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)

Please search using the search box at the top of the site. You are bound to find what you are looking for.

Useful tag. Click to see the articles: Cat behavior

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:

    1. 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!

    1. 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 @

  4. M-
    Feel free to ask me questions and I’m happy to give you the info. I may receive after our 2/12 ultrasound. His internal med doc is well known nationally so I think we will get the best info. despite there being very few cases reported. I read 32-100 cases reported – for whatever that’s worth. Mostly, I found it is rare to very rare in male cats.

    Here’s a picture from yesterday taken in one of his bare areas. It’s hard to see fur loss but it does make it easy to see fresh re-growth. I’m going to ask why we see re-growth w/out meds. Meds for the disease can bring fur back.

  5. Hey all,

    As the definitive diagnosis for Cushing’s looms, a rare diagnosis in kitties, I’m afraid the experiment will be impeded though it will continue. Fur loss comes with the territory. Though re-growth is happening, the process might be faster for a generally healthy cat. Now, the vet(s) are thinking the reddish brown fur is a sign of Cushing’s but symptoms are missed since it is so rare.

    The clue? Recent insulin resistance.

    For the record, we do have black fur coming in …and we will continue with Tyrosine. But the cause of his reddish brown fur appears to have its basis in Cushing’s.

    1. Thanks Julie very much, I think I’ll try and do another post on this subject using this information. I’ll do some more work on this.

  6. Hi everyone!

    Quick update: I had mentioned Ziggy’s alopecia which may impact the speed at which the Tyrosine experiment progresses. Zig went for bloodwork, etc on 1/16. Doc is wondering if Cushing’s is at play – and is a cause of hair loss and direct impact on diabetes. So, we will figure that out. The reason I say that is the hair regrowth is moving very slowly but we do see an increasing amount of black fur in various places on his bare patches. Enough that intrigues us but he’s still cycling through loss and regrowth. His back fur still looks promising as there is an increasing dark hue and dark roots. The experiment will continue on but it is hampered by concurrent hair loss. Once there is enough to photograph well, I’ll post photos. Happy New Year!

    1. Hi Julie. Thanks for the update. Your comment initially makes me wonder if there is a common cause of the lack of pigmentation and lack of hair. I have no idea but a cross referencing of the two conditions might through something up. I am probably barking up the wrong tree but I’d like to see Ziggy get his coat right.

  7. As I’ve said, this has been going on for 4 years which has caused most of his coat to change. Doctors, in different practices (and one a national expert in diabetes) didn’t seem phased which frustrated us. He is pretty much an asymptomatic cat. I’ve read everything and he doesn’t have other issues even with underlying but quiet kidney disease & the diabetes which requires very little insulin. But with diabetes the endocrine system is impacted. Interestingly though, this started way before the diabetes. If he has lived with mild pancreatitis for years, as the expert considered, then maybe that was the slow burning culprit- I’m thinking. Now, we have to wait & watch for the regrowth after his bout with hair loss. It’s coming in for sure but it is slow. I’m not sure he’ll get all that black back but seeing some has been encouraging (and interesting). It’s hard to be patient, to always wonder what went wrong in there, but he couldn’t be happier or more oblivious to it all.

    1. Helpful comment Julie. Interesting. It will help me research this some more. What a lovely photograph. Stunning face. He’s a beautiful and very interesting cat.

      1. Thank you! I added that last post to give you the info. I’m curious as can be and haven’t found solid answers that make sense with his symptoms, behaviors and health. Dr. Karen Becker may have insight but … The ends of the reddish fur began to feel old, coarse (r) like dead hair. I expect we have to shed that and maybe alopecia is doing that? Been on Krill for about a month. He does feel softer. 1tbsp of raw liver (frozen then thawed before meals) & given with meals – I think – is helping, too. Tyrosine has been given daily for about 6 months – between meals – Amino acids + krill + rich nutrients of liver + insulin to get him more in balance. It took time to get red. It will take time to get back to black.

          1. Michael,
            Watching for fur regrowth in areas he has lost fur. The sides of his neck, definitely coming in black. A few black hairs showing on chest. His shoulders were the last to lose or have thinning of fur. Looking carefully, can see sparse but new baby black hairs. Too small to photograph.

  8. It’s hard to get him to stay still to get a photo of his neck. He’s been putting up with a lot. Clearly, seeing it in-person gives a much better view. Recently added Krill oil to the mix. He’s been such a sport. It’s not the color we want but to find the supplements he has needed that caused the color change. He is beautiful no matter what.

