What foods can cause a fishy odor?

January 8, 2026 •

5 min read

Approximately 1% of the population may have an enzyme deficiency related to the rare metabolic disorder Trimethylaminuria (TMAU), which is primarily responsible for a fishy odor after eating certain foods. This condition, also known as 'fish odor syndrome,' causes the body to improperly break down a smelly compound called trimethylamine (TMA). A wide range of foods can trigger this condition, depending on an individual's specific genetic and metabolic profile.

Quick Summary

Certain foods, particularly those high in choline and trimethylamine N-oxide, can trigger a fishy body odor in people with Trimethylaminuria (TMAU). The inability to properly metabolize trimethylamine allows the foul-smelling compound to build up in the body and be released through sweat, breath, and urine. Understanding and managing the intake of these precursor foods is key to controlling symptoms. Foods containing choline or TMA N-oxide include seafood, eggs, legumes, and brassica vegetables, but tolerance varies.

Key Points

Trimethylaminuria (TMAU) is the primary cause: A rare genetic condition causes the body's FMO3 enzyme to fail to break down trimethylamine (TMA), resulting in a fishy odor.
Seafood is a major trigger: Marine fish and shellfish contain high levels of trimethylamine N-oxide (TMAO), a precursor to TMA, and should be avoided by those with TMAU.
Eggs and legumes are rich in choline: Egg yolks, beans, peas, and soy products are high in choline, which is converted to TMA by gut bacteria.
Brassica vegetables can worsen symptoms: Foods like broccoli, cauliflower, and cabbage can inhibit the FMO3 enzyme, intensifying the odor for some with TMAU.
Management involves a low-choline diet: A specialized diet that limits foods high in TMA precursors is the main strategy for controlling symptoms.
Dietary supplements can be a problem: Lecithin and choline supplements can significantly increase TMA levels and should be avoided or used cautiously.
Medical consultation is crucial: Consulting a doctor or specialist dietitian is essential for a proper diagnosis and safe, effective management plan.

Understanding the cause of a fishy body odor

The primary reason certain foods cause a fishy odor in some individuals is a condition called Trimethylaminuria (TMAU). TMAU is a rare metabolic disorder, often hereditary, caused by a malfunction of the flavin-containing monooxygenase 3 (FMO3) enzyme. This enzyme is normally responsible for converting the strong-smelling trimethylamine (TMA) into an odorless compound. For individuals with TMAU, this process is ineffective, leading to an accumulation of TMA in the body. This chemical is then released through bodily fluids, including sweat, urine, and breath, causing the characteristic fishy smell.

While genetics play a major role, dietary habits can exacerbate the condition. The issue is not the foods themselves being inherently 'fishy,' but rather how the body processes the compounds within them. Foods high in choline, carnitine, and trimethylamine N-oxide (TMAO) are the main culprits. These compounds are broken down by gut bacteria into trimethylamine, which then overwhelms the compromised FMO3 enzyme in individuals with TMAU.

Foods that can cause a fishy odor

Many common foods, beyond just seafood, contain the precursors that can lead to a fishy odor in susceptible individuals. Being aware of these foods is the first step toward managing the condition.

Seafood and shellfish

This is the most direct cause of odor for those with TMAU. Marine fish, crustaceans (like crab and lobster), and cephalopods (like squid) naturally contain high levels of trimethylamine N-oxide (TMAO). In healthy individuals, TMAO is harmless. However, gut bacteria in all humans can convert it to TMA, and those with TMAU cannot properly process the resulting load, leading to a strong odor. Freshwater fish have lower levels of TMAO and are generally better tolerated.

Eggs and dairy

Egg yolks are a significant source of choline, a known precursor to TMA. For those with TMAU, consuming egg yolks can trigger symptoms. Similarly, some individuals find that consuming cow's milk from wheat-fed cows can cause an issue, as it may contain higher levels of TMA.

Legumes, beans, and soy products

These plant-based protein sources are rich in choline. This group includes peanuts, peas, beans, and soybeans. For individuals managing TMAU, reducing intake of these foods can help control the build-up of TMA.

Cruciferous and brassica vegetables

This category includes common vegetables like broccoli, cauliflower, cabbage, and Brussels sprouts. They contain sulfur compounds that can increase body odor in general, but specifically, some individuals with TMAU find that brassica vegetables inhibit the function of their already compromised FMO3 enzyme, intensifying the fishy odor.

Other high-choline foods

Organ meats, such as liver and kidney, are also very high in choline and should be avoided or limited by those with TMAU. Additionally, supplements containing lecithin or high doses of choline can exacerbate symptoms and should be taken with caution.

