Is your black cat rusty red? Tyrosine deficient diet?

In the unlikely event that your black cat has turned a rusty red in normal lighting conditions, there is a possible cure: change his food. Food can alter the appearance of a cat, specifically the colour of his coat. You may have heard of this. It is an interesting topic but, if I am being honest, not of great value to cat caregivers because I believe that a rusty coloured black cat because of a lack of tyrosine is probably rare. I don’t believe that

Picture of Black Cat Fur (that is brown)

Many foods such as fish contain a ingredient called tyrosine. It is an “amino acid” but I won’t dwell on the technical stuff. I am sure it is added to commercially prepared cat food.

Tyrosine (more accurately called “l-tyrosine”) is needed for the creation of the colour in a cat’s fur. The blobs of colour – pigment – in the hair strands are made (“synthethised”) from tyrosine. There are two types of pigment in the hair strands of a cat: eumelanin and pheomelanin. Eumelanin is brown/black and pheomelanin is yellow/reddish brown. They are collectively referred to as “melanin”. The amount of melanin in the fur determines coat color.

Rusty Black Cat
Rusty Black Cat. Ziggy a black and white cat with rusty black fur. Photo: Julie.

An inadequate amount of tyrosine in the cat’s diet results in an incomplete amount of melanin deposited inside the hair fibres. It appears that this relates to the eumelanin component leaving the pheomelanin to show its color of reddish brown. Or perhaps the pigment is thinly spread through the hair turning brown/black to yellow/reddish brown.

It is interesting to note that the amount of tyrosine required to ensure a full amount of melanin in the fur is greater than the amount needed for a kitten to grow normally (as I understand this tricky subject). That would imply that black hair might normally be rusty coloured. In fact, this seems to be true because black cats look rusty red when backlit – the light shines through the hair strands (see picture).

So, in conclusion, if your black cat has turned rusty coloured just make sure he has a supplement of tyrosine. That is a simplified conclusion and don’t do anything without talking to your vet first, please. There are other potential causes of colour change.

Incidentally, tyrosine supplements for people can be bought over the counter. It is used to treat mental health conditions such as chronic fatigue syndrome and attention deficit disorders.

Interesting fact: the pattern in a cat’s coat is mirrored in the skin but I believe that this is at least partly because of the fine down hairs which are barely visible. However, polar bears have pigment-free hairs but black skin. Melanism is the effect of a patterned cat (usually brown tabby) turning black with a ghost pattern due to a genetic mutation.

Note: the information for the article comes from the Journal of Nutrition.

There are several studies on the internet on this topic one of which is headed: amino acid tyrosine. They conclude: “Reddish hair coat was induced in black kittens born to queens given a tyrosine-deficient diet during pregnancy. Black hair colour was maintained or restored by diets containing a high concentration of tyrosine or phenylalanine.” Tyrosine is one of the 20 standard amino acids that are used by cells to synthesize proteins.

Another study on tyrosine concerns humans. It’s role in the creation of melanin is the same in humans. The scientists concluded that: “Results from studies with human melanocyte cultures derived from different racial skin types reveal an excellent correlation between the melanin content of melanocyte cultures and the in-situ activity of tyrosinase.” The study is titled: Role of tyrosinase as the determinant of pigmentation in cultured human melanocytes.

Are the any other health issues due tyrosine deficiency? Apparently it might cause hyperthyroidism which is caused by low thyroid home.

The cure is to provide a high-quality balanced diet. Treats high in tyrosine are lean pork chops, chicken breast and salmon. Pumpkin seeds are rich in tyrosine containing 1079 milligrams of amino acid per 100 grams of pumpkin seeds according to my research.

What is eumelanin in cats?

Cat hair pigmentation types (fully illustrated)

44 thoughts on “Is your black cat rusty red? Tyrosine deficient diet?”

  1. That is very interesting, I have a 16 week old kitten. A foundling that had a bad diet from around 4-6 weeks when I found it. Its black coat is going a rusty red. He’s off to the vet to get neutered so I will ask her about this. He does look beautiful and appears in good health and happy. I’m vegan so they (he is one of 6 and the only one going red) get cat biscuits, water and occupational cat food in tins as a treat. They do catch mice, birds etc the only thing strange about him is that he catches earth worms and brings them in to eat – disgusting I know.

  2. Michael,

    Look at this. I was combing my fingers through his fur on his head because it, too, seems to be thinning – due to probable Cushing’s) but look what I found:

    • Michael, annoyingly your photo is too large. You can reduce it and try again. Please click on the link below the comment box to see how to reduce the size. It won’t take long.

  3. Michael,
    Alas the ultrasound, which around here, means ultra-drama. Suffice to say, this guy has some things going on which I’m happy to tell you about offline, if your quest for knowledge makes you curious. But, that’s up to you. As for the experiment, I’d suggest others try the Tyrosine, with the blessing of their vet, of course. We do see black hair coming in but his illness probably is impeding the results and pace of growth that an otherwise healthy cat would produce. Might even stop giving it to him because well… he has other priorities. Thank you so very much for all your research and interest. We all love our kitties and hate to see things go wrong or off track. It’s great when we can share information. Thank you, again!

    • Julie, I am sorry to hear that. You’ve been a great contributor. I’d like you to tell me what happened. It will be confidential. You can click on the envelope in the RH navbar below FB or email me at:

      mjbmeister [at]

      Change [at] to @


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