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New Scientist January 30,
2014
Read the whole story
here:
http://www.newscientist.com/article/mg22129540.500-sugar-on-trial-what-you-really-need-to-know.html
Sugar on trial: What you
really need to know
It has been called toxic,
addictive and deadly, the driving
force behind obesity, heart
disease and diabetes. Is sugar
really so bad?
By Tiffany O'Callaghan
IMAGINE you are sitting at a
table with a bag of sugar, a
teaspoon and a glass of water.
You open the bag and add a
spoonful of sugar to the water.
Then another, and another, and
another, until you have added 20
teaspoons. Would you drink the
water?
Even the most sweet-toothed
kid would find it unpalatably
sickly. And yet that is the
amount of sugar you are likely to
eat today, and every day –
usually without realising it.
Sugar was once a luxury
ingredient reserved for special
occasions. But in recent years it
has become a large and growing
part of our diets. If you eat
processed food of any kind, it
probably contains added sugar.
Three-quarters of the packaged
food sold in US supermarkets has
had sugar added to it during
manufacturing. You can find it in
sliced bread, breakfast cereals,
salad dressings, soups, cooking
sauces and many other staples.
Low-fat products often contain a
lot of added sugar.
It's hardly controversial to
say that all this sugar is
probably doing us no good. Now,
though, sugar is being touted as
public health enemy number one:
as bad if not worse than fat, and
the major driving force behind
obesity, heart disease and type
II diabetes. Some researchers
even contend that sugar is toxic
or addictive.
As a result, health bodies are
gearing up for a "war on sugar".
The World Health Organization
wants us to cut consumption
radically. In the US, doctors and
scientists are pressing food
companies to reduce sugar and be
more open about how much they
add; in the UK a group called
Action on Sugar has just launched
a campaign to ratchet down sugar.
Politicians are mulling taxes on
sugary drinks. But is sugar
really that bad? Or is it all a
storm in a teacup – with two
sugars please?
When nutrition scientists talk
about sugar they are not fretting
about sugars found naturally in
food such as fruit and
vegetables, or the lactose in
milk. Instead they are worried
about added sugar, usually in the
form of sucrose (table sugar) or
high-fructose corn syrup (see
"Sugar basics").
Our early ancestors would have
been totally unfamiliar with
these refined forms of sugar, and
until relatively recently sugar
was a rare and precious
commodity. Only in the 1700s,
after Europeans had introduced
sugar cane to the New World and
shackled its cultivation to
slavery, did it become a regular
feature of the Western diet. In
1700, the average English
household consumed less than 2
kilograms of table sugar a year.
By the end of the century that
amount had quadrupled (see
diagram).
The upward trend has continued
largely unbroken ever since.
Between the early 1970s and the
early 2000s, adults in the US
increased their average daily
calorie intake by 13 per cent,
largely by eating more
carbohydrates, including sugar.
In 1996, the average US adult
swallowed 83 more calories per
day from added sugar than in
1977. Today, yearly sugar
consumption in the US is close to
40 kilograms per person –
more than 20 teaspoons a day.
The sugar rush has many
causes, but one of the most
important was the invention of
high-fructose corn syrup in 1957.
HFCS is a gloopy solution of
glucose and fructose that is as
sweet as table sugar but has
typically been about 30 per cent
cheaper.
Once this source of sweetness
was available, food manufacturers
added it liberally to their
products (see charts). "Because
hunger is no longer an important
factor in most developed
countries, what can make people
eat more?" asks Serge Ahmed, a
neuroscientist at the University
of Bordeaux, France. "Food
pleasure. And what creates food
pleasure? Sugar."
Unfortunately, it is a guilty
pleasure. Not all scientists see
eye to eye on the health effects
of sugar but there is one point
on which most agree: we don't
actually need it. Luc Tappy, a
physiologist at the University of
Lausanne in Switzerland, sums it
up: "You cannot live without
essential fats. You cannot live
without protein. It's going to be
difficult to have enough energy
if you don't have some
carbohydrate. But without sugar,
there is no problem. It's an
entirely dispensable food."
