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Water BODY HANDBOOK
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Electrolytes
Your saltshaker is not the problem. Most of the sodium in your week is hidden in bread, deli meat, soup, and restaurant food, while the potassium and magnesium that balance it out sit in vegetables you didn't eat. Three minerals, one lever: too much sodium, not enough of the other two. Fix the ratio and the payoff is real. In a 21,000-person trial, one swap in cooking cut stroke by 14% and death by 12% over five years.
Do ยท Daily Evidence Moderate Chapter Water

Sodium holds water in your bloodstream and, when there's too much, raises blood pressure. Potassium is its counterweight: it relaxes arteries and tells your kidneys to dump the excess. Move a hypertensive from high sodium to low and the top number drops about 7 points in under a month โ€” roughly what a starting blood-pressure drug does 1. Raising potassium pulls another 3.5 points off and cuts long-run stroke risk about a quarter 2.

The strongest evidence combined both in one move: a salt substitute (three-quarters sodium, one-quarter potassium), used in cooking, cut stroke 14% and death from any cause 12% over five years 3. Magnesium is the third mineral: about half of adults fall short of the target, and topping up drops pressure another couple of points, with the biggest effect in those who were low 4, 5.

Swap your table salt first โ€” it does two jobs at once.

The arc, if you hold it.

  • Weeks: food tastes flatter for a few days, then sharpens as your palate resets. If you were hypertensive, the cuff reads 5โ€“7 points lower at the next physical 1.
  • Months: if you were low on magnesium, you fall asleep about a quarter-hour faster 9. The doctor talks about holding off on a pill instead of starting one.
  • Years: this is where the trial evidence pays โ€” 14% fewer strokes and 12% fewer deaths in the salt-substitute arm over five years 3.
The fine print โ€” when to skip it, and what people get wrong

"Cramps mean you're low on electrolytes." Cramping and non-cramping athletes finish races with identical sodium and magnesium levels 10; magnesium didn't beat placebo for leg cramps 11. "Less salt is always better." Below the moderate band, cutting further hasn't helped in trials 12. Magnesium oxide absorbs at 4โ€“10%; glycinate and citrate are three to four times better 13.

Kidney disease or these drugs, get a clinician's sign-off first. A potassium-enriched salt can raise blood potassium to a dangerous range if your kidneys clear it poorly, or if you take ACE inhibitors, ARBs, or spironolactone โ€” the SSaSS trial excluded advanced kidney disease for this reason 3. In heart failure, don't cut sodium aggressively on your own 14.

References
  1. 1Sacks FM, Svetkey LP, Vollmer WM et al. (2001). Effects on blood pressure of reduced dietary sodium and the Dietary Approaches to Stop Hypertension (DASH) diet. New England Journal of Medicine. link
  2. 2Aburto NJ, Hanson S, Gutierrez H et al. (2013). Effect of increased potassium intake on cardiovascular risk factors and disease: systematic review and meta-analyses. BMJ. link
  3. 3Neal B, Wu Y, Feng X et al. (2021). Effect of salt substitution on cardiovascular events and death (SSaSS). New England Journal of Medicine. link
  4. 4Zhang X, Li Y, Del Gobbo LC et al. (2016). Effects of magnesium supplementation on blood pressure: a meta-analysis of randomized double-blind placebo-controlled trials. Hypertension. link
  5. 5Rosanoff A, Weaver CM, Rude RK (2012). Suboptimal magnesium status in the United States: are the health consequences underestimated? Nutrition Reviews. link
  6. 6Cogswell ME, Loria CM, Terry AL et al. (2016). Estimated 24-hour urinary sodium and potassium excretion in US adults. JAMA. link
  7. 7NASEM (2019). Dietary Reference Intakes for Sodium and Potassium. link
  8. 8McDermott BP, Anderson SA, Armstrong LE et al. (2017). National Athletic Trainers' Association position statement: fluid replacement for the physically active. Journal of Athletic Training. link
  9. 9Abbasi B, Kimiagar M, Sadeghniiat K et al. (2012). The effect of magnesium supplementation on primary insomnia in elderly: a double-blind placebo-controlled clinical trial. Journal of Research in Medical Sciences. link
  10. 10Schwellnus MP (2009). Cause of exercise associated muscle cramps (EAMC) โ€” altered neuromuscular control, dehydration or electrolyte depletion? British Journal of Sports Medicine. link
  11. 11Garrison SR, Korownyk CS, Kolber MR et al. (2020). Magnesium for skeletal muscle cramps. Cochrane Database of Systematic Reviews. link
  12. 12Mente A, O'Donnell M, Rangarajan S et al. (2018). Urinary sodium excretion, blood pressure, cardiovascular disease, and mortality: a community-level prospective epidemiological cohort study (PURE). The Lancet. link
  13. 13Schwalfenberg GK, Genuis SJ (2017). The importance of magnesium in clinical healthcare. Scientifica. link
  14. 14Ezekowitz JA, Colin-Ramirez E, Ross H et al. (2022). Reduction of dietary sodium to less than 100 mmol in heart failure (SODIUM-HF): an international, open-label, randomised, controlled trial. The Lancet. link
Related in the handbook (8)
Helps
  • โ€” Fixing the sodium-potassium ratio is one of the few diet moves with hard blood-pressure evidence.
Related
  • โ€” Magnesium is the third mineral here โ€” heart rhythm, sleep, and a few hundred other jobs.
  • โ€” Water alone isn't the whole story โ€” when you're sweating or drinking a lot, the mineral balance matters as much as the volume.
  • โ€” It's the sodium-to-potassium ratio that matters, and most people have it backwards.
  • โ€” The win here is the sodium-to-potassium ratio, the same ratio that drives the broader electrolyte story.
  • โ€” Fixing the sodium-potassium ratio is the big lever; which salt you reach for is the small one, and it also decides whether you get enough iodine.
  • โ€” The rehydration salts in the kit are the electrolyte fix โ€” the part that actually pulls you through a night of traveler's diarrhea.
  • โ€” Both are about the minerals in your water; remineralizing puts back the calcium and magnesium RO removed.
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