this reason, I present a handy comparative analysis of commonly available electrolyte drink mixes and chewable tablets for endurance athletes on the following page.

Data was sourced data from manufacturer websites, product labels, and reliable retailers, ensuring accuracy for 500ml servings.

The table shows key electrolyte content such as sodium, potassium, calcium, magnesium, sodium-to-potassium (Na:K) ratio, as well as sweeteners, and additives when diluted in a standard 500ml flask of water. It is arranged in descending order of sodium content.

Trial dose. Find out what works for you in different training situations.

Before you take high salt content electrolytes, have a word with your general physician. Those with hypertension, kidney disease, and beginners who just exercise a few times a week in the gym should not have to consume high sodium electrolytes, especially if the diet already has a high sodium content.

7. The electrolyte data

The following table shows key electrolyte content such as sodium, potassium, calcium, magnesium, sodium-to-potassium (Na:K) ratio, as well as sweeteners, and additives when diluted in a standard 500ml flask of water. It is arranged in descending order of sodium content.

Brand	Sodium (mg)	Potassium (mg)	Magnesium (mg)	Calcium (mg)	Na:K Ratio	Carb(g)	Sweetener/Additives
SaltStick Fastchews	200*	50*	10*	5*	4:1	0.5*	Stevia, dextrose
Precision Hydration PH1500 Tab	1500	250	24	48	6:1	1.8	Sweetener Sucralose, Maltodextrin
LMNT	1000	200	60	0	5:01	2	Stevia, maltodextrin
Redmond Re-Lyte	1000	500	60	60	2:1	0	Stevia, coconut water powder, natural flavors
Precision Hydration PH1000 Tab	1000	250	24	48	6:1	2.2	Sweetener Sucralose, Maltodextrin
Raw Replenish Satchet	1000	50	50	1	20:1	16	Cane sugar, natural flavor, taurine, fermented cane sugar
WHO ORS (Novalyte, NPI etc)	901	393	0	0	2.29:1	6.75	Glucose, no artificial additives
Hydralyte Tabs	680	390	0	0	1.74:1	2	Sugars, sucralose, mannitol, kosher certified
Hydralyte Sports Satchet	575	294	24	40	1.95:1	12	Glucose, sucralose.
Liquid I.V. Hydration	530	370	0	0	1.43:1	13	Cane sugar, maltodextrin, vitamins C/B3/B5/B6/B12
Hydralyte Powder	525	400	0	0	1.3:1	3	Sugars, sucralose, mannitol.
Precision Hydration PH500 Tab	500	250	24	48	2:1	1.7	Sweetener Sucralose, Maltodextrin
Powerbar Electrolyte Tab	500	300	56.3	120	1.67:1	0	Free from aspartame, preservatives and artificial flavorings. Pink Grapefruit and Lemon Tonic: contains 150 mg caffeine per 2 tablets.
Sponsor Electrolyte Tab	400	100	20	40	4:1	0.2	Flavor, sweetener sucralose, zinc citrate, color riboflavin
Skratch Labs Everyday Drink Mix	400	100	50	50	4:1	1	Lemon Oil, Lime Oil, Lemon Juice, Lime Juice, Ascorbic Acid.
PowerBar IsoActive Powder	380	151	29	60	2.5:1	29	Natural flavors, beet juice powder
Fast&Up Reload	360	154	40	25	2.3:1	5.16	Sucralose, maltodextrin, fructose, vitamins
Koda Electrolyte Powder	360	30	20	0	12:1	1	Dextrin, sodium bicarb, red beet juice powder
Veloforte Solo Satchet	350	240	9	19	1.45:1	5	Coconut water powder, freeze-dried apricot fruit powder* (29%), pink Himalayan salt, stevia
SIS Go Hydro Tab	345	65	8.1	102	5.3:1	1	Sucralose (artificial, zero calorie), sodium bicarb
SOS Daily Hydration Tab	330	190	35	0	1.7:1	4	Sugar, stevia extract, dextrose
Tailwind Endurance Fuel	310	90	12	27	3.4:1	25	Non-GMO Dextrose, Non-GMO-cane sugar, organic caffeine
Nuun Sport	300	150	25	13	2:1	4	Stevia, dextrose, avocado oil, avocado oil, sodium bicarb
O.R.S Hydration Original	277	193	0	0	1.44:1	3.71	Sucralose, beetroot juice concentrate
O.R.S Sport	260	98.6	56	0	2.64:1	2.5	Sucralose, beetroot juice concentrate
OTE Hydro Tabs	260	22	7	30	11.8:1	0	Sorbitol, vitamins B1/B2/B6
Gnarly Nutrition Hydrate	250	100	80	100	2.5:1	7	Cane sugar, tapioca maltodextrin, stevia, sea salt, B vitamins
Pocari Sweat 500ml Drink	245	100	3	10	2.45:1	31	Sugar, high fructose corn syrup
Gatorade Thirst Quencher Orange Drink	230	70	0	0	3.28:1	31	Sugar, dextrose, artificial flavors, yellow 6.
Humantra	200	200	25	50	1:1	0	Stevia Leaf Extract, Beta-Carotene and Beetroot Powder
Maurten Drink Mix 160	200	0	0	0	N/A	40	Maltodextrin, fructose, pectin, sodium alginate
Flow Formulas Endurance	200	0	0	0	N/A	29	organic cane sugar, lemon juice, rice maltodextrin, sea salt, stevia extract
Power Life Peak Replenish	150	432	230	450	0.34:1	2	Stevia, coconut water powder, betaine, natural flavor
Hydralyte Vitamin C + Electrolytes	145	181	3.4	4.6	0.1:1	9	Glucose, sucrose, fructose, Sodium Bicarb

