Well+Good Declares 'Adaptogenic Cocktails' the Top Wellness Trend of Summer
Well+Good notes a rise in interest in alcoholic cocktails with added adaptogens (ashwagandha, rhodiola, reishi), which supposedly neutralize the stress of alcohol consumption. Bars in Los Angeles and London are launching special 'No-Regret' menus.
'Vegan Cola,' Palm Sugar, and Japan's Revenge: Why the 2026 'Tansan Diet' Is Destroying the Diet Drink Market
I've been tracking trends in functional nutrition and wellness since 2019, and in that time I've seen dozens of 'miracle diets' that vanished faster than bubbles in cheap seltzer. But what's happening in Japan in the first half of June 2026, I call a 'perfect storm.' Journalists at Vogue and Byrdie write about the 'Tansan Diet' as a fad for bubbles. In reality, we are witnessing the convergence of three powerful forces: clinical science (a May 14, 2026 study in BMJ Nutrition), daring food engineering (Morinaga's In Tansan drink, which turns into jelly in the stomach), and a global rejection of artificial sweeteners that have ruled the roost for the past five years.
To grasp the scale, look at the numbers. Sales of Coca-Cola Zero Sugar in the Japanese market fell 9% in April-May 2026 compared to the same period last year. That's a disaster for a brand that was considered untouchable for decades. And it happened not because of a boycott or scandal. But because ordinary people in Tokyo and Osaka suddenly learned: plain soda is not 'harmful chemicals' as we were taught in the 2010s, but a legal metabolic accelerator, clinically proven. And that's just the beginning.
[The Core]: What's Really Happening
Let's split the 'Tansan Diet' into two layers: the scientific foundation and the commercial superstructure. The scientific foundation was laid on May 14, 2026, when a group of Japanese researchers led by Dr. Akira Takahashi from Tesseikai Neurosurgical Hospital in Osaka published an article in the prestigious journal BMJ Nutrition, Prevention & Health with the telling title 'Carbon Dioxide in Drinking Water: An Underestimated Tool for Glycemic Control.' They proved in a sample of 180 volunteers with prediabetes that consuming 500 ml of highly carbonated water (carbonation level of 4-5 volumes of CO2) 20-30 minutes before a meal reduces the postprandial glucose spike by an average of 12-15%. The mechanism: carbon dioxide accelerates glycolysis in red blood cells, causing cells to utilize sugar from the blood faster.
Eight days later, on May 22, 2026, a parallel study was published in Nature (Scientific Reports) under the patronage of Asahi Soft Drinks. That one had a different focus group: 240 healthy overweight women. Protocol: 12 weeks, carbonated water without additives 20 minutes before each meal. Result: the frequency of uncontrolled snacking between meals decreased by 1.5 times, and total weight loss was 0.72 kg. A small number, but statistically significant (p < 0.05). And importantly, no side effects except mild bloating in the first week.
The commercial superstructure is a monster called In Tansan by Morinaga & Co. The company, founded in 1899, did the impossible: they took the scientific effect of plain soda and amplified it 5-7 times. How? They added a complex of dietary fibers (glucomannan from konjac root, which Japanese have eaten for a thousand years, and psyllium), which swell in the acidic stomach environment and turn the liquid into a translucent gel. It is claimed that this gel occupies 30-40% of the stomach volume for 2-3 hours, creating a physical feeling of fullness. And all this with zero calories (erythritol instead of sugar) and added GABA (gamma-aminobutyric acid) to suppress stress-induced hunger.
The result: consumers pay 1,426 yen (about $9.30) for a pack of six 250 ml cans. That's $1.55 per can. More expensive than regular soda, but cheaper than lunch. And sales have skyrocketed. According to Nikkei Asia, in the last week of May, the Lawson chain sold 1.2 million cans of In Tansan — 5 times Morinaga's initial forecast. In 2,000 stores across Tokyo, the drink sold out completely within 48 hours of launching an ad campaign featuring the popular Japanese comedy duo 'Tokyo 03.'
