The food data tables
have quickly become one of the most popular parts of this website.
The tables list many American
cat foods
in order of their phosphorus, protein, sodium and fat content.
These data are calculated on the basis of
dry matter analysis. I
know many people are very confused about why the data in the tables differ so much from
the percentages shown on the cans or on manufacturers' websites.
I also know many people
think they can just rush out and buy the first food on the list that their
cat will eat but unfortunately it's not that simple.
Please read below to understand why
the food data tables are calculated in this way and how best to use them.
Please read this
page before contacting me to tell my data are incorrect — chances are you
have misunderstood how I calculate the data. Yes, I know the information on the
cans is not the same.
The Different Ways of Assessing Food Content
Unfortunately there
are a number of different ways of assessing food content, which can make
choosing a cat food a very confusing exercise. All these methods have their pros
and cons.
This page explains
the differences between the different methods and why I use dry matter analysis.
Guaranteed
Analysis - Used in the USA
Virtually all US
cat food manufacturers provide their food data as Guaranteed Analysis (GA).
This is to comply with AAFCO (Association of American Feed
Control Officials) guidelines. AAFCO is responsible for overseeing pet
food production in the USA, and its guidelines cover the production, labelling,
and sale of pet foods. Guaranteed analysis is normally provided as As Fed
data.
Unfortunately,
guaranteed analysis is of only limited use when trying to compare foods for
CKD cats.
Evaluating phosphorus, calcium and magnesium content in
commercial cat foods (2020) Summers SC, Stockman J, Larsen JA,
Zhang L & Rodriguez AS Journal of Veterinary Internal Medicine34(1)
pp 266-273 states "minimum values on food packages cannot be used to
accurately estimate “as fed” amounts of Ca and P, and thus utilizing the label
to identify foods low in P or Ca is not feasible."
This is because guaranteed analysis only provides maximum and minimum values,
and the only ones which are compulsory are protein and fat (minimums), and fibre and moisture (maximums). If phosphorus is
shown (and it is not compulsory), it is usually given as a minimum. This makes it very hard
to assess whether a food is suitable for a CKD cat, for whom you
need to know the exact amount or at the very least the maximum amount of
phosphorus in particular. The minimum is potentially very misleading. For example, I could
tell you "I have a minimum income of US$25,000" when in fact my
income was US$250,000. I wouldn't have lied; on the other hand I
wouldn't have given you meaningful information either.
Here's an
example of how this affects foods. Let's say we are looking at a food with the
following GA figures:
moisture: max 80%
phosphorus: min 0.20%
If we assume these values are correct, this gives us a
dry matter analysis figure (see
below) of 1% for
phosphorus.
Now let's say the actual figures are:
moisture:
79%
phosphorus: 0.25%
This gives us a DMA figure of 1.19% for phosphorus,
some 20% higher, so very different from the
figures we came up with if we used GA figures.
Because of this,
and because so many manufacturers are unable to provide information on a Dry
Matter Analysis basis (in fact, a fair number don't even seem to realise there
is a difference), there are quite a few foods missing from the food data tables
I have created.
Nevertheless, the tables contain over 1500 individual foods.
Evaluating phosphorus, calcium and magnesium content in
commercial cat foods (2020) Summers SC, Stockman J, Larsen JA,
Zhang L & Rodriguez AS Journal of Veterinary Internal Medicine34(1)
pp 266-273 states "A change in existing regulatory guidelines with regard to P
maximums in foods formulated for cats should be considered in light of
potential safety issues potentially impacting a subset of pet cats." But until
this happens, I have to crunch numbers.
Decoding AAFCO Guidelines
(2013) Larsen J Clinician's BriefFeb 2013 pp9-11
explains more about AAFCO's guidelines.
Typical
Analysis - Used in Europe
Virtually all
European cat food manufacturers provide their food data as Typical Analysis.
This is to comply with
EU legislation. Regulation
183/2005/EC on Feed Hygiene covers the safety of all feed, including pet food,
in Europe.
The
UK Food Standards Agency has more
information about the legal requirements for pet food. In the UK, over 90% of pet food manufacturers are also members of
the Pet Food
Manufacturers Association, and comply with its guidelines.
Unfortunately,
typical analysis is of only limited use when trying to compare foods for CKD cats. This is because,
although it is more reliable than Guaranteed Analysis,
it does not allow for the moisture content in the food.
Metabolisable Energy (ME)
There are various other ways of calculating the values in cat foods, one
of which is metabolisable energy (ME).
ME is the amount of energy available from a food for your cat to use once
your cat has digested the food. It focuses on protein, fat and
carbohydrate.
Since phosphorus is the most important value for CKD cats, I do not look
at ME values, but they may be of some use for people with diabetic cats,
who often look to feed foods with an ME value for carbohydrates of 10-12%
or lower.
Dry Matter Analysis: Used on This Website
What we really need is
dry matter analysis (DMA).
Cat foods vary in
how much moisture they contain, which makes it difficult to compare them to
each other. It is very hard, for example, to compare a canned cat food to a
dry cat food because the former naturally contains much more water; and this
affects all the percentages of the different nutrients.
Dry matter analysis
is a way of comparing foods by assuming all the moisture content has been
removed: this makes it easier to compare different products. Whenever this
site mentions levels of the various components of foods, it is talking about
them on the basis of dry matter analysis, which is not necessarily the same as
what it says on the can.
