By Sono Motoyama, Pittsburgh Post-Gazette

PITTSBURGH — Depending on where you shop and in which aisle, you may have noticed the colorful packaging of “gut sodas” taking up shelf space.

These sodas may contain probiotics or prebiotics and they may or may not contain sugar or sugar substitutes. But as the newest category of “functional beverages,” they do seem to suggest that they will help your digestive system.

Recently, big players like Coca-Cola and PepsiCo have gotten into the game, as well as celebrity investors Gwyneth Paltrow, Mindy Kaling and the Jonas Brothers.

“Fizzy, fruity, tangy, spicy, gutsy,” proclaims the wording on a can of Culture Pop.

“Trust your gut!” says Cove Soda.

“Soda’s back,” the Poppi can says, implicitly acknowledging that we all know the empty calories of the previous generation of sugared sodas are not good for you.

During a quick drive around the Pittsburgh area, I found the widest selection and most prominent display of gut sodas at Whole Foods. The Target and Walmart I went to both had the sodas, but they were not as conspicuous. At the big-box stores, pride of place still seems to be reserved for another type of functional beverage that’s been around awhile: “energy drinks,” i.e., drinks loaded with caffeine.

Gut sodas were absent at the gas stations I visited. Maybe that’s understandable.

When you’re trapped in your car, you may not want to be thinking about what the “1 billion CFU [colony-forming units] probiotics” in Cove Soda are doing to your intestines.

Deciphering the label

Your digestive system contains trillions of microorganisms — the gut microbiome. Maintaining a healthy gut is important for overall health via factors like facilitating proper digestion and maintaining metabolism and immunity, according to the American Medical Association.

If you’re interested enough in your health to be curious about gut sodas, presumably you’d want to know what’s in them and how they work.

But as the three brands I tried demonstrated, figuring that out is not so easy. They all have different stuff in them, so you must be able to read and comprehend the small type.

An advanced degree in biology would not be amiss — and a pair of reading glasses.

For help, I turned to Paige Langhals-Totino, a nutrition specialist who works in Allegheny Health Network’s gastroenterology division. She also sees patients who are interested in weight management.

First of all, what’s the difference between prebiotics and probiotics?

“Probiotics are usually live microorganisms that are meant to rebuild the healthy gut bacteria,” she said.

They may come in capsules, powders, liquids and in drinks such as kombucha.

What about those 1 billion CFUs in Cove Soda? That sounds like a lot.

“It sounds like a lot,” Langhals-Totino agreed.

The theory goes that the more CFUs there are, the more likely it is that some of those beneficial organisms will survive your stomach acid and do some good in your gut, she said. The problem is that we do not know how many organisms will guarantee that benefit.

“You could take 1 billion versus 5 billion and still have the same outcome,” she said.

Prebiotics, on the other hand, are fiber alternatives or fiber-based products, Langhals-Totino said.

“It’s a food source that is meant to fuel the good bacteria that is already in the GI tract.”

Do they help?

That all sounds very scientific, but is there evidence that drinking a soda or taking a supplement actually has a health benefit?

Langhals-Totino said that for both prebiotic and probiotic supplements, “we have very much mixed data.”

The prebiotic soda Poppi ran into trouble with its exhortation to “Be Gut Happy. Be Gut Healthy.” The company, which was acquired by PepsiCo this month, faced a class-action lawsuit for false health claims. It settled for $8.9 million.

There are studies that say prebiotics and probiotics are helpful, but others that show no benefit. In the case of prebiotics, there is also evidence that promoting only one strain of beneficial bacteria — as these sodas may do — can in fact create an imbalance in the multitude of species in your gut if consumed over a long period of time, according to the academic medical center Henry Ford Health.

If there is an existing imbalance, it is difficult to know which strain may be of most benefit to you.

Langhals-Totino takes a case-by-case approach.

“Usually what I counsel my patients is, how do they feel when they’re taking it?” she said. “There’s no harm in doing a probiotic or doing a prebiotic that is not causing them new symptoms or worsening of any GI symptoms they already have.”

She said prebiotics, like fiber in general, can lead to bloating and discomfort. Carbonation in the soda may have the same effect. Particularly for patients with irritable bowel syndrome, she recommends caution.

“They’re the ones who are going to be at highest risk to see the side effects of bloating, increased gas production, nausea and discomfort,” she said of IBS patients.

Then there’s the question of sugar substitutes, which some studies paradoxically suggest may actually lead to weight gain, rather than the opposite. Some have also been linked to a reduction in the diversity of the microbiome.

How do they taste?

In my weeklong trial, I can’t say I noticed any particular effects — either positive or negative — on my, uh, gut health. The factors more likely to influence my drinking them in the future are their price and taste.

They are all more expensive than a regular can of soda, but hovering at around $2 each, they’re affordable as an occasional indulgence.

Though I don’t mind the taste of Coke Zero (which contains the sweeteners sucralose and acesulfame-k), generally speaking, I dislike the aftertaste of most sugar substitutes. That put a strike against two out of the three sodas I tried immediately.

–Cove Soda, Dr. Cove flavor. At $2.21 at Whole Foods, this was the most expensive of the sodas I tried. It contains 0 calories, using erythritol as a sugar substitute, and the aforementioned billion CFUs of the probiotic Bacillus subtilis DE111, according to the can. It had an odd orange-brown color and produced a high orange-colored head. It is a reasonable facsimile of Dr. Pepper, though it does not contain caffeine.

–Culture Pop, orange, mango and lime flavor. $1.88. I immediately loved this soda, from the pleasing peach-pink color that made me feel like I was drinking a cosmopolitan to the light fizziness and subtle flavor. Sweetened with fruit juice, it has 45 calories (compared to 140 in a can of regular Coke) and live Bacillus subtilis cultures, according to the can. Its Amazon listing further explains that each can contains “billions of CFUs of live probiotics at the time of canning.” A soda for adults, this was easily my favorite of those I tried (and also the cheapest).

–Poppi, strawberry-lemon flavor. $1.99. On the opposite end of the flavor spectrum from Culture Pop was the aggressive, candy-like taste of the Poppi strawberry-lemon soda. With 6% juice, it contains 30 calories and is also sweetened with agave inulin (both a prebiotic and sweetener) and stevia leaf extract. Besides agave inulin, it also includes cassava root fiber, presumably for its prebiotic and other potential health benefits. It was like drinking a Starburst fruit chew, but with that stevia aftertaste.

The takeaway

Rather than for any gut-health benefit, Langhals-Totino would more likely recommend these sodas to patients who are trying to lose weight, as a substitute for sugary sodas.

“If the patient likes it, if they’re seeing a benefit, I encourage them to continue it as a step to stay away from regular soda,” she said. But she wouldn’t “prescribe” them.

For digestive health, she suggests fermented foods like kombucha, sauerkraut or kimchi. For a hit of both probiotics and prebiotics, she recommends a low-sugar yogurt with live cultures mixed with berries or other fruit.

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