Never Mind the Bullocks, Here's the Science (6 page)

Mikkelson, Barbara, ‘The saltpeter principle’, Urban Legends References Pages, 13 August 2001; http://www.snopes.com/military/saltpeter.asp.

‘Raising an army’,
New Scientist
, 27 April 2002, p 73.

‘Raising an army’,
New Scientist
, 29 June 2002, p 65.

Sports Drinks
(Electrolyte Up My Life)

In general, exercise is a good thing. When you exercise vigorously, you usually get hot and sweaty, lose some body water and perhaps become a little dehydrated. So what is the best way to replenish this lost fluid? This is where it gets tricky.

Some people think that they should guzzle down plain water to rehydrate.

However, other people believe the exact opposite to be true. They believe that plain water is dangerous because it can flush essential electrolytes from their bodies and upset their metabolic balance. This is why they choose a sports drink to rehydrate.

Yet another group believe that it is impossible to drink too much.

However, none of these beliefs is entirely true.

Dehydration Can Kill

Yes, dehydration can kill you—indeed, each year nearly two million children under the age of five die from dehydration brought on by infectious diarrhoea. In severe cases, water alone cannot rehydrate you—you need water with the right amounts and types of sugars and salts added.

This knowledge is not new. The great Indian physician and surgeon, Sushruta—a truly wise person—was aware of this 2,500 years ago. He was skilled in nose and eye surgery and was the first person known to operate on bladder stones. He knew of heart pain (angina), seemed to understand the concept of blood flow in arteries and veins, and accurately described the illnesses leprosy, diabetes and hypertension.

He also recommended that infectious diarrhoea be treated by drinking not plain water, but rather a mixture of rice water, carrot soup and coconut juice. He was right. Plain water was not the best fluid for treating infectious diarrhoea, such as that caused by cholera.

In fact, it was the modern treatment for cholera, based on Sushruta’s traditional ideas, that led to the first generation of sports drinks.

Cholera Today?

Amazingly, the disease cholera still exists today.

According to the World Health Organization in 2002, about ‘88% of diarrhoeal diseases in the world are attributal to unsafe water, sanitation, and hygiene’.

In July 1994, thanks to yet another war, over half a million Hutu refugees were interned in a camp in Zaire in Africa. Over 12,000 died from cholera. The death rate of those infected with cholera was about 50%, ‘as a result of inadequate supplies of water, sugar and salts’.

There was an outbreak of cholera in Zimbabwe in late 2008. By April 2009, about 100,000 people had been infected, and about 4,000 had died.

It’s Enough to Give You the….

Cholera is the illness caused by the bacterium
Vibrio cholerae.
It is usually spread by drinking water contaminated with the bacteria. The infective dose in healthy adults is about 100 million bacteria. The incubation period is about 1.5 to 5 days. It kills people by giving them such copious diarrhoea, that they dehydrate.

The modern treatment for cholera led to the first generation of sports drinks.

Cholera—Natural History

Cholera is the illness caused by the bacterium
Vibrio cholerae.
It is usually spread by drinking water contaminated with this
bacterium. The infective dose in healthy adults is about 100 million bacteria, with an incubation period of about 1.5 to 5 days. It kills people by giving them such copious diarrhoea that they become severely dehydrated.

The bacterium makes a toxin (Cholera Toxin) that poisons the cells lining the gut. (By the way, to medical people, the gut is the hollow 10 m long tube that begins at the mouth and finishes at the anus.) These cells then exude—into the hollow pipe of the gut—huge quantities of a liquid rich in sodium, potassium and bicarbonate. The amount of liquid secreted is too much for the lower gut to re-absorb. The victim dehydrates rapidly thanks to their producing vast quantities of the infamous, so-called ‘rice water stools’. Someone with cholera can easily lose 0.5-1 litre/hr of fluid from their body.

The bacterium makes a toxin (Cholera Toxin) that poisons the cells lining the gut. These cells then exude (into the hollow pipe of the gut) huge quantities of a liquid rich in sodium, potassium and bicarbonate. The amount of liquid secreted is too much for the lower gut to re-absorb. The victim dehydrates rapidly thanks to their producing vast quantities of the so-called ‘rice water stools’.

Cholera Toxin

(a simplified view)

Cell Membranes

The amount of water that crosses the cell membranes in the human body is simply astonishing.

Water molecules jump into the Red Blood Cells (RBCs) and then out again, and then in again, and so on. They do this very frequently. In fact, in just one second, a volume of water equal to about 100 times the volume of the RBC passes in and out of the RBC membrane. Obviously, these are mostly the same water molecules jumping in and out, over and over again. Assuming that you have about 2 litres of RBCs, this means that a total of about 17 million litres of water go in and out of your RBCs each day – that’s 17,000 tonnes of water!

This 17,000 tonnes of water is just for the 2 kg of RBCs. The tonnage of water must be correspondingly higher for the remaining kilograms of your body.

With such a huge flow, you need only a slight interference with the flow in one direction to rapidly over-hydrate or dehydrate you.