  9. Progress on this front is slow but we are seeing it. We are seeing the darker parts getting darker and creeping toward the middle of his back. Seeing tinged of darker new growth where he lost fur. Going to post two pictures: one of his back; and another of the side of his neck – both sides have fresh black fur. Previously, I showed a photo if the fresh black fur on the surface of his skin. Here it’s grown. He wiggle when I shoot photos but.. I’ll keep updating.

    1. Hi Julie, thanks for the update. Great photos again. I am always startled when I see these photos because his coat is so strange.

      As you say progress is a bit slow. There may be something else going on at the same time. I just don’t know.

      Maybe it just takes a long time. I’ll see if I can do a bit more work on this.

      Thanks again Julie.

  10. November 1st Update:

    We ran into, what appears to be, unexplained Alopecia (or hair loss). I’m figuring it has to do with this year’s recurrence of kitty diabetes. However, the L-Tyrosine experiment continues. We believe we are seeing darker fur from his head to midway on his back and increasingly getting closer or meeting the darker fur on his tush. His base fur on his flanks (sides of tummy), which began to disappear with the Alopecia, seems to have a darker hue building. This picture will show what’s happening on his both sides of his neck. Fresh, black fur.

    We weren’t sure at first because it was growing in so close to his skin. It is now at a point that I could more aptly photograph it on a wiggly kitty. We weren’t sure what to expect with regrowth or turning the reddish brown back to black. It’s a daily experiment to see what happens. We are quite intrigued. Again, docs said it can’t hurt to try it with him as L-Tyrosine is an amino acid. But, no one knows what to expect. Zig’s had some health issues that I believe threw off his nutritional balance resulting in this color change. Not sure.

    1. Hi Julie, thanks for the updating photo and report. I believe this is the only live example, on the internet, of testing L-Tyrosine as cure for rusty black fur and it is fascinating. The fur seems to be black at its base as you state. If that is true it makes sense as the pigment (melanin) is produced in pigment producing cells in the skin. The hair next to the skin seems to get the melanin first and it gets pushed up the hair shaft as new pigment is added. I am guessing. Great to see and the best of luck to Zig. It is slow progress but it is nature’s speed.

      I look forward to the next update.

      1. I’ll post again soon when I can get photos that best show the changes. To the naked eye, we believe we are seeing it in other areas but will wait & report. Thank you for the melanin explanation!

  11. Here’s a better look at the roots. The fur on his head and hindquarters does look darker. Again, he was black-black & white 4-4.5 years ago.

    1. You have taken some unique photos. This is another one. A one-of-a-kind cat photo. The way this develops is going to be very interesting.

  12. For those following my experiment… our eyes could be deceiving us but there looks to be some blackness returning to Zig’s fur. I’ll post another photo that shows some black roots. Couldn’t find guidance on the L-Tyrosine dosage but I’ve been giving him 1/2 a capsule nightly between meals. Additionally, he’s getting 2 tsps of raw liver daily in an experiment to reduce his attempts to steal food from all sources – as he is a low level diabetic. The raw liver has helped to satiate him NO DOUBT. Remarkable, if not miraculous, response to the raw liver. I keep it frozen til just before meals. Both the liver and the L-Tyrosine, I feel, are most likely, filling the void of the amino acids/enzymes he’s been missing. We’re tracking him….

    1. Thanks for showing us an updating picture. It is am astonishing photo because as I said before I have never seen such a distinctly two-tone cat. The rust colour is a colour you never see on a cat.

      It will be great is this works for your Ziggy. I await the outcome with anticipation.

  13. My 13 year old kitty has been changing to reddish from black and white for 4 years. Only the area behind his head still looks black-black. I started Tyrosine last week after reading about the UC Davis study. Vets say it can’t hurt to try. Fiddling with dose as I can’t find, online, a starting point.

    1. Interesting Julie. Thanks for sharing that experience. In some lighting conditions, my cat looks quite rusty. I just accept it but it would nice of you could come back in month or so and tell us if it worked.

      1. People say he looks beautiful. Maine Coon in his blood. I will definitely come back and report. I’m glad to see people talking about it. The idea of safely bringing the color back is intriguing but I love him beyond … regardless.

          1. Here’s a recent picture of 13 year old Ziggy. His color started changing 3-4 years ago. Lot of sunlight in his world so first we felt it was ‘rusting’ from the sun. After all, that’s what the vet said. It has become quite pronounced. We started Tyrosine one week ago. Gotta restart the clock because I read that, at least for people, it should be taken on an empty stomach, not with protein or that makes it ineffective. I’m trying 250mg or 1/2 capsule per evening.

