The Economist Asia - February 10, 2018

72 Science and technology The EconomistFebruary 10th 2018

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ORNWALL, a rugged peninsula that

forms Britain’s south-western extrem-

ity, has a history of mining going back

thousands of years. Its landscape is dotted

with the ruins of long-closed tin and cop-

per mines, along with mountains of spoil

from the extraction of china clay (also

known as kaolin), a business that still

clings to life today. Now, though, prospec-

tors are back on the ground. Or, rather, they

aren’t. Instead, they are peering down

from space. And what they are searching

for is not tin, nor copper nor kaolin, but a

material that has come into demand only

recently: lithium.

The high-flying prospectors in question

are a group led by Cristian Rossi, an expert

on remote sensing, which has been organ-

ised under the auspices of the curiously

named Satellite Applications Catapult, an

innovation centre backed by the British

government. The plan isto use satellites al-

ready in orbit to detect and map geological

and botanical features that might betray

the presence of subterranean lithium.

Though satellite prospecting of this sort

has been employed before, to look for met-

als such as gold and copper, using it to

search for lithium is new.

Satellite prospecting

There’s lithium in

them hills

Searching from outerspace for minerals

on Earth

Remember the past. Look to the future

such a laser system can spot, track and aim

at its target, and how longthe beam must

play on the target in order to destroy it. The

whole process is likely to take several sec-

onds, and until it is complete, the laser can-

not move on to repeat the procedure on an-

other target. As with Phalanx, a simple

calculation suggests individual anti-drone

lasers would be able to deal with only a

small number of attackers. If even one

drone got through, the laser would proba-

bly be the priority target—for destroying it

would leave the way open for a subse-

quent, unchallenged attack.

An American army document from

2016 thus emphasises the importance of

stopping drones “left of launch”—that is,

before they can take off. ISdrone work-

shops and operators have been attacked to

stop the drone threat. The Russians say

they destroyed the unnamed group re-

sponsible for the massdrone attack in Jan-

uary, along with their drone-assembly and

storage facility in Idlib, using laser-guided

artillery. But when there are no runways or

hangars, and drones can be operated from

houses and garages, finding bases to attack

is far from easy. Until adequate defences

are in place, then, guerrilla drone swarms

will be a real danger. 7

F

RUCTOSE is the sweetest of the natural

sugars. As its name suggests, it is found

mainly in fruits. Its job seems to be to ap-

peal to the sweet tooths of the vertebrates

these fruit have evolved to be eaten by, the

better to scatter their seeds far and wide.

Fructose is also, however, often added by

manufacturers of food and drink, to sweet-

en their products and make them appeal to

one species of vertebrate in particular,

namelyHomo sapiens. And that may be a

problem, because too much fructose in the

diet seems to be associated with liver dis-

ease and type 2 diabetes.

The nature of this association has been

debated for years. Some argue that the ef-

fect is indirect. They suggest that, because

sweet tastes suppress the feeling of being

full (the reason why desserts, which come

at the end of a meal, are sweet), consuming

foods rich in fructose encourages over-

eating and the diseases consequent upon

that. Others think the effect is more direct.

They suspect that the cause is the way fruc-

tose is metabolised. Evidence clearly sup-

porting either hypothesis has, though,

been hard to come by.

This week, however, the metabolic hy-

pothesis has received a boost from a study

published in Cell Metabolismby Josh Ra-

binowitz of Princeton University and his

colleagues. Specifically, Dr Rabinowitz’s

work suggests that fructose, when con-

sumed in large enough quantities, over-

whelms the mechanism in the small intes-

tine that has evolved to handle it. This

enables it to get into the bloodstream along

with other digested molecules and travel

to the liver, where some of it is converted

into fat. And that is a process which has the

potential to cause long-term damage.

Dr Rabinowitz and his associates came

to this conclusion by tracking fructose, and

also glucose, the most common natural

sugar, through the bodies of mice. They did

this by making sugar molecules that in-

cluded a rare but non-radioactive isotope

of carbon,^13 C. Some animals were fed fruc-

tose doped with this isotope. Others were

fed glucose doped with it. By looking at

where the^13 C went in each case the re-

searchers could follow the fates of the two

sorts of sugar.

The liver is the prime metabolic pro-

cessing centre in the body, so they expected

to see fructose dealt with there. But the iso-

topes told a different story. When glucose

was the doped sugar molecule,^13 C was car-

ried rapidly to the liver from the small in-

testine through the hepatic portal vein.

This is a direct connection between the

two organs that exists to make such trans-

fers of digested food molecules. It was then

distributed to the rest of the body through

the general blood circulation. When fruc-

tose was doped, though, and administered

in small quantities, the isotope gathered in

the small intestine instead ofbeing tran-

sported to the liver. It seems that the intes-

tine itself has the job of dealing with fruc-

tose, thus making sure that this substance

never even reaches the liver.

Having established that the two sorts of

sugar are handled differently, Dr Rabino-

witz and his colleagues then upped the

doses. Their intention was to mimic in

their mice the proportionate amount of

each sugar that a human being would in-

gest when consuming a small fructose-

enhanced soft drink. As they expected, all

of the glucose in the dose was transported

efficiently to the liver, whence it was re-

leased into the wider bloodstream for use

in the rest of the body. Also as expected, the

fructose remained in the small intestine for

processing. But not forever. About 30% of it

escaped, and was carried unprocessed to

the liver. Here, a part of it was converted

into fat.

That is not a problem in the short term.

Livers can store a certain amount of fat

without fuss. And Dr Rabinowitz’s experi-

ments are only short-term trials. But in the

longer term chronic fat production in the

liver often leads to disease—and is some-

thing to be avoided, if possible. 7

Diet and health

Bitter fruits

How a sweetness enhancer may cause

liver damage