Are Vegetables Really Half as Nutritious as They Were in the 1960s?

Last week a headline went around the world saying fruit and vegetables are half as nutritious as they were in the 1960s. The version that reached the New York Post said it was about American produce. It isn't. The report is British, and its modelling is about the UK.

It's called Hollow Harvests, and it was produced by Deep Science Ventures, a venture firm, with The Mark Leonard Trust. Its executive summary says many crops bred and managed for yield since the 1960s have lost roughly 20 to 50 percent of several nutrients, in cereals and in vegetables. It also says cereal yields per hectare have risen 215 percent over the same period.

So I went back to the studies underneath it. Some of the decline is real. The cause most people reach for first is not the main one.

What actually fell

The UK figures come from one place: the government's food composition tables, which have measured the same fruit and vegetables in different decades.

In 2021, researchers at Coventry University compared three editions of those tables, from 1940, 1991 and 2019. They could match 29 fruit and vegetables across all three. Every mineral they tracked fell except phosphorus.

The biggest drops were sodium at 52 percent, iron at 50 percent and copper at 49 percent. Magnesium fell 10 percent. Sodium leads that list, and it's the one mineral most of us are trying to eat less of.

Potassium fell by 4.7 percent, and the change wasn't statistically significant.

That matters, because the line that travelled furthest was that you'd need to eat twice as many carrots to get the same potassium. The report's own wording is conditional: if a carrot had 50 percent less potassium, you would need to eat twice as many. It's an illustration. The UK tables don't show it happening. I'm not about to eat twice as many carrots on the strength of a hypothetical.

The Coventry authors are frank about the iron and copper. They suggest the later iron figures could be lower partly because vegetables are washed more thoroughly now, taking soil particles with them. They suggest the earlier copper figures may have been inflated by copper-based fungicides, which newer chemicals largely replaced after the Second World War. The dates are publication dates, not testing dates. The 1940 figures come from analyses done between 1925 and 1939, the 1991 figures from 1982 to 1990, and the 2019 figures from 2011 to 2015. The paper also notes the produce sampled in each edition could have been grown in the UK or imported.

The American data tells a smaller story. A 2004 study of USDA tables compared 43 garden crops measured in 1950 and 1999. It found reliable declines in six of 13 nutrients, with median drops ranging from 6 percent for protein to 38 percent for riboflavin. About 28 percent of the individual crop comparisons went up, not down.

Australia ran the check more recently. A 2023 analysis of Australian food composition databases compared 53 foods re-tested between 1991 and 2022. Iron in fruit fell 55 percent, but that was a fall of about 0.2 milligrams per 100 grams. Magnesium in fruit rose 27 percent. The authors warned that sampling, varieties and lab methods had all changed between the two dates, and concluded any real drop was unlikely to make much difference to what people take in.

I couldn't find anyone who has run the same comparison on New Zealand's own food tables. The tables exist. The New Zealand Food Composition Database is jointly owned by the Bioeconomy Science Institute, formerly Plant & Food Research, and the Ministry of Health. Its about page says nothing about tracking nutrient levels over time.

Why it fell

The clearest evidence comes from a field in Hertfordshire.

Rothamsted's Broadbalk experiment has grown wheat since 1843, and it keeps the grain. A 2008 study tested those archived samples. Zinc, iron, copper and magnesium in the grain held steady from 1845 until the mid-1960s. Then they fell, at the same time semi-dwarf, high-yielding wheat varieties arrived.

The minerals in Broadbalk's soil didn't fall. They held steady or rose.

And the grain declined the same way on every plot: the ones given no fertiliser, the ones given synthetic fertiliser, and the ones given farmyard manure. The researchers found the drop was explained by rising yield and by harvest index, the share of the plant that ends up as grain.

That's the dilution effect. The Coventry paper describes it simply: as yield rises, the plant makes more dry matter, mostly carbohydrate, and the minerals don't keep pace. The 2004 American study reached the same view, saying any real declines were most easily explained by changes in the varieties grown.

The Hollow Harvests report names three causes: breeding for yield, fertiliser regimes that build bulk faster than mineral uptake, and soil degradation. For wheat, the evidence above points squarely at the first. For fruit and vegetables it points the same way, less firmly.

There's a fourth, still arriving. In a 2014 Nature study, wheat grown in open fields at the carbon dioxide levels expected mid-century had 9.3 percent less zinc, 5.1 percent less iron and 6.3 percent less protein than wheat grown at today's levels. Rice lost 7.8 percent of its protein. Maize and sorghum were much less affected. Hollow Harvests projects bigger losses than that by 2050, up to 12.7 percent of wheat protein and 36.5 percent of zinc.

So is organic better for you?

This is the question the headline was really asking, and the report's own author gave his answer.

Will Summers of Deep Science Ventures told AgFunderNews that organic and regenerative need to be separated. He pointed to a review showing organic production doesn't correlate with nutritional quality. He said the evidence for regenerative practices appears stronger, but that "the key thing is soil health, regardless of what practices best deliver it."

