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The secrets of spit

A spit sample.
A spit sample.
Photo by EricaJoy via Flickr Creative Commons

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Saliva might seem gross when the stuff unintentionally flies out of your mouth, or you see the person sleeping on the seat next to you drooling, but researchers are finding new uses for saliva that could open the way to big changes in the world of medicine.

Researchers are using spit to determine everything from dietary habits to whether you may have certain life threatening illnesses.

The study of spit is relatively new - around 10 years ago the National Institutes of Dental and Craniofacial Research issued a series of grants to scientists willing to explore the hidden properties of spit. Since then, labs across the country have crafted all kinds of tests for slobber – including a recent one from the David Geffen School of Medicine at UCLA that uses saliva to predict your age.

Sven Bocklandt, one of the researchers on this project, is collecting saliva samples to examine DNA and study the way sexual identity is linked to our genes.

As he studied the spit samples he collected, he noticed that as we age our DNA seems to age too, through a process called methylation. It’s sort of like seeing wrinkles on your genome. He found that the pattern of methylation shown in a given gene strongly correlates with a person’s age.

So his team developed a way to take a spit sample, check out this methylation pattern - and predict your age within five years. It’s the first time researchers can start with a biological sample and get an idea of how old someone is.

Bocklandt said the real beauty of it lies in its potential forensic uses. “Until now all you could say from a DNA sample was whether or not it was a man or a woman. Now we can actually say this is probably going to be a 20- to 25-year old male or a 40- to 45-year old female."

This study offers just one example of the bounty of information hidden in your saliva. The UCLA School of Dentistry’s Dr. David Wong studies spit full time – he’s kind of a salivary evangelist.

“Women in the Greek culture spit on the bride’s gown during the wedding ceremony as a gesture to cast off the evil spirit," said Wong. "And when the priest lifts the infant out of the holy water, he spits three times onto his or hers forehead as another gesture to cast off the evil spirits.”

Dr. Wong likes to call spit “the window to the body" because it contains a lot of genetic information and also has proteins and other useful bacteria and cells.

Spit is made up of the same fluid as blood but without the blood cells, so Dr. Wong says it carries a lot of the same information.

“If that concept of saliva as a mirror of our blood. Then what you could do with blood could be done in saliva – easier, non-painfully and non-embarrassingly," he said.

There are already quick-result tests on the market for HIV that rely on spit samples rather than blood. That’s useful because spit doesn’t carry the same risk of disease that working with blood does.

Dr. Wong and his team have found it’s possible to detect other illnesses in spit too - like diabetes, breast cancer and lung cancer – even before a person shows symptoms.

One of the problems though, is that much of the medical world doesn’t embrace saliva science yet. Researchers like Dr. Wong have to conduct a lot more studies to prove these tests are accurate before the federal government approves this as a valid diagnostic tool.

But Dr. Wong said that they should have a test for oral cancer ready for use in about two years.