What is an acceptable amount of phosphorus?

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Doug N Libby

Doug N Libby

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I keep reading that phosphorus content in food shouldn't be too high for cats with some conditions and aging cats, but I can't seem to find what 'too high' means. Can someone, please, point me in the right direction? Hershey has no other conditions at this point, but would just as soon be aware now, know what I mean?

Thanks!

Libby (and Hershey, too!)
 
Phosphorus content is mostly a concern if your cat has chronic kidney disease because it makes the kidneys work a little harder which causes cats to feel bad. The aim would be for a phosphorus level as low as possible as long as its food your cat will eat. If your cat is diabetic then you would look for a low carb/low phosphorus combo if possible. Merricks seems to be one of the better low carb/phosporus combinations.
 
The recommendation for cats with kidney disease is to try and stay as low as possible under 250 mg/100kcal (or less than 1% if looking at Tanya's list of phosphorus values). Phosphorus is not the only thing you're looking at, though. You want to make sure that the protein source is high quality protein (to help lessen protein metabolism residue), and high in moisture content (adding water to meals is always a good idea for CRF kitties).

However, most senior cats (especially if they were fed a dry diet for most of their lives) will have loss of kidney function as they age. Kidney disease is usually not detected in blood tests until a cat has already lost 75% of their kidney function, but that doesn't mean you want to wait until the disease has progressed that far to start a kidney-friendly diet. Cats with 25% or 50% of their kidney function benefit from the same concept--you want to halt kidney deterioration before it gets any worse. So it's a good idea to feed foods with lower phosphorus and high quality protein to any senior cat.

Here's an updated chart with the values for some premium cat foods: https://docs.google.com/leaf?id=0B8...MzhkYTkxOGM4NThk&sort=name&layout=list&num=50. Do not use Janet and Binky's chart for phosphorus values--while the carb content has remained mostly the same for most foods over the years, the phosphorus values have changed radically.
 
Yep, sorry--should have clarified my thoughts a bit there. I try to stay within the recommendations for CKD even though my cats are very young and don't have it. I don't want to tax their kidneys any more than I have to, since so many cats end up with kidney problems. This is pretty easy since they will mostly eat anything that's not nailed down. If they had allergies or some other issue going on, or were picky, I might not worry so much about the phosphorus issue. I just figure by going low carb, high-quality protein, high-moisture, and lower phosphorus, I am doing what I know of to try and keep them healthy. Of course there are probably tons of other factors I don't know about that might be just as important. For most of Saima's life, I had no clue that dry food might be bad for her. :cry:

I feed them selected kinds of Merrick and Wellness... Wellness comes in convenient large cans that are cheaper, which is nice because my kittens eat a lot. (If they eventually go to 1 regular can each per day, I might switch to all Merrick.) But it is higher in fat, which I know Dr. Lisa mentioned as a possible issue as well. I guess that's the factor I decided to let slide for now in favor of focusing on the carbs and phosphorus.
 
What I have read and heard from vets is that if the kitty does not have kidney problems, a reduced phosphorus diet does not prevent any problems in the future.
 
Larry and Kitties said:
What I have read and heard from vets is that if the kitty does not have kidney problems, a reduced phosphorus diet does not prevent any problems in the future.
Click to expand...

It is true that a low phosphorus diet will have no effect on cats with no loss of kidney function, which is why phosphorus is not a concern for younger cats. However, kidney disease is very common in senior cats, and virtually undetectable until later stages. Which is why it's not a bad idea to just assume a senior cat has early stage kidney disease (since most do), and watch the diet to help prevent further deterioration.
 
Julia & Bandit said:
The recommendation for cats with kidney disease is to try and stay as low as possible under 250 mg/100kcal (or less than 1% if looking at Tanya's list of phosphorus values). Phosphorus is not the only thing you're looking at, though. You want to make sure that the protein source is high quality protein (to help lessen protein metabolism residue), and high in moisture content (adding water to meals is always a good idea for CRF kitties).

However, most senior cats (especially if they were fed a dry diet for most of their lives) will have loss of kidney function as they age. Kidney disease is usually not detected in blood tests until a cat has already lost 75% of their kidney function, but that doesn't mean you want to wait until the disease has progressed that far to start a kidney-friendly diet. Cats with 25% or 50% of their kidney function benefit from the same concept--you want to halt kidney deterioration before it gets any worse. So it's a good idea to feed foods with lower phosphorus and high quality protein to any senior cat.

