Food Foundation’s reaction to Cheap as Chips

Last week the Institute of Economic Affairs published Cheap as Chips, asking whether a healthy diet is affordable.  It concludes that healthy food is generally cheaper than less healthy food.  They say  that  cost-per-calorie analysis used by researchers and organisations – including the Food Foundation – is flawed.

Cheap as Chips instead uses cost-by-weight analysis and compares “regular food products and their healthier [direct] substitutes” and “food products that are typically regarded as being unhealthy… compared… with… food products that are generally regarded as healthy” – to reach its own conclusion.

Does it matter how we measure the cost of food?

Cheap as Chips rightly notes that the way we compare food costs (e.g. cost per calorie; cost per kg; cost per portion) has a drastic effect on the results.  Indeed, Cambridge University researchers Jones and Monsivais reason that cost-by-weight analysis is the most appropriate metric to use when comparing the costs of food products that serve the same purpose within diets.  If, for example, you wanted to find out whether butter or margarine was the cheapest fat to use in cooking, you could look at the cost of 100g of each, as it is reasonable to assume a similar amount of each product would be used in preparing otherwise identical meals.

This is the approach the paper takes in the first half of Cheap as Chips, directly comparing the cost-by-weight of substitutable products (e.g. different types of breakfast cereals) from two different supermarkets in November 2016.  The conclusion to this tranche of analysis was that “there was little or no difference in the price of healthy and unhealthy brands of most direct substitutes.”

However, it is impossible to judge the validity of this analysis.  The author does not explain on what basis their two supermarkets and the 43 ‘direct substitute’ products, were selected for assessment:  they explain that they examined cost of the cheapest brand, including home brands, of each product examined, but do not detail how they selected the products in the first place.   Likewise, the paper does not clarify whether they assessed like-for-like packet sizes when comparing prices per 100g/litre of substitutable goods. Crucially, while the paper classed “low-fat, low-sugar or low-calorie alternatives” as “healthier substitutes”, it unclear whether a nutrient profiling model used to systematically categorise foods into the ‘healthier’ and ‘less healthy’ categories.  In comparison, a Cambridge University study, which Jones and Monsivais co-authored, used the nutrient profiling model devised by the Food Standards Agency, and used the products included in the Consumer Price Index basket of goods.

Cheap as Chips goes on to assess – now using data from only one supermarket, for reasons left unexplained – the cost-per-weight of “20 food products that are typically regarded as being unhealthy… compared… with 23 food products that are generally regarded as healthy”. Again, no justification is given as to which products were included in analysis, and here it appears no nutrient profiling model was used to systematically categorise these products into healthy and unhealthy.

But more importantly, when comparing the cost of very different food categories it makes little sense to use cost-by-weight analysis, as people consume different food products in very different ways, and as equal weights of different food products provide very different amounts of sustenance:  100g of pasta could easily be served as the main component of a filling meal; 100g of lettuce however would not make for a filling main course.  Comparing the cost-by-weight of each therefore has little value, as consumers can’t realistically substitute one for the other.

Indeed, when comparing the cost of diets, rather than individual food products, cost-per-calorie becomes the preferable unit for analysis.  Everyone requires a certain amount of energy (i.e. calories) per day to sustain themselves.  To adequately assess whether a healthy diet is affordable in comparison to a less healthy diet, as Cheap as Chips purports to do, you should consider the costs involved in two or more different diets used to meet an individual’s energy requirement – as counted in calories – and assess the nutrient profile of these diets to robustly categorise their relative healthiness.

Cheap as Chips fails to do either.  When researchers at Cambridge University did this by looking at national datasets on the prices of goods within the CPI basket,  they found that healthy foods were consistently more expensive than less healthy foods, and rose more sharply in price over the course of a decade.

Any implications for policy?

Of course, price is not the sole determinate of consumers’ dietary choices.  As described in Cheap as Chips, taste and convenience also have an impact, alongside a myriad of other influences.  However,  meta-analysis of the academic literature shows that price is an important factor affecting individuals’ diets.

Yet, on the back of this paper, the Institute of Economic Affairs (IEA) will suggest that the relative price of healthier and less healthy food is a public policy distraction.  IEA will use its ‘findings’ to undermine arguments in favour of food taxes and subsidies, or other public policy responses which could rebalance the costs of healthy and less heathy foods; to attempt to change the policy goalposts as evidence on the effectiveness of tax and subsidy interventions to change diet for the good of public health mounts up in countries as varied as Mexico, Netherlands, South Africa, USA and New Zealand.

Like the methodology employed in this paper, the motivations of the IEA here are opaque.  Indeed, the think tank was recently awarded a transparency rating of zero out of five stars by Transparify, and not once in its 60 year history has it acknowledged the source of its funding.

Christopher Snowden, head of the IEA’s Lifestyle Economics unit and author of Cheap as Chips, has previous suggested it is “irrelevant” whether IEA is funded by the food industry.  However, we suggest that, at a minimum, IEA holds itself to the same level of accountability that the researchers contained within the paper’s literature review are subject to, and detail their financial affiliations when publishing quasi-academic papers designed to impact on public policies around food and health.