Trimethylaminuria (TMAU)

What is Trimetylaminuria?

Trimethylaminuria is characterized by a fishy odour resembling that of rotten or decaying fish that results from excess excretion of trimethylamine.

No physical symptoms are associated with trimethylaminuria. Affected individuals appear normal and healthy; however, the unpleasant odour often results in social and psychological problems. Symptoms are usually present from birth and may worsen during puberty. In females, symptoms are more severe just before and during menstruation, after taking oral contraceptives, and around the time of menopause.

What causes Trimethylaminuria?

The odour associated with trimethylaminuria is caused when trimethylamine is released through the affected person's sweat, breath or urine. Normally, the enzyme flavin-containing monooxygenase 3 (FMO3) transforms trimethylamine into a compound (trimethylamine-N-oxide) that has no odour. However people with trimethylaminuria have an impaired version of FMO3.

People are usually born with trimethylaminuria; they inherited a faulty gene for FMO3 from one of their parents. However, environmental factors, such as large doses of the dietary supplement L-carnitine, and liver or kidney disease, may also play a role. Which types of bacteria are living in the gut also influences how the disorder is manifested. Some researchers believe that some types of bacteria might produce more trimethylamine than others, thus increasing symptoms. The severest cases, manifested by individuals with FMO3 mutations are generally present from birth.

Treatment of symptoms

Currently, there is no cure and treatment options are limited. Although there is no perfect cure for trimethylaminuria, it is possible for some people with this condition to live relatively normal, healthy lives without the fear of being shunned because of their unpleasant odour. Getting tested is an important first step. Ways of reducing the odour include:

  • Dietary restrictions (See below).
  • Taking low doses of antibiotics to reduce the amount of bacteria in the gut. Such treatment may be useful when dietary restrictions need to be relaxed (e.g. for important social occasions), or when trimetylamine production appears to increase (e.g. during infection Avoiding foods that contain choline, nitrogen, and sulfur (See dietary, emotional upset, or stress).
  • It has been suggested that the daily intake of charcoal and/or copper chlorophyll in may be of significant use in improving the quality of life of individuals suffering from TMAU,

Also helpful are:

  • Behavioral counseling to help with depression and other psychological symptoms.
  • Genetic counseling to better understand their condition.

Dietary restrictions

Particularly in cases of mild to moderate forms of TMAU the disorder can be successfully managed by dietary restriction of precursors of trimethylamine.

One of the most important dietary sources of trimethylamine is choline. Dietary choline is absorbed through the small intestine; however, when the absorptive capacity of the small intestine is overloaded, gut bacteria metabolize choline into trimethylamine, which is readily absorbed into the bloodstream.

Choline can be found in eggs, liver, kidney, peas, beans, peanuts, Soya products and brassicas. (Brussels sprouts, broccoli, cabbage and cauliflower.).

Importantly foods such as the above contain "indoles" which can inhibit FMO3 enzyme activity causing an increase of trimethyamine in the urine

Research undertaken in Japan shows that the mushroom extract "CHAMPEX" suppresses indoles in the intestines showing a clear drop in both ammonia and indole levels in the urine.

Trimethylamine-oxide is found in some marine fish (such as tuna) and so again affected individuals should avoid eating seafood.

© 2009 Direct Food Ingredients Limited.