Here's an updated chart with the values for some premium cat foods: https://docs.google.com/leaf?id=0B8...MzhkYTkxOGM4NThk&sort=name&layout=list&num=50. Do not use Janet and Binky's chart for phosphorus values--while the carb content has remained mostly the same for most foods over the years, the phosphorus values have changed radically.
Click to expand...
CKD can be detected, it's just not normally looked for unless there are symptoms and those don't usually show up until the cat is pretty bad off. Hobbs has no symptoms what so ever, we caught his CKD totally by accident. He's not at 75% loss or even close yet.

Still, add the whole dry food thing to "things I wish I knew years ago" list.
 
Thanks, y'all. Hershey is almost 10 years old, raised on dry food (I just thought cat food was cat food - *smacks forehead*) with a little canned at night as a treat. I have no idea about kidney function as the vet doesn't really share with me what she's doing (but that's another thread!); I don't even know what all she checked when she was ruling out thyroid and finding diabetes. Anyway - I now feel like a salmon swimming upstream, trying to 'catch up' on all I wish I had known earlier!

Hershey is eating Wellness <7% carbs and we're fixing to stop buying the chicken and herring so that'll be down to <6% carbs at that point. I was hoping that by feeding a more senior friendly diet it might head off any future problems, but it doesn't sound like that's necessarily the case. But, considering his age and the dry food, he may have some undetected kidney issues. :YMSIGH:

Sabrina - How did you happen to detect Hobb's? I don't even know the symptoms/treatment...add that to the list of reading materials...

And, now fat content, too?! Guess I should figure out what kind of numbers to look at for that, too...Hershey really likes the Wellness, so I hope it meets whatever that amount is. But, at this point with just trying to figure out what dose actually works with him, I think I, too, may have to put fat content on the back burner.

(*Any idea why the phosphorus values have changed radically?)

Thanks, again!
 
SabrinaFaire said:
CKD can be detected, it's just not normally looked for unless there are symptoms and those don't usually show up until the cat is pretty bad off. Hobbs has no symptoms what so ever, we caught his CKD totally by accident. He's not at 75% loss or even close yet.
Click to expand...

Gabby's was detected at around 50% loss by complete accident as well--which is why I said that usually it isn't detected until late in the game. There are lucky exceptions, though! :smile:
 
If Hershey is only 10 and he hasn't been diagnosed with kidney disease, I wouldn't worry about phosphorus right now (although I would not feed foods exceptionally high in phosphorus to any cat regardless of age). It might be something you want to consider once he's around 12 or 13, but it's unlikely he'd develop kidney problems on his own so young.

Bandit just turned 10 this month, and what I look for when picking out his food are high protein, lower fat, and low carbs. This is because Bandit was formerly very obese, so now he gains weight easily and has difficulty taking it off. He also doesn't handle high fat foods very well--they irritate his gastrointestinal tract. So he eats mostly Merricks and some Fancy Feast, and does exceptionally well on these foods (since the switch to Merricks, he's actually gaining a lot more muscle). However, every cat is different! If Hershey maintains a good weight on the Wellness, and he handles the food just fine, you're all good. One of my friends feeds her 18 year old cat with kidney disease Wellness Turkey, and she's been doing great on it for 2 years now.

Cat food companies are constantly tweaking their formulas every so often--and while the basic ingredients usually don't change (which is where carb levels would be affected), the mineral content can (which is where phosphorus values are affected).
 
I am a little confused about phosphorus level now--I always assumed that older cats were prone to kidney disease because something in their diet throughout their life had overtaxed their kidneys and sort of "worn them out" so to speak. If that is the case, aren't there ways we can feed early in life to sort of go easy on the kidneys? Are older cats just prone to kidney disease no matter how you feed them? Or maybe phosphorus is not the issue that makes a healthy kidney "sick" (to use really oversimplified language, I am sure).

It probably won't change what I feed b/c it's more selecting flavors within brands that I would buy anyway, but I was just curious what my rationale should be when selecting food, if I do need to change in the future for some reason. I was going for high quality, low phosphorus, high moisture, low carb but maybe that low phosphorus thing doesn't need to be a concern.

