Coconut water vs water: no better for hydration, more potassium to watch

Coconut water did not beat plain water in the one head-to-head exercise trial we found. Ten trained men cycled for an hour and then raced 10 km, and their times were 971 seconds on coconut water and 967 on water, with no significant difference in any physiological measure. When allowed to drink freely they took less of the coconut water, 3.9 fl oz (115 ml) against 7.1 fl oz (209 ml), and the authors put that down to taste. Ten men and one session per drink is a small test. In 32 women with prehypertension, 20 fl oz (600 ml) a day of tender coconut water for 14 days left plasma potassium no different from the same volume of water, and the abstract reports no blood pressure result. By US survey data, a 8.5 oz (240 g) serving of unsweetened coconut water carries about 396 mg of potassium, 62 mg of sodium and 43 calories, a figure scaled from 100 g that varies by brand.

How much is actually in it

• Coconut water from 45 coconuts aged 6 to 9 months had a median of 64 mEq/L potassium but only 3 mEq/L sodium, and potassium fell as the coconuts matured. — 45 coconuts from 8 dwarf palms, inland Brazil, 6th to 9th month of maturity (n = 45) Evidence C source
  Median potassium 64 mEq/L (46-99), sodium 3 mEq/L, osmolarity 419 mOsmol/L

What a real portion looks like

• A typical 8.5 oz (240 g) serving of unsweetened coconut water carries about 396 mg potassium, 62 mg sodium and 43 calories in US survey data, and one coconut yields about 206 g. — US survey food code, FNDDS (n = 1 food code) Evidence E source
  Per 100 g: potassium 165 mg, sodium 26 mg, energy 18 calories; per 240 g: 396 mg, 62.4 mg, 43.2 calories

What your body absorbs

• In an RCT in 19 young adults drinking 1.1 quarts (1 liter), electrolytes alone did not consistently improve fluid retention over water, while carbohydrate plus electrolytes raised the hydration index to 1.15 at 120 minutes. — 19 healthy young adults, 4 randomized sessions, 1.1 quarts (1 L) beverage at rest, 240 min follow-up (n = 19) Evidence B source
  Beverage hydration index 1.15 +/- 0.17 for carbohydrate-electrolyte vs water (1.0) at 120 min

What it does to your health

• In an RCT in 32 women with prehypertension, 10 fl oz (300 ml) tender coconut water twice daily for 14 days did not raise plasma potassium more than the same amount of water. — 32 women aged 25-44 with prehypertension; 20 fl oz (600 ml) a day of tender coconut water or water for 14 days (n = 32) Evidence B source
  No significant difference in plasma potassium between groups (p = 0.247)

Safety, limits and interactions

• In a double-blind RCT in 95 adults with mild to moderate ulcerative colitis, 14 fl oz (400 ml) coconut water daily for 8 weeks added to standard therapy gave 53.1% remission versus 28.3% with placebo, with no hyperkalemia. — 95 patients with mild to moderate active ulcerative colitis, India, 8 weeks, adjunct to standard therapy (n = 95) Evidence B source
  Remission 53.1% vs 28.3% (OR 2.9, 95% CI 1.2-6.7); no hyperkalemia
• A case report describes a 78-year-old man on losartan and spironolactone with kidney failure whose potassium reached 7.02 mEq/L, with paralysis, after a week of drinking large amounts of king coconut water. — 1 man, 78 years, renal failure, diabetes, on losartan and spironolactone (n = 1) Evidence D source
  Serum potassium 7.02 mEq/L; recovered within 24 h without dialysis

What people believe that the data does not support

• In a crossover RCT in 10 trained men, coconut water did not beat plain water on hydration markers or 10-km cycling time (971 vs 967 s), and they drank less of it voluntarily (3.9 vs 7.1 fl oz / 115 vs 209 ml). — 10 men, mean age 27.9; 60 min submaximal cycling plus 10-km time trial, 8.5 fl oz (250 ml) three times then ad libitum (n = 10) Evidence B source
  Time trial 971.4 vs 966.6 s (p = .698); ad libitum intake 3.9 vs 7.1 fl oz (115 vs 208.7 ml) (p < .001)
• A systematic review found no benefit from drinking 8 glasses of water a day in people without kidney stones. — studies 1972-2017 on water intake and disease risk Evidence C source
  Level 1 evidence for kidney stones only; no support for cardiovascular disease, constipation, headache, cognition, bladder cancer

Who this works differently for

• For people who form calcium kidney stones, a systematic review suggests hard water or mineral water high in magnesium and bicarbonate may help, and drinking more fluid prevents stones. — studies over 3 decades on water type and kidney stone disease Evidence C source
  Direction only: higher fluid intake prevents stones; hard or mineral water may reduce calcium stones

