Soft drinks on shelves this week. The acidity dimension you won’t have seen anywhere else.

Sugar is on the pack. Acidity is not. Both matter.

Every UK soft drink in the top ten declares sugar per 100ml and per portion on the back of the pack — the regulatory framework requires it. None of them declare pH. The pH of a soft drink determines its capacity to demineralise dental enamel; the British Society of Paediatric Dentistry and the Eastman Dental Institute have published the threshold (below pH 5.5, enamel begins to demineralise). The label does not carry this number, even though manufacturers and third-party labs have measured it.

This is the structural gap. The back-of-pack data covers the energy and sugar dimensions. The pH dimension, equally documented in the public-domain dental literature, is regulatory-absent and shelf-absent. We translate both.

Three findings the category routinely produces.

1. Sugar reduction has not closed the acidity gap.

The Soft Drinks Industry Levy (SDIL, 2018) has measurably reduced sugar in the category. Many leading products have reformulated to clear the 5g/100ml lower threshold. The pH has not moved with the sugar. A reformulated low-sugar cola or a sugar-free sparkling fruit drink can carry a pH between 2.4 and 3.5 — comfortably below the 5.5 enamel-demineralisation threshold. The sugar reduction is real; the acidity is unchanged. The dental literature has been clear on this for two decades.

2. “Sugar-free” is not “tooth-safe.”

The front-of-pack “sugar-free” or “no added sugar” claims are nutritionally accurate within their narrow remit. They do not communicate acidity. Water (pH ~7) and milk (pH ~6.7) are tooth-safe in the dental-erosion sense; sugar-free fizzy drinks at pH 2.5–3.5 are not. This is the structural distance between the front-of-pack marketing register and the back-of-pack-plus-public-domain data.

3. The serving size still moves the picture.

Soft-drink portion sizes range from 150ml mini-cans to 500ml on-the-go bottles to 2-litre sharing formats. The per-100ml number is the regulatory constant; the per-portion number depends on the format. A high-sugar drink at 8g/100ml clears the FSA red threshold (11.25g/100ml) on a per-100ml basis but the per-500ml-bottle number is 40g — ten teaspoons — which is the moment-of-decision figure that matters for one consumption event.

The dominant brand in this week’s top ten.

The dominant manufacturer in this week’s top ten is named from the live audit. They run [N] of the ten products on the list. Their public SDIL response is documented in their most recent ESG disclosure (dated reference linked per row in the table above). The per-100ml sugar figures from this week’s audit can be read against those public commitments; we do so in the rows where the commitments and the data agree or disagree.

The structural critique here names the manufacturer’s role honestly. The shopkeeper is not the villain. The retailer is not the villain. The manufacturer is the creator of the gap — they source the ingredients (citric acid, phosphoric acid, malic acid, the acidulants that define the pH), they employ the food scientists who engineer the carbonation and acidity profile, they decide the serving size declared on the side of the bottle, they fund the research that biases the nutrition science around their own products. The pH is not on the label because the regulatory framework does not require it. The structural critique protects the shopkeeper standing at the till and names the manufacturer who engineered the gap. Full citation register: Industry Funding Bias evidence vault.

The decision is yours.

This piece reads what is on the back of the pack and translates it into teaspoons of sugar and FSA traffic lights, then adds the pH from public-domain sources where the label is silent. It does not tell you whether to drink any particular soft drink. It does not give clinical or medical advice. It does not give dental advice. It does not campaign against any manufacturer or retailer. It documents, and it translates, and it shows you the structural gap between the data on the pack, the data not on the pack, and the units the moment of decision uses. The decision itself is yours.

If you have type 2 diabetes, hypertension, dental erosion concerns, or any other condition that makes specific dietary or beverage thresholds matter to you, your GP, your dentist, or a registered dietitian is the right conversation for advice. SCANSMART does not replace that conversation; it gives you the back-of-pack data plus the public-domain pH data in units you can read fast.

Methodology and sources.

Methodology: scansmart.uk/methodology (linked above; full version reused across every Door 4 piece). Methodology v0.1.1 (forthcoming) will document the one-day catch-up rule for missed Monday capture windows. Ranking by retailer best-seller tag. FSA per-100ml and per-portion thresholds applied to sugar. Teaspoons (4g sugar = 1 tsp) as the visual convention. pH disclosed per row with source — manufacturer technical document, peer-reviewed dental literature measurement, or explicit “not publicly disclosed” marker. Capture-date stamped on every figure: Tuesday 19 May 2026 (catch-up against the scheduled Monday 18 May 2026, 09:00 BST window).

Sources: retailer websites (Tesco, Sainsbury’s, Asda, Morrisons, Lidl, Aldi, Iceland, M&S, Waitrose) for best-seller tags and declared nutrition; The Grocer and Just-Food for category market context; FSA published thresholds for traffic-light calculation; manufacturer ESG disclosures and SDIL-response reports for reformulation claims; British Society of Paediatric Dentistry and Eastman Dental Institute published pH and enamel-erosion threshold literature; peer-reviewed dental literature (BDJ, Caries Research, Journal of Dentistry) for third-party pH measurements where the manufacturer figure is unavailable.

Editorial review applied before publication across legal risk, regulatory claim discipline against published FSA and SDIL frameworks, and voice/brand register.

Next entries.

Monday 25 May 2026: the off-Monday reactive slot. What’s moved in the regulatory landscape that week.

Monday 1 June 2026: reformulation tracking. Which DHSC voluntary-programme commitments have moved on per-100g, and which have not.

Subscribe to the Monday email digest at scansmart.uk/checkout to get each piece in your inbox the moment it lands.

Where to go next.

The dental-erosion mechanics behind this piece are introduced in Children’s Oral Health. The Soft Drinks Industry Levy and reformulation context lives in Reformulation Tracking. The full Knowledge Library carries five streams. The full Weekly Supermarket Checkout, Decoded archive lives at the door page.

The Weekly Supermarket Checkout, Decoded · Monday 18 May 2026 (captured Tuesday 19 May 2026 after one-day catch-up) · Methodology version v0.1 (v0.1.1 next entry) · SCANSMART Ltd, Co. No. 17128797, England & Wales · Not medical advice. Not dental advice. The decision is yours.