Mission control: salty diet makes you hungry, not thirsty

We've all heard it: eating salty foods makes you thirstier. But what sounds like good nutritional advice turns out to be an old-wives' tale. In a study carried out during a simulated mission to Mars, an international group of scientists has found exactly the opposite to be true. "Cosmonauts" who ate more salt retained more water, weren't as thirsty, and needed more energy.

Salt shaker, by Dubravko Sorić SoraZG on Flickr [CC BY 2.0 (http://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons

For some reason, no one had ever carried out a long-term study to determine the relationship between the amount of salt in a person's diet and his drinking habits. Scientists have known that increasing a person's salt intake stimulates the production of more urine - it has simply been assumed that the extra fluid comes from drinking. Not so fast! say researchers from the German Aerospace Center (DLR), the Max Delbrück Center for Molecular Medicine (MDC), Vanderbilt University and colleagues around the world. Recently they took advantage of a simulated mission to Mars to put the old adage to the test. Their conclusions appear in two papers in the current issue of The Journal of Clinical Investigation.

What does salt have to do with Mars? Nothing, really, except that on a long space voyage conserving every drop of water might be crucial. A connection between salt intake and drinking could affect your calculations - you wouldn't want an interplanetary traveler to die because he liked an occasional pinch of salt on his food. The real interest in the simulation, however, was that it provided an environment in which every aspect of a person's nutrition, water consumption, and salt intake could be controlled and measured.

The studies were carried out by Natalia Rakova (MD, PhD) of the Charité and MDC and her colleagues. The subjects were two groups of 10 male volunteers sealed into a mock spaceship for two simulated flights to Mars. The first group was examined for 105 days; the second over 205 days. They had identical diets except that over periods lasting several weeks, they were given three different levels of salt in their food.

The results confirmed that eating more salt led to a higher salt content in urine - no surprise there. Nor was there any surprise in a correlation between amounts of salt and overall quantity of urine. But the increase wasn't due to more drinking - in fact, a salty diet caused the subjects to drink less. Salt was triggering a mechanism to conserve water in the kidneys.

Before the study, the prevailing hypothesis had been that the charged sodium and chloride ions in salt grabbed onto water molecules and dragged them into the urine. The new results showed something different: salt stayed in the urine, while water moved back into the kidney and body. This was completely puzzling to Prof. Jens Titze, MD of the University of Erlangen and Vanderbilt University Medical Center and his colleagues. "What alternative driving force could make water move back?" Titze asked.

Experiments in mice hinted that urea might be involved. This substance is formed in muscles and the liver as a way of shedding nitrogen. In mice, urea was accumulating in the kidney, where it counteracts the water-drawing force of sodium and chloride. But synthesizing urea takes a lot of energy, which explains why mice on a high-salt diet were eating more. Higher salt didn't increase their thirst, but it did make them hungrier. Also the human "cosmonauts" receiving a salty diet complained about being hungry.

The project revises scientists' view of the function of urea in our bodies. "It's not solely a waste product, as has been assumed," Prof. Friedrich C. Luft, MD of the Charité and MDC says. "Instead, it turns out to be a very important osmolyte - a compound that binds to water and helps transport it. Its function is to keep water in when our bodies get rid of salt. Nature has apparently found a way to conserve water that would otherwise be carried away into the urine by salt."

The new findings change the way scientists have thought about the process by which the body achieves water homeostasis - maintaining a proper amount and balance. That must happen whether a body is being sent to Mars or not. "We now have to see this process as a concerted activity of the liver, muscle and kidney," says Jens Titze.

"While we didn't directly address blood pressure and other aspects of the cardiovascular system, it's also clear that their functions are tightly connected to water homeostasis and energy metabolism."

For more information visit:-

https://www.sciencedaily.com/releases/2017/04/170417182920.htm

http://www.prlabs.co.uk/lab-supplies.php?N=carboxymethylcellulose-sodium-salt&Id=57938
https://en.wikipedia.org/wiki/Salt

On this day in science history: chewing gum was patented

In 1869, William Finley Semple of Mount Vernon, Ohio, was issued the first U.S. patent for chewing gum (No. 98,304), made of "the combination of rubber with other articles adapted to the formation of an acceptable chewing gum", but he never commercially produced gum. That was done by Thomas Adams of Staten Island, N.Y., who knew that chicle, a natural tree gum, could be chewed. His first experiments to vulcanize chicle for use as a rubber substitute were unsuccessful until he boiled a small batch of chicle in his kitchen and created the first chicle-based chewing gum. Testing sales at a local store, he found people liked his gum. In 1871, Adams patented a gum-producing machine so he could increase production.

