Historical changes in the ways we cook and eat have dramatically altered public health.
Bee Wilson is the author of Consider the Fork, which documents the evolution of cooking and eating technology. In the book, Wilson describes many unintended consequences of new methods of or materials for cooking and eating. Here she talks about some of the health ramifications of such changes.
I was struck while reading your book by how changes in the instruments we use to cook and eat can have large-scale health implications. It's especially fascinating that overbites didn't become standard until we all started eating with a knife and fork. Can you describe how that happened?
Yes, I found to be this one of the most fascinating and surprising changes to be brought about by kitchen utensils.
Until around 250 years ago in the West, archaeological evidence suggests that most human beings had an edge-to-edge bite, similar to apes. In other words, our teeth were aligned liked a guillotine, with the top layer clashing against the bottom layer. Then, quite suddenly, this alignment of the jaw changed: We developed an overbite, which is still normal today. The top layer of teeth fits over the bottom layer like a lid on a box.
This change is far too recent for any evolutionary explanation. Rather, it seems to be a question of usage. An American anthropologist, C. Loring Brace, put forward the thesis that the overbite results from the way we use cutlery, from childhood onwards.
"Women were particularly at risk from open hearths, on account of the combination of billowing skirts, trailing sleeves, and open flames."
What changed 250 years ago was the adoption of the knife and fork, which meant that we were cutting chewy food into small morsels before eating it. Previously, when eating something chewy such as meat, crusty bread or hard cheese, it would have been clamped between the jaws, then sliced with a knife or ripped with a hand -- a style of eating Professor Brace has called "stuff-and-cut."
The clincher is that the change is seen 900 years earlier in China, the reason being chopsticks.
As with any such thesis, we will probably never have definitive proof that the overbite results from the adoption of the fork, but it does seem the best fit with the evidence.
The first time I read Brace's work, I was truly astonished. So often, we assume that the tools we use for eating are more or less irrelevant -- at most, a question of manners. I found it remarkable that they could have this graphic impact on the human body.
At the same time, you write in the "Pots and Pans" chapter how until the 18th century most families had one big pot, a cauldron, that had a sort of palimpsest porridge in it -- they just kept adding new things to cook along with whatever was left over from the day before. So a lot of what people ate was soft. Were there dental changes once other ways of cooking became readily available?
The big dental change that was seen with pots happened with the initial adoption of pottery for cooking around 10, 000 years ago. Until the cooking pot was invented, no one who had lost all their teeth would survive into adulthood. There are no traces of edentulous -- toothless -- skeletons in any population without pottery. Pots made it possible for the first time to cook nourishing stew-like meals that required no chewing but could, rather, be drunk. So having teeth was no longer necessary for survival. This is another clear example of how utensils have acted as a kind of robotic extension of the human body.
On the question of why eating these soft foods didn't lead to dramatic dental changes -- such as is seen with the fork and the overbite -- I think the answer must be that they tended to be eaten alongside other, tougher foods.
But switching from a diet of mostly chewy foods to one of very soft foods can definitely have an impact on human teeth. Studies of Australian aboriginals have found that within a single generation of leaving their homes in the Outback and moving to cities (where the diet becomes one heavy in refined white flour and sugar), teeth have far less attrition (wear and tear from chewing) but many more cavities.
The big cauldron was heated over an indoor fire that, you write, was the center of the typical home. What happened after the hearth was replaced by a more removed kitchen?
One change is fewer accidental deaths from young children toddling into fires by mistake or women's billowing skirts catching ablaze as they cooked. Women were particularly at risk from open hearths, on account of the terrible combination of billowing skirts, trailing sleeves, open flames, and bubbling cauldrons. With the emergence of enclosed brick chimneys and cast iron fire grates in the 17th century, many more women became professional cooks: At last they could cook with only a minimal risk of setting fire to themselves.
Have there been any big changes in health caused by the materials used to make what we cook in?
Yes, a good example of this would be copper pans, which when poorly lined led to copper poisoning (causing severe gastrointestinal troubles). "Let your pans be frequently re-tinned" is an instruction you see in cookbooks from the 19th century. But clearly not all cooks were vigilant enough about keeping the surface of the pans intact. Indeed, some cooks positively preferred to use unlined copper pans because they liked the green color they gave when cooking pickles.
What change in the last hundred years in how we cook has been most beneficial for public health?
Refrigeration is a very important one, not just for its role in individual kitchens but for the way it transformed the whole food supply, making fresh meat and green vegetables available year-round in all parts of the States for the for the first time in history.
But I'd argue that the most crucial of all was the gas oven, for saving millions from the smoke and indoor air pollution associated with open-fire cookery. The World Health Organization estimates that open cooking fires still kill 1.5 million people every year in the developing world, mostly from respiratory disease. The emergence of gas stoves at the end of the 19th century must have saved millions of lives.
What's caused the most harm?
The microwave has often been seen as a threat to public health but radiation from microwaves has been exonerated of most risks -- except those associated with any device that makes food get hot.
The most harmful change is probably the decline in cooking itself, which has resulted in much of the population having far less control over the ingredients they put in their mouth, as well as a huge rise in the consumption of obesogenic ingredients that no home cook would use, such as high fructose corn syrup.
Is there any evidence that universal refrigeration is altering our guts? I'm thinking here of a food version of the theory that overly sanitized homes contribute to increased asthma because children don't develop natural defenses.
There have been suggestions (see, for example Malekzadeh et al, 2009) that the near-universal refrigeration of so many foods in the "cold chain" could be a risk factor for Crohn's Disease. But the theory is not that the risk is the result of lack of exposure to germs, but rather because there are certain bacteria -- including Listeria and Clostridium botulinum -- that are capable of surviving or developing at low temperatures. And further research needs to be done. For those of us not at risk of developing Crohn's, the benefits of refrigeration seem to vastly outweigh the risks.
What recent widespread change in how we cook or eat might, 100 years from now, be seen as having unintended consequences?
From the point of view of the average home cook, I'd argue that the developments in mechanical food processing of the past hundred years -- whether it's a Cuisinart on the worktop or the fact that we can purchase ready-powdered sugar and ready-ground meat -- have been truly liberating. They have freed up hours of time and spared so much pain and labor.
But we are already seeing unintended consequences in eating a diet consisting of food that undergoes so much more processing than it did in the past. Various studies have suggested that the current obesity crisis is partly caused by the degree to which food has been processed before we eat it. Rats fed on soft food pellets gained more weight than those eating hard pellets, even though the calories were identical. This is a clear example of how food technology can impact health. When we eat chewier, less processed foods -- a raw apple rather than apple puree -- it takes us more energy to digest them, so we receive less energy.
The aim of mechanized food processing was to save time and effort, but an unintended consequence may be contributing to the worst public health crisis of this generation. Most cooking technologies, from fire onwards, have attempted to make the job of eating easier. Maybe in the future we need to design some that make it a bit slower and more challenging again -- or at the very least ones that require a bit of jaw action.