Play Live Radio
Next Up:
Available On Air Stations
Watch Live


What Can A Strand Of Hair Reveal About Our Eating Habits?

What Can A Strand Of Hair Reveal About Our Eating Habits?
What exactly are you eating when you bite into that cheeseburger or potato chip? You might be surprised. We interview "The Hair Detective," Dr. Stephen Macko, to find out how the food you eat shows up in your hair.

MAUREEN CAVANAUGH (Host): I'm Maureen Cavanaugh and you're listening to These Days on KPBS. We're doing a series here at KPBS about the food we eat. Our reporters on radio, TV and the web are tracing the food from your dinner plate back to the farm, field and ocean and apparently also straight to the hair follicle. We submitted hair samples from several KPBS employees for scientific analysis to see what the results could tell about their health and diet. Most of us are familiar with forensic hair analysis that determines what chemicals or poisons have been introduced into the system. But some scientists say a diet analysis of the hair can be a window, not just into our own health but to the hidden ingredients in the food we eat. I’d like to welcome my guests. Dr. Stephen Macko, Professor of Environmental Sciences, the University of Virginia. Dr. Macko, welcome to These Days.

Hair Detective Steve Macko Investigates

DR. STEPHEN MACKO (Professor of Environmental Sciences, University of Virginia): Thank you. It’s nice to be here.

CAVANAUGH: And the testees. KPBS investigative reporter Amita Sharma. Welcome.


AMITA SHARMA (KPBS Investigative Reporter): Thank you, Maureen.

CAVANAUGH: And Joe Spurr, KPBS web developer. Welcome to These Days.

JOE SPURR (KPBS Web Developer): Thanks, Maureen. Good morning.

CAVANAUGH: Okay, so we have the two people, I will not call them guinea pigs here. There are also two other people at KPBS. We sent along the hair samples to the University of Virginia. First of all, Dr. Macko, what can you find out about a person by testing their hair follicles?

DR. MACKO: Well, what we’re looking at what are called the stable isotopes and using these components of the hair—they make up the proteins, the amino acids in the hair, we can tell a lot about where their foods are originating. Whether they’re coming from the marine environment or from the terrestrial and the kinds of terrestrial plants they originate in as well as how far up the food chain their diet is.


CAVANAUGH: And you can tell that how? From the chemical composition of the hair?

DR. MACKO: Well, sort of. They – the foods that you eat have proteins in them and they are amino – they are made up of amino acids and the amino acids, you metabolize them and they become your proteins that end up going into your hair. Your hair is a protein and so as your hair grows, it becomes this recorder of what amino acids you’re eating.

CAVANAUGH: I see. So it’s all protein but it’s different types of amino acids making up the protein.

DR. MACKO: Well, that’s close because…

CAVANAUGH: But no cigar. Okay.

DR. MACKO: …but because what it is, is that pretty much all the hairs that we have and all hair have about the same amino acid compositions because since it’s protein and the protein sequences are controlled by our genetic code, that really doesn’t change a lot. But what changes is the elemental compositions. The elements are made out of different forms. You’re probably familiar with one of the forms of carbon, they call it carbon-14 that’s radioactive…


DR. MACKO: …and that’s how we determine the ages of things. Well, we measure, using machines that are in my lab, called mass spectrometers, other forms of carbon that are naturally occurring but they’re not radioactive like – and the carbon has one form, it’s called carbon-13, and that’s about one percent of all the carbon in your body. There’s nothing you can do with – about it as long as you stay on the Earth. And nitrogen is another component, another element that’s in amino acid and that has another small abundance, about .3% nitrogen-15, and that tells us how much the trophic level you are, the – what – how far along the food chain you are. So those are the different forms of the elements inside the amino acids that make up the protein. So it’s a kind of a cascade down to this really microscopic, if you will, level.

CAVANAUGH: Okay, let’s delve in a little bit to these trophic levels a little bit. What does it mean, the trophic level, determines how you’re eating, whether you’re eating high up on the food chain or low on the food chain? Is that correct?

