Study Reveals Stark Caffeine Disparities Across Major High Street Coffee Chains

Key facts

According to reporting published by RTÉ on August 25, 2026, a new comparative analysis of high street coffee chains revealed extreme discrepancies in the caffeine levels delivered across major retail outlets. Researchers examining popular espresso-based beverages found that standard menu items sold under identical descriptions—such as a simple cappuccino—yielded vastly different chemical profiles depending on the brand preparing the drink.

The most striking contrast highlighted in the study was between international giants Costa Coffee and Starbucks. The data demonstrated that a cappuccino sourced from Costa contained approximately three times the caffeine content found in a cappuccino purchased from Starbucks. Beyond this specific pairing, the report noted that caffeine levels across the broader high street market varied wildly, meaning consumers purchasing daily hot drinks face unpredictable chemical dosages without explicit point-of-sale disclosures.

The investigation examined standard drink offerings across high street chains, where consumers typically assume uniform standards for familiar espresso-based recipes. However, differences in bean composition, espresso shot counts, cup volume, and extraction techniques lead to substantial swings in caffeine concentration. While pre-packaged canned and bottled energy drinks or ready-to-drink iced coffees in retail stores are required by consumer protection laws to display nutritional data and specific caffeine advisories, counter-served hot beverages in coffee shops operate under no such mandatory disclosure framework. As a result, customers routinely order drinks without clear knowledge of whether they are receiving a mild stimulant dose or a high-potency caffeine intake approaching daily recommended health ceilings.

Why it matters

The extreme variance in caffeine levels across popular retail chains carries direct consequences for consumer health, particularly for individuals managing cardiovascular conditions, anxiety disorders, sleep disturbances, or pregnancy. Under established medical guidelines published by the European Food Safety Authority (EFSA) and the U.S. Food and Drug Administration (FDA), a daily intake of 400 milligrams of caffeine is generally considered safe for healthy non-pregnant adults, while single doses should ideally remain below 200 milligrams. For pregnant or breastfeeding women, public health bodies recommend capping total daily consumption at 200 milligrams due to potential risks associated with fetal development and low birth weight.

When a single commercial cappuccino can range from a modest dose to triple that strength, a consumer drinking two large cups from one chain might stay comfortably below recommended boundaries, whereas consuming two equivalent cups from a higher-potency chain could push them well beyond safe daily thresholds. Furthermore, many consumers intentionally seek out coffee for predictable cognitive stimulation or, conversely, attempt to limit their intake later in the afternoon to protect sleep hygiene. Without transparent labeling at the point of order, patrons cannot accurately moderate their intake.

From a market perspective, these findings place renewed pressure on restaurant chains and commercial coffee vendors to publish voluntary nutritional data. As consumer watchdog groups highlight these disparities, retail franchises may face regulatory scrutiny regarding whether freshly prepared caffeinated drinks should remain exempt from point-of-sale nutritional disclosure requirements currently imposed on packaged food and beverage products.

The wide divergence in caffeine content between commercial coffee brands stems fundamentally from differences in agronomic sourcing, roast profiling, and operational beverage preparation. In the global coffee industry, commercial coffee beans primarily belong to two species: Coffea arabica (Arabica) and Coffea canephora (Robusta). Arabica beans, which are generally prized for sweeter, softer, and more nuanced flavor profiles, contain an average caffeine concentration of 1.2% to 1.5% by weight. By contrast, Robusta beans, which are hardier to cultivate and offer a darker, more bitter flavor with thicker crema, possess nearly double the caffeine concentration, ranging from 2.2% to 2.7% by weight.

Historically, retail coffee chains have utilized distinct blending strategies. Many chains, including Starbucks, emphasize 100% Arabica bean recipes across their standard core espresso offerings. Other major chains, such as Costa Coffee, have traditionally relied on proprietary blends—such as Costa's long-established Mocha Italia blend—that combine both Arabica and Robusta beans to achieve a specific flavor profile and visual foam consistency. This structural inclusion of Robusta naturally elevated the baseline caffeine levels in espresso shots prepared by Costa compared to 100% Arabica competitors.

