Against the grain (salt)

[Guest guest]

Against the grain

http://www.guardian.co.uk/medicine/story/0,11381,1304653,00.html

 

Health campaigners say it is implicated in tens of thousands of strokes and

heart attacks each year. Now the government wants to persuade us all to eat

less of it. But is salt really as bad for us as the health lobby insists?

Sarah Boseley and Tim Radford investigate

 

Wednesday September 15, 2004

The Guardian

 

Civilisation is built on salt. The discovery of its power to preserve food

enabled wandering tribes to put down roots. Men and women could hunt and

gather today and eat tomorrow. A life that was no longer hand to mouth

allowed time to sit and think. Salt became as precious as any metal, was

traded between nations and offered as gifts. Its influence lingers in our

linguistic value judgments: a good man is the salt of the earth and worth

his salt, but a social inferior sits below it.

 

But the white crystals have lost their magic. " It wasn't a gift for

civilisation. It was a poison, " says Graham MacGregor, professor of

cardiovascular medicine and the one man who has probably done more than any

other to shake our confidence in a substance traditionally offered with

bread as a sign of friendship to strangers.

 

MacGregor is chairman of Cash (Consensus Action on Salt and Health) and is

this week savouring the sweet taste of success. Ten years after he and

fellow experts on blood pressure began pressing for limits on the amount of

salt we eat, which they say is implicated in 120,000 heart attack deaths a

year in the UK, the Food Standards Authority has launched a £4m campaign to

persuade us to eat less of it - and manufacturers to cut the sackfuls they

pour into our processed foods.

 

But it isn't the salt on your table that does the damage - it's the salt in

your lasagne and, more alarmingly, your bread. The FSA says that 75% of our

salt comes from processed foods, and that an adult consumes 9.5g a day,

though we don't need more than 6g. Baked beans, breakfast cereals, pizza,

soup and cooking sauces tend to be salt-lavish, but so are some sweet

foods, such as biscuits and hot chocolate.

 

Why does our food contain so much salt? Not only because manufacturers

found it made their products taste more interesting, but also because it

binds in water, thus cheaply adding " texture " or bulk. It also makes you

thirsty - another knock-on effect for the food and drink industry.

 

MacGregor argues that thousands of lives could be saved by cutting the salt

content of processed foods by 10-20%. " If salt intake was reduced to 6g a

day, it would prevent 70,000 heart attacks per year, 35,000 of which are

fatal. It is as big an improvement as when they put drains into London, " he

says.

 

Unusually for a bunch of scientists, Cash is extremely media-savvy. It was

naming and shaming high-salt foods, lambasting individual manufacturers and

barbecuing supermarkets long before health minister Melanie Johnson got in

on the act. This month it scored a direct hit on Sainsbury's, fingering the

company's " Be good to yourself " flakes and orchard fruits as one of " the

UK's saltiest foods " . One 50g portion contained 1.84g of salt, it said.

Sainsbury's immediately pulled the product off the shelves.

 

Back in 1994, the government's advisory Committee on Medical Aspects of

Food and Nutrition (known as Coma) recommended a model diet for the UK,

including a reduction to 6g of salt a day. The food industry obtained a

leaked draft and four heavyweight food manufacturers, Cadbury Schweppes,

Tate and Lyle, United Biscuits and Mars demanded a meeting with the

department of health. They did not get the reassurance they wanted. That

same year, United Biscuits and Tate and Lyle cut their contributions to the

Tory party.

 

MacGregor is convinced that this contributed to the government's rejection

of the recommended salt level which has now been espoused by the FSA. " That

really infuriated us - that for a few thousand pounds, the health policy of

the UK could be altered, " he says.

 

Cash was formed in 1996 to press the case through the media instead of

polite government channels. It has worked better than they imagined. " If

you had said to me in 1996 that in 2004 the FSA would launch a £4m campaign

about the dangers of salt, I'd have said you were joking, " says MacGregor.

It took almost 40 years to get serious action on smoking, he points out.

 

As any school child knows, salt is scientifically known as sodium chloride.

It's a simple combination of two molecules, easily extracted from water.