DR. MACKO: Yeah, exactly. There is the base of all productivity, all life on earth, are the plants. And the plants take in nitrogen either from the air or from the waters that – or the soils that they live in and that creates this base troph – the base of the food chains. As animals eat those plants, and so you might have an herbivore – if you are human, we’d call you a vegan and, a pure vegan, and that signal that you have inside of your body reflects just the plants. But if you become an omnivore or if you are a top predator, a carnivore, then you eat – the carnivores eat only meats and so we can pick that signal out because there are other isotopes. And the amino acids that end up being part of your body are also slightly different and your body has to change them. And so when it changes them, it writes that signal in their isotopes.

CAVANAUGH: Now when you do all this research, what – Dr. Macko, what predictions can be made about a person’s health by looking at the levels, the trophic levels, in their hair and what it’s made up of?

DR. MACKO: Well, I’m not a nutritionist…


DR. MACKO: …and I’m not a medical doctor, but we make estimations on how important certain types of foods are in your diet. For example, if you have – if you eat a lot of meat, we can pick that out. If you eat a lot of fish, we can certainly, using another isotope, sulphur isotopes, we can pick that out. So we can give an indication of the kinds of foods that you’re eating and if you have an over – like if you were to become mostly a top carnivore, we could see that and you might say, well, is this a healthy point to be, you know, in that trophic level.

CAVANAUGH: And have you taken the study farther to ask is this a healthy point to be in the trophic level? I mean, if you are eating a lot of meat, if you – In other words, a person would already know they were eating a lot of meat, right? It would seem to me that what else can we learn from this analysis?

DR. MACKO: Well, what we’re trying to do is really not look that much at modern humans but we’re trying to take it into the past and look at other humans, whether they were people that lived in Peru or in Chile like a thousand years ago, or Egyptian mummies. You know, we – So wherever we have hair, we can – we’ve been trying to investigate those types of diets. A parallel to that, though, is we need modern studies of people that have certain types of diseases like diabetes or Alzheimer’s that might inscribe some signal in their hair so then we can take those signals and roll it back to those ancient people and see, well, what’s the incidence of diabetes in this population that lived 2000 years ago or 3000 years ago.

CAVANAUGH: Well, let’s bring it up to date and talk to the testees about the testees that you had from KPBS. And you had tested hair follicles from four members of our staff. So Amita Sharma, our investigative reporter, is one of those. What were the results when you tested Amita’s hair?

DR. MACKO: Well, Amita was a little bit unusual because the ranges that we see in modern humans go anywhere between the vegan and omnivores that have a large portion of meat in their diet. And with Amita, she was a little bit above what I would call a vegan and her – so that would be one signal in the nitrogen. And in the carbon, her signal showed that she had very little of the type of terrestrial plant that we – that gives a special signal, and that’s corn. Corn is ubiquitous in American society. It – We raise cows and pigs and chickens on this huge amount of corn that we grow across the country. The United States grows about half the corn in the world, and we grow something on the order of 90 million acres of corn that ends up going – a large amount of that goes into animal feeds and that ends up showing up in the diet and in the hairs. And just to correct it, we did more than a hair follicle, which is the root of the hair. We actually can look at the hair as it’s – the whole shaft of the hair and so you can see the diets as they change.

CAVANAUGH: So in Amita’s hair you found very little corn.

DR. MACKO: Right, there was very little corn and also she was feeding at – her diet is very, very low on this trophic level.

CAVANAUGH: Okay, so, Amita, do you eat anything?

SHARMA: I do. I do. Joe can testify to that. He…

SPURR: Sometimes.

SHARMA: …he sits near me. I – I’m a vegetarian. I eat a lot of fruits, a lot of vegetables, carrots, broccoli and, you know, I eat a lot of Indian food. I don’t call it Indian food, I just call it food but – which is, you know, lentils and rice. I’m interested to know, Dr. Macko, you know, I believe that you classified me as sort of an honorary vegan.

DR. MACKO: Right.

SHARMA: But I do occasionally have yogurt. Did that not show up?

DR. MACKO: Well, what happens is if you have yogurts or cheese or milk products, all of those are products, animal products, and the signals that I pick up show that – would show, say, that if you ate those, you would be a trophic level, a step up the food chain above those products. So there is a little bit of that showing up and that’s why you’re not a true vegan. You are what – a vegetarian.