Beyond bean agronomics, store-level operational metrics create further divergence. Differences in machine calibration, water volume per extraction, espresso basket size, and the number of espresso shots included in standard drink sizes contribute significantly to the final caffeine output. A chain that uses a double espresso shot as its baseline for a medium cup will naturally deliver higher caffeine than a competitor using a single shot or a lighter extraction volume.

Regulatory frameworks across Europe and North America have historically distinguished between packaged goods and freshly prepared cafe items. Under European Union Regulation (EU) No 1169/2011 on the provision of food information to consumers, pre-packaged beverages containing more than 150 milligrams of caffeine per liter must carry clear labeling stating "High caffeine content. Not recommended for children or pregnant or breast-feeding women," accompanied by the exact caffeine content per 100 milliliters. However, freshly crafted drinks sold in coffee shops, restaurants, and fast-food outlets remain largely exempt from these mandatory packaging rules, leaving point-of-sale nutritional disclosures entirely optional for operators.

Reaction

Following the release of the study, public interest group responses and consumer health advocacy discussions are anticipated across Ireland and the broader European market. Consumer protection organizations frequently cite such comparative studies to advocate for standardized menu labeling, arguing that high street coffee chains should provide accessible nutritional information at ordering counters or on digital menu boards.

While official corporate responses from Costa Coffee and Starbucks regarding the specific test measurements reported by RTÉ were not detailed in the initial report, major commercial coffee brands typically defend variations by pointing to differences in proprietary drink formulations, cup sizing, and the natural agricultural variability of coffee beans. Industry trade groups generally maintain that handcrafted beverages inherently experience minor batch-to-batch variations due to barista extraction techniques, water temperature, and bean harvest batches.

Public health specialists and dietary advisory bodies are expected to reiterate calls for sensitive groups—such as pregnant women, adolescents, and individuals with cardiac conditions—to exercise caution when purchasing non-labeled commercial espresso drinks, recommending that customers explicitly request single-shot options or decaffeinated alternatives when seeking to moderate their caffeine consumption.

What we don't know yet

Several critical details regarding the comparative study remain unquantified in the initial reporting by RTÉ. The exact milligram amounts of caffeine measured in the tested Costa Coffee and Starbucks cappuccinos were not specified in the initial summary, leaving the absolute chemical values unknown despite the relative three-to-one ratio reported.

Additionally, the testing scope leaves open questions regarding sample size, geographical distribution, and batch sampling protocols. It is unclear how many individual store locations were sampled, whether drinks were tested across multiple days to control for barista consistency, or what specific cup sizes (such as small, medium, or large) were used for the comparative baseline.

Furthermore, the full list of other high street coffee chains included in the broader study—and their respective ranking order regarding caffeine content—has not been fully detailed. It remains unknown whether other popular European and regional chains, such as Caffè Nero, Insomnia Coffee Company, or fast-food chains like McCafé, fell closer to the high caffeine threshold seen in Costa or the lower threshold observed in Starbucks.

What to watch

In the coming weeks, consumer interest will center on whether Costa Coffee, Starbucks, and other major coffee chains issue detailed statements clarifying the precise shot count, bean blend composition, and target caffeine metrics for their standard menu items.

Observers will also monitor whether consumer advocacy groups or public health organizations use these study findings to submit formal petitions to food safety regulatory authorities—such as the Food Safety Authority of Ireland (FSAI) or the UK Food Standards Agency (FSA)—calling for mandatory caffeine disclosures on freshly prepared retail coffee menus.

Additionally, coffee drinkers and industry analysts will watch to see if retail chains respond by updating their digital apps, physical menus, or in-store signage to publish accessible caffeine content guides, enabling consumers to make fully informed decisions based on their personal health requirements.

This report is based on original news reporting published by RTÉ.