What we eat can influence more than our waistlines. It turns out, our diets also help determine what we smell like.
A recent study found that women preferred the body odor of men who ate a lot of fruits and vegetables, whereas men who ate a lot of refined carbohydrates (think bread, pasta) gave off a smell that was less appealing.
Skeptical? At first, I was, too. I thought this line of inquiry must have been dreamed up by the produce industry. (Makes a good marketing campaign, right?)
But it's legit. "We've known for a while that odor is an important component of attractiveness, especially for women," says Ian Stephen of Macquarie University in Australia. He studies evolution, genetics and psychology and is an author of the study.
From an evolutionary perspective, scientists say our sweat can help signal our health status and could possibly play a role in helping to attract a mate.
How did scientists evaluate the link between diet and the attractiveness of body odor?
They began by recruiting a bunch of healthy, young men. They assessed the men's skin using an instrument called a spectrophotometer. When people eat a lot of colorful veggies, their skin takes on the hue of carotenoids, the plant pigments that are responsible for bright red, yellow and orange foods.
"The carotenoids get deposited in our skin," explains Stephen. The spectrophotometer "flashes a light onto your skin and measures the color reflected back," says Stephen. The results are "a good indicator of how much fruits and vegetables we're eating," he says.
Stephen and his colleagues also had the men in the study complete food frequency questionnaires so they could determine the men's overall patterns of eating. Then the men were given clean T-shirts and asked to do some exercise.
Afterward, women in the study were asked to sniff the sweat. (Note: The methodology was much more scientific and precise than my breezy explanation, but you get the picture.) "We asked the women to rate how much they liked it, how floral, how fruity," and a bunch of other descriptors, explains Stephen.
It's a small study, but the results were pretty consistent. "Women basically found that men who ate more vegetables smelled nicer," Stephen told us.
Men who ate a lot of meat did not produce a sweat that was any more — or less — attractive to women. But meat did tend to make men's odor more intense.
"This is not the first study to show that diet influences body odor," says George Preti, an adjunct professor in the dermatology department at the University of Pennsylvania and a member of the Monell Chemical Senses Center in Philadelphia.
A study published in 2006 found that women preferred the odor of men who ate a non-meat diet, "characterized by increased intakes of eggs, cheese, soy, fruit and vegetables."
But Preti points out that the relationship between diet and body odor is indirect.
Some people think if they eat a garlic or onion — or a piece of meat — they will smell like that food. "But that's not what happens," Preti says. Your breath might smell like the food you eat, but not your sweat.
Body odor is created when the bacteria on our skin metabolize the compounds that come out of our sweat glands.
"The sweat doesn't come out smelly," Preti explains. "It must be metabolized by the bacteria that live on the surface of the skin."
Now, of course, at a time when good hygiene and deodorant use are commonplace, is the smell of our sweat a big concern?
I put that question to the happy hour crowd at a bar down the street from the NPR headquarters in Washington, D.C.
"I'm pretty OK with my smell," Stefan Ruffini told me. That evening he was ordering a burger on a bun and a side of fries, along with a beer. When I told him about the findings of the study, he laughed it off.
"I've got a girlfriend, so I don't worry about these things," he said.
The study did not assess diet and odor attractiveness among same-sex couples.
"As a lesbian, I haven't smelled a man in several years," Stacy Carroll, who was also at happy hour, told me. "I eat a lot of produce, I have a girlfriend, so it's working out."
Carroll says people who eat a lot of fruits and vegetables are more likely to be interested in their health — "feeling good, looking fit" — than their smell.
RACHEL MARTIN, HOST:
What we can eat can influence more than our waistlines. It turns out, our diets also help determine what we smell like. Evolutionary scientists wondered whether this might play a role in attracting a mate. And as NPR's Allison Aubrey reports, a recent study finds that women prefer the body odor of men who eat a certain diet.
ALLISON AUBREY, BYLINE: Sometimes a study finding makes for good cocktail-party banter. So a few evenings ago, I ducked out of the newsroom, wandered down to a happy hour just a few blocks from the NPR building here. I was in search of guys who were willing to talk to me about their diets, their sweat and their dating status.
So you guys are willing to talk to me for my story?
STEFAN RUFFINI: Sure.
JACK NEWMAN: Sure.
AUBREY: OK. I met up with Stefan Ruffini and Jack Newman. They're friends. They work together. But when it comes to food, they have very different habits. Newman says he goes heavy on the greens.
NEWMAN: Always a salad with cucumbers, tomatoes, extra lettuce, romaine, kale, all the mixtures.
AUBREY: His buddy Stefan Ruffini tends to go heavy on the carbs. Tonight, it's a beer, a burger on a bun and...
RUFFINI: Definitely some fries with it. Yeah, that's the way to do it.
AUBREY: Now, according to the new study, one of these guys diets creates a body odor that women find more attractive.
Have you ever thought about how your diet might influence how you smell?
NEWMAN: No, never. Never, no, it's all about how I feel, not how I smell.
AUBREY: But all those leafy greens that Newman eats could also be making him smell good to the opposite sex.
NEWMAN: That's surprising.
AUBREY: So how did researchers nail this down?
IAN STEPHEN: We've known for a while that odor is an important components of attractiveness, especially for women.
AUBREY: That's researcher Ian Stephen of Macquarie University in Sydney, Australia. He recruited a bunch of healthy, young men and tracked their diets. He also gave them clean T-shirts and instructed them to exercise. Afterwards, a group of women were asked to sniff the sweat on the T-shirts.
STEPHEN: We asked them to rate how much they liked it, how attractive they thought it smelt, how floral, how fruity.
AUBREY: Neither the researchers nor the women knew beforehand who had eaten what. But the results were very consistent.
STEPHEN: Women basically found that men who ate more vegetables smelled nicer.
AUBREY: But men who ate a lot of carbs produced an odor that women did not like. Back at the happy hour, carb-lover Stefan Ruffini wasn't too upset.
RUFFINI: I'm definitely pretty OK with my smell right now I think, you know. I have a girlfriend. So I don't generally worry about these type of things.
AUBREY: There was another surprise from the study, too. Some researchers thought that meat might make men's sweat more appealing. From an evolutionary perspective, men who hunted were perceived to be good providers. But in this study, a meaty diet didn't make men smell any more or any less attractive. Turns out that the way food influences the way we smell is very indirect.
GEORGE PRETI: A lot of people walk around thinking that because I ate a lot of onions and garlic, my sweat smells like onions and garlic. And that's not really what happens.
AUBREY: That's scientist George Preti of the Monell Chemical Senses Center in Philadelphia. He says our body odor is created when the bacteria on our skin metabolize the compounds that come out of our sweat glands.
PRETI: The sweat doesn't come out smelly already. It has to be metabolized by the bacteria.
AUBREY: So it's pretty complex. But given what we eat may make us smell more or less attractive, maybe that's another reason to think more carefully about our diets. Allison Aubrey, NPR News. Transcript provided by NPR, Copyright NPR.