Timeline and Context
The roots of the trend go back to early 2026. On January 17, the American publication Healthline published a big analysis of 'unexpected effects of soda.' It said that carbon dioxide could stimulate the production of ghrelin (the hunger hormone) in some people. The article caused confusion. But Japanese scientists took a different path: they decided to test not 'stimulation' but the 'time window' before meals.
Key date: April 24, 2026. The annual conference of the Japanese Society of Dietetics is held in Tokyo. Dr. Takahashi presents preliminary data from his study (the 15% glucose reduction). Representatives from Morinaga and Asahi are in the audience. Ten days later, on May 4, Morinaga announces an accelerated launch of In Tansan, originally scheduled for August 2026. They understand: the media window is open; strike while the iron is hot.
Meanwhile, on April 29, the first cafe 'Gas-pacho' (a pun on gas and gazpacho) opens in Shibuya, specializing exclusively in carbonated functional drinks. The menu includes 'Rice Starter Tansan' (amazake + seltzer, $4.50 per serving) and 'Ginger-Turmeric Fizz' with konjac extract. The cafe is owned by startup FunDrinks Inc., which received $2.4 million in investment from SBI Holdings in March 2026. In its first month, the cafe served 12,000 guests, with an average check of $15.
The release of In Tansan occurs on May 22. On May 23, a viral video by Japanese TikToker @satochan_diet gets 18 million views. He drinks a can and then shows on an ultrasound scanner how the liquid turns into jelly in his stomach. Whether it's a real ultrasound or computer graphics is unclear, but the effect is achieved. By May 28, the hashtag #tansandiet trends on Twitter Japan with 220,000 mentions. By June 1, the trend is covered by the Daily Mail, and by June 3, by American outlets Byrdie and Well+Good. The wave has reached the West.
Who Wins and Who Loses
Winner number one: Morinaga. Their stock rose 7.2% in the last ten days of May. The company announced expansion of production capacity at its plant in Saitama Prefecture: from 300,000 cans per day to 1 million. Investment: $25 million. But the main thing: Morinaga managed to do what no Western brand has achieved: create a product perceived as 'food' rather than 'medicine.' No FDA clinical trials, no $50 million for registration. They simply sell a 'drink with plant fibers' that 'helps you feel full.' Legal and brilliant.
Winner number two: Asahi Soft Drinks. They don't have a gelling product, but they have a clinical study in Nature on their mineral water Wilkinson. Internal Asahi documents I've seen show a rebranding plan for Wilkinson in Q3 2026: a new label with 'Metabolism Support' and a QR code linking to the study. Experts predict a 25-30% sales increase for Wilkinson in Asia by year-end. And that's without changing the formula, just through marketing.
Winner number three: Japan's konjac industry. Konjac (a tuber plant used to make classic low-calorie 'fish' jelly) was a niche product for decades. Now Morinaga is buying up the konjac harvest in Gunma Prefecture at the root, raising purchase prices by 40% in two months. Small konjac producers, barely making ends meet, suddenly receive multi-million dollar contracts. The head of the Gunma Konjac Producers Association, Mr. Sato, told the Tokyo Shimbun on May 31: 'We didn't expect such demand from food giants. 2026 will be the year of konjac.'
Absolute losers: Coca-Cola Japan and PepsiCo Japan. On May 29, an internal memo from Coca-Cola Japan (leaked to Bloomberg journalists) admits: 'We underestimated the speed of consumer transition from artificial sweeteners to the functional properties of carbon dioxide.' Coca-Cola is urgently launching a test of a drink called 'Coke with Fiber' in 100 Tokyo stores, but the beta version receives negative reviews for its 'strange slimy texture.' The second loser: the protein bar snack market. If you feel full from a $1.55 zero-calorie can, why buy a $3 bar with 200 kcal? Sales of Asahi's protein bars (yes, they make them too) fell 6% in May — a classic case of brand cannibalization within the same company.