The bottom line

Coconut water is high in potassium and low in sodium. Coconuts analyzed in Brazil at 6 to 9 months held a median of 64 mEq/L potassium and only 3 mEq/L sodium, from one region and one variety. In a separate trial of 19 young adults that did not test coconut water, electrolytes alone at sports drink levels did not consistently help the body hold on to a liter of fluid better than water. Adding carbohydrate raised retention to 1.15 times that of water at 120 minutes. Water has its own myth. A systematic review found no benefit from drinking 8 glasses a day in people without kidney stones. For people who form calcium stones, drinking more fluid prevents stones, and a second review suggests hard water or mineral water might help, with no pooled numbers behind that. In 95 adults in India with mild to moderate ulcerative colitis, 14 fl oz (400 ml) of coconut water a day for 8 weeks on top of standard treatment gave remission in 53.1 percent against 28.3 percent on placebo (OR 2.9, 95% CI 1.2 to 6.7). That is one center and patients with a disease, and no one in it developed high potassium. Potassium is the real caution. A 78-year-old man with kidney failure who took losartan and spironolactone reached a blood potassium of 7.02 mEq/L, with paralysis, after a week of drinking large amounts of king coconut water. That is one case with several triggers at once. If you have kidney disease or take drugs like these, coconut water is a question for the person treating you.

Sources

1. cvw-daily-r3-06 · composition analysis
   The analysis of coconut water from the sixth to ninth month did not find any differences in the median concentrations of sodium (3 mEq/L; 2 and 3), glucose (0.6 g/L; 0.3 and 17.3) or total proteins (9 g/L; 6 and 12), but detected a reduction in the concentration of potassium (64 mEq/L; 46 and 99), calcium (6.5 mmol/L; 5 and 8.5), magnesium (8 mmol/L; 3.9 and 9.8), chloride (38.5 mEq/L; 30 and 48.7) and osmolarity (419 mOsmol/L; 354 and 472).
   J Pediatr (Rio J), 2006 · checked 2026-09-30
2. cvw-daily-r3-07 · reference dataset
   FNDDS 2707572 Coconut water, unsweetened: Potassium 165 mg/100 g, Quantity not specified 240 g 396.0 mg, 1 coconut yields 206 g 339.9 mg · Sodium 26 mg/100 g, 240 g 62.4 mg · Energy 18 kcal/100 g, 240 g 43.2 kcal
   USDA FNDDS 2021-2023 (FDC 2707572, food code 42403010) · checked 2026-09-30
3. cvw-daily-r3-02 · randomized crossover trial
   Compared to W, BHI was higher (p = 0.007) for C + E (1.15 ± 0.17) after 120 min and for AG + E (p = 0.021) at 240 min (1.15 ± 0.20). ... The addition of electrolytes alone (in the range of sports drinks) did not consistently improve BHI versus water; however, the combination with carbohydrate or dipeptides increased fluid retention, although this occurred earlier for the sports drink than the dipeptide beverage.
   Nutrients, 2021 · checked 2026-09-30
4. cvw-daily-r3-03 · randomized controlled trial
   After 14 days treatment, potassium plasma level between T and C groups were not significantly different (p=0,247).
   Curr Hypertens Rev, 2017 · checked 2026-09-30
5. cvw-daily-r3-04 · randomized controlled trial
   Clinical response (57.1% vs 28.3%; odds ratio [OR], 3.4; 95% confidence interval [CI], 1.4-7.9; P = .01), remission (53.1% vs 28.3%; OR, 2.9; 95% CI, 1.2-6.7; P = .02), and proportion of patients with fecal calprotectin (FCP) <150 μg/g (30.6% vs 6.5%; OR, 6.3; 95% CI, 1.7-23.6; P = .003) were significantly higher in CW. ... Adverse events were comparable, and no patient developed hyperkalemia.
   Clin Gastroenterol Hepatol, 2024 · checked 2026-09-30
6. cvw-daily-r3-05 · case report
   He was on Losartan and Spironolactone for ischemic heart disease. Dietary history revealed excessive intake of king coconut water (Cocos nucifera) over past one week.
   Case Rep Neurol Med, 2018 · checked 2026-09-30
7. cvw-daily-r3-01 · randomized crossover trial
   CW did not significantly improve time trial performance compared with PW (971.4 ± 50.5 and 966.6 ± 44.8 s respectively; p = .698) and there was also no significant differences between trials for any of the physiological variables measured. However there were subjective differences between the beverages for taste, resulting in a significantly reduced volume of voluntary intake in the CW trial (115 ± 95.41 ml and 208.7 ± 86.22 ml; p < .001).
   Int J Sport Nutr Exerc Metab, 2017 · checked 2026-09-30
8. cvw-daily-r3-08 · systematic review
   The available reviewed literature suggests no benefit to drinking 8 glasses of water per day in patients without nephrolithiasis.
   J Urol, 2018 · checked 2026-09-30
9. cvw-daily-r3-09 · systematic review
   Increased fluid intake prevents stone formation. Our review of the literature suggests that hard water and bottled mineral water might be helpful for calcium stone formers.
   Curr Urol Rep, 2020 · checked 2026-09-30