What is taurine?
Also known as 2-aminoethanesulfonic acid, taurine is a sulfur-containing amino acid that was first isolated in the bile of an ox in 1827 by Austrian scientists Friedrich Tiedemann and Leopold Gmelin. Most mammals can synthesise taurine from other sulphur amino acids such as methionine and cysteine; however, while cats can manufacture some taurine, it is not in adequate amounts to meet their needs. This is due in part due to the low activity of two enzymes essential for taurine synthesis; cysteine dioxygenase and cysteine sulfinic acid decarboxylase.
Cats have a high metabolic demand for taurine because they only use taurine for bile-salt formation; other animals can conjugate bile acids with glycine in the absence of taurine. Fecal losses also occur from the incomplete recovery of bile salts by the enterohepatic circulation.
Why do cats need taurine?
Taurine is found in the highest concentrations in the heart, muscles, brain and the retina of the eye and is essential for several functions which include:
- The formation of bile salts from bile acids through conjugation (binding). Bile salts help the body absorb and digest the fats and fat-soluble vitamins that the cat has eaten
- For normal heart function, a deficiency results in dilated cardiomyopathy (DCM) due to decreased myocardial contractility
- The development and function of the photoreceptor cells in the retina where it regulates the flux of calcium and potassium ions across the photoreceptor cell pigment-epithelial cell barrier, in the absence of taurine, the photoreceptor cell membranes become dysfunctional and eventually causes the death of the cells
- Female reproduction and fetal growth
- Maintains a healthy immune system
What foods contain taurine?
Meat, especially dark meats and organ meats, as well as seafood, contain taurine.
Commercially prepared cat foods have been fortified with taurine since the late 1980s after Dr Paul D. Pion of UC Davis California who was researching blood clots in cats had asked veterinarians to refer cats with heart disease to him. What he discovered was that every cat with dilated cardiomyopathy had low taurine levels in their blood. Sixteen out of the first 21 cats had been on a diet of Hill’s Science Diet Maintenance, or Hill’s H/D and three on Purina Cat Chow.
The results were published in the mid-1980s, which led to cat food manufacturers fortifying commercial cat food with taurine.
How does taurine deficiency occur in cats?
- Taurine deficiency occurs most often in cats who are fed dog food or some homemade diets which are low in taurine rich foods.
- Loss of taurine during cooking in water. Taurine is water-soluble and will be lost if the meat is cooked in water and the water is then discarded.
- Loss of taurine during defrosting. Freezing doesn’t cause a loss of taurine, but the water leeches out of meat that is often discarded.
- Loss of taurine in the enterohepatic circulation associated with increases in bacterial flora that degrade taurine.
Always speak to your veterinarian or preferably a veterinary nutritionist if you plan to feed a home-prepared diet to ensure it contains adequate nutrients to meet your cat’s needs.
Symptoms
While the exact mechanism taurine has on these organs is still not understood, what we do know is that a diet deficient in taurine can over time lead to feline central retinal degeneration (FCRD), eventually causing irreversible blindness, dilated cardiomyopathy (DCM) and reduced fertility in female cats.
Clinical signs of taurine deficiency can take months or years to develop, by which time, permanent damage may have developed. The myocardium (heart wall) and retina contain the highest concentrations of taurine in the cat, and it stands to reason that these organs are most often affected by taurine deficiency.
Retinal degeneration:
- Decreased vision such as bumping into objects
- Night blindness
- Dilated pupils
Dilated cardiomyopathy:
- Lethargy
- Weakness
- Hypothermia
- Dehydration
- Loss of appetite
Other:
- Tooth decay
- Hair loss
- Immune function impairment
Effects on breeding females and kittens:
- Reduction in reproductive performance in females
- Low number of kittens
- Abortions and reabsorption of unborn kittens
- Birth defects
- Low birth weight
- Poor growth
Diagnosis
The veterinarian will perform a complete physical examination of your cat and obtain a medical history from you, which will include the onset of symptoms as well as the cat’s diet. Tests will be necessary to reach a diagnosis as well as evaluate the impact of the taurine deficiency on the cat’s health.
Diagnostic workup:
- Complete blood count, urinalysis, and a biochemical profile to evaluate the overall health of your cat. These tests will usually not reveal any abnormalities.
- A specialised blood test to evaluate levels of taurine in the blood.
If a taurine deficiency is diagnosed, the veterinarian will recommend additional tests to check for dilated cardiomyopathy and feline central retinal degeneration.
- Ultrasound of the heart to evaluate the muscle for signs of thickening and the ability of the heart to contract.
- Detailed eye examination to check the retina for signs of retinal degeneration and lesions on the eye.
Treatment
Feed a good-quality, premium diet with adequate levels of taurine, and in some cases, taurine supplementation will be required for the rest of the cat’s life.
Most cats who survive for more than seven days after beginning taurine supplementation will recover, and most will ultimately need no ongoing therapy; however, if taurine deficiency goes on for too long, heart failure will develop, which is irreversible.
If feline central retinal degeneration has occurred, taurine supplementation may halt the progression of the disease; however, it is not possible to reverse the damage.
Prevention
All good quality commercial brands of cat food should meet the cat’s needs for taurine; therefore, supplementation should not be necessary. Always check for an AAFCO statement on the label.
If you decide to feed a homemade diet, it must meet all of the cat’s nutritional requirements. There is no exact guide to how much taurine your cat should have per day.
Several factors at play include:
- The age of the cat
- Type of meat
- If it is cooked or raw
- How the meat is processed (ground, in chunks, or whole)
- How much fibre is in the diet (fibre reduces the absorption of taurine)
Certain processes destroy taurine:
- Cooking destroys 50-75% of taurine
- Freezing can reduce taurine levels, as the meat defrosts, some water is lost, taking taurine with it
- Mincing and grinding meat destroys taurine, cut up the meat in chunks rather than mincing
As cooking destroys 50-75% of taurine, it will be necessary to supplement if you feed a home-prepared cooked diet. There is no data to suggest excess taurine is harmful to cats; as it is water-soluble, what isn’t used by the body will be excreted via the urine. It is recommended you speak with your veterinarian before giving any supplements to your cat.
- When feeding a raw diet, including organ meats, particularly heart as this contains high levels of taurine
Taurine is water-soluble, meaning that it is lost in the water. Trying to preserve levels of taurine can help with the following:
- If you do cook your cat’s meat, try to do so in as little water as possible, and place this water in the bowl with the food.
- When feeding defrosted meat, again, save the water and add it to the food.
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