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Claims that 'deep ocean water' rehydrates athletes twice as fast don’t hold up

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While the premium bottled water may hold promise, more research is needed

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Anyone looking to enter the growing and crowded premium water market has to differentiate themselves somehow, whether it's with a unique bottling source or a diamond-encrusted bottle cap. Kona Deep's sell goes like this: deep ocean water, unlike regular water, has minerals that may help with athletic performance. Kona Deep is the first company to sell bottled deep ocean water in the US.

To understand where Kona Deep comes from, it helps to understand the history of deep ocean water. During the 1970s oil crisis, as scientists were scrambling to find energy alternatives, they thought a solution might lie at the bottom of the ocean. They built a plant in the town of Kona, Hawaii, where just a few hundred feet off the coast, the ocean floor drops precipitously. There they began extracting what they hoped would power American homes — the lowest and coldest layer of water in the ocean. The depths of the ocean typically range in temperature from 32 degrees Fahrenheit to a balmy 38 degrees, which is much cooler than the surface temperatures (which vary depending on the ocean). In the 1970s, scientists hoped that the temperature difference could be used to generate electricity. But this idea, called ocean thermal energy conversion, proved to be impractical on a large scale.

So researchers began scrounging for other applications for deep ocean water, which has a high mineral content in part from hydrothermal vents on the ocean's floor. In the seemingly endless supply of water, two Hawaiian entrepreneurs saw another large and competitive market to shake up: premium bottled water.

Deep ocean water is high in minerals, including electrolytes

But having perhaps the most unique source of all wasn't enough of a marketing push for Kona Deep. (Because, let's be real, "deep ocean water" sounds like the kind of bunkum Gwyneth Paltrow would sell.) So the company, which was eventually taken over by Pat Turpin, the founder of Popchips, worked with researchers at the University of Arizona to study how the sea water's properties might impact athletic performance. Deep ocean water is rich in naturally occurring electrolytes, which are electrically charged minerals, including sodium, calcium, and potassium.

"I was surprised by our data; I didn't think it would matter, quite frankly," says John Konhilas, a member of the research team and faculty at the University of Arizona. But according to results published in April in the Journal of the International Society of Sports Nutrition, which will print research for a fee, deep ocean water rehydrated athletes twice as fast as spring water and carbohydrate-based sports drinks.

Typically, scientific journals made money by charging readers, but a new model of "open-access journals" instead charges scientists who wish to publish their research. Many of these journals are legitimate and the research they publish is subjected to industry standards, like peer review. But scientists are concerned because predatory journals publishing unreviewed research at high fees are becoming increasingly common in the open-access world. The Journal of the International Society of Sports Nutrition, which is part of the BioMed Central platform, is transparent about its fee structure and review process. However, the University of Arizona's findings lack many of the criteria JISSN suggests for reviewers, including information on subjects who drop out of the study, and results presented as mean numbers with standard deviations.

Scientists are increasingly concerned about "pay-for-play" journals

Konhilas explained in an interview with The Verge the findings were published as a "short report," meaning the team had the word-count of their article capped by the pay-to-publish journal. Because of this limitation, important information about the study's design and findings had to be left out.

For instance, the research team used "well-conditioned student athletes," for the experiment. The abstract says there were eight subjects, but the "Methods" section says "subjects were randomized to one of three experimental groups, Kona (n = 6), Sports (n = 8), or Spring (n = 6)." This discrepancy isn't explained in the study. Konhilas says that the study used only eight subjects who were supposed to do all three trials. Not all participants completed the three trials, but the authors included their results in the short report anyway.

"We were really fascinated by the data," Konhilas says. "So we included the subjects that didn't complete even the three trials."

He mentioned the team is planning a more extensive follow-up study, in which 12 subjects, six male and six female, would be required to complete all three trials, with at least a week between each. The order of the rehydration fluids would be randomized and the results would be broken down by sex. This is called "crossover" study design and is considered the gold standard for study design in the sports nutrition and performance world, according to Dan Baur, a research assistant in the field at Florida State University.

Published results included subjects who did not complete trials

Without a crossover study, however, it's difficult to know whether variability in the results is due to the way individual people's bodies responded to the fluids differently, or whether it is due to the effectiveness of the fluid itself. For example, there was greater deviation from the mean amount of time it took to rehydrate when subjects were given deep ocean water than when they were given spring water or sports drinks.

Sometimes small groups can have unusual results just through chance. The deviation from the known amount of time it takes for people to be rehydrated may hint the product is useful; it may also be an artifact of the study design. It's also possible that the product is useful, but some people respond much better than others, Baur says. A crossover study would eliminate any elements of variability between subjects, and allow researchers to focus solely on whether or not deep ocean water works across the board. And a bigger study would give more reliable results.

For the short report, subjects were put in an 86-degree Fahrenheit room where they pedaled on a stationary bike for more than two hours in some cases, until they lost 3 percent of their body mass through dehydration. They were then rehydrated, drinking one liter of fluid per kilogram of body mass lost. They were given half the fluid immediately, and the other half 30 minutes later.

Studies disagree on whether saliva is a good measure of hydration

All the while, experimenters were taking saliva samples from the subjects, approximately a dozen over the course of the experiment. They were measuring change in salivary osmolality, which is basically the amount of water in saliva compared to its other components, which include electrolytes, mucus, and enzymes.

This is one of three primary ways to test for dehydration, the other two being through urine and blood samples. Studies disagree, however, on the effectiveness of salivary osmolality as a measure of hydration. A study from 2014 by the University of Connecticut reported salivary osmolality is one of the best ways to measure dehydration when people are exercising in a hot environment.

But a 2013 study conducted by the Army and cited in the University of Arizona's work, used saliva to try to measure dehydration of fluid outside human cells. This extracellular fluid makes up 20 percent of body weight. They found that changes in salivary osmolality were "marginal" and "weakly correlated" with dehydration. Nevertheless, the University of Arizona researchers referenced this 2013 Army study to support using salivary osmolality "as a measure of hydration status."

The team is planing a follow-up crossover study

"There certainly is variability," Konhilas says of the metric. "When looking at exercise performance and exercise-induced dehydration salivary osmolality was best correlated with that measure. So that's the reason why we stuck with that." He and his colleagues considered using blood or urine samples, but the study's design required approximately 12 samples in two hours; they felt drawing blood that frequently would be too invasive.

However, the short report explains none of this. Because the team knew they would continue the work with a more rigorous crossover study and produce a "more extensive write-up of the data where we go into the real hard numbers of it all," they wanted to make sure the short report left readers wanting to know more, Konhilas says.

But with so much detail missing from the published results it would be easy for a reader to question the validity of the research, rather than be left wanting to know more. Baur says this lack of scrutiny of results leads to a problem in the field of nutrition and performance, where scientists, readers, and media are too quick to jump to conclusions.

Scientists, readers, and media can be too quick to laud nutrition studies

"There's a lot of studies like this where there might be a signal there, but there's a lot of noise that makes me very concerned about really buying into it," he said

All that noise common to his field makes Baur a tad skeptical. Despite his qualms about the University of Arizona study, he thinks deep ocean water is an interesting area that merits more investigation, including replication of the findings and an examination of why deep ocean water may be an effective rehydrator — something people have yet to study.

In the meantime, Kona Deep is already leaning heavily on the findings to help market the water as the natural option for people who want the mineral content of spring water with the electrolytes of a sports drink. While it may not be a diamond-encrusted bottle cap, it's a potent claim that is helping the company carve out a niche in the premium water market — since most consumers probably aren't checking out research results. Nor are they likely aware the results appeared in a pay-for-play journal.