Agricultural Biodiversity Weblog

Fruit and vegetables sold in the UK are ‘half as nutritious’ as 80 years ago due to depleted levels of iron, magnesium, sodium and copper, study shows

That’s the headline in the Daily Mail. But is it true?

Well, the study in question didn’t actually measure anything. It looked at the UK’s Composition of Foods Tables1 for 1940, 1991 and 2019, and compared the levels of 7 nutrients in 29 fruits and vegetables2 sold (but not necessarily grown) in the UK for which the data were roughly comparable. That is, for which results were presented in the tables for raw samples of the same part of the same sort of plant prepared in the same way: unpeeled eating apples, say.

To be clear, this analysis can say nothing about whether modern vegetable or fruit varieties are on average more or less nutritious than older ones. In the jargon, any differences between old and new varieties are confounded in this dataset with differences in growing conditions and agronomic practices, for example, and more besides. There’s no way to disentangle one from the other, and the authors of the paper make this clear.

So what can the study say? Is the “half as nutritious” thing justified? Predictably, it’s more complicated than that. I’ll reproduce the key findings verbatim (though ever so slightly edited) to preserve the nuance:

1. In the first period, from 1940 to 1991, there were significant reductions (p < 0.05) in Na, Ca, Mg and Cu. The greatest reductions were Cu (60%) and Na (32%). There were also increases in water content. This is of interest because it shows that by 1991 the fruits and vegetables contained more water, and nutrient density (on a fresh weight basis) has consequently decreased...
2. In the second period, from 1991 to 2019, there was a significant reduction in Fe (36%) and a significant increase in Mg (18%). There was also a further reduction in Na and increase in water that was not statistically significant (p < 0.05).
3. The overall longer-term comparison of data from 1940 to 2019 shows that the mineral contents of fruits and vegetables remain lower than in 1940. The greatest overall reductions during this 80-year period were Na (52%), Fe (50%) Cu (49%) and Mg (10%). There was a 12% decrease in dry matter content that was not statistically significant.

Some notable reductions, then, but hard to say that fruits and vegetables are “half as nutritious” now compared to 80 years ago. Not for the first time, the Daily Mail somewhat overcooks the vegetables, as it were.

Do the reductions matter? That would, of course, depend on a bunch of other things, including whether people eat more or less of these (and other) fruits and vegetables, and whether any losses in nutrient supply from fruits and vegetables are made up from other sources. As the authors say: “For some vulnerable groups, and those with poor diets, these reductions are important because they make a bad situation worse – teenagers are at particular risk of inadequate diets.” But that assumes that teenagers are scoffing down the same amount or less of old carrots and unpeeled eating apples than formerly, which may in fact be likely but needs proof.

Anyway, there are some useful recommendations at the end of the paper, both for the UK and globally. I’ll just highlight a couple here:

• With the seemingly systematic reductions, it is necessary to have a holistic approach rather than an approach that takes each nutrient one at a time. It is important that all foods are grown and processed in a way that optimises their nutrient content from production through to consumption.
• Plant breeding should aim to improve a whole basket of mineral nutrients, not just targeted to one nutrient at a time, as is the current approach of biofortification programmes.

Perhaps it was too much to hope the Daily Mail would have gone for that in their headline.

1. Otherwise known as “McCance and Widdowson’s ‘composition of foods integrated dataset’ on the nutrient content of the UK food supply.” [↩]
2. Cabbage – winter, carrots – old, cauliflower, celery, cucumber, leeks, lettuce, mushrooms, onions, peas, potatoes – old, radishes, runner beans, tomatoes, watercress, avocado, bananas, blackberries, cherries, eating apples, grapefruit, grapes, nectarines, oranges, pears, pineapple, plums, raspberries, strawberries. [↩]