As a personal example, I knew one woman who suffered from pre-eclampsia (nothing to do with diarrhoea, but lots to do with keeping too much water in the tissues). The ‘cure’ for pre-eclampsia is immediate delivery of the baby. After delivering her lovely baby (in a bit of a hurry), she then urinated away 10 litres of water that same day, and another 10 litres over the next two days.

Incredibly, in some cases, the patient can actually die of dehydration
before
they have their first episode of diarrhoea—this is called Cholera Sicca. In these victims, the poisoned cells that line the gut dump litres of fluid into the hollow pipe that is the gut. This fluid cannot be re-absorbed into the bloodstream. In Cholera Sicca, this happens so quickly that the victims do not have time for a bowel motion. In fact, they die before they even go to the toilet. When a cholera pandemic hit Paris in 1831, it killed so many people so quickly that François Magendie, the French physiologist, wrote that it was ‘a disease that begins where other diseases end, with death’.

Typically, the death rate for cholera is about 50% if untreated, and 1% if treated. In India alone, between 1816 and 1917, nearly 30 million human beings died from cholera. Most deaths from cholera occur on the first day of infection.

The disease will resolve itself in a few days, when healthy gut cells replace the poisoned ones. However, in the 50% of cases of untreated cholera that lead to death, the victim dies from dehydration before the poisoned cells can be replaced.

Cholera—Treatment

You would think that the treatment for massive diarrhoea from cholera would be easy—simply replace the water at one end as fast as it is being lost from the other end. But it doesn’t work like that. The problem is that the water you drink does not get absorbed by the gut.

Giving water to cholera victims only increases the loss of water as rice water stools. The ‘replacement’ water does not leave the gut to enter the bloodstream, it just passes through until it leaves the ‘other end’. And, all the time, the victim is losing water and electrolytes that desperately need to be replaced.

Gut Absorption

Human beings are approximately 45-75% water. One of the body’s major ‘water pumping stations’ is the small intestine.

Surprisingly, the small intestine is not short. It makes up about 70% of the gut. It is called ‘small’ because it is narrow, with an internal diameter of about 2.5-3.0 cm. It has a massive surface, thanks to all the folds on its inner surface – 250 square metres, instead of just 0.5 square metres if it were a smooth tube.

The small intestine begins at the end of the stomach and finishes before the large intestine. (The word ‘stomach’ does not mean ‘all that stuff between the bottom of the ribs and the top of the legs’. Instead, I use the word ‘stomach’ in its anatomical sense, as the organ between the oesophagus and the small intestine.)

It absorbs water and nutrients through the cells that line it, sending them to the bloodstream.

However, under certain circumstances, the small intestine can stop absorbing.

Each day, you take in about 1.5 litres of fluid. Your gut secretes a further 7 litres or more, giving a total of 8-9 litres per day.

Your small intestine normally absorbs about 7 litres each day, leaving 1.5 litres to enter the colon. But, if required, your small intestine can absorb about 20 litres or more each day (as well as lots of nutrients). And your large intestine can absorb even more water (but virtually no nutrients). Overall, absorption is greater, leading to relatively dry faeces.

However, in diarrhoea, the normal balance is upset, with a combination of increased secretion from the gut wall and/or reduced absorption from the gut wall.

Either way, diarrhoea is defined by the World Health Organization as ‘passage of loose or watery stools at least three times in a 24-hour period’. But their definition also emphasises the importance of change in stool consistency.

The first scientific approach to the problem of cholera deaths occurred in 1831. At the age of just 22, Dr William Brooke O’Shaughnessy, an Irish doctor, scientist and inventor, read out to the Westminster Medical Society the results of his analysis of the blood of cholera victims in India. He discussed how dehydrated the ‘thick, cold, black blood of cholera’ was, and said that this might be reversed by injecting suitable fluids directly into the veins. He published his observations in
The Lancet
in December that year. (Dr O’Shaughnessy also introduced medical uses of marijuana to Western medicine and received a knighthood for his later work on electric telegraph systems.) In June 1832, Dr Thomas Latta, following on from Dr O’Shaughnessy’s work, published in
The Lancet
a recounting of the first successful use of intravenous (IV) rehydration to treat the diarrhoea of cholera.

The principle was simple: a needle was inserted into a patient’s vein, and large quantities of sterile water gradually dripped into the vein. But still, it did not always work. Why? Because in many cases the treatment was not aggressive enough—too little fluid was entering the patients’ veins. In addition, the fluids themselves were often unsterile, chemically impure and not formulated to the same ‘saltiness’ as blood.

But even if the IV fluids were sterile and pure, and given in large enough quantities, they were still very expensive. So even today, IV treatments are not really suitable for the mass treatment of cholera diarrhoea.

Cholera Resistance

Surprisingly, a person can be somewhat resistant to cholera. There are at least two factors – blood type and the inherited disease cystic fibrosis.

We do not fully understand why, but there appears to be a spectrum of resistance to cholera based on blood type – AB being most resistant, followed by Type A, then Type B, with Type 0 the most susceptible.