Comparison of food effects on odor


Food Category	Primary Precursor	Typical Impact on TMAU Sufferers	Effect on General Population
Marine Fish/Shellfish	Trimethylamine N-oxide (TMAO)	High impact; often a primary trigger due to very high TMAO content.	No impact; TMAO is processed into an odorless compound.
Freshwater Fish	Trimethylamine N-oxide (TMAO)	Low impact; contains much lower TMAO levels than marine fish.	No impact.
Eggs (especially yolks)	Choline	High impact; a significant source of choline converted to TMA.	No impact; enzyme activity is sufficient.
Legumes/Soy	Choline	Moderate to high impact; contains choline that can increase TMA levels.	Negligible impact.
Brassica Vegetables	Indoles	Moderate impact; can inhibit FMO3 enzyme function, worsening symptoms.	Minimal impact; may cause general sulfurous body odor or gas in some.
Red Meat	Carnitine	Variable impact; some individuals report increased odor, but less common than with choline sources.	May cause 'meat sweats' or more intense body odor due to fatty acids.

Managing fishy odor through diet

For individuals affected by TMAU, managing symptoms often involves a targeted dietary approach. It is essential to consult a specialist dietitian to ensure nutritional needs are met while limiting odor triggers. A trial period of 3 to 6 months on a low-choline diet can help determine its effectiveness.

Dietary strategies to reduce trimethylamine

Eliminate Marine Seafood: Strictly avoid all seafood derived from saltwater, including crabs, lobsters, shrimp, and most ocean fish. Freshwater fish can often be included in moderation. This is one of the most effective steps to take.
Reduce High-Choline Foods: Limit or remove egg yolks, organ meats, and specific legumes and brassicas from the diet. A vegetarian diet utilizing lower-choline protein sources like lentils and chickpeas is often beneficial.
Limit Lecithin and Choline Supplements: Be cautious with dietary supplements, as many contain high concentrations of lecithin or choline and can worsen the condition.
Utilize Probiotics: In some cases, a short course of oral antibiotics or probiotics may help modulate the gut bacteria that produce TMA. This should only be done under medical supervision.
Hydrate Adequately: Drinking plenty of water can help flush toxins and odor-causing compounds from the body.

When to seek medical advice

Experiencing a persistent fishy odor, particularly after consuming certain foods, is a strong indicator of potential TMAU. This condition can be a source of significant psychological distress, and a proper diagnosis is key to managing it effectively. Consultation with a healthcare provider can rule out other potential causes and provide access to a specialist dietitian. Genetic testing is also available to confirm a diagnosis of primary TMAU. Treatment is centered on dietary management and may involve short-term courses of specific antibiotics to alter gut flora. While there is no cure, understanding the condition and adopting a low-choline diet can significantly improve quality of life.

For more detailed information on living with Trimethylaminuria, the Metabolic Support UK website is an authoritative resource that provides comprehensive guidelines and support for individuals with metabolic conditions.

Conclusion

Certain foods can cause a fishy odor, not in everyone, but in those with the rare metabolic condition Trimethylaminuria. The key dietary culprits are foods rich in choline and trimethylamine N-oxide, such as marine fish, eggs, and specific vegetables and legumes. These foods are broken down by gut bacteria into a smelly compound called trimethylamine, which the body cannot properly metabolize in affected individuals. By understanding which foods are triggers and adopting a specialized low-choline diet, individuals can effectively manage their symptoms. Working with a healthcare professional and a specialist dietitian is crucial for a successful dietary management plan that supports overall health and well-being while minimizing the characteristic odor.

Frequently Asked Questions

Trimethylaminuria (TMAU), or 'fish odor syndrome,' is a metabolic disorder where the body cannot properly break down trimethylamine (TMA). TMA is a volatile compound with a fishy smell that then accumulates in the body and is released through sweat, breath, and urine.

Yes, some foods can cause a temporary, mild body odor due to sulfurous compounds, such as certain vegetables. However, the persistent, strong fishy odor associated with TMAU is specific to that condition and is a result of the body's inability to process trimethylamine from certain foods.

Marine fish and shellfish contain a high amount of trimethylamine N-oxide (TMAO), which is converted to TMA by gut bacteria during digestion. In people with TMAU, this TMA isn't properly metabolized, leading to a build-up and the release of a fishy smell.

Freshwater fish contain significantly lower amounts of TMAO compared to their saltwater counterparts and are therefore generally better tolerated by those with TMAU. Many individuals with the condition can consume them without issue, but individual tolerance varies.

Eggs, particularly the yolks, are rich in choline, a precursor to TMA. For individuals with TMAU, the digestion of choline can lead to an increase in TMA production by gut bacteria, which can then cause a fishy odor.

There is currently no cure for Trimethylaminuria. Treatment focuses on managing the symptoms through dietary modification, such as avoiding foods high in choline and TMAO precursors. Lifestyle adjustments, like stress management, can also help.

Yes, a low-choline diet is a primary treatment strategy for managing the fishy odor associated with TMAU. By reducing the intake of foods high in choline, such as marine fish, eggs, legumes, and certain vegetables, the production of TMA by gut bacteria is decreased.