My understanding is you can test positive for opiates by eating a poppy-seed bagel.
When I was in flight school, the hangar had a lunch bar in one of the rooms on the hangar deck. They served the best sandwich that had a poppy-seed bun. That was, until students popped on the urinalysis that we had monthly. No more poppy-seed bun sandwiches.
Man those sandwiches were good...
I used to handle the initial drug screening for a small service sector company. This was late 90’s - early 2000’s, so things may have changed a bit, but the way it was explained to me when I would talk to our lab, it went something like this:
The basic tests - urine, hair follicle, saliva - can test positive for a particular drug due to consumption of a non-illegal drug substance or a particular medical condition. Consuming enough poppy seeds can probably make you test positive for opiates, just as amoxicilin or diabetes can, in a few cases, test false positive for cocaine use. Such things are rare, but they do happen once in a while. That’s why we also called/considered these tests as “presumptive”.
Whenever we had an applicant test positive on the presumptive test, we had the lab do a follow-up test with a GCMS (gas chromatograph, mass spectrometer). These tests look at the substance at the molecular level, and can distinguish between the opioid-like compounds in poppy seeds and say, heroin. These tests are more expensive, but done properly, there’s no fooling them.
You won’t get high from eating poppy seeds, not even a lot of them - there is poppy seed filling for pastries and you could eat several ounces of it and not get high.
And poppy seeds are expensive, compared to wheat or rice, so you couldn’t put a lot them in your noodle dough and make a profit.