All that unnecessary sugar
adds calories to our diet, so it
is no surprise that the rise in
consumption coincided with the
rise of obesity and related
problems such as type II
diabetes. In 1960, around 1 in 8
US adults was obese; today more
than a third are. Since 1980,
obesity levels have quadrupled in
the developing world to nearly 1
billion people. One recent study
found that for every additional
150 calories' worth of sugar
available per day in a country
there is an associated 1.1 per
cent rise in diabetes.
So far so simple. But some
researchers see something more
sinister going on. To them, sugar
isn't just a source of excess
calories: it is a poison.
The most outspoken is Robert
Lustig, an endocrinologist at the
University of California, San
Francisco. Described by some of
his peers as an anti-sugar
evangelist, Lustig's main beef is
with fructose, a simple sugar
found naturally in fruit but
which is also a component of
sucrose and HFCS.
The case against fructose is
built on the fact that, unlike
glucose, it doesn't play an
essential role in human
metabolism (That is not to say we
need to eat glucose; complex
forms of carbohydrate such as
starch supply all the glucose our
metabolisms need). Our ancestors
would have encountered fructose
in fruit but in nothing like the
quantities we eat today, so part
of the argument is that our
bodies are simply not adapted to
deal with it.
To begin with, fructose is
almost exclusively metabolised by
the liver. When we eat a lot of
it, Lustig and others say, much
of it is converted into fat. Fat
build-up in the liver can lead to
inflammation and scarring and
progress to cirrhosis. Fatty
liver has also been linked to
insulin resistance, a precursor
to diabetes.
Toxic attack
Fructose is converted into
energy, but Lustig claims that,
unlike glucose breakdown, this
produces lots of oxygen radicals,
dangerously reactive chemicals
that attack our bodies and cause
ageing. To mop these up requires
antioxidants, but how many you
get often depends on the quality
of your diet. "People who can't
afford better food don't get the
antioxidants. That's one of the
reasons why people in the lower
socio-economic strata get sicker
on the same dose of sugar,"
Lustig says.
What's more, unlike glucose,
fructose isn't regulated by
insulin. This hormone keeps blood
glucose levels stable and spurs
the production of leptin, the
hormone that lets you know when
you are full. Fructose doesn't
affect leptin production; one
small study even suggests it ups
the level of its counterpart,
ghrelin, the hormone that makes
you feel hungry. In other words,
fructose encourages
overeating.
Finally, eating lots of
fructose has been shown in both
animal and human studies to boost
levels of triglycerides in the
blood, which increase the risk of
hardened arteries and heart
disease.
It's a compelling argument
that has captured imaginations: a
lecture Lustig gave in 2009 has
been viewed more than 4 million
times on YouTube. Still, many
nutrition scientists remain
unconvinced. A number of studies
have failed to find evidence that
fructose is uniquely harmful
– though these have been
criticised because their authors
received funding from food and
beverage companies.
More credibly, in 2012 Tappy
reviewed the case against
fructose for the journalBMC
Biology. He concluded that while
there is cause for concern in
people who already have a
metabolic disease or are at risk
of developing one, there is no
evidence that fructose is the
sole, or even the main, cause of
these diseases. But the case
remains open. "There are many
unanswered questions," he
says.
Another sinister claim against
sugar is that it warps eating
habits by altering brain
chemistry to make us want more.
For several years neuroscientists
have found it useful to compare
energy-dense foods to addictive
substances such as cocaine –
at least in a metaphorical sense
– because it equips them
with the language to discuss
their habit-forming properties.
But is this anything more than a
metaphor?
Several studies in rats have
shown that a burst of sweetness
affects the reward system in the
brain in a similar way to
cocaine. One study even gave
cocaine-addicted rats the option
between cocaine and sugar water.
"Most turned away from the drug
for the sweet reward," says
Ahmed, who ran the study.