Salt's primitive appeal must have to do with its bodily familiarity - our

tears are salty; our blood is salty. But the question is how much we need

of it. Chimpanzees and orang-utans get their sodium from plants they eat,

not the salt cellar, and they have perfect blood pressure of around 90 over

70. High blood pressure, increasingly common in the UK where it rises

steadily with age, is responsible for half the heart attacks and strokes

that kill people here - 120,000 out of 240,000 a year.

 

MacGregor claims there is virtually no scientific dispute in the UK over

the link between salt, high blood pressure and heart attacks. Excess salt,

says MacGregor, leads to water retention. People who eat too much salt

could have a litre and a half of extra fluid sloshing around in their

veins, he says. That means there is more blood for the heart to pump, and

the blood pressure goes up.

 

The question of how much is too much, however, seems to vary from person to

person. It's quite possible that some of us can eat salt without living

dangerously. Five years ago a team from the University of Utah school of

medicine (in Salt Lake City, of course) identified three variations in a

bit of human machinery called the angiotensinogen gene. High levels of a

hormone produced by this gene also correlated with high blood pressure.

They reported in 1998 that variants in the gene made some people much more

sensitive to salt. So for some, a low salt diet had a significant effect on

blood pressure.

 

There is more than one cause of high blood pressure. But most people in the

field believe that maybe one third of all hypertension sufferers are

reacting to the buildup of sodium. Yet some humans feel they need salt, and

some feel the need for salty food at all times. Six years ago Ilene

Bernstein, of the University of Washington, proposed that babies might

arrive with a taste for salt implanted at birth.

 

It depended, she and colleagues claimed, on just how nauseous and

uncomfortable their mothers felt during early pregnancy. They reported in

1998 that adult children of mothers who had experienced morning sickness to

conspicuous levels were also very keen on salty snack foods. Babies at 16

weeks old were more likely to show a fondness for salty water if they had

previously sent their mothers-to-be retching to the bathroom. Her guess was

that dehydration linked with vomiting might have something to do with a

fondness for salt.

 

" Fluid depletion in the mother triggers the hormonal system in the blood

and kidneys to restore the normal fluid level, " said Bernstein. " We don't

know if these hormones cross the placental barrier and affect the baby or

if dehydration causes the baby to release its own hormones to restore fluid

balance. These hormones can have powerful effects on the brain. "

 

Such claims are contentious. But they do illustrate the complex link

between salt and the functioning of the human machinery. Some babies show a

distinct response to (very slightly) salty tastes within three days of

birth, the response being strongest in those babies who have at least one

grandparent with a history of hypertension, according to the journal

Hypertension in 2002. A team from Mount Auburn Hospital in Cambridge

Massachusetts tested 283 babies in their sucking response to the taste of

salt and sugar. The 67 babies that seemed to like salt most already had, at

three days, higher blood pressure levels than those who seemed to object to

the taste.

 

Such research seems to suggest that appetite, inheritance and environment

all play a part in the link between salt and hypertension. But this is not

saying very much: appetite, inheritance and environment play a role in

practically everything. Nobody is yet prepared to suggest that a warm

response to a hint of the flavour of salt is really an indicator of some

future cardiovascular troubles to come.

 

Salt manufacturers are unsurprisingly unhappy at the turn of events in the

UK, in spite of the fact that most of what they produce ends up on the

roads rather than in our baked beans. " The biggest problem we have is that

the deer on the roads lick up the salt - they like it just as we do, " says

Peter Sherratt, general secretary of the Salt Manufacturers' Association.

 

While the food manufacturers agree to salt reductions here and there -

although not as comprehensively as the FSA and Cash want - Sherratt insists

much of the science is nonsense. " A heck of a lot of literature says the

government is wrong. "

 

He cites two documents that have come out within recent months. The

national diet and nutrition survey commissioned by the government says salt

has no effect on the blood pressure of healthy people, while the National

Institute for Clinical Excellence says that people with high blood pressure

should be on drugs to control it. " I don't understand where salt comes into

the equation, " he says. " There is no problem with a healthy person, and an

unhealthy person should be on drugs. "

 

If some of us are more susceptible to salt-related damage than others,

maybe there is an element of sense in that, but that's not how public

health strategies work. We all have to eat less salt because we don't know

who the lucky people are who can eat crisps with impunity. And if we won't

even notice a small cut in our salt intake, then it's hard to see the

problem for anybody except a salt manufacturer - or a processed food

company that has to have another think about how to make its pizzas taste

good.