Short answer: yes, modestly — and not for the reason you have been told. Vegetables are less nutritious than they were in 1950 by most measures, but the cause is almost certainly the varieties being planted, not depleted soil. Here is what the studies actually found, the strongest argument against them, and the much larger nutrient loss sitting in your refrigerator right now.
You have seen the claim. It usually arrives as a number with no source attached: you would have to eat eight oranges today to get the vitamin content your grandparents got from one. Or five. Or ten, depending on which account you land on.
I have gone looking for the primary source behind that particular figure more than once and never found one. That is worth saying plainly, because I am about to argue that something real did happen to the nutrient density of produce — and the fastest way to lose that argument is to lead with a statistic nobody can trace.
So here is the actual literature, including the parts that cut against the conclusion I would prefer.
What the studies on nutrient decline in vegetables found
The most-cited work is a 2004 analysis by Donald Davis, a biochemist at the University of Texas at Austin, with Melvin Epp and Hugh Riordan. They compared USDA nutrient composition data published in 1950 against data published in 1999, covering 13 nutrients across 43 garden crops — mostly vegetables, plus melons and strawberries.
Considered as a group, six of the thirteen nutrients showed what Davis called “apparently reliable declines”: protein, calcium, phosphorus, iron, riboflavin, and vitamin C. The size of the drop ran from about 6 percent for protein to about 38 percent for riboflavin.
Across the Atlantic, Anne-Marie Mayer ran a similar comparison in 1997 using the UK government’s Composition of Foods tables from the 1930s and the 1980s, and found statistically significant reductions in several minerals in both fruits and vegetables. She and colleagues extended that work through 2019, reporting declines across nearly every element they tracked over the 80-year window, with iron and copper among the largest.
| Study | Data compared | Headline finding |
|---|---|---|
| Davis, Epp & Riordan (2004) | USDA tables, 1950 vs 1999, 43 US garden crops | 6 of 13 nutrients down; declines from ~6% (protein) to ~38% (riboflavin) |
| Mayer (1997) | UK Composition of Foods, 1930s vs 1980s | Significant mineral reductions in both fruits and vegetables |
| Mayer, Trenchard & Rayns (2022) | UK Composition of Foods, 1940 / 1991 / 2019 | Nearly all elements down over 80 years; iron and copper largest |
| Marles (2017) | Review of the above plus archived soil samples | Rebuttal: changes are within natural variation; soil depletion unfounded |
Three separate datasets, two countries, eight decades, same direction. That is not nothing.
Why “the soil is depleted” is the wrong explanation
Here is where the popular version of this story goes off the rails.
The claim you hear repeated is that the soil is depleted — that industrial farming has stripped the minerals out of the ground, so the plants have nothing left to take up. It is an intuitive story. It fits a certain moral shape. It is also not what Davis concluded.
Asked what caused the decline, Davis said the most likely explanation was “changes in cultivated varieties used today compared to 50 years ago.” His reasoning: for half a century, plant breeding has optimized hard for yield. “When you select for yield, crops grow bigger and faster, but they don’t necessarily have the ability to make or uptake nutrients at the same, faster rate.”
The distinction matters because the two stories imply completely different fixes. If the soil is empty, you remineralize. If the varieties are the issue, no amount of compost changes the outcome — you have to plant something else.
The dilution effect: what breeding for yield really does
A tomato bred to be twice as large is not necessarily pulling twice the minerals out of the ground. It is pulling somewhat more mineral and considerably more water and carbohydrate, and the concentration per hundred grams falls as a result. The plant is not starving. It is being diluted.
That is the dilution effect, and it is the one mechanism nearly everyone in this debate agrees is real. It is also why the fix is a purchasing decision rather than a soil amendment. Somebody has to choose to grow the denser variety, and somebody has to be willing to pay for it — a variety that yields 30 percent less has to earn that back at the till.
The best argument that vegetables are not less nutritious
The strongest rebuttal comes from Robin Marles, writing in the Journal of Food Composition and Analysis in 2017. His review concluded that mineral composition is not meaningfully declining and that the soil-depletion explanation is unfounded.
His methodological objection is a good one, and anyone citing Davis honestly has to sit with it. When you compare food composition tables published fifty years apart, you are not running an experiment. You are comparing two snapshots that differ in laboratory technique, sample size, sampling protocol, geographic origin, ripeness at harvest, and statistical treatment. Any of those can move a number by more than the effect you are trying to detect. Davis said as much himself — he could not rule out that changes in analytical methods affected some of his results, which is why he argued the group average was more trustworthy than any single food.
Marles also checked something clever: archived soil samples from intensively farmed locations. Soil mineral content had not declined. That is a direct hit on the depletion narrative.
But notice what he conceded. When modern and older varieties are grown side by side under the same conditions — a real experiment, not a table comparison — the high-yield varieties do show lower mineral concentrations. Marles’s position is that the effect sits within natural variation and is not nutritionally significant. Davis’s position is that it is real and adds up. Both agree the mechanism is varietal.
The honest summary: the direction is probably real, the magnitude is genuinely disputed, and the popular explanation is the weakest part of the whole story.
Rising CO2 dilutes crops too
There is a third mechanism with much cleaner evidence behind it, because it comes from controlled field trials rather than archival comparison.
