Salt Science ● by Braeden
My sister Kaiya has POTS. For years I watched her piece together salt tablets, broth and powders to reach the number her doctor gave her. I wanted to know why that number mattered. Here is what the research says.
The 30-second version
- Standing pulls blood toward your legs. Your heart speeds up to keep blood moving.
- In a 2025 study, women with POTS had about 14% less blood volume than expected.
- In a 2021 trial, high sodium raised plasma volume and shrank the heart-rate jump on standing.
- Guidance is often written in salt. Labels list sodium. Track sodium, and let your doctor set the number.
What happens when you stand
Gravity pulls blood down toward your legs and belly. Within seconds, your blood vessels tighten and your heart beats a little faster. In most people, heart rate goes up a little and then settles.
How POTS is defined
All of these must be true (Raj et al., 2022):
- Heart rate rises 30 or more beats per minute within 10 minutes of standing (40 or more for ages 12 to 19).
- Blood pressure does not drop a lot at the same time.
- Symptoms happen often when upright and have lasted 3 months or more.
- No other condition explains the fast heart rate.
Less blood to work with
A 2025 study measured blood volume directly (Kulapatana et al., 2025):
Blood volume and standing heart rate
21 women with POTS compared with 19 healthy women
Total blood volume (mL per kg of body weight)
Heart rate when standing (beats per minute)
The women with POTS averaged about 14% below their expected blood volume. And the bigger the shortfall, the higher their heart rate went when they stood. In plain words: less blood means the heart works harder.
Where sodium comes in
Your body holds on to water along with sodium. A 2021 trial tested what that means for blood volume in POTS (Garland et al., 2021):
Six days of low sodium vs six days of high sodium
The POTS group in a 2021 crossover trial (14 people)
Heart-rate jump when standing (beats per minute)
Plasma volume below expected
What this trial does not show
- It was small and short: 14 patients, 6 days on each diet.
- The high-sodium diet was far above usual advice. It tested how the body responds; it did not set a target.
- Symptom scores trended lower on high sodium, but the difference was not statistically significant.
Salt is not sodium
Salt is only about 39% sodium by weight. Published guidance is often written in salt, sometimes in teaspoons (Raj et al., 2022). Food labels list sodium in milligrams.
| Salt | Sodium in it |
|---|---|
| 1 g | about 390 mg |
| 5 g | about 1,970 mg |
| 10 g | about 3,930 mg |
Ask your doctor one question: “Is that salt or sodium?”
What we still don’t know
- Experts do not yet agree on the best amount, form or length of time for added salt (Williams et al., 2022).
- It is suggested mainly for people without heart conditions whose lying-down blood pressure is not high (Williams et al., 2022).
- Long-term high salt can affect blood pressure and organs. Modest increases may be enough (Stock et al., 2022).
That is why your number comes from your doctor, not from a blog post. Including this one.
Braeden, co-founder, +Pouch
Sources
- Raj SR, Fedorowski A, Sheldon RS. Diagnosis and management of postural orthostatic tachycardia syndrome. CMAJ. 2022;194(10):E378-E385. PubMed 35288409
- Kulapatana S, et al. Blood volume deficit in postural orthostatic tachycardia syndrome assessed by semiautomated carbon monoxide rebreathing. Clin Auton Res. 2025;35(2):267-276. PubMed 39614968
- Garland EM, et al. Effect of high dietary sodium intake in patients with postural tachycardia syndrome. J Am Coll Cardiol. 2021;77(17):2174-2184. PubMed 33926653
- Williams EL, et al. Salt supplementation in the management of orthostatic intolerance: vasovagal syncope and postural orthostatic tachycardia syndrome. Auton Neurosci. 2022;237:102906. PubMed 34823150
- Stock JM, et al. Dietary sodium and health: how much is too much for those with orthostatic disorders? Auton Neurosci. 2022;238:102947. PubMed 35131651
This post is for education and is not medical advice. Talk with your doctor before changing how much salt or fluid you take in.
More from +Pouch: what an electrolyte pouch is and customer reviews.
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