SHARMA: Umm-hmm.

DR. MACKO: And I actually was going to ask if – you know, one thing that masks diets when – because we now have these grocery store diets and I wondered if you ever, in your vegetarian – if you had any kind of other meat products?

SHARMA: No. Unless they’re in supplements. I mean, I do take a megas – a mega supplement.

DR. MACKO: Uh-huh.

SHARMA: So that might…

DR. MACKO: The – the fish oil.

SHARMA: Yeah, the fish oil.

CAVANAUGH: Yeah, right.

DR. MACKO: Well, that wouldn’t show up as amino acids but those are in fats so that probably wouldn’t be what some of that signal would be. But what – The signals that were there – and I don’t want to go into the technol – the technological terms very much but you didn’t have as much carbon-13 as I would have suspected that you could have and that would be – that’s what shifted your abundance of corn down a bit. I mean, in fact, that’s what – you were – you ended up having, if you remember my percentages, even a little bit less corn in your diet than Joe.

CAVANAUGH: And Joe is a vegan.

DR. MACKO: Yeah.

CAVANAUGH: Joe Spurr, KPBS web developer, is a vegan. What kind of results did you get when you tested his hair?

DR. MACKO: Well, we had – I had the common number for nitrogen that I’ve seen in vegans all the way – Joe, you came in very close to Ötzi the Iceman, so that’s how far back we’ve taken it which is about 5000 years, to modern day vegans, some of my own students. We had one student that we tested periodically to make sure that she was staying honest and staying a vegan.

CAVANAUGH: That’s very bad.

DR. MACKO: It was but – So, Joe, you were right there as – at the very lowest level that I’ve seen for humans for nitrogen content. And your carbon content had the number that showed that, well, maybe 30%, somewhere around 30, and that number’s very, you know, flexible because, you know, we just ran one small sample of your hair but that number indicated that, well, maybe 30% still of what ends up in the proteins of your hair is somehow related to this plant called – we call corn, maize and do…


DR. MACKO: How do you feel about that?

CAVANAUGH: I was – Yeah, I was going to ask him, how long have you been a vegan?

SPURR: Since about May. I was pescetarian before that. But I – I don’t know, Doctor, is May far back enough that that would skew…

DR. MACKO: Well, what it would be – so this is – you sent me a sample and I’m trying to remember, one, it was either you or John was very stingy with your hair sample.

CAVANAUGH: It would be John Decker, our program director.

DR. MACKO: Okay, and so I did not look much down the length of the hair but in order to pick up where you were – so by test – you were eating – still eating fish? Ocean fish?

SPURR: Yeah.

DR. MACKO: Okay, and so we would’ve been able to pick up your change in diet if you had sent me samples that were probably two to three inches long and so I don’t think you sent me samples that were that long.

SPURR: Right.

CAVANAUGH: Now let me ask you, Doctor, you gave, you know, about the nitrogen level and so forth, is – and do we know anything about whether that’s good or bad or that it predicts a future good health?

DR. MACKO: That – I don’t think that would be the purpose of – for the kinds of analyses that I was doing. Now if we were to have outside studies that would relate it to nutritionists – and so this is a field that’s still pretty much in its infancy and, as I said, we were aiming more at the anthropological uses. But there’s potential that we’d be able to say, well, given this combination, you might have a bit more healthy diet if you – you know, but if you ate a little bit less meat or something like that.


DR. MACKO: But where we’ve been looking at is this corn influence because that’s ubiquitous on American society and there’s a lot of corn influence that comes from, I said, the meats and everything but there’s a lot of corn influence also that’s coming from unknown – like you wouldn’t think of them as sources, like ketchup or mayonnaise or any – pretty much – almost all the foods that we eat have some kind of corn related to them.

CAVANAUGH: I want to ask you a little bit more about this ubiquitous corn in our diets now but besides the corn, the content of corn and corn products, when you test hair from the past, you’ve tested hair from George Washington, from Edgar Allan Poe, from the Iceman, what have you picked up about how people’s diets have changed?

