Oral rehydration therapy, usually shortened to ORT, is a rehydration method built around one idea: drink water that contains a precise mix of glucose and sodium. When those two are present together in the small intestine in the right proportions, the gut absorbs them as a pair and pulls water along with them. That lets your body take in fluid faster than it can from plain water alone. It is the science behind every serious hydration product on the market, and it is the foundation GREEN is built on.
This is not a wellness trend. ORT is one of the most studied ideas in hydration science. A 1978 editorial in The Lancet called the discovery behind it "potentially the most important medical advance this century." Here is what it is, where it came from, and what the numbers actually look like.
The short answer
ORT means rehydrating by mouth with a solution of water, glucose, and sodium in a ratio your small intestine is built to absorb. The World Health Organization and UNICEF have relied on it for roughly half a century in cholera outbreaks and disaster relief, because a correctly mixed oral solution can rehydrate a person nearly as well as an IV drip at a tiny fraction of the cost. The WHO puts it plainly: oral rehydration salts are "a mixture of clean water, salt and sugar," and a batch costs just a few cents to make.
The key word is ratio. Sugar and salt are not there for taste. They are the transport mechanism.
How ORT works in the body
The mechanism is called sodium and glucose co-transport. In the wall of your small intestine there are transporter proteins that only move sodium and glucose across together, like a door that needs two keys.
Here is the sequence:
- You drink a solution with matched amounts of sodium and glucose.
- In the small intestine, sodium ions and glucose molecules bind to the co-transporter in the intestinal wall.
- The transporter carries both across into the body.
- Water follows the absorbed sodium and glucose by osmosis.
- Fluid moves out of your gut and into your bloodstream faster than plain water would on its own.
That last step is the whole point. Plain water still hydrates you, but it moves passively. A correctly balanced glucose and sodium solution actively pulls water across the intestinal wall, which is why ORT is used worldwide as an oral alternative to IV rehydration, per WHO guidance.
Get the balance wrong and the effect weakens. Too much sugar raises the osmolarity of the drink, which can slow fluid absorption and even draw water back into the gut. Too little sodium and you are just drinking sweetened water. The formula is the product.
The exact WHO formula
Since 2005 the WHO and UNICEF have specified a reduced osmolarity ORS formula. Per liter of water, it contains:
| Ingredient | Amount per liter |
|---|---|
| Glucose | 13.5 g |
| Sodium chloride | 2.6 g |
| Potassium chloride | 1.5 g |
| Trisodium citrate | 2.9 g |
That works out to 75 mmol/L of sodium and 75 mmol/L of glucose, a one to one molecular match, with a total osmolarity of 245 mOsm/L. Those numbers come straight from the WHO's ORS production guidelines. Notice the molecular precision: the formula pairs one glucose for one sodium because that is what the transporter carries.
From global relief efforts to your water bottle
ORT was developed in the 1960s as researchers worked out the co-transport mechanism and tested glucose and electrolyte solutions in the field. The breakthrough moment came in 1971, during the refugee crisis of the Bangladesh war of independence, when cholera swept through camps that had nowhere near enough IV supplies. Relief workers turned to an oral sugar and salt solution instead, and the results, published in the Johns Hopkins Medical Journal in 1973, were far better than anyone expected from an oral approach.
The WHO and UNICEF took the method worldwide, and it has been a cornerstone of global public health ever since. A 2021 history in Tropical Medicine and Infectious Disease credits ORS programs with driving global childhood mortality from acute watery diarrhea down dramatically over the past five decades.
So when you see "oral rehydration" on a modern hydration product, that is the lineage. The same absorption science that works in a relief camp also rehydrates a hiker, a nurse coming off a 12 hour shift, or anyone sweating through an August afternoon.
Why sports drinks are not ORT
Most sports drinks were designed in a different direction: flavor first, carbohydrates for athletes, and only a modest amount of sodium. Compared to the WHO formula, a typical sports drink carries considerably more sugar per liter and considerably less sodium, which means it is not built around the co-transport ratio. It hydrates the way sweetened water hydrates. It is not oral rehydration therapy.
That distinction is why ORT based products exist as their own category. If the drink is not formulated around the sodium and glucose pairing, it is not using the mechanism.
How GREEN applies ORT science
GREEN is our product, so read this section knowing that. But the numbers are on the label.
GREEN's formula is tuned to the WHO's ORT guidelines. One serving delivers 9 grams of organic sugar and 410 milligrams of sodium, a deliberate pairing built for the co-transporter, not a flavor accident. You can see the full breakdown on our science page.
Here is how a clinical ORS and GREEN compare, and where they part ways:
| WHO ORS (per liter) | GREEN (per serving) | |
|---|---|---|
| Job | Clinical and relief rehydration | Daily hydration and energy |
| Sugar | 13.5 g glucose | 9 g organic sugar |
| Sodium | About 1 g | 410 mg |
| Extras | Potassium, citrate | 80+ ionic trace minerals, coconut water, pink Himalayan sea salt |
| Caffeine | None | 180 mg natural caffeine from green coffee beans |
| Taste | Famously clinical | Cacao (Hot Mix) or tropical citrus (Cold Mix) |
A clinical ORS is built for hospitals and relief work, and nobody drinks it for pleasure. GREEN takes the same absorption science and builds a daily drink around it: hydration from the sodium and glucose pairing, plus 180 mg of natural caffeine, about three shots of espresso, so it replaces your morning coffee instead of sitting next to it. Coffee gives you caffeine with no hydration. GREEN gives you the caffeine and the fluid absorption in one cup.
The rest of the label stays clean: USDA Certified Organic, Non-GMO, vegan, gluten-free, 40 to 45 calories, and $2.50 per serving. GREEN was founded in Hawaii by an airline pilot and an ER doctor, two careers that run on long shifts and dry environments, which is exactly the problem ORT science solves. It was a NEXTY Award finalist for Best New Organic Product at Expo West 2024.
If you want to see the same science compared against a mainstream hydration brand, read our GREEN vs Liquid IV breakdown. And if the caffeine number raised an eyebrow, here is what the FDA says about daily caffeine limits.
The bottom line
Oral rehydration therapy is drinking water with glucose and sodium in the ratio your small intestine is built to absorb, so fluid gets into your body faster than plain water can manage. It has been a cornerstone of global public health since the 1970s, the WHO publishes the exact formula, and the research behind it is about as solid as hydration science gets.
GREEN puts that science in a packet you will actually look forward to drinking: WHO guided sugar and sodium levels, 80+ trace minerals, and enough natural caffeine to retire your coffee maker. Start with the Hot Mix, the Cold Mix, or grab a sample and feel the difference a real formula makes.
Sources
- World Health Organization, Oral Rehydration Salts: Production of the New ORS (2006)
- World Health Organization, Diarrhoeal Disease Fact Sheet (2024)
- The Lancet, Water with Sugar and Salt (1978)
- Mahalanabis et al., Oral Fluid Therapy of Cholera Among Bangladesh Refugees, Johns Hopkins Medical Journal (1973)
- Nalin, Issues and Controversies in the Evolution of Oral Rehydration Therapy, Tropical Medicine and Infectious Disease (2021)
