One of the rare inherited metabolic disorders that we work with is TMAU. It is a disorder that doesn’t cause any physical harm, but causes psychological distress. Over that past few years we have had increasing number of people being referred to our service with suspected TMAU. This is mainly due to increased exposure of the disorder on popular TV programs. I thought I would give you a little insight into what it is and how it is treated.

What is TMAU?

Trimethylaminuria (TMAU) or Fish Odour Syndrome is a very distressing rare inherited metabolic disorder that causes the sufferer to smell of a variety of malodours including rotting fish, eggs and rubbish. The smell comes from their sweat, breath and urine. Although only recently discovered in the 1970’s, there has been references to it in history, for examples in Shakespeare’s The Tempest, Trinculo talks about a man who smells of a fish! It has been in the spot light more recently after being highlighted on TV programs such as Embarrassing Bodies, The Food Hospital, The One Show and This Morning.

Psychological Effects

Often the person themselves cannot smell it, but other people can, resulting in the person staying away from social situations and can become very withdrawn, lonely and depressed as they are worried about what people will say and think about them. 

Causes of TMAU

TMAU is caused by the inability of the person to break down a smelly chemical in the body called Trimethylamine (TMA) into the non-odorous form Trimethylamine oxide (TMAO). The TMA builds up in the body and is excreted via urine and sweat producing the smell.

Treatments for TMAU

There are various treatments that can be tried to try and reduced the smell. These include restricting foods high in choline (as they are converted to TMA in the gut), the use of acidic (pH 5.5-6.5) soap and body lotions to help neutralise and remove TMA from the skin. Using a short course of oral antibiotics to decrease the amount of bad bacteria in the gut that produces TMA and probiotics to change the balance of the gut flora.

Getting diagnosed

Often people have the symptoms for years before getting diagnosed. GP’s have little knowledge of this disorder as it is so rare and it is often the patient that comes up with the diagnosis and then has to persuade the GP to get them tested or to be referred to a specialist centre.Getting referred to a specialist metabolic service is very important to obtain the correct treatment and management. There is information on the internet, but is often factually incorrect or interpreted the wrong way.

Specialist Dietary advice

Many people try to follow the diet without help from a dietitian, they restrict their diet too much, leaving themselves at risk of nutritional deficiencies and weight loss. Our bodies need a minimum amount of choline per day and below this level it is harmful and liver complications can develop. Getting referred to a specialist dietitian for advice is essential so that they can help the person follow a low choline diet that provides adequate amounts of protein, carbohydrates, fats, vitamins and minerals.

Diet for TMAU

The aim of the diet is to reduce the amount of Trimethylamine (TMA) and choline (which is converted by bacteria in the gut to TMA) in the diet.

It is important to eat a wide variety of foods to ensure that the diet provides adequate amounts of essential nutrients and protein. The diet must not be too low in choline as this can lead to liver damage and nutritional deficiencies. Low levels of choline are present in many foods so it is impossible to avoid all dietary choline.

Carbohydrate foods

Most carbohydrate foods are low in choline and can be eaten with each meal as a source of energy. This includes bread, crackers, pasta, rice, potatoes, chips, non-bran cereals, oats. White, brown and whole meal varieties are all low in choline. Bran cereals are higher in choline so you may wish to avoid these.

Protein foods

Protein is needed for growth and repair so protein should be eaten with at least 2 meals per day. Sea fish and crustaceans (crabs, lobster) are high in trimethylamine so should be avoided. Offal (liver, liver pate, kidney, tripe), egg yolks and soybeans very high in choline so should also be avoided. Meat and fresh water fish are good sources of protein and nutrients, sticking to a small to medium sized portions (no bigger than your hand) will ensure the choline content is not too high. Vegetarian sources of protein are lower in choline (i.e. beans, lentils, chick peas, tofu, cheese, egg white, nuts and seeds) so aiming for a mainly vegetarian diet will lower the choline content. Eating meat / fish 2-3 times a week will provide essential nutrients such as vitamin B12, zinc and selenium. 


Dairy foods (milk, cheese, yoghurt) are a good way to increase the calcium of the diet for bone health, and they are fairly low in choline. 2-3 portions of dairy foods will not increase choline intake greatly. If drinking more milk then nut / rice / coconut milks are a low choline alternative, but need to ensure they are fortified with calcium. It is advised by the government that we get adequate vitamin D for bone health, this can be via sunlight or to take a vitamin D supplement especially in winter.

Fruit and vegetables

All fruit and vegetables are very low in choline so can be eaten without restriction. A group of vegetables called Brassica vegetables are thought to inhibit the enzyme that converts trimethylamine into a none smelly chemical in the liver. These include Brussel sprouts, cauliflower, broccoli and cabbage. This might not be the case for everyone, so check your tolerance to these vegetables.

Food additives

Lecithin, of which choline is a constituent, is a commonly used emulsifier (E322) added to such foods as ice cream, mayonnaise, chocolate and many other manufactured foods.
Some people find foods with large amounts of lecithin exacerbates symptoms so they should try to avoid it. Other people may tolerate it in small amounts therefore tolerance should be tested before avoiding all together.

Vitamins and Minerals

It is important to have a varied diet to ensure adequate intakes of vitamins and minerals. If this can’t be managed then a multivitamin and mineral supplement should be taken, always speak to your dietitian or doctor.


If you are losing weight unintentionally, then your diet may be too restrictive. Please speak with a specialist dietitian.

How long should the diet for TMAU be followed for?

The diet should be trailed for 3-6 months to see if it helps symptoms. It may not work for everyone and other treatment options can be tried. If it does not help then go back to a normal healthy diet. If the diet is helpful, then to continue and ensure it is adequate by having a review with a specialist dietitian.

The diet is only to control symptoms, so if you are having a quite weekend in then the diet can be relaxed. 

Diet Examples

Low choline diet

  • Breakfast: cereal and milk, toast x 2 with butter and jam
  • Mid am: piece of fruit
  • Lunch: cheese salad sandwich with 2 slices of bread, apple, yoghurt and 2 biscuits
  • Dinner: small chicken breast, mashed potato, carrots and sweetcorn, stewed fruit and cream

Very low choline diet

  • Breakfast: toast x 2 with butter and jam or cereal and rice milk (fortified with calcium)
  • Mid am: piece of fruit
  • Lunch: cheese salad sandwich with 2 slices of bread, apple, yoghurt and 2 biscuits
  • Dinner: kidney bean and vegetable casserole with rice, cake


The above is a guideline, not to replace tailored advice by a specialist dietitian. If you suspect you have TMAU then ask your GP to refer you to a specialist inherited metabolic disorders centre to check the diagnosis is correct before making changes to your diet.

Resources for article

Ellerton C, Chan H, Maritz C. Trimethylaminuria – Fish Odour Syndrome. Complete Nutrition Vol. 10, No.4, August 2010.

Busby M, Fischer L, Da Costa K, Thompson D, Mar M, Zeisel S. Choline- and Betaine- Defined diets for use in clinical research and for the management of Trimethylaminuria. Journal of American Dietetic Association. 2004. Vol 104, 1836-1845.