If you can't tell, I feel an enormous amount of guilt over Saima's early death and am trying to arm myself with as much knowledge as possible to keep the new kitties healthy. (She didn't have kidney disease, but her levels were creeping up there, and I just feel like most of her health problems could have been prevented by diet if I had known what to feed her earlier on.) So I get a little obsessed with food selection...
 
My experience

This is my blue creme female Tjejen http://felinediseases.weebly.com/renal-failure.html when she is slowly dying of renal failure. She was born 1988 and died 2002, 14 years old. It's 10 years ago this summer.

If only going by the visuality, renal failure and diabetes almost starts out identical - increased, very increased thirst, hunger, loss of weight, and loss of muscle mass.

Difference is that the loss of muscle mass, athrophy in renal failure, isn't reversible, nor is the abnomral thirst or hunger. One can see how normal my Tjejen looks at the first 2 pictures. At the third she has already started to get high creatinin values and renal failure, and the pics where she is so thin thin thin, only skin and bone, it is almost animal abuse, and how she started wanting to constantly drink from high up areas she never had been up drinking from. Her blood values creatinin, bun and more ..... just got higher and higher. It took a year for her to diminish and die from start of the hunger and thirst.

The last picture is the last picture of her, it is a Sunday summer 2002, and I have arranged with the animal hospital that we are coming in, for our last time together. Since she had lost all her muscle mass, but still thought she could jump down from high things, she had become a hazard for herself, prone to break bones etc. So I had to let her go.

She knew Gustav and Simba from 1995 and 1996, but I don't know why she developed renal failure so early at age 13-14, when Gustav has made it to 17 and Simba has made it to 16, in spite of him having diabetes and thus should be more prone to renal failure.
 
Jennifer, there are many causes of kidney disease in cats, including other diseases and infections, as well as chronic dehydration. Low phosphorus diets might help manage the disease, but that doesn't mean that high phosphorus diets cause it. While dry food does tend to be high in phosphorus, it's the dehydration it causes that's the real bad guy in CKD. So any canned diet is going to help prevent kidney disease, because it's maintaining proper hydration. Does that make sense?
 
That does make sense--thanks. I think I'll keep with the current strategy for now since they like their food and it's not lacking in anything else (as far as I know), but if I need to change varieties, I may branch out a bit.
 
Julia - How was Gabby's detected? The vet never said if she thought Hershey was obese. I thought he looked good at 12 pounds, so I'm feeding calories based on getting him back there. He does like to eat, though, but pretty sure a lot of that is the unregulated diabetes. I know Oreo is obese...round even - even though he eats less and gets more exercise. I've been counting his calories, too, trying to get him back to 12 pounds, also.

Jennifer - I understand, completely about the guilt. I'm a mom, guilt is what I do - to myself and others ;-) After Hershey was diagnosed with diabetes and I started doing research, I felt so guilty that I didn't know better about what to feed him. I read labels for my family and kind of know what to avoid for each of us. So, WHY had I never thought of doing that for my kitties? People here have been so kind to tell me not to feel guilty because I didn't know, but when I look in Hershey's face, that's easier said than done. We've been feeding Turkey, Chicken, Turkey & Salmon, Chicken & Beef and Chicken & Herring. But, as I said we're going to stop buying the Chicken & Herring to get all of the foods under 6% carbs. Been thinking of eliminating the Turkey & Salmon, too, but he does love seafood every now and then!

Do you know how much fat is considered too much?

Ann - My heart just ached as I read your post about your beautiful Tjejen and looked at the photos you shared. I am so sorry you and she had to go through that. Cats never cease to amaze me, how they just keep going even when their little bodies have been through so much. Our Smokey was born with feline leukemia and we lost him in 2000. A few weeks before he died, he was staying at the vet's for more tests. His white count was down to only 4, yet he was able to get out of the crate and trip the alarm! Deciding to let them go is so SO difficult. I just couldn't make that decision with Smokey. The downhill slide had been so fast that I thought surely he would rally. Two weeks before he died, our preacher spoke about finding peace, but I could find no peace in that decision. One day, I finally called the vet, said it was time and they said to come the next morning. Sometime overnight, he lost the battle; he was almost 2.
 
