From the Guidelines
Diarrhea associated with omega-3 supplements is primarily caused by the oil's effect on intestinal motility, irritation of the intestinal lining, and incomplete absorption of the fatty acids, leading to an increase in intestinal transit time and water draw into the intestines. The mechanism of diarrhea associated with omega-3 supplements can be attributed to several factors, including the stimulation of contractions in the digestive tract, which accelerates intestinal transit time 1. Additionally, omega-3 fatty acids, particularly docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), may irritate the intestinal lining, especially at higher doses. The body's inability to fully absorb large amounts of fish oil can also lead to unabsorbed fats in the colon, drawing water into the intestines and stimulating bowel movements. Some key points to consider when taking omega-3 supplements to minimize the risk of diarrhea include:
- Starting with a low dose (around 500-1000mg daily) and gradually increasing if needed
- Taking supplements with meals to improve absorption
- Considering enteric-coated or emulsified formulations, which may be gentler on the digestive system
- Spreading the total daily dose across multiple smaller doses rather than taking all at once If diarrhea persists despite these measures, trying a different brand or formulation may help, as the quality and content of omega-3 supplements can vary significantly 1.