            He is a high functioning diabetic as of 2013. Low numbers just not low enough. For the last 6 months or so, he’s been on insulin and gets his shot at 5a/5p. And for 6 months, he has been pacing and squawking incessantly from 4-5 A.M. Not saying it is connected but since taking Tyrosine… um… the morning squawks have vanished. Tyrosine has helps with sleep and anxiety… It is used as a natural depression remedy also. I’m just sayin’… Keeping tabs. Will report back. Vet is eager to hear how the ‘study’ goes.

            1. I have never seen black hair go so rusty. Astonishing. I hope it works out and look forward to an update if you can find the time.

              Thanks for sharing. Very useful first hand experience, which are always the best.

            2. I had never heard of Tyrosine before, this is a very interesting subject.

              Julie, Ziggy is so handsome and so lucky to have you caring so well for him. I hope he continues to do well.

              Recently a friend took his 8 year old cat to the vet for her annual check up, she’s very fit and well. My friend asked about her insistence on waking him up at 04:00hrs, the vet told him that as cats are crepuscular creatures, dawn and dusk are peak activity times for hunting and it’s at that time that they have the most efficient mix and amount of acids and enzymes in their stomachs ready to digest food.

              I wonder if Tyrosine has an effect on this mix of digestive enzymes? Just a thought!

              Gerry, my scruffy little black cat is gradually turning red, his tail has had tinges of red for years. He had his mouth wrecked by calici virus and for the first months we had him his saliva was awful. Eventually, the vet removed all his teeth and he was put on Interferon which allowed his mouth to heal up. It has remained perfect ever since.

              I wondered at the time of the terrible saliva, if it had affected the hair follicles, and the sunshine over the years had done the rest, but this info about Tyrosine is fascinating!

              1. I’m sorry! I didn’t see this post/response.

                His waking at the ungodly hour after 12 years of sleeping in – came after the 2nd diabetes diagnosis Jan. 2013. Later, we began L-Tyrosine. Interestingly, his voracious -nearly feral-type food foraging, stealing, etc…has dramatically calmed down since I’ve added 1 tsp. of raw (previously frozen) top-shelf liver with his regular food. Dramatic improvement. I just started to add a bit to his night time snack to see if we can calm him in the morning a bit more. There is improvement. My theory? His amino-acids/enzymes were out of whack. It affected his saliva thus fur after grooming and made him less able to absorb the nutrients he needed for fur and for digestion. His grooming breath is back to normal 🙂 Not sure what will come of the reddish fur as we await the darker fur to come to the surface. Eagerly watching! There is now a small black patch growing on his white neck now. Hard to get him to sit still for that photo. Thought it was skin pigment but it is dark black fur.

                Again, I’m no vet but I needed answers to these things. Zig doesn’t understand what all the fuss is about but he’s been a champion trooper! He’s not a good boy at the clinic – RED CAUTION cat – but at home, he let’s me try to find solutions for a great quality of life for all. He deserves it most of all. Photos soon when I feel there’s enough change to show.

  14. My Ozzie is supposed to be Black but has a Auburn coat with Grey underneath. I love all of his colours 🙂 I especially love the fact that his back paws are Black with Grey tufts like cotton sticking through his toes.

  15. Ruth aka Kattaddorra

    Very interesting!
    Strangely enough I just noticed yesterday how reddish Narla’s fur is going, she is an elderly black cat who lives a few doors away from us and doesn’t come out that often now, but when she does she always visits us.
    I’ll find out more about tyrosine so I can mention it next time I chat to her ‘dad’

    1. I would be very interested to know what her diet is. It may be that age affects melanin production too. The creation of it may slow down etc. Still, a dose of tyrosine may cure it. Great if it did.

      1. My Lilly has redish hair in the right light, just as in the photo. I’ll have to see if I can get a photo of it. It looks almost identical. Are you sure it’s unusual? I thought it was totally normal somehow. It didn’t change or anything it was always like that since we got her from the shelter at about 4-5 months old. She’s about 3 years old now.

        1. Are you sure it’s unusual?

          It is usual and normal to see rust in a black when the light is brightly behind the fur shinning through it but when the light is from the front I think it is unusual to see rust. Also the point I was making was that the if the cause is a lack of tyrosine – that would probably be rare but I am guessing. Sorry I wasn’t clear. I’ll amend it slightly. I would like to see your photo of rusty black fur.

Leave a Reply to Julie Cancel Reply

Your email address will not be published. Required fields are marked *

follow it link and logo

Note: sources for news articles are carefully selected but the news is often not independently verified.

I welcome and value comments. Please share your thoughts. All comments are currently unmoderated.

This blog is seen in 199 of the world's country's according to Google Analytics which is pretty much the entire world.

Scroll to Top