Spit is central to the conversation for salivary researchers at the Johns Hopkins University School of Nursing, who are discovering new ways to keep people healthy and well.
In four new studies, these researchers are delving into the scientific promises of spit to screen for heart disease, explain the body’s stress response, and study a person’s genetics, too.
“There’s lots of potential in exploring what’s in saliva,” says Professor Doug Granger, PhD, Director of The Center for Interdisciplinary Salivary Bioscience Research. “At the Center, we have a mission to push the edge of the envelope. What can be measured? Why should we care? And how it can make a difference in people’s lives?”
It’s a good question: Why should we give a spit? Saliva contains dozens of substances—proteins, enzymes, hormones, and DNA—that can be easily collected and inexpensively analyzed. It’s a treasure trove of data for researchers to make advances in combating disease, understanding biological function, and studying genetics. For patients, the most obvious benefit is that saliva can be a low-cost, painless, easy method of screening for infectious and chronic diseases. Take, for example, cardiovascular disease.
Spit Screening for Heart Disease—The risk of heart disease may be obvious for a person who smokes, has high cholesterol, and is hypertensive. But for the rest of us—including the one-third of heart attack victims who drop dead without having any of these signs—the risks can remain hidden until it’s too late. “If people were to know more about their potential risk for cardiovascular diseases, that might be useful in changing their health behavior,” says Postdoctoral Fellow Dorothée Out, PhD.
Today’s standard CRP test is a blood test, and getting people to take it as often as they should is a challenge. Patients have to go to a medical facility; a specially trained professional has to draw the blood; the samples are shipped to a lab for testing; they have to wait days or weeks for results. And, oh yeah, getting a blood test hurts. In a ground-breaking study, Out, Granger, and Page discovered that saliva can be used to measure CRP, and a new saliva test could potentially be used in screening for heart disease as well as monitoring response to treatments. Granger says more research needs to be done to make the predictions even more accurate and to then create a test kit that could be used at a patient’s bedside. Once a saliva test is available, says Granger, “more people would be willing to have the test done. It could be done on a more regular basis, even in their homes. People would be more informed about their risk.” [“Assessing salivary C-reactive protein: Longitudinal associations with systemic inflammation and cardiovascular disease risk in women exposed to intimate partner violence,” Brain, Behavior, and Immunity, 2012]
Daughters’ Spit Shows Dads Affect Stress—Early family dynamics can have profound effect later in life—on social interactions, relationship decisions, and sexual and reproductive choices. Research has shown over and over again that daughters who have warm relationships with their fathers come into puberty later, wait longer to begin dating and having sex, and are more likely to be monogamous. But why? In “The Father-Daughter Dance,” Granger finds that negative father-daughter relationships—those characterized by rejection, chaos, and coercion—led to lower morning cortisol levels and elevated cortisol response when discussing problems with friends, indicating they are more emotionally sensitive to stressful situations. Granger explains, “Some people are more biologically sensitive to stress, and some people aren’t, but it’s not just about the person and the situation. It’s about the relationships those persons have as well. This study links the father-daughter relationship as an important influence.” [“The Father-Daughter Dance: The Relationship Between Father-Daughter Relationship Quality and Daughters’ Stress Response,” Journal of Family Psychology, February 2012.]
Mom’s Spit Gives Clues to Baby’s Health—Common wisdom tells us that psychological distress is good for neither a pregnant woman nor her unborn child. Today’s science is backing up that claim, finding that mom’s experiences can affect the fetus a number of ways, including through her body’s biological response to stress. When stress hits, the body’s response includes a fight-or-flight rush of adrenaline, increased heart rate, and, as it turns out, a stimulated salivary gland. The glands produce the enzyme salivary alpha-amylase (sAA), which can be measured as a marker of the body’s autonomic nervous system response to stress. In women, Granger wondered, how might sAA levels change over the course of pregnancy? Granger sampled saliva of 96 pregnant women and discovered that sAA levels changed predictably across the course of the pregnancy, and vary throughout the day in a distinct pattern, which differs according to stage in pregnancy and prior pregnancy history. His findings allow future researchers will be able to monitor sAA levels over the course of a pregnancy and look at how mom’s emotional life has an impact on baby’s health. [“Salivary Alpha-Amylase During Pregnancy: Diurnal Course and Associations with Obstetric History, Maternal Demographics, and Mood, Developmental Psychobiology, February 2012]
Spit Keeps It All In The Family—For researchers who want to look at how genetic variation is related to other biological markers, spit may hold a wealth of data. The usual method of collecting DNA has been to swab cells from the inside of a patient’s cheek, but nucleic acid is also present in saliva. Granger and his colleagues wondered: Could samples of spit be used to get high-quality DNA? In the first research of its kind, Granger and his team conducted five studies to assess how sample volume, handling and storage conditions, type of collection devices, and oral sampling location affect the amount of DNA present in the sample—and whether the samples would be useful to DNA researchers. As it turns out, says Granger, “one-half of an eyedropper drop is enough to get a reasonable sample of DNA. Samples can be frozen and thawed multiple times. They can be sent through the mail, and we’re able to extract high-quality, high-quantity DNA.” [Assessing genetic polymorphisms using DNA extracted from cells present in saliva samples,” BMC Medical Research Methodology, December 2011.]
Global Salivary Science—The JHUSON Center for Interdisciplinary Salivary Bioscience Research is collaborating with scientists around the globe to discover new ways that spit can be used to improve health. Principal investigators on these four studies are:
- Spit Screening for Heart Disease—Dr. Dorothée Out, Postdoctoral Fellow at JHUSON, is from the Netherlands
- Daughters’ Spit Shows Dads Affect Stress—Dr. Jennifer Byrd-Craven is Assistant Professor at Oklahoma State University
- Mom’s Spit Gives Clues to Baby’s Health—Dr. Gerald F. Giesbrecht is on the Faculty of Medicine at the University of Calgary in Alberta, Canada
- Spit Keeps It All In The Family–Dr. Zsofia Nemoda is an Assistant Professor at Semmelweis University in Budapest, Hungary
*In the interest of full disclosure, Dr. Granger is founder and Chief Scientific and Strategy Advisor of Salimetrics LLC (State College, PA), and this relationship is managed by the policies of the Johns Hopkins University School of Medicine Conflict of Interest Committee.