Value Village ／ Health
This answer is a draft. It stays unpublished until legal review and source verification are complete.
Unsweetened sparkling water (炭酸水, tansansui) took off in Japan in the 2010s, and you will find it in every convenience store and vending machine. People ask whether it can replace plain water, and whether it harms bones or teeth. The same questions come up abroad. Here is what public sources let us say.
| Item | Details |
|---|---|
| pH of unsweetened sparkling water | About 4.5–5.5 (weakly acidic). Cola and similar drinks are about 2.5–3; lemon juice is about 2 |
| Teeth | Enamel is generally described as starting to dissolve at a pH of about 5.5. Unsweetened sparkling water sits near that boundary, and the scale of its effect differs from fizzy drinks with sugar and citric acid. The general dental advice is do not hold it in your mouth for long, and drink water afterwards |
| Bone | No evidence has been confirmed that carbonation itself lowers bone density. Past studies linked cola consumption with bone density, but phosphoric acid, caffeine and cola replacing milk are described as the factors |
| Hydration | If unsweetened, it counts the same as water. It falls within the scope of the MHLW's "Drink Water for Your Health" campaign (Ministry of Health, Labour and Welfare) |
| Stomach | Carbonation expands the stomach and gives a temporary feeling of fullness. Studies find that a large amount before a meal reduces food intake, while a small amount stimulates appetite (varies by person) |
| Labels | "Sparkling water" (炭酸水, tansansui) is unsweetened; "carbonated drink" (炭酸飲料, tansan inryō) usually contains sugar, flavourings and acidulants. A "lemon flavour" product is still sparkling water if it is unsweetened |
[Verify] Check the pH figures against general measured values, the effect on teeth against materials from the Japan Dental Association and similar bodies, and the effect on bone against nutrition research reviews.
No evidence has been confirmed that the carbonic acid formed from carbon dioxide dissolves bone. The cola effect seen in past studies is attributed to phosphoric acid, caffeine and cola replacing milk.
Unsweetened sparkling water is only weakly acidic, and its effect differs greatly from fizzy drinks with sugar and citric acid. Do not hold it in your mouth for long, and drink water before bed. That is enough.
If unsweetened, it hydrates just like water. It contains no caffeine, and it works at room temperature too.
There are many unsweetened flavoured sparkling waters. Check "sugars" (糖類) and "energy" (エネルギー) on the nutrition label. Products labelled "carbonated drink" usually do contain sugar.
If unsweetened, it has 0 kcal, so there is nothing to make you gain weight. There is also no evidence of a weight-loss effect: its effect on how much you eat works in opposite directions depending on amount and timing.
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https://www.mhlw.go.jp/stf/seisakunitsuite/bunya/topics/bukyoku/kenkou/suido/nomou/index.html
https://www.jda.or.jp/
https://www.caa.go.jp/policies/policy/food_labeling/nutrient_declearation/
⚠️ Editorial note: the source URLs above were identified by search. Our working environment cannot reach go.jp domains, so the contents have not been checked against the text. Verify every source before publication and record who checked it and when.
What we share here are ideas and everyday practices passed down among people living in Japan, together with general information drawn from public sources. They are not official recommendations, and they are not professional instruction. Practices vary between households and regions.
This is general information. Results vary from person to person and depend on your own conditions and surroundings.
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This article is not meant to diagnose or manage any specific medical condition. If you are worried about your health, see a doctor rather than relying on your own judgement.
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