https://www.livestrong.com/article/480939-can-ground-flaxseed-cause-obstructed-bowels/
What is Flaxseed?
Flaxseeds are tiny, dark seeds that are around the size of a sesame seed. You can often find them whole in multigrain breads or in certain cereals. Flaxseeds can be purchased whole or ground, and are also available as over-the-counter dietary supplements. Because you can purchase them without a prescription, flaxseeds are a popular natural source of dietary fiber. According to Medline Plus, this is their most common reported use. However, like any supplement ground flaxseeds can cause unpleasant side effects, including severe constipation.