DR. MACKO: Well, there’s some of the curious ones. If you go back really far to some of the mummies we’ve had from Peru, there were some surprising instances that there were people that lived right on the coast. You’d think, you know, they had all the fish that they could possibly want and there were the – I would call them the more aristocracy of that period, they had – they were eating much in the way of terrestrial, animals, they were also eating corn or corn related plants and so, you know, that was kind of a surprise that, you know, why would these people not be eating fish? And although other people in the same area today that live, you know, pretty much in the same potential diet – they live pretty much off the ocean. And so, you know, that’s the kind of thing that we can pick out.

CAVANAUGH: It is odd. Now, well, let’s say these earlier Americans, George Washington and Edgar Allan Poe, can they tell us anything about the early American diet?

DR. MACKO: Well, the story I tell with George Washington, I was working with a museum in Richmond, it was called the Wilton House Museum, and they wanted to have some sort of display on the anniversary of Washington’s death and so they gave me a small sample of hair and when I analyzed it, it came out and like who do you compare George Washington to, right? There’s not a lot of other people that you’d have samples of hair from that time period. And so I ended up comparing it with other Virginians that I had collected over the time and most of those were my students and other students that were taking my classes.

CAVANAUGH: You’re from the University of Virginia, yeah.

DR. MACKO: And so at the University of Virginia. And so we put him on this chart of this – all these different diets and that included vegans and vegetarians and people that ate fish and I had one UVA baseball player who was – his reputation was he ate hamburgers three meals a day. And George Washington came out right in the middle of all of them, and the Wilton House Museum people wanted the – you know, an interpretation of that and I said, well, you know, if you think about it that George Washington, he wasn’t a vegan, he didn’t – he wasn’t a top carnivore and he didn’t eat just the corn fed products or he also didn’t eat just wheat and beans. He was kind of in the middle. And they said, yes, and can you tell us what that means? And I said, well, think of it this way, he was a centrist, the perfect Father of the country.

CAVANAUGH: And Edgar Allan Poe. Can drug abuse be told out of a hair sample all this time?

DR. MACKO: We were looking for some story like that. I was working with a pediatrician who was a member of the Poe Society and so there were samples of Poe’s hair around. And he wanted to know if – at the time that Poe lived, they made gas in the city of – natural gas from coal so – and the coal gas was – it’s a terrible smelling thing and he thought, well, maybe that was an influence on Poe’s writing style. And I said – I told him that given that chemical composition, it would get into his hair as a coating and we would be able to suggest whether the coal gas was important. And what happened was I said I needed a control and the control for the time period actually was Virginia Poe, Edgar Allan Poe’s spouse, who never had lived in that time period. She had – she died of tuberculosis in upstate New York but presumably had about the same kinds of diet as Edgar did. And so I analyzed them both and they came out to be nearly identical, and so we came to the conclusion that Edgar was a natural. He didn’t need the coal gas.

CAVANAUGH: Okay. I’m speaking with Dr. Stephen Macko. He’s Professor of Environmental Sciences at the University of Virginia. We’re talking about some tests he ran on some hair samples given by several KPBS staffers including our investigative reporter Amita Sharma and Joe Spurr, KPBS web developer. I want to talk, if I may, Dr. Macko, a little bit about the ubiquity of corn based products. Why has that happened?

DR. MACKO: Well, it – there’s a long history of American agriculture and with the advent of the ability to raise corn with great intensity and there’s also corn subsidies from the federal government, you know, we’ve now become the greatest corn producer on the planet. And so with all of this corn – and I refer to – there’s a wonderful film out that’s called “King Corn,” K-i-n-g C-o-r-n…


DR. MACKO: …and it goes through some of the I guess they’re results of us producing so much corn, and that documents it far better than I could over this short period. But because of all this corn, we’ve now developed industries that include the animal – raising animals inexpensively on this excess of corn but I say inexpensively but that is actually qualified because what – the expense you don’t see are the farm subsidies that go into raising that. So it’s our tax dollars that are paying for raising all this corn which goes into the animal food. Corn itself is not a great food by itself. Corn has – doesn’t have enough lysine in it, one of the important amino acids and so – and we raise the animals really fast and so we have to give them supplements of vitamins and antibiotics in order to keep them healthy enough so that they will survive to the slaughterhouse. And so the animals are this – now this signal of corn. We’ve developed an industry of taking corn and turning it into high fructose corn syrup and that’s finding its way in pretty much all foods. If you look at the sweetened orange juices and apple juices that we have, those all have corn syrup added to it, the high fructose corn syrup. And there’s some evidence that the rise in obesity in the United States and the rise of Type II diabetes has been correlated with this rise in the ubiquitous use of high fructose corn syrup in all of our food.