The review he pointed to is a 2009 systematic review funded by the UK Food Standards Agency. Of 162 studies, it rated 55 as satisfactory quality. Across those, it found no difference in eight of 11 crop nutrient categories, including vitamin C, magnesium, potassium, calcium, zinc and copper. Organic crops had more phosphorus. Conventional crops had more nitrogen. The review didn't look at pesticide residues at all.

The Coventry team behind the UK figures doesn't accept that verdict. They argue the review threw out so many studies it lost the power to find a difference. They point to a later review that put organic crops about 6 percent ahead on micronutrients. And they suggest modern organic produce is the nearest thing we have to food grown before farming industrialised.

The Broadbalk manure plot complicates it from the other side. Feeding the soil with manure didn't stop the decline. The varieties changed, and the minerals fell however the soil was fed.

But there is a mechanism that favours the organic side, and it's underground. Many crops work in partnership with soil fungi called mycorrhizae, which reach into far more soil than the roots can and bring minerals back to the plant. The Coventry paper notes that heavy doses of nitrogen and phosphorus fertiliser inhibit iron, manganese and zinc uptake in plants that rely on that partnership. It also notes that organically farmed soils have been found to hold more of the fungi's spores. Avoiding synthetic fertiliser and fungicides, and tilling less, all tend to encourage them.

The Coventry authors think the loss of that partnership could at least partly explain the historical decline. The trial evidence is patchy. Leeks and tomatoes inoculated with the fungi came out higher in several minerals. Wheat and field peas mostly didn't, apart from zinc. It's a real mechanism, and nobody has yet measured how much it adds up to on the plate.

Minerals aren't the only thing in a vegetable, though. A 2014 meta-analysis of 343 studies, which I went through in September, found organic crops had higher levels of several antioxidant compounds. The estimates ran from 19 percent more phenolic acids to 69 percent more flavanones. It also found less cadmium in organic crops, and pesticide residues four times as often in conventional ones: 46 percent of conventional samples against 11 percent of organic.

On minerals, even that paper mostly came up empty. It found no significant difference for most of them, and only small gaps for zinc and magnesium. Organic crops also had about 15 percent less protein. The paper carries caveats of its own, including likely publication bias on about half of what it measured, and they're in that post.

So if you're weighing what an organic carrot buys you over a conventional one, minerals are the thinnest part of the case. Antioxidants are a stronger part. The strongest is what isn't there: pesticide levels fall in people who switch.

And regenerative?

The paired-farm study Summers cited is a 2022 paper in PeerJ led by David Montgomery at the University of Washington. It compared farms that had used no-till, cover crops and diverse rotations for five to 10 years with nearby conventional farms that were synthetically fertilised and sprayed with herbicide. The regenerative farms had more soil organic matter, and their crops had more of certain vitamins, minerals and phytochemicals.

According to Baking Business's report on the paper, the regenerative crops averaged 34 percent more vitamin K, 27 percent more copper and 11 percent more calcium. The same report says two of the authors run a ranch that was one of the farms sampled.

The paper calls itself preliminary and says its samples were small. Its regenerative farms aren't described as organic, and its own conclusion talks about improving conventionally grown food. We've been here before with regenerative beef: the word describes practices, not a standard anyone checks.

Hollow Harvests links to one more study for its claim that rebuilding soil improves nutrient density. It's a University of Lincoln proof-of-concept carried out with Little Origins, a family food start-up, and funded by Innovate UK. It compared crops from what it calls regenerative organic farms, four to seven per crop, against two conventional samples bought from supermarkets. Carrots, kale and dried peas came out ahead. Broccoli was mixed. Oats showed no significant difference. The university's own foreword says it was an exploratory step, not designed to settle the question statistically.

One detail in it stood out. The team found the official UK reference values were often higher than the conventional supermarket samples they actually tested. If that holds, the tables may be flattering the food on the shelf.

Where that leaves it

Hollow Harvests wants nutrient density measured and paid for. It says the UK's tables for fruit and vegetables were last comprehensively updated in 1991. It also says Deep Science Ventures and the Mark Leonard Trust see helping farmers through the slow early years of rebuilding soil as a venture-creation opportunity, which is worth knowing when you read its recommendations.

What the studies underneath it actually show is narrower than the headline, and more useful. Some minerals have fallen. Higher-yielding varieties are the best-supported cause, firmest for wheat. Healthier soil life may claw some back. Washing and where the produce came from both muddy the numbers.

A certified organic label tells you how a crop was grown and what wasn't sprayed on it. It doesn't tell you which variety went in the ground, and variety is the part almost nobody gets to choose. In Riverton, two people have kept 400 apple varieties going. The supermarket sells about six.

The test I'd want to see here is easy to describe. Take one variety of carrot. Grow it on certified organic, regenerative and conventional farms on similar soil. Harvest at the same ripeness, store it the same way, and send it all to the same lab. It might put the organic carrots ahead. It might show nothing. Either answer would tell New Zealanders more than another headline from overseas.

The minerals in Broadbalk's soil held steady or rose for 160 years. The wheat's fell anyway.

Before you go

If this was useful, you can sign up for free to get new posts by email, or leave a one-off tip to help keep the research going.