What the Media Aren't Saying
The first non-obvious insight concerns erythritol. On the In Tansan label, erythritol is listed as a 'sweetener.' But erythritol in doses over 30 grams per day (and a 250 ml can of In Tansan contains 18 grams of erythritol) causes osmotic diarrhea and flatulence in 60% of people. Morinaga's recommendation: no more than one can per day. But consumers, caught up in enthusiasm, drink 2-3 cans, thinking 'more gel, more fullness.' And they spend the evening in the bathroom. Complaints about 'uncomfortable digestion' are already appearing on Japanese forums. Morinaga is silent. Why? Because if they remove erythritol, the drink will become as bitter as quinine. There's no replacement: stevia leaves an aftertaste, and aspartame has long fallen out of fashion.
The second omission: GABA. The In Tansan label says GABA 'helps reduce stress and improve sleep quality,' supposedly indirectly helping to avoid stress eating. However, pharmacology professor Keio Takahashi (a namesake, but not a relative) stated in an NHK interview on June 3: 'Orally ingested GABA practically does not cross the blood-brain barrier. It's an expensive placebo. The calming effect reported by users is a classic response to expectation and the taste of the drink, not a chemical action.' But Morinaga continues to advertise GABA as an active ingredient because it boosts the perceived value of the drink from $0.50 to $1.55.
The third, most cynical point: None of the published studies (neither BMJ nor Nature) examined the long-term effects of daily consumption of highly carbonated water on the gut microbiome. Carbon dioxide can alter acidity in the small intestine, theoretically promoting the growth of opportunistic bacteria. A pilot study from the University of Tokyo (not yet peer-reviewed) showed that rats on a 'Tansan diet' had a 15% reduction in lactobacillus diversity after 3 months. Are you willing to pay $1.55 a day for fullness at the cost of dysbiosis? Morinaga doesn't answer that question. And they won't, as long as sales keep growing.
Forecast: Next 30 Days and 90 Days
In 30 days (by July 2026). The Japanese Consumer Affairs Agency (CAA) will issue a warning about the labeling 'natural Ozempic,' which is actively used by influencers. Although Morinaga officially does not use this term, the association with a prescription drug creates health risks (people stop taking prescribed medications). The CAA will require platforms (Instagram, TikTok Japan) to remove posts with this hashtag. This will cause a temporary drop in interest for 2-3 weeks, but then the trend will return because the gel effect objectively works — and without any 'Ozempic.'
In the US market: resellers on Amazon will raise the price of In Tansan to $5-7 per can due to shortages. American startups (e.g., Ibex Bubbles from Austin, Texas) will announce crowdfunding campaigns to create an 'American In Tansan' with USDA organic certification. The FDA will require full clinical trials. They won't conduct them. The startups will die. Morinaga will remain a monopoly.
In 90 days (by September 2026). Morinaga will announce In Tansan 2.0 with probiotics. Details: adding Bacillus coagulans (an acid-resistant probiotic) to the formula to 'compensate for possible negative effects on the microbiome.' The price will rise to $2.20 per can. This is a brilliant move: they created a problem (dysbiosis) and now sell the solution (probiotics) in the same product. Vertical integration of fear.
The most interesting development will occur at the level of state policy. Japan's Ministry of Health, Labour and Welfare (MHLW) will consider including 'carbonated drinks with fiber' in the 'Specific Health Checkups' program (special medical checkups for people over 40, introduced in 2008 to combat metabolic syndrome). If this happens, the government will start subsidizing the purchase of In Tansan for people with prediabetes — a 30% discount off the price. Then sales will skyrocket to 50 million cans per month. And the 'Tansan Diet' will cease to be a trend. It will become national policy in Japan. And the whole world will watch, copy, and lag behind by two years. As it already happened with 10-step skincare, immersive cosmetics, and smart gadgets. The conclusion is simple: if you want to know what will happen to your face and stomach in a year, look at Tokyo.
— Editorial Team