Chewing gum stick by Lusheeta, via Wikimedia Commons

Humans have used chewing gum in some form for at least 100,000 years. Modern chewing gum today is made from butadiene-based synthetic rubber. Most chewing gums are considered polymers. Longer polymers can produce larger bubbles due to increased intermolecular forces.

Chewing gum in many forms has existed since the Neolithic period. 6,000-year-old chewing gum made from birch bark tar, with tooth imprints, has been found in Kierikki in Finland. The tar from which the gums were made is believed to have antiseptic properties and other medicinal benefits. It is chemically similar to petroleum tar and is in this way different from most other early gums. The Aztecs, as the ancient Mayans before them, used chicle as a base for making a gum-like substance and to stick objects together in everyday use. Forms of chewing gums were also chewed in Ancient Greece. The Ancient Greeks chewed mastic gum, made from the resin of the mastic tree. Mastic gum, like birch bark tar, has antiseptic properties and is believed to have been used to maintain oral health. Both chicle and mastic are tree resins. Many other cultures have chewed gum-like substances made from plants, grasses, and resins.

The American Indians chewed resin made from the sap of spruce trees. The New England settlers picked up this practice, and in 1848, John B. Curtis developed and sold the first commercial chewing gum called The State of Maine Pure Spruce Gum. In this way, the industrializing West, having forgotten about tree gums, rediscovered chewing gum through the First Americans. Around 1850 a gum made from paraffin wax, which is a petroleum product, was developed and soon exceeded the spruce gum in popularity. To sweeten these early gums the chewer would often make use of a plate of powdered sugar, which they would repeatedly dip the gum into to maintain sweetness.

For more information visit:-

http://www.prlabs.co.uk/lab-supplies.php?N=balls-rubber-20mm-&Id=46943

https://en.wikipedia.org/wiki/Chewing_gum

https://todayinsci.com/12/12_28.htm

On this day in history: the first manned voyage of a hydrogen balloon left Paris

In 1783, the first manned voyage of a hydrogen balloon left Paris carrying Professor Jacques Alexander Cesar Charles and Marie-Noel Robert to about 600 m and landed 43 km away after 2 hours in the air.

Robert then left the balloon, and Charles continued the flight briefly to 2700 m altitude, measured by a barometer. This hydrogen-filled balloon was generally spherical and used a net, load ring, valve, open appendix and sand ballast, all of which were to be universally adopted later. His hydrogen generator mixed huge quantities of sulfuric acid with iron filings.

On 27 Aug 1783, Charles had launched an unmanned hydrogen balloon, just before the Montgolfiers' flight.

Hot air balloon, by Kropsoq (photo taken by Kropsoq) [GFDL (http://www.gnu.org/copyleft/fdl.html), CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/), CC BY-SA 2.5 (http://creativecommons.org/licenses/by-sa/2.5) or CC BY-SA 2.1 jp (http://creativecommons.org/licenses/by-sa/2.1/jp/deed.en)], via Wikimedia Commons

There are three main types of balloon:

The hot air balloon or Montgolfière obtains its buoyancy by heating the air inside the balloon; it has become the most common type.

The gas balloon or Charlière is inflated with a gas of lower molecular weight than the ambient atmosphere; most gas balloons operate with the internal pressure of the gas the same as the pressure of the surrounding atmosphere; a superpressure balloon can operate with the lifting gas at pressure that exceeds that of the surrounding air, with the objective of limiting or eliminating the loss of gas from day-time heating; gas balloons are filled with gases such as:

• Hydrogen – originally used extensively but, since the Hindenburg disaster, is now seldom used due to its high flammability;
• Coal gas – although giving around half the lift of hydrogen, extensively used during the nineteenth and early twentieth century, since it was cheaper than hydrogen and readily available;
• Helium – used today for all airships and most manned gas balloons;

Other gases have included ammonia and methane, but these have poor lifting capacity and other safety defects and have never been widely used.

The Rozière type has both heated and unheated lifting gases in separate gasbags. This type of balloon is sometimes used for long-distance record flights, such as the recent circumnavigations, but is not otherwise in use.

Both the hot air, or Montgolfière, balloon and the gas balloon are still in common use. Montgolfière balloons are relatively inexpensive, as they do not require high-grade materials for their envelopes, and they are popular for balloonist sport activity.

For more information visit:-

http://www.todayinsci.com/12/12_01.htm

https://en.wikipedia.org/wiki/Balloon_(aeronautics)

https://www.prlabs.co.uk/lab-supplies.php?N=urea-hydrogen-peroxide&Id=1606