It's known all over the world, and is a big splash with celebs (like Madon­na.) Here are the re­al facts about this wa­ter craze.

The talk It: speeds up your me­tab­o­lism

The truth: "This is an ur­ban leg­end," said Liz Ap­ple­gate, PhD, di­rec­tor of sports nu­tri­tion at the Uni­ver­si­ty of Cal­i­for­nia in Davis. "There is no valid re­search prov­ing it." An­oth­er, al­beit con­tra­dic­to­ry, myth: Co­conut wa­ter makes you fat. This bad rap came from co­conut milk, which is made from pressed co­conut meat and packs 445 calo­ries per cup, most from sat­u­rat­ed fat. The wa­ter (the flu­id in young co­conuts) has on­ly 46 calo­ries per cup. Of course, for a tru­ly trim­ming sip, opt for ze­ro-calo­rie wa­ter, cof­fee or tea.

The talk: It's na­ture's sport drink

The truth: It's a fine post­work­out chug for the av­er­age ac­tive Jane, but it falls short for more hard-core ath­letes. The gist: When you ex­er­cise, you sweat out a lot of sodi­um and some potas­si­um. You should re­place both af­ter in­tense sweat ses­sions (more than an hour a day), so your mus­cles con­tract prop­er­ly. Co­conut wa­ter is a potas­si­um pow­er­house, de­liv­er­ing rough­ly 600 mil­ligrams per cup, about 175 mg more than a ba­nana does and 13 times what most sport drinks of­fer.

"The prob­lem is that it has on­ly about 30 mil­ligrams of sodi­um per cup; we lose much more than that dur­ing a long work­out," Ap­ple­gate said. Thus, se­ri­ous ath­letes may need a sport bev­er­age with a high­er sodi­um-to-potas­si­um ra­tio, such as Gatorade or Pow­er­ade Ion4; lighter ex­er­cis­ers can re­hy­drate with what­ev­er they like best, in­clud­ing co­conut wa­ter or plain H2O.

The talk: It makes you look younger

The truth: Co­conut wa­ter con­tains cy­tokinins, plant hor­mones shown to slow the ag­ing process in plants and fruit flies, ac­cord­ing to a study in Mol­e­cules. Alas, the ben­e­fits aren't yet proven in hu­mans. The search for the foun­tain of youth con­tin­ues.

The talk: It's a hang­over helper

The truth: There's a rea­son the morn­ing af­ter a ben­der is so painful: Al­co­hol de­hy­drates you, lead­ing to nau­sea and headaches. Like any drink, co­conut wa­ter re­fills your H2O stores, but plain wa­ter does the job just as well, not­ed Samir Za­khari, PhD, di­rec­tor of the Di­vi­sion of Me­tab­o­lism and Health Ef­fects at the Na­tion­al In­sti­tute on Al­co­hol Abuse and Al­co­holism.As for elec­trolytes, our kid­neys pre­serve them when we drink, so there's no need to re­place them with co­conut wa­ter. If the taste lifts your post­spir­its spir­its, go for it; but you can save cash (and calo­ries) with the tap.

The talk: It pro­tects your tick­er

The truth: Di­ets high in potas­si­um can help low­er blood pres­sure and pro­mote heart health, said An­drea Gi­an­coli, RD, spokes­woman for the Amer­i­can Di­etet­ic As­so­ci­a­tion. Co­conut wa­ter is a good source of the min­er­al, but it's bet­ter to get it from whole foods like veg­gies (spinach, sweet pota­toes) and low­fat milk, which sup­ply ad­di­tion­al heart-healthy nu­tri­ents such as fiber and vi­t­a­min D.

Three more ways to crack this nut

• Co­conut milk: A sweet al­ter­na­tive to reg­u­lar dairy, co­conut milk is de­rived from the white meat of a ma­ture co­conut, and it pro­vides al­most as much healthy potas­si­um as co­conut wa­ter does. But be­ware its high sat­u­rat­ed-fat con­tent: One cup has about 43 grams.

• Co­conut milk bev­er­age: Di­lut­ed with wa­ter, it con­tains about five times few­er calo­ries than con­ven­tion­al co­conut milk.

It tastes rich­er than co­conut wa­ter.

• Shred­ded co­conut: Co­conut meat isn't as high in potas­si­um or sodi­um as co­conut wa­ter, and it has about 388 calo­ries and 22 grams of sat­u­rat­ed fat per cup. If you're tempt­ed to cov­er yours in choco­late, opt for a snack-sized can­dy bar dipped in an­tiox­i­dant-rich dark choco­late, which has on­ly 80 calo­ries and 3.5 g of sat­u­rat­ed fat.