There are many risks to eating a lot of it. As with most things, because a little is good, does not mean a lot is better.
It can cause gastrointestinal (GI) side effects such as bloating, gas, abdominal pain, constipation, diarrhea, stomachache, and nausea. Higher doses are likely to cause more GI side effects.
There is some concern that taking large amounts of flaxseed could block the intestines due to the bulk-forming laxative effects of flaxseed. Flaxseed should be taken with plenty of water to prevent this from happening.
Partially defatted flaxseed might raise triglyceride levels.
Don’t eat raw or unripe flaxseed. Flaxseed in these forms is thought to be poisonous.
Flaxseed can act like the hormone estrogen. Some healthcare providers worry that this might harm the pregnancy, although to date there is no reliable clinical evidence about the effects of flaxseed on pregnancy outcomes. The effect of flaxseed on breast-fed infants is unknown at this time. Stay on the safe side, and don’t use flaxseed if you are pregnant or breast-feeding.
Flaxseed can slow blood clotting. This raises the concern that it could increase the risk of bleeding in people with bleeding disorders.
There is a concern that blood sugar could drop too low,especially for those with diabetes that take other medications to lower blood sugar.
Gastrointestinal (GI) obstruction: People with a bowel obstruction, a narrowed esophagus (the tube between the throat and the stomach), or an inflamed (swollen) intestine should avoid flaxseed. The high fiber content of flaxseed might make the obstruction worse.
Because flaxseed acts somewhat like the hormone estrogen, there is some concern that flaxseed might make hormone-sensitive conditions worse. Some of these conditions include breast, uterine, and ovarian cancer; endometriosis; and uterine fibroids. Until more is known, avoid excessive use of flaxseed if you have a hormone-sensitive condition.
High triglycerides: Partially defatted flaxseed (flaxseed with less alpha linolenic acid content) might increase triglyceride levels. If your triglyceride levels are too high, don’t take flaxseed.