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Modern-Day Diets Are Changing Human Chemistry, Study Finds

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Modern-Day Diets Are Changing Human Chemistry, Study Finds
Eating mass-produced food grown with synthetic fertilizers is changing hair, nails and bones. d3sign / Getty Images

By Malavika Vyawahare

"Tell me what you eat, and I shall tell you what you are," the French lawyer Jean Anthelme Brillat-Savarin wrote in his 1826 opus, Physiologie du Goût. This is quite literally the case, scientists decoding the human body have found.


Now, an analysis of chemical signatures in human hair and nails shows that as more of our food is mass-produced, we are beginning to "look" increasingly similar. If not in the flesh, then in the bones.

"Reliance on international food distribution and industrial agriculture has changed the chemistry of the entire human race," said Michael Bird, first author of a recent paper in the journal Proceedings of the National Academy of Sciences. Only communities that rely on subsistence agriculture have bucked the trend, the paper found.

This change is especially true for urbanized and wealthier communities. In nations where annual per capita income exceeds $10,000, supermarkets supply most of the food. Another hallmark of the modern diet is the reliance on wheat, maize, rice, and a handful of other starchy cereals.


A supermarket in North America. Image courtesy of Flickr

Archaeologists routinely draw conclusions about past diets from skeletal remains. Bird and his collaborators analyzed hair and nail samples from present-day populations and compared them with archaeological data on the diets of people living before 1910. It was around this time that synthetic nitrogen fertilizer, one of the pillars of industrial farming, came into widespread use.

The researchers looked specifically at the ratio of different isotopes of nitrogen and carbon found in corporal remains. Isotopes are versions of the same element that differ in mass. By studying these ratios, scientists can draw conclusions about the food that people eat.

In the case of nitrogen-based fertilizers, the proportion of nitrogen isotopes reflects their ratio in the atmosphere, not what would exist in naturally fertile soils. When nitrogen-fixing microbes extract nitrogen from the atmosphere, it yields a different ratio of the two isotopes than chemical fertilizer.

When plants take up nitrogen from the soil, they absorb two stable nitrogen isotopes in a fixed proportion. This ratio changes as the nutrients make their way up the food chain via the guts of other organisms. The lighter form of nitrogen is more likely to be used for bodily functions and excreted as waste, but the body retains heavier isotopes. Thus, more of the heavier nitrogen isotope survives the ascent from prey to predator.

For folks buying food at mega marts supplied by factory farms, nitrogen isotope values across populations are in general lower and lie within a narrower band. If you consume meat from cows on large industrial-scale farms or plants grown in monoculture fields with the help of fertilizers, the nutrients come to you through an artificially shortened route.

"We're sort of short-circuited many of the natural processes that go into making the food for people in prehistory, or people who still live a subsistence lifestyle," Bird said.

Carbon isotopes, in turn, shed light on what kinds of foods people consume: a diet rich in corn or one where rice is a staple will leave behind a different carbon isotope signal in human tissue. The range of values for carbon isotopes has also shrunk today, the analysis found, because we're eating similar kinds of food.

"We know that agricultural production and food consumption patterns were narrowed down globally over the last 100 years due to research and policy concentrating mostly on a few major crops — cereal grains, oilseeds, sugar — while neglecting many others," said Matin Qaim, an agricultural economist at the University of Goettingen, Germany, who was not involved in the study. "Of course, food collection from the wild — roots, leaves, berries — also declined in importance for most humans in modern times."

However, communities that rely on subsistence agriculture exhibit isotope ratios that are similar to pre-1910 human diets.

That's not necessarily a good or bad thing in terms of health. "The authors of this paper show that diets were more diverse on average before 'industrial agriculture' started, but this does not mean that people had a better nutritional status back then," Qaim said.

The problem with this mode of sustenance, divorced from natural complex food chains, is a loss of resilience. The simplification of the food chain and overreliance on one- or two-step food chains worry researchers like Bird. "It's a demonstration that being reliant to a very great degree on technology in the form of industrial agriculture is potentially a risk," he said.

A disruption, like a plant disease, locust invasion, or pandemic, can throw the entire system into disarray. Short of dismantling the industrial, agricultural complex, there is no way to revert to earlier production modes. Given the ballooning human population, such a campaign would also undermine the food security of millions of people. According to economic historians, the availability of chemical fertilizers is one major reason for the burgeoning human population in the first place.

"Agricultural production and food consumption patterns should be diversified, meaning that more different types of crops should be produced and consumed locally and globally. This would have nutritional, health, and environmental benefits," Qaim said. "We cannot roll back agricultural technology to what it was 100 years ago. We need technology, including new technologies to feed and nourish the world, but need more diversity and reduce the environmental footprint."

Reposted with permission from Mongabay.

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