Zembrin is a dual PDE4 and serotonin reuptake inhibitor, and in a placebo-controlled fMRI study a single dose reduced amygdala reactivity to fearful faces. Now it's in a soda. On the Brightside puts 15mg in every can of Guava Glow and Strawberry Sunshine.
On the Brightside just planted a flag in the fastest-growing corner of the beverage aisle: the non-alcoholic, functional "feel-good" drink.
Its debut lineup, featuring Guava Glow and Strawberry Sunshine flavors, is a zero-sugar, zero-calorie sparkling soda built around one active ingredient, Zembrin®, the standardized kanna (Sceletium tortuosum) extract from PLT Health Solutions. Where a lot of "chill" drinks stack five or six under-studied botanicals and hope something lands, On the Brightside bet on one ingredient with real clinical data behind it instead.
The brand comes from Brighter Beverages, Inc., led by co-founder and CEO Adam Terry, who previously co-founded Cantrip, one of the earlier hemp-derived beverage brands. Terry has described Zembrin as less of an adaptogen and more of what he calls a "connectogen", something meant to quiet enough mental noise that it's easier to actually connect with the room in front of you instead of a phone.
This article is in partnership with PLT Health Solutions, which has spent the last few years building out a beverage-stable version of its cognitive ingredient portfolio specifically because standardized botanical extracts don't always survive canning and pasteurization. Both flavors carry the same 15mg Zembrin dose and the same base formula, sweetened with a fermented Rebaudioside M rather than stevia extract or anything artificial.
Guava Glow (guava, orange, and passionfruit) and Strawberry Sunshine (strawberry lemonade) launch together as the brand's initial two-flavor lineup. The full analysis of Zembrin is below:
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On the Brightside Guava Glow Nutrition Facts
Serving size: 1 can (12 fl oz / 355mL)
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Calories - 0
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Total Carbohydrate - 0g
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Total Sugars - 0g
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Added Sugar - 0g
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On the Brightside Guava Glow Ingredients
Each can (12 fl oz / 355mL) provides the following:
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Sceletium Tortuosum Extract (Zembrin®) - 15mg
Sceletium tortuosum, commonly called kanna, is a succulent native to South Africa's Western Cape that the Khoi and San peoples have chewed, smoked, or brewed into tea for centuries for its calming, mood-lifting effects.
Zembrin® is PLT Health Solutions' patented, standardized extract of a specific kanna cultivar, grown under a seed-to-shelf traceability program and verified at harvest against a target alkaloid profile before it goes into production. That standardization is incredibly important: wild kanna's alkaloid content varies considerably from plant to plant, while Zembrin is fixed to a consistent ratio of mesembrenone, mesembrenol, and mesembrine, the three primary alkaloids responsible for its effects.
Zembrin's mechanism is well-characterized for a botanical. It acts as a dual inhibitor of phosphodiesterase-4 (PDE4) and serotonin reuptake, a combination not found in most other calming botanicals. In a placebo-controlled fMRI study, a single 25mg dose attenuated amygdala reactivity to fearful faces and altered its connectivity to the hypothalamus, the regions most responsible for triggering a stress response.[1] That finding lines up with what a single dose does in practice: in a separate placebo-controlled trial, 25mg lowered subjective anxiety and blunted the heart-rate response to a simulated public-speaking task, one of the more reliable ways researchers provoke stress in a lab setting.[2]
The longer-term data holds up too. Sixty adults between 50 and 80 years old took 25mg or 50mg of Zembrin daily for six weeks in a randomized, placebo-controlled trial, and the higher dose produced a statistically significant drop in Hamilton Anxiety Rating Scale scores alongside EEG changes consistent with a calmer brain state.[3] Safety data covers doses well above the 15mg found in each can: a three-month trial found 8mg and 25mg daily doses were well tolerated with no clinically meaningful changes in vital signs, bloodwork, or ECG readings.[4] Zembrin carries self-affirmed GRAS (Generally Recognized As Safe) status for beverage use at up to 50mg per day, more than three cans' worth. Because Zembrin's serotonergic activity overlaps with SSRIs, SNRIs, and MAOIs, anyone taking those medications should talk to a doctor before adding it to their routine. PLT Health has also been steadily expanding where Zembrin shows up, from capsules and gummies to RTD beverages like this one.
