25 July 2020 | New Scientist | 31T
ODAY I searched my kitchen
cupboards for dark matter, and
found it in a packet of Korean instant
noodles. The food label ran to 38 ingredients,
many of them additives. But it also listed
some real foods, including soy, chilli,
sesame, shrimp, cabbage, seaweed,
mushroom, anchovy and cuttlefish.
And also the one I was looking for, garlic.
To be clear, I’m not suggesting that garlic
contains actual dark matter, the 85 per cent
or so of material in the universe that
physicists say is there but cannot observe
directly. But it does contain what has
been called “nutritional dark matter”:
the thousands and thousands of compounds
that are in food but which, until recently,
were totally unknown, and which may
be affecting our health. Given that eating
is one of the big human universals, that’s
a mind-boggling oversight.
“Our understanding of how diet affects
health is limited to 150 key nutritional
components,” says Albert-László Barabási
at Harvard Medical School, who coined
the term nutritional dark matter. “But
these represent only a small fraction of the
biochemicals present in our food.” It is time,
he says, for nutritionists to go dark-matter
hunting, to massively expand our knowledge
of what is on our plate and its impact on us.
The idea that food is a rich and complex
mix of biochemicals is hardly news. Even
the well-known macronutrients – proteins,
carbohydrates and fats – are hugely diverse.
There’s also a vast supporting cast ofmicronutrients: minerals, vitamins and
other biochemicals, many of which are only
present in minuscule quantities, but which
can still have profound health effects.
The official source of information on this
complex biochemical soup is the National
Nutrient Database for Standard Reference,
maintained by the US Department of
Agriculture (USDA). It contains information
on the composition of hundreds of
thousands of foods, broken down into
188 different nutritional components.A lot to digest
Search for “garlic”, for example, and the
database serves up 58,055 foodstuffs
that contain it, ranging from whole, raw
garlic to processed foods such as instant
noodle soup. The entry for raw garlic lists
67 macro- and micronutrients, some
quantified down to micrograms per
100 grams, or concentrations of less than
0.00001 per cent. That may seem detailed,
but is far from comprehensive. For example,
it omits some of the quintessential flavour
compounds in garlic, such as alliin.
This is a general problem across the
USDA database, says Barabási. It tracks
only common nutritional components
in many foods, and so omits many rarer
ones. The USDA began to fill this gap
in 2003 by adding 38 flavonoids – plant
compounds associated with a lower risk of
cardiovascular disease – to its existing panel
LE of 150 components. But that is as far as it went. >
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The dark matter
in your diet
There’s a giant hole in our knowledge of what we
are eating. It’s time to hunt for some answers,
finds Graham Lawton
Around 10 years ago, an international
team of researchers decided to compile a
more comprehensive database after trying
and failing to get detailed information
on the composition of various foods. “We
could only track down lists of a few dozen
compounds, not the hundreds or thousands
we expected,” says David Wishart at the
University of Alberta, Canada, one of the
project’s founders. “The fact that there was
so little known about the micronutrients in
commonly consumed foods really bothered
us.” So they trawled the literature and filled
in other blanks through their own chemical
analyses in the lab.
The result is a massive database called
FooDB, which Wishart says now holds
information on about 70,000 nutritional
compounds – nearly 400 times more
than the USDA database. For example,
the USDA lists 67 compounds in raw garlic,
but FooDB has 2306.
By that reckoning, with the USDA as your
guide, 99.5 per cent of the components in
food are a mystery. Even FooDB is incomplete.
Of the 2306 compounds in garlic it lists, for
example, only 146 have been quantified,
meaning that more than 2000 others
are known to be present but at unknown
concentrations. This problem is writ large
across the whole of FooDB, with a total of
about 85 per cent of nutritional components
as-yet unquantified.
In other words, when it comes to the
make-up of the food we eat, we have only
assessed the tip of the iceberg lettuce