We have all heard at one time or another that spinach has much more iron than other vegetables. And perhaps you are also familiar with the famous idea that this is due to a misplaced comma in a work about the amounts of this nutrient in vegetables published in 1870 by Emil Wolff.

Interestingly, Popeye was created because of that mistaken belief and contributed to a one-third increase in spinach consumption in the United States. They are myths upon myths, a test that sometimes what we have known "all our lives" rests on feet of clay.

Wolff's study, which was taken for good until the 1930s, contained an error in one table, but this affected equally all foods for which it reported their nutritional value. Thus, the decimal point story is a 1981 simplification that reinterprets other errors by dealing with a few data.

For his part, Popeye did not start eating spinach until 1932, three years after the comic was created. But not because of the iron but because of vitamin A, the same vitamin that was later used - this time deliberately - in the carrot myth.

By then, spinach consumption had already increased because the iron fallacy had become popular, although many children continued to "suffer" a spinach-rich per diem expenses thanks to the recommendations of the staunch vegetarian sailor.

Frozen myths
Another example of a stony decision based on data has to do with a belief about which there is an entire industry regulated by law: that frozen foods must be kept at -18 °C or colder.

Why precisely this temperature? One would expect that, as a result of scientific programs of study or industry experience. After all, if this were not the case and a few Degrees above or below mattered little, why is it set so rigidly?

First of all, microbiology tells us that the microorganisms that spoil food stop their growth in the cold. But it was shown years ago that keeping products at -12 °C is sufficient to stop bacterial growth and activity.

Another scientific discipline , nutrition, explains that some vitamins remain stable at -18 °C for a year, but others can degrade significantly even at -60 °C after a few months without a few Degrees up or down changing much result.

So why was the temperature of -18 °C chosen as reference letter to achieve the necessary food safety? According to a recent study signed by the director general of the International Institute of Refrigeration (an independent intergovernmental organization that collects scientific and technical evidence on cooling) and five co-authors, it appears that it was selected in the mid-twentieth century because within the temperatures considered safe corresponds precisely to the 0 Degrees Fahrenheit.

It would have been an easy case of rounding off. Engineers would have picked up the gauntlet, routinely designing equipment and processes based on that mythical 0°F temperature, and legislation would have done the rest.

The environmental impact of each Degree
However, if we introduce Ecology into our narrative, we might consider that cooling involves heating the sink to which the removed heat goes, which is the environment, as well as consuming energy resources to do so. While engineering is constantly increasing the efficiency of equipment, there are insurmountable physical limits.

All energy consumption translates into an impact on the environment, which today can often be measured in terms of carbon footprint. But what if there were no need to cool so much? Would it be possible to keep frozen food safely at a higher temperature and, in the process, reduce energy consumption? The answer seems to be yes, and it is proposed that it should be with the reference letter of -15 °C so that, in the event of a problem, it would take time to reach the still safe (microbiologically) limit of -12 °C.

Rational and ecological choice of temperature
The report mentioned sample that this simple measure would mean almost a 5% reduction of what is consumed in maintaining the cold chain at the current temperature. We would save 25 terawatt hours (TWh) per year (one terawatt hour is equivalent to the annual electricity consumption of 150,000 people living in the EU), equivalent to 10 million tons (Mt) of greenhouse gases, or what is emitted by three million cars, as many as circulate throughout Denmark. This would be another reasonable step in the direction of reducing the human footprint on the environment.

Living sustainably costs, but it will cost more to do it in an unsustainable way. The more the different branches of science help each other to dismantle legends, the sooner we will reach the goals of a sustainable development more necessary than ever.

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Enrique Baquero researcher of Biodiversity and Environment Institute (BIOMA) and professor of the School of Sciences, University of Navarra 05.05.2024

Arturo H.Ariño Professor of Ecology, researcher senior of the Institute of Biodiversity and Environment and manager of research of the Science Museum, University of Navarra. 05.05.2024