Is Soil Degradation Reducing the Nutrition of Fruits and Vegetables?

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Internet articles and the popular press frequently state that the mineral nutrient composition of crops has been declining over the past 50 years, with titles like “The great nutrient collapse,” blamed in part on the purported nutrient depletion of the soil. This narrative is touted by the leading dietary supplement trade association. But is it true?

This is probably the most cited study, comparing the nutrient content of US fruits and vegetables between 1950 and 1999, and about half, seven out of 13 nutrients tested, showed no significant decline, and the six that did only declined by about 15 percent, on average. A similar study in the UK looking at mineral content had similar findings with declines in about half. Of course, the drop in sodium doesn’t matter. We get too much as it is, and most people get more than enough copper. But the 10 percent drop in magnesium is significant. And though the drop in iron looks precipitous, the absolute drop is tiny, since fruits and veggies have so little to begin with.

Australian researchers had similar findings: a halving of iron in fruit over the last few decades. But the absolute drop is like 0.2 mg per serving, which is about 1/ 50th of the recommended daily allowance for most people. And the same with zinc. And there was actually an increase in grains. As you can see, there was just a few milligrams difference in calcium and magnesium, where the RDA is in the hundreds of milligrams. So, with such small absolute differences, any true decrease in mineral content is unlikely to have a large impact on nutritional intake.

And it’s not clear if these changes are even real. These comparisons of historical food composition tables are not a reliable way to determine changes in nutrient composition of foods over time, since they are just unmatched snapshots in time not meant to sync up. So, these may have been different varieties, or there may have been differences in ripeness, season, location. If you look at the levels of minerals in the soil itself, you don’t tend to see declining levels, and in some cases, we can actually see a significant rise in mineral levels nearly across the board over the last half century. So, where is this gloomy supplement industry propaganda coming from?

There’s been a concern that rising CO2 levels might reduce nutrients in crops, but the largest recorded change was a 59 percent increase in total antioxidant content, thanks to higher phytonutrient levels.

What about the concern that modern varieties grow so much larger and faster, potentially creating a trade-off between yield and nutrient concentration? One way to study this is to grow a whole bunch of different varieties released over the years under the same conditions, which is what these researchers did with broccoli. There were 14 cultivars released over 50 years, and they found there was no clear change over time in mineral content, though they did find that larger heads of broccoli did tend to have lower mineral content—something to keep in mind next time you shop.

As for the dietary supplement trade association’s claim that Americans don’t get the nutrients they need from foods? Well, for example, only half of Americans reach even 75 mg of vitamin C a day—less than the amount in a single orange. So, why aren’t Americans getting enough fruit and vegetable nutrients? Because they aren’t eating enough fruits and vegetables. They don’t need pills; they just need produce.

So even if there really is 15 percent less vitamin C in today’s broccoli, that just may mean you have to eat six florets of today’s broccoli instead of five florets from yesteryear.

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• Marles RJ. Mineral nutrient composition of vegetables, fruits and grains: The context of reports of apparent historical declines. J Food Compos Anal. 2017;56:93-103.
• Bottemiller Evich H. The great nutrient collapse. Politico. September 13, 2017.
• Rynfield R. Nutrient depletion of U.S. farmlands and soil: a critical review. JACN. 2022;1(1):19-20.
• Council for Responsible Nutrition. Americans do not get all the nutrients they need from food. CRNUSA.org.
• Davis DR, Epp MD, Riordan HD. Changes in USDA food composition data for 43 garden crops, 1950 to 1999. J Am Coll Nutr. 2004;23(6):669-682.
• Is the nutrient content of our food falling? Arbor Clin Nutr Updates. 2007;270:1-3.
• Mayer AMB, Trenchard L, Rayns F. Historical changes in the mineral content of fruit and vegetables in the UK from 1940 to 2019: a concern for human nutrition and agriculture. Int J Food Sci Nutr. 2022;73(3):315-326.
• Rangan A, Jenkins A, Murthy DA, Cunningham J. Temporal changes in mineral content of fruit, vegetables and grains in Australian food composition databases. Proc Nutr Soc. 2023;82(OCE2):E91.
• Soinne H, Kurkilahti M, Heikkinen J, et al. Decadal trends in soil and grain microelement concentrations indicate mainly favourable development in Finland. J Plant Nutr Soil Sci. 2022;185(5):578-588.
• Environmental and Energy Study Institute. Climate change will reduce nutrients in crops. EESI.org. August 31, 2018.
• Dong J, Gruda N, Lam SK, Li X, Duan Z. Effects of elevated CO2 on nutritional quality of vegetables: a review. Front Plant Sci. 2018;9:924.
• Davis DR. Trade-offs in agriculture and nutrition. IFT.org. March 1, 2005.
• Farnham MW, Keinath AP, Grusak MA. Mineral concentration of broccoli florets in relation to year of cultivar release. Crop Sci. 2011;51(6):2721-2727.
• Fulgoni VL, Keast DR, Bailey RL, Dwyer J. Foods, fortificants, and supplements: where do Americans get their nutrients? J Nutr. 2011;141(10):1847-1854.

Motion graphics by Avo Media

• antioxidants
• broccoli
• fruit
• grains
• iron
• magnesium
• oranges
• vegetables
• vitamin C