When taken at reasonable doses, flaxseed oil
is unlikely to cause side effects. For most people, any side effects that occur are usually just bothersome. However, flaxseed
oil can theoretically cause serious side effects as well, especially at high doses.
(This article covers many, but not all, of the possible side effects with flaxseed oil. Your healthcare provider can discuss a more complete list of side effects with you.)
Bothersome Side Effects of Flaxseed Oil
If you take more than 30 grams of flaxseed oil (about two tablespoonfuls a day), you might experience diarrhea
or loose stools.
Flaxseed oil is obtained from flaxseed, but does not cause all of the bothersome flaxseed side effects
. Flaxseeds (which have a high fiber content) often cause gas and bloating. Flaxseed oil (which does not contain fiber) is not likely to cause such side effects.
There are a few side effects with flaxseed oil that you should report to your healthcare provider and which may indicate that you should stop taking the supplement. These include but are not limited to:
- Any signs of bleeding (which may theoretically occur with high doses of flaxseed oil), such as:
- Easy bruising or cuts that do not stop bleeding
- Black, tarry stools; bright-red blood in the stool; or vomiting blood (signs of gastrointestinal bleeding)
- Signs of a hemorrhagic stroke (bleeding in the brain), such as vision or speech changes, weakness or numbness in an arm or leg, or a severe headache
- Signs of an allergic reaction, including:
- An unexplained rash
- Unexplained swelling
- Difficulty breathing or swallowing.
Flaxseed oil contains alpha-linolenic acid (ALA), and research suggests that diets high in ALA from meat and dairy may increase the risk of prostate cancer
. However, this does not seem to apply to plant-based ALA, such as that found in flaxseed oil.