Turns out pregnant women aren't the only ones who eat dirt. A new study reveals a surprising incidence of pica—craving and consuming nonfood substances—among men.
Conducted in Madagascar, where pica is common, the research is the first to identify a population where the practice is highly prevalent among men, the scientists say. In fact, the men in the study ate nonfood items at least as much as pregnant women and adolescents, whom previous case studies had shown to be the main pica practitioners.
So why this sudden appearance of pica-practicing men?
"My guess, which is not substantiated, is that prior research study designs may have ignored men in their study samples as an artifact of studying pregnant women," said study author Christopher Golden, an eco-epidemiologist and National Geographic Society Conservation Trust grantee. (National Geographic News is part of the Society.)
Pica researcher Laura Beatriz López, nutrition director at the University of Buenos Aires, agreed.
"Traditionally studies of geophagy [eating earth] and pica have focused on describing the prevalence in children and pregnant women," López wrote in an email, which has been translated from Spanish.
"Personally, I think the work is pioneering," she said, because it reveals "such a high prevalence of pica in men and also found no significant differences with women."
Pica for Better Health?
Golden and colleagues—advised by Cornell nutritional anthropologist Sera Young—surveyed pica behaviors in a random sample of 760 people in 16 villages of Madagascar's Makira Protected Area in 2009. (See Madagascar pictures from National Geographic magazine.)
The study subjects—male and female—identified eating 13 nonfood substances, including sand, soil, chicken feces, uncooked rice, raw cassava root, charcoal, salt, and ash, according to the new report, which appeared Wednesday in the journal PLOS ONE.
More than 53 percent of the survey respondents reported engaging in pica. For adult men alone, that number was 63 percent.
Bucking the stereotype, less than one percent of nonpregnant women said they ate any nonfoods only during pregnancy.
Why Eat Dirt, Chalk, or Uncooked Rice?
Many people reported eating nonfoods for their healing powers, especially for stomach troubles, Golden said. And many believed that pica would bring good luck for better overall health. (Explore an interactive of the human body.)
Previously, scientists had suggested people practice pica for two reasons: to fulfill a deficiency of trace minerals in their diet and to cleanse and deworm the intestinal tract.
The nutrition theory would make sense for pregnant women and children, whose dietary needs are greater those of the rest of the population.
Even so, there's no evidence that the human body can actually absorb trace minerals from soil, said Golden, adding that pica "may not serve any health purpose."
The University of Buenos Aires's López added that the cultural norms of Madagascar contribute to the high rate of eating inedible substances. For instance, many Malagasy don't consider eating raw starches, such as uncooked rice, to be a form of pica.
(See video: "Clay Eating Discouraged.")
Eating Inedibles Stigmatized, Underreported
Pica, study co-author Golden emphasized, "is not exclusive to rural populations in developing countries."
For example, many Americans do it, Golden said, and he speaks from experience. "A close college friend of mine," he said, "is a frequent consumer of chalk.
"It is very prevalent, yet stigmatized, and thus underreported."
Added Cleveland Clinic psychologist Susan Albers by email: "Pica is an eating disorder that gets far less attention and research than other eating disorders such as anorexia and bulimia, yet it is important, as it can lead to significant health consequences, due to the possibility of consuming toxic substances.
"We've seen more attention on men and eating disorders over the last few years," Albers said. "This study notes the importance of further research on men and pica and making sure they are adequately represented in the sample."
Study co-author Golden said he isn't quite ready to label pica an eating disorder, since it's not yet clear whether the practice is harmful. But he agreed that more pica research is needed, especially among men.
The new Madagascar study may be a big step in that direction. To Golden, the discovery "opens up this whole field of research, to have fellow researchers acknowledge both men and women in their studies."