What is Soil Depletion?
“Is modern agriculture causing soil depletion and making our food less nutritious?” I see this claim a whole lot.
You’ve probably seen the infographics about how we need to eat ridiculous amounts to get our vitamins and minerals because our food isn’t nutritious anymore. Like this one that says we need to eat eight oranges to get the same nutrients as there were in one orange in 1980:
Or this soil depletion infographic, ragging on modern broccoli:
How about this one, claiming that apples were once a great source of iron (I’m calling BS):
Or, you might have read something like the quote below:
Fruits and vegetables grown decades ago were much richer in vitamins and minerals than the varieties most of us get today. The main culprit in this disturbing nutritional trend is soil depletion. Modern intensive agricultural methods have stripped increasing amounts of nutrients from the soil in which the food we eat grows. The solution is to purchase local, organic food from farmers that value their soil. Know your farmer, know your food!
This sort of narrative has been around for a really long time – like, since 1936 – and it makes me suspicious. Does our food really lack nutrients compared to years past? If so, why? And just as importantly, who is saying these things (and what do they have to sell)?
Let’s get after this.
The Research Behind Soil Depletion
It’s so easy to get into the weeds with this topic, because it’s complicated and complex. I’m going to try and make it as simple as possible for you…and for me!
Is food actually less nutritious than it was before?
A lot of articles, like this one from Scientific American, cite the same studies to ‘prove’ that your food is less nutritious now than it used to be. The Kushi Institute study (biased, non peer-reviewed, and faulty methodology) and the Davis study (doesn’t prove the author’s point at. all.) are two favorites that sound trustworthy, but frustratingly, they aren’t for the reasons I indicated above.
Let’s look at some legit research about nutrients in our food, then and now version. There’s one study that stands out in that category: this 2017 review in the Journal of Food Composition and Analysis. The authors of the review apparently had enough of this ‘soil depletion’ and ‘food less nutritious’ stuff too, because they went above and beyond to figure out the sources behind the claims of ‘apparent historical declines’ of nutrients in food, and hold them up to the light to see if they’re accurate.
The review included at least 17 peer-reviewed studies that looked at nutrient comparisons in fruits, vegetables, and grains over the years, and that are frequently cited to support the claims.
One of the reasons I love this review, aside from the fact that it’s so thorough, is that the authors weren’t sponsored at all by any government agency. So, the conspiracy theorists who try to debunk this sort of work ‘they work for the FDA! The corrupt USDA!’ don’t really have a leg to stand on.
As it turns out, there are many reasons why taking one food, say, carrots – from the 1980s, or the 1950s, and comparing its nutrients to carrots now, can be inaccurate.
Here’s what was explored – and exposed – as limitations in these studies:
Plant cultivars. There are a lot of people on the planet, and as much as some people don’t like this fact, we need to feed everyone. We can’t feed all the people with the old varieties, because their yields aren’t as high. But does that mean that the new varieties are so much less nutritious than their heirloom counterparts?
The proponents of the less-nutritious claims use the same trick as the media does when writing clickbait headlines about nutrition studies: they fail to differentiate or explain the absolute effect of something, versus the relative effect.
In the nutrient studies, the relative decrease of minerals in a food can look huge, but in reality, is very, very small and therefore insignificant to human health.
I love this example from the review:
Apparent declines, e.g., the extreme case of copper from −34% to −81%, represent small absolute changes: per 100 g dry weight vegetables have 0.11–1.71 mg (1555% natural range of variation), fruit 01–2.06 mg (20,600% range), and grains 0.1–1.4 mg (1400% range).
In other words, what looks like a massive decline in nutrition is actually a small deviation that’s well within the acceptable and known natural variation for that food. Natural variations in nutrients are normal for the food we grow: the place where the food was harvested, the season in which it was harvested, and the degree of its ripeness all impact its nutrient content.
And now that we know that our food – past and present – is within these ranges, we can look at why samples from different years might not be comparable to one another.
First off, the methods of analysis differ decade to decade. With the advances in science has come different ways of analyzing the nutrients in our foods. So while some studies used analytic processes that date back to the 1920s, current analyses use more updated methods, and will be different as a result.
You also can’t lump different varieties together under one group, like ‘wheat.’ Wheat has a lot of different varieties, all of which will be different in terms of nutrient values.
But these are all variables that aren’t accounted for in those ridiculous ‘eat 12 heads of broccoli to your grandparents’ one’ infographics, or some of the studies *ahem* Kushi Institute *ahem*
So is it Soil Depletion?
As far as soil depletion, this is also untrue for the simple fact that farmers couldn’t grow anything in depleted soil. Soil on farms is constantly analyzed and nourished using the latest technology so plants stay healthy and yields remain high. Nutrients in the soil most definitely affect the nutrients in the plants, but the review also found no evidence that soil depletion is present and/or affecting our food in any way.
I think the willingness to believe that our food isn’t nutritious stems from an overall distrust in our food system and the perception that in the past, food was simpler and more wholesome than it is now. From artisanal and heirloom to Panera’s ‘food as it should be’ ads, the ‘back to basics’ movement is pretty much everywhere. That’s fine, but using anti-science rhetoric to push an agenda isn’t. The reality of the situation is that our food has never been safer or more plentiful than it is now.
Who’s Saying this Stuff About Soil Nutrient Depletion?
The people who perpetuate myths about our food being less nutritious are usually biased, or they’re looking to profit. They include chiropractors and companies selling supplements (SHOCK), farms selling organic produce, and activist organizations promoting their own agendas. It’s all the opportunistic use of twisted data and the fear of consumers. For the record, supplements can’t replace the nutrition in whole fruits and vegetables, and organic produce hasn’t been proven to be superior to conventional in any way.
James Wong, a botanist and writer for The Guardian, who I trust, told me that the bottom line is this: if fruits and vegetables were far lower in nutrients than they were in past years, we would be seeing an increase in nutrient deficiencies in humans. This just isn’t happening.
And just for your viewing pleasure, here’s a tweet about how our nutrient-depleted foods are ‘starving us’ by James DiNicolantino, a ‘doctor’ of pharmacy and Mercola buddy who I also *exposed* ahem discussed in my ‘Is Sugar Addictive’ post. James Wong later tweeted it out with the information that DiNicolantino’s tweet had actually come from a 1936 edition of Cosmo Magazine:
In short, our food is fine.
The real issue? We don’t eat enough fruits, vegetables, or whole grains in the first place. The other issue? Fooling people into believing that their food is somehow bad or wrong seems to be very lucrative.
If you see somebody making this ridiculous claim, know that it’s a red flag and completely untrue.