Elsie Campbell's love of salad became more than a healthy habit when she started eating three or four heads of iceberg lettuce each day for several months.
"After work, I'd go straight to the fridge and cut a wedge out of the lettuce and just eat it right there," said Campbell, 59, of Derby, England. "It was bizarre."
Around the same time in 2002, Campbell noticed a small dimple on her breast. After visiting the doctor and waiting for her diagnosis, Campbell's husband Jim, a forensic scientist, began researching natural compounds in lettuce.
"Jim thought there had to be some reason for eating all that lettuce," said Campbell. "He thought it was very strange."
He found that sulforaphane, a natural compound found in leafy greens, exhibits anticancer traits.
Doctors diagnosed Elsie with early stage breast cancer. It made sense to Jim—he believed his wife's body was craving the leafy greens to fight off the cancerous cells.
But before lettuce lovers make an oncology appointment, experts contacted by ABC News were quick to note that hard science is not available to back up the Campbells' theory.
"I have never heard of cravings as a signal for cancer and cannot think of a reason that they would be, outside of old-fashioned things like iron deficiency from chronic blood loss, most often seen with colorectal cancer," said Dr. Lisa Carey, medical director at the University of North Carolina Breast Center.
Carey said some scientific evidence shows that people who are iron deficient are more likely to compulsively chomp on ice cubes or show other signs of pica, a condition that causes people to eat non-food substances such as dirt, chalk and paper.
"Ironically, these items have no iron," said Keith Ayoob, associate professor of pediatrics at Albert Einstein College of Medicine in Bronx, N.Y. "If I get a report of any of these cravings, I recommend a workup for iron-deficiency anemia, and that's usually what it is."
Certain cravings, particularly those of non-food materials, can also be signs of mental illness, extreme diet restrictions or malnourishment.
"Studies have looked at food cravings, but most indicate a learned behavior that, over time, develops into a response pattern," said Connie Diekman, director of University Nutrition at Washington University in St. Louis. "While some studies do show changes in brain chemicals similar to what is seen with drugs, the question is if the chemicals trigger the craving or if the learned connection with food and the desired response triggers the chemicals."
Food cravings are often associated with pregnancy, but experts say even those cravings are not based on what the woman's body actually needs.
"There's no question that different physiological states can alter cravings, and in some ways those changes can be informative," said Dr. David Katz, founder of the Yale Prevention Center. "The best example of when a change in appetite is helpful is during the first trimester of pregnancy, but in my experience, people don't reliably crave foods they actually need."
While they may not be indicative of a disease or illness, uncontrollable cravings, particularly those out-of-character for the person, do deserve attention, experts said.
"Cravings that result in consumption of large quantities of food, an inability to control the amount of food consumed and certainly intake of non-food items should all be times to talk with your doctor," said Diekman.
But don't tell Elsie, who has been cancer-free for eight years, that there's no legitimacy behind her claim.
"After my lumpectomy, the craving was gone," said Elsie. "I have no particular interest in lettuce anymore."