While you might have known your hair and bodily fluids reflect what you eat and drink, you probably didn’t know they reflect where you’ve traveled as well. For biomedical scientists, archaeologists and criminologists, a novel application of hair and urine analysis conducted at UAF has shown promise for tracking human movements and in forensic cases where DNA or other traditional means have been unsuccessful.

The idea began in the lab of Matthew Wooller, director of the UAF Stable Isotope Facility, who uses a technique called stable isotope analysis to track the migratory routes of birds such as coastal plain swamp sparrows and king eiders.

Stable isotopes are non-radioactive, naturally occurring forms of an element that contain the same number of protons, yet vary in the number of neutrons in their nuclei. The result is that isotopes possess slightly different atomic masses. Isotopes are incorporated into human and animal tissues through eating, drinking and inhalation, and the differences in atomic mass make them useful as markers or indicators.

Water consumed by birds is incorporated into feathers and other tissues and varies in its composition of oxygen and hydrogen isotopes, depending on the geographic origin of the water. Birds moving between isotopically distinct areas carry with them information from those places where they consumed water.

Migration is a not uncommon theme in Wooller’s life. After first meeting at a scientific convention on stable isotope analysis a number of years ago, Wooller and Diane O’Brien—then a biology professor at Wellesley College in Massachusetts—began a long-distance relationship in which they frequently traveled back and forth to see each other. During one of these trips, an idea struck Wooller that had the makings of a dating experiment only a fellow scientist would appreciate.

“It struck me that our very regular flying backwards and forwards between these two locations was a little like some of the animal migrations that many other researchers use stable isotopes to track,” Wooller said. “It seemed like an ideal opportunity to take advantage of our long flights between these different locations.”

O’Brien, now an assistant professor of biology and wildlife at the UAF Institute of Arctic Biology and researcher with the IAB Center for Alaska Native Health Research, was game to participate in Wooller’s human migration project.

“Matt came up with the idea to start sampling hair on one of his visits,” O’Brien said. “He would shave a little bit of beard hair everyday, and then we started clipping our nails.”

Just like the birds and the water they consume, elemental isotopes from the food and water a person consumes are incorporated into their hair and nails as they grow, creating a geographic timeline of where that person has been. The stable isotopic ratios of water are a function of latitude. Water from higher latitudes is relatively depleted in the heavier oxygen isotope 18O and hydrogen isotope 2H, when compared to lower latitudes. The superscript number preceding the element symbol represents the number of neutrons and protons in the nucleus of that element.

 Using an instrument called an isotope ratio mass spectrometer, Wooller analyzed small samples of beard, head hair and nail clippings. The clipping samples were chopped, weighed and placed in tin capsules, which were crushed into balls. The balls were then dropped into a high temperature conversion/elemental analyzer (TC/EA), which uses temperatures exceeding 1400°C (2552°F) to combust the samples into pure gases that then travel into the mass spectrometer, which uses a magnetic field to separate and count the heavy and light isotopes.

Wooller and O’Brien expanded their personal pool of hair samples by recruiting friends and family members in Fairbanks, a high-latitude location at roughly 65° north latitude, and East Greenbush, New York, a low-latitude location at roughly 43° north latitude, to contribute hair. All those who donated hair were in Fairbanks or East Greenbush for at least two months prior to donating, thus the collected hair reflected local water. Wooller and O’Brien found little isotopic variation between bottled water in Fairbanks and in East Greenbush, which made it possible that bottled water might erase or minimize the effects of local water, O’Brien said. “But the fact that we did find differences between sites that were pretty big and signatures within sites that were consistent gives us confidence that if people were drinking bottled water it wasn’t enough to erase the geographical signal.”

Because water from Fairbanks and East Greenbush has distinctly different isotopic signatures, the scientists hypothesized that hair samples would reflect those differences. When you drink water from a new place, said O’Brien, “it mixes with the existing water in your body, and then over time, as you continue to drink the water in the new place, the water in your body is going to look like your new drinking water.”

It was not long after Wooller began collecting hair and nail clippings that he decided to add another item to his analysis —his urine. According to Wooller, the addition had scientific merit. “The change over from one location to another location’s isotopic signature is much more clear and quick in urine than in hair,” Wooller said.

