Processed foods, particularly of the ‘ultra-processed’ variety, are one of the nutritional hot topics of the moment. Most people, whether or not they work in nutrition, have an opinion about processed foods, and it does not tend to be positive.
This is, however, an overly simplistic view of a nuanced topic. And you don't need to look far for evidence that not only that processing can be good, but that it may have been crucial to our survival as a species.
Take, for instance, corn. From tortillas, tamales and corn on the cob itself, it's the foundation of Mexican cuisine. There is a good historical reason for this, and food processing has played a key role.
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For starters, Mexico is quite literally the birthplace of corn. Maize or corn was domesticated in Oaxaca, a region at the southern end of the country, around 9,000–10,000 years ago.
Corn is tremendously versatile, and depending on how it is processed, results in a huge variety of foods with different textures and tastes. If you simply dry out the corn and grind it up finely, as you would do with wheat, you end up with cornflour, which is often used as a thickening agent in gravies or sauces. On the other hand, grinding the kernels coarsely, results in cornmeal or polenta.
The ubiquitous corn tortilla, however, is not made from cornflour, but from ‘masa harina’. While both are flours made from corn, masa harina is instead milled from corn kernels that have first been processed by soaking them in lime – not the fruit, but the mineral calcium hydroxide, solution. This process, it turns out, was critical for the survival of indigenous Mexicans.
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The alkalinity of the lime helps dissolve hemicellulose, the major glue-like component of the maize cell walls, loosening the hulls from the kernels, softening the corn, and the resulting product is ground into a dough to create the fresh masa used to make tortillas and tamales.
This process is called ‘nixtamalization’, a word with roots in the Aztec language. The process plays a crucial role in unlocking the full nutritional potential of corn. Corn is particularly rich in niacin, otherwise known as vitamin B3. But without processing, this key nutrient is chemically unavailable to the human digestive system and passes right through us.
So if the grain you ate was primarily corn, you could end up with niacin deficiency, resulting in a disease called Pellagra. It's an illness characterised by diarrhoea, dementia, and rashes on the hands and feet. If left untreated, it is lethal.
Processing the corn by soaking it in an alkaline solution liberates the niacin, making it available to humans during digestion. Over the 10,000 years since corn was domesticated, the indigenous Mexicans developed the technique, which, probably by happenstance, made this staple food far more nutritious, and Pellagra was never a problem.
However, an issue arose after the arrival of Europeans in the Americas, who quickly added corn to their diets. None of the newly arrived immigrants knew how to process corn using nixtamalization – or if they did, they certainly didn’t grasp the significance of that process.
For most non-indigenous Americans, the unavailability of niacin from corn was not a problem, as it was available from other food sources, such as meat and other grains.
However, corn was cheap and easy to grow, so it ended up being a primary staple to those in poverty, causing a sharp increase in the incidence of Pellagra amongst the poor. It wasn’t until the mid-1930s and early 1940s that Pellagra was recognised as a disease resulting from niacin deficiency and was eventually eradicated by the fortification of grains and flour.
This is an example of how food processing was critical to our ability as a species to survive and thrive, ensuring that we had a predictable source of calories through seasonal changes in the availability of fresh food, and buffering against environmental crises such as drought.
So while the term ‘processed food’ is associated with a whole host of negative connotations, the devil truly is in the detail.
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