Doug: It was a total fluke. Hobbs had been peeing outside the box (which turned out to be b/c he hated the litter) and I was concerned that he had a UTI (he had one when he was younger) so to make sure, I took him to the vet. Vet ran some tests and "something" looked off. I don't remember what that something was but she asked for the OK to do further tests to make sure and I said sure go ahead since he was already there (he spent the day at the vets office because I couldn't get him in after my work hours at the time). They did a full blood panel and found that his numbers for kidneys was high. So I owe it all to Fresh Step. If they hadn't started offering their Extreme Odor Control litter and my cat hadn't hated it, I would never have taken him in. That was in September, and his BG level was fine (100) and we discovered his diabetes when I took him back in December for his 3 month follow up. He did have diabetes symptoms, but I didn't realize it until after I found out what they were. I thought his drinking/peeing more was due to his kidneys working better.
 
The vet told me Gabby had kidney disease when she had a urinalysis done in conjunction with her annual bloodwork for some reason--possibly a suspected UTI? She was drinking excessively for quite a while--and it wasn't until I made the switch to canned food that I noticed how much more water she was consuming as opposed to Bandit--and Bandit was in the beginning stages of his diabetes. She also had other symptoms, like an acidic stomach. I completely depend on the vet to explain test results to me, but I believe it was the decreased specific gravity value that indicated her kidney disease.

Here's some good info: http://www.felinecrf.org/diagnosis_urinalysis.htm. USG stands for Urine Specific Gravity.

As long as you limit the Turkey and Salmon to a few times a week, there's no harm feeding it!

Here's another section of Dr. Lisa's web site that I find incredibly useful when talking about what foods to buy: http://catinfo.org/?link=cannedfoods
 
Thanks, Julia, for the links to check out.

Wow - it is pretty lucky how y'all found out. I have no idea how often the vet does regular labwork type checks. Honestly, I have pretty much blindly trusted - she was so good with Smokey and his feline leukemia - and just never questioned. Boy - when I did question about feline diabetes - talk about seeing a different side! Anyhoo - We actually took Hershey in April, 2010 because he was spending so much (unproductive) time in the litterbox; I thought maybe he was constipated or had a blockage or UTI or something. We had been giving him pumpkin and even rubbing mineral oil on his nose, trying to figure out something to help him. The vet said he was fine. No, he wasn't fine. He eventually started spending less time in the litterbox, but then started drinking more and going more and you know the story...lost a lot of weight, increased shedding/dander, we took him in and - feline diabetes. The good news is that he is currently in the litterbox once, no more than twice a day. But, it makes me wonder if that wasn't the early signs of diabetes or maybe even something else that is still lurking under the surface...

I just can't say enough how glad I am that I stumbled on this forum! Y'all are such a wonderful group of people who so kindly share what you've learned - I REALLY appreciate it!!

Libby (and Hershey, too!)
 
Libby--I have to admit I don't know much about this subject--it just caught my eye at one point on catinfo.org here (http://catinfo.org/?link=cannedfoods) that it said:

"The composition of a feline diet is important because cats are designed to eat a high protein (~50% of calories, or more), moderate fat (~40% of calories or less), and very low carbohydrate (well below 10% of calories) diet." It also said "Update July, 2011: It is no secret (among those who know me well) that the commercial pet food industry frustrates the heck out of me. With regard to the comment above advising to look for a muscle meat as the first ingredient, please be aware that most of the grain-free/no by-product/muscle meat choices such as Wellness, Nature's Variety, EVO 95%, etc. are very high in fat and relatively low in protein in order to keep the profit margin high. Given this fact, I can't help but wonder if Friskies, 9-Lives, etc. (all by-products, no muscle meat) may actually be better diets because many of these by-product foods are higher in protein and lower in fat than the more expensive diets that are free of by-products."

She also gave Merrick Cowboy Cookout on that page as an example of a food that has a good protein/carbohydrate/fat profile, but it was just one example.

I guess, having heard what is often in "by-products," that I made a personal decision to go with the Wellness anyway (especially seeing as it's no more expensive than Fancy Feast when I buy in the large cans), but by no means do I necessarily think this is the "right" decision. I hope I'm doing OK by the kitties but I am always open to being convinced otherwise. I would like to feed all Merrick, but it is a tad pricey right now given the amount they eat. Of course, as soon as I do that, I'm sure they will change their formula too and I'll have to start all over... ohmygod_smile
 
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