New Scientist - USA (2020-01-25)

24 | New Scientist | 25 January 2020

Y

OU could be forgiven for

thinking we are living in

the midst of a nutritional

apocalypse. “You’d have to eat 10

tomatoes today to get the same

level of nutrients as one in the

1950s,” declared an activist on

the radio recently.

On Twitter, there was more

of the same: “One would have to

eat eight oranges today to derive

the same amount of vitamin A

our grandparents would have

gotten from one.” And at a farming

conference, a speaker proclaimed

that modern farming means that

fruit and vegetables have been

“drained of their nutrients”,

showing falls of “up to 50 per

cent over 50 years”. But what

evidence are these claims based

on? I thought I’d better take a

closer look.

Perhaps the most commonly

cited study used to support this

narrative is a 2004 paper in the

Journal of the American College

of Nutrition. It analyses nutritional

data for 43 garden crops in the US

from 1950 and 1999. But scan the

results and a rather different

picture emerges to the popular

idea that modern food is lacking.

Instead of showing a nutritional

collapse across the board, the

research found only about half of

the 13 nutrients checked showed a

statistically reliable decline, while

others remained unchanged. For

those nutrients that were found

to have declined, the falls reported

across all 43 crops ranged from a

modest 6 per cent for protein to

a 38 per cent drop for riboflavin,

which is a B vitamin.

What about the 90 per cent

reduction in the overall nutrient

levels in tomatoes I had heard?

Well, no such figure appears to

exist in this study. The single

largest fall in the study, which was

in an individual tomato crop,

appears to be a 54 per cent drop

in calcium, however most other

vitamins and minerals stayed

pretty stable. What about the

“eight oranges” claim for vitamin

A? Oranges weren’t even part of

the study, so it is unclear exactly

where that statistic originated.

And the 2004 study is only so

reliable. In the decades between

the 1950 and 1999 data sets it used,

everything from crop varieties and

testing techniques have changed

significantly. So this type of study

is unlikely to be a like-for-like

comparison. This was something

the authors were careful to point

out: “There is no way that you can

reliably measure the decline for

single foods.” This is the opposite

of what I keep hearing.

Is there any other evidence on

nutrient changes? The Broadbalk

Wheat Experiment is a pioneering

study that has been gathering

samples of wheat grown in the

same field in England for 175 years,

making it the world’s longest

running agricultural trial. Between

the 1800s and the late 1960s, the

nutrient levels in the grain grown

there stayed relatively stable.

However, from then onwards

there have been significant falls,

especially for minerals like zinc

and iron, which neatly coincided

with the introduction of a modern

variety of wheat. These findings

are potentially concerning.

But while it was an excellent

review of the nutrient content for

a single crop in a single field in one

place, extrapolating its results as

representative of all crops across

the whole world, or frankly even

the same wheat variety in the

next county, are problematic.

Trials have shown, for example,

that identical types of wheat

grown in two different fields in the

same US state can show an eight-

fold difference in key minerals like

selenium. Such a difference far

outweighs the declines observed

in the English single-field study.

Arguably the best evidence

comes from studies that grow

historical and modern varieties

side-by-side in the same fields,

replicating the exercise at various

locations. Results have been

mixed. In one study by the US

Department for Agriculture,

broccoli didn’t show a clear trend

nutritionally speaking either way

in terms of differences between

old and new varieties. While

nutritional differences were

recorded in terms of the size of

the broccoli head, factors such

as weather showed an effect on

nutritional content up to 10 times

greater than crop size. For wheat,

while some nutrients did decline

in newer varieties, many were

stable. This suggests a far more

complex picture than many

have claimed.

Most pertinently of all, if the

nutrient content of crops had

indeed collapsed to the degree so

frequently claimed, this would

be clear in terms of human health.

Yet nutrient deficiencies have

actually declined worldwide by

roughly 40 per cent since 1960,

according to a University of

California study, and by as much

as 80 per cent in regions like east

Asia. This was partially due to

fortification of foods, but mainly

attributed to modern agriculture

resulting in a more diverse diet. It

seems modern farming isn’t quite

the dietary demon some say it is.

I for one can’t wait to see what

further research uncovers, but

there is no need to panic just yet. ❚

This column will appear

monthly. Up next week:

Chanda Prescod-Weinstein

“ If the nutrient levels

in modern crops

had collapsed to the

degree claimed, it

would be clear in the

human population”

The great nutritional collapse Claims that our food is becoming

less nutritious are often bandied about, but the truth is far more

complicated, writes James Wong

#FactsMatter

What I’m reading

As usual, an awful lot

of very dry academic

journals. The data

tables are the best bit.

What I’m watching

Mindhunter on Netflix.

Often with my hands

over my eyes.

What I’m working on

Filming a new

documentary series

for the BBC.

James’s week

James Wong is a botanist and
science writer, with a particular
interest in food crops,
conservation and the
environment. Trained at the
Royal Botanic Gardens, Kew, he
shares his tiny London flat with
more than 500 houseplants.
You can follow him on Twitter
and Instagram @botanygeek

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