Coconut water, quinoa and chia have three things in common: they're popular, they're expensive and they're often marketed as ultra-healthy "superfoods."

Marketplace recently reviewed the labels of nearly 100 so-called superfood products as part of an investigation to see whether the trend is actually about better health or simply marketing hype.

Friday night's episode (8 p.m. CBC, 8:30 p.m. in Newfoundland) reveals how any product can be labelled as a superfood in Canada without actually having to prove it has superior health benefits — an accountability gap that experts warn could lead consumers to overpay for foods that under-deliver.

Marketplace also decided to pit three of the most popular superfood staples head-to-head against three cheaper Canadian alternatives to see which ones provide the best nutritional bang for your buck.

Here are the results of the food faceoff.

COCONUT WATER VS. TAP WATER

Sales of coconut water have skyrocketed in the past two years, and anecdotally, several fitness buffs interviewed by Marketplace said they believe it hydrates better than tap water.

So Marketplace decided to conduct an experiment comparing the popular drink to Ontario tap water to determine which one provides better hydration during exercise.

Producers approached Stephen Cheung, a Canada Research Chair in environmental ergonomics at Brock University in St. Catharines, Ont., to run the test in his lab where he routinely conducts extreme sport experiments, often in different climates to determine optimal athletic performance.

Host Charlsie Agro drank 500 millilitres of coconut water that has 45 calories, 11 grams of carbohydrates and 11 grams of sugar per cup. Its label says it's full of natural electrolytes and has more potassium than a banana.

Agro then ran 11 km/h for 60 minutes on a treadmill with a slight incline in a temperature-controlled setting of 35 C and 40 per cent humidity.

Cheung took measurements throughout, including multiple urine samples, weigh-ins, core temperature and heart rate, and gathered anecdotal evidence on how Agro was feeling.

Agro drinks 500 millilitres of tap water before running on the treadmill. (CBC )

The same experiment was repeated less than 24 hours later with tap water.

Cheung concluded the two liquids have roughly the same ability to keep Agro hydrated during a workout.

"I would sum everything up by saying coconut water can hydrate you, but it doesn't necessarily do a better job than water," he said.

Some recent small studies came to similar conclusions.

The International Journal of Sport Nutrition and Exercise Metabolism, for example, published a report that said during exercise and measured physical performance, coconut water "does not improve markers of hydration."

Top-selling brands

Marketplace approached two of the most popular brands of coconut water for their reaction.

Pepsico, O.N.E. coconut water's parent company, declined an interview.

In an emailed statement, Arthur Gallego, Vita Coco's global director of corporate communications, said it's the product's potassium, an electrolyte, that helps when working out. Its labels and advertising underscore that point.

Cheung said many people don't need to add electrolytes when they work out unless they are exercising intensely for a long time and lack a diet of fruits and vegetables, which supply natural potassium.

He also said with the calories, sugar and carbohydrates in coconut water, "you're gaining extra calories that you may not really need" and that may be counterproductive.

Not to mention, coconut water typically sells for $3 to $6.50 per litre.

The bottom line, Cheung said, is consider good-old Canadian tap water to stay hydrated when exercising — it's cheaper, calorie-free and as effective as coconut water.

QUINOA VS. POTATO

In 1993, NASA scientists wrote a scientific paper promoting quinoa as a strong candidate for astronaut food because of its nutritional properties.

Fast-forward 20 years and the United Nations declared 2013 the International Year of Quinoa, in part because it has all essential amino acids and the potential to offer good nutrition, especially in developing countries.

Quinoa is often marketed as a grain that's high in protein and low in carbs, and its sales have nearly doubled in the past two years in 62 of the world's major economies, according to market research firm Mintel.

But is it the nutrition-packed powerhouse that so many people seem to think it is?

Dietitian Jen Sygo, who works with Canada's Olympic track athletes as well as the Toronto Maple Leafs and Raptors, said quinoa isn't "a major protein source like a meat or eggs, or even foods like beans and lentils and chickpeas."

A cup of quinoa has eight grams of protein compared to a typical chicken breast with 30 grams or more.

Quinoa is also quite high in calories, she said, so it's also not a weight-loss alternative to other starches.

Dietitian Jen Sygo says a potato is an excellent — and less expensive — alternative to quinoa. (CBC)

Sygo said the nutritional value of quinoa is further diminished when it's processed in chips, crackers and other products.

"We basically have taken a quinoa grain kernel and highly processed it into this until you've obliterated a lot of the nutrition and turned it into something that probably makes your blood sugar go up, might be high in salt and sugar," she said.

So what does Sygo recommend as an overlooked and affordable alternative to quinoa?

"The beautiful, noble Canadian potato."

She said it's on par with quinoa in terms of calories, and there's the added benefit of its potassium and vitamin C — a decent trade-off for what's sacrificed in terms of protein.

"They're so underappreciated," she said, and much cheaper at $4 for a 4.5-kilogram bag of potatoes compared to that price for a 400-gram package of quinoa.

CHIA VS. SALMON OR FLAX

Chia seeds have become a trendy staple of smoothies and salads, with sales spiking by more than 200 per cent in just the past two years.

One of chia's key selling points is the fact it's high in omega-3 fatty acids, which are believed to reduce the risk of heart disease and help brain function.

But Sygo said there's an important catch. For the body to use chia, it has to convert the seeds to acids and the average body only converts "between about zero and 10 per cent of that into a usable form of omega-3."

And that's only if the seeds are all digested, which is also unlikely.

"It's an inconvenient way to get your omega-3s," Sygo said. "You'd have to eat a lot of it." And that could spike your fibre intake — which could cause other issues, she said with a laugh.

Instead, she suggests salmon, which has a more easily digestible and pure form of omega-3 fatty acids.

Chia seeds have about 17 grams of omega-3s per 100-gram serving, and that sounds pretty good when you compare it to a piece of Atlantic salmon, which has 2.2 grams.

But applying the conversion Sygo described takes those 17 grams down to less than two grams — less than what's found in the salmon.

For vegetarians or others who prefer seeds, Sygo suggests switching to a Canadian alternative to the imported chia: flax seeds.

Besides the nutritional similarities, flax is about a third of the price. A 400-gram bag of chia can be $15 or more compared to about $5 for the same-size bag of flax.