The Reasons Fish Oil Can Cause a Fishy Odor
For many, fish oil is a staple supplement for its omega-3 fatty acids, but it can come with the unpleasant side effect of a lingering fishy scent. This odor can manifest as fishy-tasting burps, bad breath, or even a noticeable smell in sweat and urine. Several factors contribute to this phenomenon, and understanding them is the first step toward finding a solution.
- Rancid or Oxidized Oil: Fish oils are highly susceptible to oxidation, especially when exposed to light and heat. If a supplement is old, improperly stored, or of poor quality, the oil can become rancid. Rancid oil breaks down more easily and releases foul-smelling compounds that contribute to both bad taste and odor. A quick test is to break open a softgel; if it smells overwhelmingly fishy, it may be rancid.
- Poor Digestion and Fishy Burps: One of the most common reasons for fishy breath is indigestion. When a fish oil capsule dissolves in the stomach, it can trigger burping that brings the oily, fishy taste back up the throat. Taking the supplement on an empty stomach exacerbates this effect, as the oil has more time to sit and create discomfort.
- The Role of Trimethylamine (TMA): The chemical compound trimethylamine is responsible for the distinct fishy odor. In rare cases, some individuals have a genetic disorder called trimethylaminuria (TMAU), where the body is unable to properly break down TMA. For these individuals, consuming fish oil can lead to an accumulation of TMA, which is then released through sweat, breath, and urine, causing a strong, persistent fishy smell. High doses of choline, sometimes included in supplements, can also contribute to TMA production.
- Excretion Through Pores and Kidneys: As your body metabolizes and processes the omega-3 fatty acids, some of the compounds from the oil can be excreted through your sweat glands and kidneys. This can lead to a fishy-smelling sweat, which can be particularly bothersome for those who work out or perspire frequently.
Practical Steps to Prevent Fishy Smells
If you want the health benefits of fish oil without the unfortunate odor, several practical adjustments can help. Here are some strategies to consider:
- Always take your supplements with a meal. Eating fish oil with food, especially a meal containing other fats, helps improve digestion and reduces the chances of fishy burps.
- Look for enteric-coated capsules. This special coating prevents the softgel from dissolving in the stomach. Instead, it breaks down in the small intestine, where the oil is less likely to cause burping.
- Reduce your dosage. A high dosage of fish oil can overwhelm your body's digestive system. Try lowering your daily intake to see if the odor subsides. Starting with a smaller dose and gradually increasing it is a good approach.
- Store your fish oil correctly. Keep your supplements in a cool, dark place, or even in the refrigerator or freezer. Freezing capsules can also slow down their digestion, which may reduce the fishy aftertaste.
- Choose a higher-quality brand. Reputable brands use careful processing to minimize oxidation. If your current supplement smells bad, it may be time to switch.
- Consider alternatives like algae oil. Algae-based omega-3 supplements contain DHA and EPA but are completely plant-based, eliminating the risk of a fishy odor. This is an excellent option for those who are highly sensitive to fishy tastes or follow a vegan diet.
Comparison of Omega-3 Sources
| Feature | Standard Fish Oil | Enteric-Coated Fish Oil | Algae Oil (Vegan) |
|---|---|---|---|
| Fishy Odor | Prone to fishy burps and aftertaste | Significantly reduced fishy burps and aftertaste | No fishy taste or smell |
| Digestion | Capsule dissolves in the stomach, potentially causing GI issues | Capsule dissolves in the small intestine, bypassing stomach breakdown | Easily digested, often better for sensitive stomachs |
| Omega-3s | Contains EPA and DHA | Contains EPA and DHA | Contains EPA and DHA |
| Source | Oily fish (anchovies, salmon, etc.) | Oily fish with a special coating | Algae, the original source of omega-3s |
| Best For | General supplementation, not sensitive to taste | Those prone to fishy burps or indigestion | Vegans, vegetarians, or those avoiding all fishy smells |
When to See a Doctor
For most people, the fishy odor from fish oil is a minor, manageable nuisance. However, if the smell is severe, persistent, and affects your body odor, breath, and urine, you should consult a doctor. In some rare cases, it could indicate trimethylaminuria (TMAU), a genetic condition that requires medical advice. A healthcare provider can help determine if the supplement is right for you, or if there's an underlying issue.
Conclusion
While taking fish oil can, in fact, make you smell, it is not an unavoidable consequence. By choosing high-quality, fresh supplements, taking them with food, or opting for special enteric-coated capsules or algae-based alternatives, you can significantly reduce or eliminate the unpleasant odor. If the problem persists or is particularly strong, speaking with a healthcare provider is recommended to rule out other medical conditions and ensure your supplementation is appropriate for your body. The benefits of omega-3s can be achieved without the unwanted side effects, making it a manageable concern for most people.
For more information on the FMO3 gene and trimethylaminuria, consult MedlinePlus.gov