Because a portion of the hydrogen and oxygen in humans derives from diet as well as from drinking water, O’Brien and Wooller also examined a collection of food items from Fairbanks and East Greenbush. They found that the average stable isotope signatures between the two locations did not differ significantly, which is consistent with the fact that American diets typically include a majority of nonlocally grown and nationally distributed foods.

Wooller and O’Brien’s results showed Fairbanks tap water was, as expected, depleted in the heavier stable isotopes of oxygen and hydrogen relative to tap water from East Greenbush. Hair from East Greenbush participants contained significantly more of the heavier stable isotopes of oxygen and hydrogen when compared with hair from Fairbanks participants.

Results from the isotopic analysis of Wooller’s urine samples were dramatic. Values of oxygen and hydrogen changed rapidly in response to his travels between high and low latitude locations. Samples of Wooller’s hair showed similar changes, but at a slower rate. 

Wooller and O’Brien’s results demonstrate that residents of different geographic locations can have discrete isotopic signatures even when their diet is isotopically similar. As with studies of animal migration, isotopic changes in humans resulting from travel will be most apparent when individuals move between distinctly different latitudes.

“This project was never intended to be published and started out as a lark,” said O’Brien. However, after presenting their findings to fellow researchers at an isotope conference, the two professors rethought the potential scientific value and applications of what they had done. “It started to really have a serious science edge to it,” Wooller said. People were really interested in the study, said O’Brien, because there hasn’t been a lot of published data on the analysis of stable isotopes in hair and urine of individuals who have traveled between two locations.

“We went to visit my parents for Christmas, and there was a day when my folks were off doing something, and I said, ‘Hey Matt, let’s go to the coffee shop and bring our laptops and bang out this paper,’” O’Brien laughed. “And so we did.” The paper, “Tracking human travel using stable oxygen and hydrogen analyses of hair and urine,” was published in Rapid Communications in Mass Spectrometry in August 2007.

“To our knowledge, we provided one of the first estimates of the percent of oxygen in human hair to derive from drinking water, based on stable isotope analyses,” O’Brien said. “The tendency for human hair to reflect local water oxygen as well as hydrogen provides another tool for tracking human movement or origin in forensic applications.”

O’Brien and Wooller are now married and living in Fairbanks. O’Brien researches how naturally occurring variations in stable isotope ratios can be used as markers for nutritional and physiological processes. She is currently working on using stable isotopes as dietary biomarkers in Yup’ik Eskimos with the IAB Center for Alaska Native Health Research.

Wooller directs the Alaska Stable Isotope Facility and is a faculty member with the Water and Environmental Research Center and the School of Fisheries and Ocean Sciences at UAF. His research focuses on applications of stables isotope techniques to various past and present ecological systems.

Researchers at the Institute of Arctic Biology Center for Alaska Native Health Research seek to understand how a subsistence diet protects and/or predisposes Yup’ik people to disease. To do this, scientists need to easily and accurately measure how much subsistence foods people eat.

Dietary assessment based on self-reporting is problematic due to bias, memory, cost and the time investment and compliance required of participants.

Diane O’Brien is leading a project to develop a novel method to measure subsistence food intake by matching natural isotopic signatures in blood or hair samples with those in foods. Isotopic signatures are incorporated into human tissues, and reflect diet at the time the tissue was formed. They could provide practical biomarkers of diet pattern that are quick, inexpensive to measure and don’t rely on memory and lengthy interviews.

“In humans, isotopes are informative about what you eat and what you drink,” said O’Brien. “The nice thing about a biomarker like an isotope signature is, it’s unbiased and it’s accurate.”

Because Yup’ik Eskimos are a high-latitude population which relies on a mix of local marine and terrestrial subsistence and market foods, they are an ideal population of validity study of isotopic dietary biomarkers.

There is a great need for accurate, easily-collected dietary information in Yup’ik Eskimos, both on variation in usual diet among individuals and on dietary change across seasons, according to O’Brien. The marine subsistence-based diet of the Yup’ik may historically have served to protect them from chronic, obesity-related diseases, via high levels of polyunsaturated fatty acids, or a low glycemic index.

However, many Alaska Native populations are transitioning from subsistence to market-based diets. If subsistence-based diets are protective, then a shift toward market foods may affect the risk of chronic obesity-related disease in this population.

Understanding how the unique diet of Yup’ik Eskimos either protects or predisposes them to disease and indentifying those changes that are associated with markers of health risk will help scientists address the health needs of this underserved population.

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