Have you ever had an usual food craving? One that lasted for months? If the answer’s “yes,” then beware. Some scientists say it could be a sign that you’re suffering from anything from cancer to mental illness.

For example, one woman we read about started craving salads out of the blue. She’d devour 4 heads of lettuce a day just to get her fix. This went on for months until she researched leafy greens, and discovered they’re packed with cancer-fighting properties. She immediately went to a doctor and was diagnosed with early stage breast cancer. She’s since made a full recovery, and credits her body for clueing her in early enough to save her life. 

And a lot of scientists agree with her, saying that your body can physically warn you if something’s up. For example, surveys show that a lot of people who suffer from bipolar disorder suddenly had a huge appetite for carbohydrates, like potatoes, right before they were diagnosed. That’s because carbs help regulate your serotinin levels, the feel-good hormone that’s out of whack in people with mental disorders.

But you may not want to race to call your doctor just because you’ve been scarfing down onion rings. Most people simply crave certain foods because they taste good. The dividing line is this: if you have any type of unusual craving that lasts for a couple months, see a doctor. It could be nothing.  It could also be a sign of malnourishment. Or in rare cases – it could be cancer.