A 2014 study in Nature led by Samuel Myers grew crops under elevated atmospheric CO2 at open-air field sites. Wheat grown at the CO2 levels projected for mid-century showed zinc down about 9 percent, iron down about 5 percent, and protein down about 6 percent versus wheat grown at ambient CO2. Rice showed similar losses. Corn and sorghum, which use a different photosynthetic pathway, were largely unaffected.
Same underlying physics as the breeding story: more carbohydrate per plant, the same minerals, lower concentration. Dilution again, from a different direction.
The nutrient loss nobody talks about: the ten days after harvest
Here is what frustrates me about this entire debate. People argue about whether spinach lost 20 percent of its iron since 1950 while ignoring a much larger effect sitting in their own refrigerator.
Researchers at Penn State tracked commercially packaged fresh spinach in cold storage and found it retained only about 53 percent of its folate after eight days at 39°F — and that was the good condition. At 50°F the same loss took six days. At 68°F, four. The underlying study, by Srilatha Pandrangi and Luke LaBorde, tracked carotenoids and general quality alongside folate retention.
Nearly half the folate, gone in a week and a half, in a working refrigerator.
Now put that next to the supply chain most produce actually travels: picked underripe so it survives shipping, trucked across a continent, warehoused, displayed, then held in your kitchen for another four days. The nutrient loss between the field and your fork routinely dwarfs the nutrient difference between a 1950 variety and a 2026 one.
How to actually buy nutrient-dense produce
Buy from someone who picked it recently. That is the whole trick.
A grower selling at a Saturday farmers market harvested Thursday or Friday, and — just as importantly — chose that variety for how it tastes rather than for how it survives a thousand miles in a truck. Those are the same decision. Shipping durability and nutrient density are frequently in tension, and the producer standing behind the table is optimizing for the person in front of him.
Three practical rules follow from the research above:
- Shorten the clock, not the distance. Days since harvest matters more than miles travelled. Ask the grower which day it was cut.
- Buy in season. Out-of-season produce is out-of-season because it had to travel or sit in controlled storage. Both cost you nutrients.
- Ask what variety it is. A grower who can name the variety chose it. A supplier who cannot is selling whatever shipped best.
The same logic runs through animal products. A 2010 review in Nutrition Journal by Cynthia Daley and colleagues found grass-finished beef carried substantially higher omega-3 fatty acids and antioxidants including vitamin E than grain-finished, though the magnitude varies enormously with forage, finish, and season. Not a different animal. A different input — which is also the arithmetic behind what a quarter cow actually costs.
You can find both — growers and markets — in the directory. That is what it is for.
Why nutrient density is a money story
The reason varieties got bred for yield instead of density is not that anyone decided nutrition was unimportant. It is that yield is what the price signal rewarded, and the price signal is downstream of the money.
Commodity crops are priced by the bushel and the ton. Nobody at the elevator pays a premium for zinc concentration, because nobody measures it at the point of sale. Layer on decades of cheap credit pushing farms toward scale and capital intensity — the mechanism I walked through in How Money Broke Food — and you get an industry that got extraordinarily good at producing tonnage and roughly indifferent to what is in the tonnage. Weight is what gets paid for. Weight is what you get.
This is the same time-preference problem I keep circling in Time Preference and the Plate, and the same one that shows up in how people hold savings. When the unit of account degrades, everyone optimizes for the near-term measurable thing. I write about the monetary side of that at Modern Wealth Model; this site is where I work out the food side.
Frequently asked questions
Are vegetables less nutritious than they used to be?
By most published comparisons, yes — modestly. The largest US analysis found six of thirteen nutrients declined between 1950 and 1999, ranging from about 6 percent for protein to about 38 percent for riboflavin. The magnitude is disputed, and at least one major review argues the changes fall within natural variation.
Is soil depletion the reason vegetables have fewer nutrients?
Probably not. The researcher behind the most-cited study attributed the decline to crop varieties bred for yield, not to soil. A 2017 review that compared archived soil samples from intensively farmed land found no decline in soil mineral content.
What is the dilution effect?
When a crop is bred to grow larger and faster, it gains water and carbohydrate faster than it gains minerals. Nutrient concentration per hundred grams falls even though the plant is healthy. Rising atmospheric CO2 produces the same effect through a different route.
Does organic produce have more nutrients?
Organic certification governs inputs, not variety selection or time since harvest — the two factors the research points at hardest. A freshly picked conventional vegetable from a local grower can easily beat organic produce that spent ten days in transit.
Should I take a multivitamin because of nutrient decline?
That is a question for you and a clinician, not a blog. What the research supports is narrower and cheaper: shorten the time between harvest and your plate. This is not medical advice.
So — are vegetables less nutritious than they used to be?
Somewhat, and mostly because of what got planted rather than what happened to the dirt. The effect size is contested and I am not going to pretend otherwise. And it is probably smaller than what you lose to a ten-day supply chain.
That last part is the good news, because it is the part you can do something about this week. You cannot re-breed the commodity seed supply. You can buy from someone who picked it two days ago.
Everything my great-grandparents knew about food — the subject of an earlier piece here — was learned without a single nutrient assay. They just ate things that had not travelled far. That heuristic holds up better than most of the numbers.
Not medical advice. Nutrient figures above come from the peer-reviewed sources linked inline; where the literature disagrees, I have said so rather than picking the number that suits the argument.