That sounds damning, but is it
also true in humans? Foods high
in fat and sugar – called
"hyperpalatable" foods – are
known to trigger our reward
systems by boosting dopamine
levels much as addictive drugs
do. And there is research
suggesting that most people with
conditions such as binge-eating
disorder display similar
psychological characteristics to
people with substance abuse
problems. But is that enough to
condemn sugar as addictive? And
how can you distinguish the
allure of sugar from that of fat
and salt in these foods?
Although some doctors find the
evidence compelling enough that
they treat obesity using
techniques for treating
addiction, the scientific case
for food addiction is far from
iron clad. Last year, for
example, NeuroFAST, an
independent, European
Union-funded collaboration
between 13 universities that
produces "consensus statements"
on controversial issues in
nutrition science, reviewed all
the relevant evidence from human
studies. Its conclusion: there is
"no evidence" that food can be
addictive.
Unsurprisingly, the sugar
lobby agrees. "There is little
evidence available from human
studies, performed in a way that
is representative of how food is
consumed as part of everyday
life," says Glenys Jones from
Sugar Nutrition UK, which is
mainly funded by UK sugar
manufacturers.
So if we can't conclude that
fructose is the culprit or that
sugar is addictive, where does
that leave us? Is it simply that
too much sugar equals too many
calories? Or has the entire case
against sugar been
overstated?
This question is now in the
hands of the World Health
Organization. Alarmed by reports
of sugar's dangers, its Nutrition
Guidance Expert Advisory Group
has been carrying out a review of
the evidence with a view to
making some recommendations.
As part of that process, last
year Lisa Te Morenga, a
researcher in human nutrition at
the University of Otago in New
Zealand, reviewed the research on
the relationship between sugar
and body weight. She concluded
that it wasn't necessarily eating
too much sugar that was making us
fat, but eating too much of
everything. "There was no
difference between higher and
lower sugars when the energy
people were consuming was exactly
the same," says Te Morenga. In
other words, if total calorie
count was controlled for, people
didn't get any fatter when more
of those calories came from
sugar. These findings, too, were
welcomed by the sugar
industry.
So is the white stuff off the
hook? Not so fast. When Te
Morenga looked at studies that
more closely replicate food
choices in real life – that
is, when participants weren't
held to precise calorie counts
– those who ate a lot of
sugar tended to consume more
calories overall and gained more
weight. And the most important
source of sugar was one that has
been high on the list of obesity
campaigners' concerns for years:
sugary drinks. This was yet more
evidence that sweetened drinks
really do cause weight gain
– which is the strongest
reason to point the finger at
sugar.
Why does it matter if we
consume calories in liquid rather
than solid form? Think of it this
way. It takes about 2.5 oranges
to make a glass of juice. But
drinking a glass doesn't make you
feel as full as eating
two-and-a-half oranges. That's
because the fibre in the fruit
makes you feel fuller for
longer.
As Te Morenga puts it, "all
sugar-sweetened drinks really do
is contribute calories to the
diet" – but without making
you full. This is partly because
fructose – which can make up
65 per cent of the sugar in
drinks from soda fountains –
doesn't activate the fullness
hormone leptin.
This lack of satiety from
sugary drinks makes it possible
to consume many more calories at
a sitting than you would
otherwise. Having a sugary drink
with a meal, for example, doesn't
make you eat less (and replacing
it with a diet drink might not
help – see "Just one
hit").
This lack of satiety in
exchange for calories seems to
have long-term consequences.
Several epidemiological studies
have linked the consumption of
sugary drinks with increased risk
of obesity, type II diabetes and
heart disease. That's why soda is
a prime target for public health
officials: so far legislators in
30 US states have tried and
failed to restrict sales in some
way, the most famous being New
York City's thwarted attempt to
ban super-sized sodas last
year.
The failure, in part, can be
put down to campaigns by the food
industry, which has a long
history of waging war against
threats to its profits – as
the WHO knows only too well.
The WHO's upcoming sugar
advice won't be the first of its
kind. Ten years ago it tried
something similar. After
reviewing the evidence it
concluded that people should get
no more than 10 per cent of their
calories from "free sugars" (see
"Sugar basics"), otherwise they
wouldn't be getting a balanced
diet. That was about half of what
people were actually
consuming.