Footnotes:

• SaltStick Fastchews: Values per 2-chew serving. 4–6 chews may be needed for 500ml equivalence (400–600 mg sodium, 1–1.5 g carbs).
• Gatorade Sports: Scaled from 1 scoop (591ml, 450 mg sodium, 150 mg potassium, 34 g carbs) to 0.85 scoops for 500ml.
• Raw Replenish: Scaled from 1 scoop (240ml, 180 mg sodium, 70 mg potassium, 8 g carbs) to 2 scoops for 500ml.
• O.R.S: Scaled from 2 tablets (200ml, 260 mg sodium, 78 mg potassium, 1 g carbs) to 5 tablets for 500ml.
• NovaLyte WHO ORS: Sodium from 2.6 g NaCl (1024 mg Na) + 2.9 g trisodium citrate (~11 mg Na); potassium from 1.5 g KCl (780 mg K).
• Some items in this table such as the Powerbar Isoactive Powder, Tailwind Endurance Fuels are drink mixes supplying both electrolytes and carbohydrates.

 

References

• Baker, L. B. (2016). Sweat testing methodology in the field: Challenges and best practices (Sports Science Exchange Series, No. 161). Gatorade Sports Science Institute. Link
• Braun, M. M., Barstow, C. H., & Pyzocha, N. J. (2015). Diagnosis and management of sodium disorders: Hyponatremia and hypernatremia. American Family Physician, 91(5), 299–307. Link
• Campbell, B. I., Costa, R. J. S., et al. (2020). Impact of 3‑day high and low dietary sodium intake on sweat sodium concentration and cardiovascular responses during 2 h exercise in the heat: a double-blind randomized crossover trial. Journal of Applied Physiology, 128(5). Link
• Dziedzic, C. E., Ross, M. L., & Burke, L. M. (2014). Variability of measurements of sweat sodium using the regional absorbent-patch method. International Journal of Sports Physiology and Performance, 9(5), 832–838. Link
• Veniamakis, E.; Kaplanis, G.; Voulgaris, P.; Nikolaidis, P.T (2022). Effects of Sodium Intake on Health and Performance in Endurance and Ultra-Endurance Sports. Int. J. Environ. Res. Public Health 2022, 19,3651. Link