Where food miles came from
The food miles idea entered public discussion as a way of making an abstract question concrete: how far has this travelled. It is intuitive, it is easy to communicate, and it captures something real about a globalised food system.
It also turned out to be a weak indicator of what people were using it for. Research commissioned by government examined the validity of food miles as an indicator, and the broad finding, which has been reinforced by subsequent work, is that distance alone does not track environmental impact well.
That does not make the concept worthless. It makes it a measure of one thing being used as a proxy for another, which is a specific and common failure of consumer indicators.
Why distance is a poor proxy
Three reasons, and each is sufficient on its own.
Transport is usually a small share of total emissions. For many foods, the dominant contributions come from agricultural production itself: land use, fertiliser, livestock and energy in growing. Where production dominates, transport differences are second-order.
Mode matters more than distance. Emissions per tonne kilometre differ by orders of magnitude between sea freight, road freight and air freight. A long sea journey can involve less emission per unit than a much shorter road journey, and the pack tells you neither.
Production conditions vary by place. The same crop grown in a climate suited to it, outdoors and in season, can involve less energy than the same crop grown locally under heat and light. Location affects production, not just distance.
Once these are combined, distance can point in the opposite direction to impact, which is the definition of a bad proxy.
| Stage | Why it matters |
|---|---|
| Agricultural production | Frequently the dominant contribution, driven by land use, inputs and livestock |
| Processing | Energy intensity varies enormously by product and process |
| Packaging | Usually small relative to production, and often the subject of the claim |
| Transport | Depends far more on mode than on distance |
| Retail | Chilled and frozen storage is a real contribution |
| Consumer use | Cooking and storage at home, frequently excluded from assessments |
| End of life | Disposal and food waste, sometimes excluded by the boundary |
Structure set out by this newsroom from the published rules named in the sources below. It is not a survey, a measurement or a market study.
What life cycle assessment attempts
Carbon footprinting replaces the proxy with a calculation. A life cycle assessment sums greenhouse gas emissions across the stages of a product's life: raw material production, processing, packaging, distribution, retail, consumer use and end of life.
Published specifications set out how this should be done. A publicly available specification for the assessment of life cycle greenhouse gas emissions of goods and services has been in use for product footprinting, and international standards address product carbon footprint quantification. These documents exist precisely because the calculation involves choices that need to be standardised.
Done properly, the result is far more informative than a distance. It identifies where the emissions actually are, which is the information that would let anyone act on them.
Why the numbers are hard to compare
The difficulty is not accuracy but comparability, and it comes from four sources.
System boundaries. Whether the assessment covers cradle to gate, cradle to retail or cradle to grave changes the total substantially. A figure without a stated boundary is uninterpretable.
Allocation. Where a process produces several outputs, the emissions have to be divided between them, and the division can be done by mass, by economic value or by other methods. The choice changes the answer.
Data. Primary data from a specific supply chain and secondary data from a database produce different results, and both are legitimate for different purposes.
Land use and its treatment. How land use change is accounted for is methodologically contested and can dominate a result for some products.
None of this means footprinting is unsound. It means a figure is only meaningful alongside its method, and that comparing two figures from different methods is an error rather than an approximation.
The regulatory position on carbon claims
Carbon claims on food are environmental claims, and they are governed by consumer protection law rather than by a food-specific regime. The CMA Green Claims Code sets out the principles, including that claims must be substantiated, must consider the full life cycle and must not omit important information.
The Digital Markets, Competition and Consumers Act 2024 gave the CMA direct enforcement powers over unfair commercial practices, which raises the stakes for claims that cannot be supported.
The practical implication for a reader is that a claim referencing a named specification is a materially different proposition from a bare number or a general phrase. The reference is what makes the claim checkable.
What a shopper can reasonably do
Be sceptical of distance as a measure, because it is one. Treat a carbon figure without a stated method as uninterpretable rather than as approximate. Where a method is named, that is a genuinely stronger claim. And recognise that the dominant contributions for most foods sit in production rather than in transport, which means that the questions worth asking are about how something was produced rather than about how far it came.
This publication does not advise anyone on what to buy on environmental grounds, and it does not rank foods. What it can do is describe what the indicators measure.
Where this stops
This is a description of measurement methods and claim rules. It is not an environmental assessment of any food, any transport mode or any production system, and it makes no recommendation. The standards bodies and the CMA guidance are the sources for the technical detail.
Elsewhere on Feedworthy. QUID: why some ingredients carry a percentage and others do not. Artisan, farmhouse, handmade: the words with nothing behind them.