Industry threats
The sugar industry went
ballistic. The US Sugar
Association wrote to the director
general of the WHO, pointing to a
report from the US Institute of
Medicine suggesting that 25 per
cent of daily calories was an
acceptable sugar intake, and
threatening to put US funding for
the WHO in peril if the report
was widely circulated. It sent a
similar letter to then-US Health
Secretary Tommy Thomson.
The report and its 10 per cent
figure were still published, but
with little fanfare – and
almost no impact. Many
researchers contacted by New
Scientist were unsure whether it
had ever been released, or if it
had, if the 10 per cent figure
was included.
The new WHO guidelines are
still a work in progress, but an
early leak suggests they are
likely to go further and
recommend that just 5 per cent of
daily calories come from free
sugars. That would mean cutting
current consumption by
two-thirds, to about 8 teaspoons
a day for men and 6 for women. By
way of comparison, a standard can
of cola contains 10
teaspoons.
This figure won't go down well
with the industry. Marion Nestle,
professor of nutrition, food
studies and public health at New
York University, expects them to
play dirty again, citing
parallels between their tactics
and those used by the tobacco
industry of yesteryear.
"This is about marketing," she
says. "They lobby behind the
scenes to make sure that no
government agency makes
regulations they don't like, they
fund election campaigns to do the
same thing, they attack critics."
They also try to influence the
science: "In general the food
companies sponsor research to
give them the answer they want."
WHO director Margaret Chan has
echoed Nestle's concerns.
So what can be done? There are
signs that the WHO has learned
lessons from 2003. The
anticipated 5 per cent
consumption figure appears to be
based not on evidence about
sugar's link to obesity, but to a
less controversial condition:
tooth decay.
One of the WHO's analyses
looked at the relationship
between sugar and dental
cavities. Led by Paula Moynihan
at Newcastle University in the
UK, the review concluded that
there was evidence – albeit
of very low quality – to
justify reducing intake to 5 per
cent to minimise risk of tooth
decay.
If correct, that might look
like smart tactics by the WHO. It
will be harder to attack this
recommendation as everybody knows
that sugar rots your teeth. But
the poor quality of evidence
leaves plenty of room for the
industry to manoeuvre.
Not all anti-sugar
campaigners, though, see the
industry as the enemy. For the
past two decades, Graham
MacGregor of the Wolfson
Institute of Preventive Medicine
in London has been spearheading a
global campaign against dietary
salt. He and his colleagues have
persuaded the food industry to
reduce added salt by about 30 per
cent. Now they are trying to do
the same with sugar. "There's no
point screaming at the industry,
it doesn't do any good," he says.
"You have to work with them."
That, however, is a long-term
project, which is why many
public-health researchers
advocate more aggressive tactics.
In October, for example, the
BMJpublished projections that a
20 per cent tax on sugary drinks
could reduce the number of obese
people in the UK by 180,000.
Of course, taxes drop the
debate squarely into familiar
political territory: the nanny
state versus individual
responsibility. Do governments
have a duty to intervene or is it
down to people to look after
themselves?
Te Morenga isn't convinced
that sugar is the uber-villain of
our health woes, but is confident
that the way sugary foods are
marketed makes us eat more than
we need. "Maybe people should
take more personal
responsibility," she says. "But
we're letting food companies
spend millions of dollars to
convince people to buy their
products – or that soft
drinks are a perfectly normal
thing to have with a meal."
While politicians weigh up
their options, for individuals,
the advice is quite simple: try
to reduce how much sugar you are
consuming. Above all, avoid
sugary drinks. "It's the easiest
thing to do," says Tappy.
Of course, critics of efforts
to curb sugar intake will counter
that if you simply eat well and
exercise, sugary drinks and
snacks can be reasonable
indulgences. That's true, so far
as it goes. But there is also
another simple truth about sugar:
however much you might want it,
you really don't need it.
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