There's only one patented, standardized, and clinically-studied kanna extract on the market: Zembrin from PLT Health Solutions.
You can read more about the clinically-studied ingredient in our article, "Zembrin: The Best-Studied Kanna Extract on the Market, by PLT Health Solutions".
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Fermented Reb M (Onosweet®)
Both flavors are sweetened with Onosweet®, a fermented form of Rebaudioside M (Reb M), the steviol glycoside found only in trace amounts in the stevia leaf. Reb M is one of the cleanest-tasting steviol glycosides available: consumer sensory panels comparing it against Rebaudioside A found Reb M rated significantly less bitter at every tasting interval, with in-mouth sweetness statistically indistinguishable from real sugar.[5] It also backs up the "zero glycemic impact" claim with some real human data: in a randomized crossover trial, food reformulated with Reb M produced significantly lower post-meal insulin and glucose responses than the same food made with sucrose.[6]
The rest of the can is built for taste, not function. Citric acid and malic acid provide the tartness expected of a real soda, a small amount of vegetable juice supplies color, and organic natural flavors round out the fruit profile. None of these carry an active dose or a claim beyond how the drink tastes and looks.
Flavors Available
On the Brightside launches with two flavors built around the same Zembrin-powered base. Here's the current lineup:
One ingredient, seven delivery formats. Zembrin®, the standardized kanna extract from PLT Health Solutions, is now showing up in RTD energy drinks, stress and sleep gummies, capsules, liposomal sachets, and dissolvable strips.
How to Use
- When to take it: Anytime. Zembrin is non-sedating and each can is caffeine-free, so there's no wrong part of the day for it, whether that's a morning meeting, an afternoon slump, or in place of an end-of-day drink.
- Other notes: Most people notice an effect within 20 to 30 minutes of the first can. With 15mg of Zembrin per serving and a self-affirmed GRAS threshold of 50mg per day, there's room for more than one, though it's worth starting with a single can to see how it feels first.
Who It's For
- The sober-curious and moderation crowd: On the Brightside is built to replace a nightly glass of wine or beer, or to "zebra stripe" alongside alcohol, without the next-morning cost.
- Anyone who wants an afternoon reset without more caffeine: for people who don't want another energy drink, a non-sedating, caffeine-free option covers the 2pm slump without disrupting sleep later.
- Social settings where staying present matters: first dates, work events, and gatherings where the goal is feeling looser and more engaged, not impaired.
Conclusion: One Epic Ingredient Instead of Ten
On the Brightside enters a beverage aisle already crowded with ashwagandha blends, adaptogen stacks, and low-dose three-letter psychoactive seltzers, all chasing some version of the same "better than alcohol" pitch. Its point of difference is narrower by design: one standardized botanical, Zembrin, at a dose with real clinical backing behind it, rather than a proprietary blend built on hope. That's also the ingredient PLT Health Solutions has spent the last few years pushing into beverage formats specifically, and On the Brightside is one of the more visible results so far.
PLT Health Solutions: Growth Through Innovation
That focus should make Guava Glow and Strawberry Sunshine easy to evaluate on their own terms. The base formula and the Zembrin dose stay identical across both cans, so the choice comes down to whether a tropical guava, orange, and passionfruit profile or a strawberry lemonade profile sounds better in the moment, not which one works better.
Both flavors are available now, with autoship pricing for anyone who wants to make it a daily habit rather than a one-off try. PricePlow will keep tracking pricing and availability as On the Brightside expands into retail. Sign up for On the Brightside and PLT Health news alerts below to catch new flavors, formats, or Zembrin research as they land.
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Disclosure: PricePlow relies on pricing from stores with which we have a business relationship. We work hard to keep pricing current, but you may find a better offer.
Posts are sponsored in part by the retailers and/or brands listed on this page.
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