New Scientist - USA (2021-07-17)

24 | New Scientist | 17 July 2021

I

LOVE playing detective.

So when I found myself on

a train scrolling through

hundreds of shocked responses

to yet another viral tweet claiming

that the proportion of nutrients

in our fruit and veg has collapsed

over recent decades, I thought

I better do some digging.

This ubiquitous, yet generally

poorly evidenced, claim is one

that I have explored in a previous

column. However, as the new

tweet cited a 2018 study that is

more recent than many I have

looked into before, it seems

important to return to the issue,

particularly given its new-found

influence on social media.

After all, one of the hallmarks

of good science is the flexibility

to change your stance as new

evidence surfaces. So, with a

4-hour journey ahead of me,

I started delving into the stats

used to underpin this claim.

Centred on a steep line graph

extracted from a paper (doi.org/

gf75hz) published in the journal

Nutrients, this tweet suggested

there has been a catastrophic

collapse in the average levels

of calcium, magnesium and

iron in cabbage, lettuce, tomatoes

and spinach of up to 90 per cent

in the past hundred years.

With a link to the paper in

an academic journal, it outwardly

seemed very convincing. So

why did it pique my interest?

Well, as a botanist fascinated

by food crops and how they

have shaped human history,

understanding how the handful

of plants on which civilisations

are built have changed over

the centuries is one of my key

research areas. The only problem

is that it is very hard to study.

One of the biggest problems

we have when it comes to

answering what can seem

like simple questions about

things like nutrient density

in crops is finding like-for-like

comparisons to establish how

these change over time.

There are so many factors that

have a measurable impact on

crop chemistry, including weather,

soil make-up, harvest stage and

the unique genetics of a crop,

that agreeing on a universal value

for a “typical” tomato today is

a challenge, let alone doing the

same for one more than a

century ago. It is rather like

picking a random New Yorker

and expecting them to be

representative of not just every

other inhabitant of the city,

regardless of race, gender,

age, class, education or income,

but all of humanity.

When you start to compare

these randomly selected single

values over time, created

by an enormous range of

environmental variables, things

get even more complicated.

But let us just imagine the world

isn’t as complex as we know it is,

and think of this methodology

as a legitimate one. In any case,

science inevitably relies on a

certain amount of generalisation.

Taking a closer look at the

individual data points on the

graph revealed that three out of

seven were marked with asterisks

(1914, 1941 and 1992), which

according to the paper indicated

that these stats couldn’t be

independently verified.

Now, if it were the case that

these asterisked stats were in

some way unreliable and should

be removed, the graph would

actually show a stable level from

2000 to 2018, with just a single

outlying data point, showing

an atypically high level for 1948,

with no consistent trend for a

decline. How curious.

So, do these asterisked data

points stand up to scrutiny?

Well, the extremely high levels

of minerals seen in the 1914 stat,

which is essential to the “90 per

cent decline” claim, doesn’t

appear to be from a peer-reviewed

paper. In fact, it seems to come

from a book entitled Nature

Cure by Henry Lindlahr, which

made for an eye-opening read

when I eventually tracked down

a dusty copy.

An early 20th-century

physician, Lindlahr believed that

sunbathing could cure cancer,

vaccines caused smallpox and

only “civilised races” could

succumb to ill health. Even at

the time, he was widely criticised

as a quack for his outlandish

views, so his book may hardly

be a good source for a scientific

paper more than a century later.

I also found the affiliations

of the three authors of the paper

interesting. Two of them were

listed as working for a corporation

that sells nutritional supplements,

and under the conflicts of interests

section in the paper, the third

author was described as being

a paid consultant for the same

company and sitting on its

scientific advisory board.

I suppose the moral of the story

is that even graphs from published

journals may not tell the full story

of the facts or any possible vested

interests until you start digging.

And sometimes the data behind

the claim doesn’t come from

scientific research at all. But

who has 4-hour train journeys

to do the detective work to check

out each viral “science” tweet? ❚

This column appears

monthly. Up next week:

Chanda Prescod-Weinstein

“ Even graphs from

journals may not

tell the full story.

The data may not

come from scientific

research at all”

The mysterious case of declining nutrition I’ve debunked the

claim that food is getting less nutritious before, but when a new

study turned up, I had to investigate further, writes James Wong

#FactsMatter

What I’m reading

The fascinating 1914 book

Nature Cure by Henry

Lindlahr (see main story).

What I’m watching

The final season of a

sitcom called Superstore,

which has to be the most

wholesome, uplifting

comedy antidote to

increasingly uncertain

times.

What I’m working on

I am filming a new season

of the BBC documentary

Follow the Food.

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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