SHARMA: Dr. Macko, this is Amita. I’ve got a question for you. I’m curious. Because corn syrup is in ketchup and candy and bread and Tater Tots, have you tested the hair of children and are you finding that their hair has higher levels of corn in it than adults’, if so?

DR. MACKO: I think their consumption of corns in the form of all these high fructose corn syrups is probably not – is not going to be any greater. I have run some children. In fact, I have just kind of, must to my wife’s chagrin, I ran the first baby curls of my own kids and…

CAVANAUGH: That was predictable.

DR. MACKO: …and the babies – Well, I’m the barber and the tooth fairy in my house, so – but what happens is that when children are born, they’re often born with hair and they are, in essence and my wife won’t like to hear this but parasitic actually that they’re living off the mother and so they end up being a trophic level higher than the mother and so the hair changes from a baby. Well, as they start to pick up all of the Tater Tots and the, you know, Sugar Pops and all the corn foods that they might be eating, their signal changes but not to anything that I’ve seen greater than a lot of Americans. There was one other reporter that I interviewed and I ran her hair and she came out to be like 85% corn.


SHARMA: Wow, what was she eating?

DR. MACKO: Well, the rumor was that she was just like my student, a top carnivore, a lot of beef products all the time.

CAVANAUGH: And the beef…

DR. MACKO: Yeah.

CAVANAUGH: …eats the corn.

DR. MACKO: Yeah.

CAVANAUGH: Joe, I’m wondering, were you surprised that the results of your vegan diet, because you’ve only been a vegan since May, showed up so quickly?

SPURR: I wasn’t sure what to expect really. I guess for that amount of time, that makes sense. It’s still kind of striking that you can get all this information out of a strand of hair but not particularly.


CAVANAUGH: And I – Yes, go ahead, Doctor.

DR. MACKO: …it takes about seven days for your body to start showing any kind of change at all.

CAVANAUGH: Really? Just seven days.

SHARMA: Seven days.

DR. MACKO: Yeah, there’s been a lot of research that’s been done on hair. I think probably the driver is male pattern baldness but what happens is that as you start to consume something that’s completely different, that signal starts taking over your body in seven days or so and it does – but there are some residuals that – The guys who did the movie “King Corn” went on a corn free diet for the month of November and they dropped down substantially. They thought they were on a corn free diet but then they realized how much corn there was. They did it during the month of November, which is Thanksgiving and so you couldn’t get the corn fed turkeys and…


DR. MACKO: …and you couldn’t eat potato chips that have been fried in corn oils and you couldn’t eat the cookies that had high fructose corn syrup in it. It was kind of amazing when you start reading the labels.

SPURR: Yeah.

DR. MACKO: And also corn gluten’s in a lot of things so it’s, you know, you have to be really careful in what you – if you – as you read the labels. In fact, my cat food even has corn in it.

SHARMA: Oh, my gosh.

CAVANAUGH: Oh, gosh.

SPURR: It is amazing. I do read the labels a lot more closely now. It’s amazing what you can see in there.

CAVANAUGH: I think we’ve run out of time but I want to thank my guests so much. Dr. Stephen Macko is Professor of Environmental Sciences, University of Virginia, and he tested the hair of these KPBS employees. Thank you, Dr. Macko.

DR. MACKO: It’s been a pleasure.

CAVANAUGH: And the testees, KPBS Investigative Reporter, Amita Sharma, and Joe Spurr, KPBS Web Developer. Thanks for speaking with us this morning.

SHARMA: It’s good to be here.

SPURR: Thanks.

CAVANAUGH: Listen for more KPBS team coverage about the food we eat. You can see all the reports from the series at and our TV special Envision San Diego “Food” airs November 16th at 9:00 p.m. You’re listening to These Days on KPBS.