Let's take an
example. Let's say:
you give your cat a
food with 80% moisture, a typical level for many canned foods;
the food apparently
has phosphorus of 0.25%;
your cat eats 100g
of the food.
It therefore
appears that your cat is eating 0.25g of phosphorus (100g x 0.25%).
However, the food
is 80% water. So of the 100g your cat has just eaten, 80g (80%) of it was
simply water, and only 20% was actual food, or dry matter. So the amount of
phosphorus is actually higher in percentage terms than it first appeared,
i.e. your cat has eaten 0.25% divided by (100%-80%) or 1.25% phosphorus.
Another way of
looking at it is to say that your cat food initially had 1.25% phosphorus.
Then the manufacturer added 80% water. There is still the same total amount
of phosphorus in the food, but at first the percentage appears lower because
of the diluting effect of the water. So in order to understand exactly how
much phosphorus your cat is eating, you need to discount the water in the
food.
Dry Matter Analysis: Why My Figures Differ
to Other Websites
I am sometimes
asked why my data differ to those on other websites such as catinfo.org.
The values on that
and some other sites provide figures on the basis of % caloric distribution
for protein, fat and carbohydrate, and the number of mg of phosphorus in every
100 calories of food.
There is nothing
wrong with calculating figures in other ways, it is just a different way of
looking at things. Catinfo.org, for example, was designed for people with
diabetic cats, where the nutritional focus is different.
My site gives the figures as a percentage of the food. In other words, whether
you feed one ounce of food, or four ounces of food, my figures remain the
same.
The main reason I
use Dry Matter Analysis % is because that is the format which leading vets use
when making recommendations for target nutrient intake in CKD cats.
Since I doubt you
give food to your cat measured by calories, I would stick with my figures if
you have a CKD cat. In addition, catinfo was last updated in 2017, so many of
the data will be out of date, whereas the data on my site are more recent
(2020).
Calculating
Dry Matter Analysis Yourself
You shouldn't often
need to calculate dry
matter yourself because I've already done it for many foods. If you do
want to do it yourself, you need to know the amount of moisture in the food and the
amount of whatever you are measuring (often this will be phosphorus), and then
you need to crunch the numbers a little.
Let's assume you
have a food with a moisture content of 76% and a phosphorus content of 0.2% on
an As Fed basis. This is the formula:
The dry matter in a
food is always 100 - (% moisture in the food). So in this example, with 76% moisture,
100-76% leaves 24% dry matter.
You then have to divide the phosphorus content by the dry matter.
In this case, you would divide 0.2% phosphorus by 24% dry matter, which gives 0.833% phosphorus content of this food on a
Dry Matter Analysis basis.
Remember, using the data from cans of food in
the USA for this exercise is often unreliable because the data on the cans
tend to be maximums or minimums rather than actual data.
Please don't just
rush out and buy the first food at the top of the list! There are a number of
issues to consider when choosing the best food for your cat's particular
needs.
The tables
simply provide information on the amount of the various components of the
foods. This is only half the story. There is also the question of the quality of
different cat foods, particularly what constitutes a
high quality protein and which ingredients are the best. You can read more about these issues on the
Which Foods to Feed and
Nutritional Requirements pages.
If you want to
check the actual ingredients in a food, either visit the brand's
website (there is a list of US brands
here) or
visit a site such as
Chewy which tells you the
ingredients of the foods it sells. If you would like to discuss the various foods
and ask what has worked for other people, join
Tanya's CKD Support Group.
You also need to
consider the
calories in a food. Generally speaking, lower fat foods have fewer
calories, as do gravy foods.
AAFCO Minimum
Levels
US commercial adult
foods certified as complete must meet the AAFCO guidelines
for adult maintenance foods. These were reviewed in 2015 and new guidelines
published in 2016.
These are the minimum levels permitted by AAFCO
(fibre is the only component which has a maximum level):
Dietary Component
Minimum Level for Adult Cats % on a DMA Basis
Phosphorus
0.50
Protein
26.00
Sodium
0.20
Fat
9.00
Phosphorus
If your cat's
phosphorus level in blood tests is too high, this will make your cat feel ill
and may make the CKD progress faster.
In order to reduce
these risks, your goal is to have your cat's serum level of phosphorus (i.e.
what your vet tests in bloodwork) no higher than 4.5 mg/dl (USA) or 1.5 mmol/L
(international).
The easiest and
most effective way to control blood phosphorus levels is by feeding foods low in
phosphorus.
People sometimes think that if a food does not mention phosphorus on the
label, it must not contain any. This is virtually impossible, especially if
the food contains animal-based protein, as most cat foods do. As outlined in
the table above, any American food labelled as an adult maintenance food must
contain at least 0.5% phosphorus on a dry matter analysis basis and many foods
contain far more than this.
Ideally you want to
feed a food with a phosphorus level
under 0.5% according to Dr Scott Brown in Management
of feline chronic renal failure
(1998) Waltham Focus8 (3). No commercial adult food which meets
AAFCO guidelines will meet this requirement because the minimum phosphorus
level required by AAFCO is 0.5%.
If your cat won't
eat a therapeutic kidney diet, you still need your cat to eat. Since the minimum
level of phosphorus in a non-therapeutic kidney food is 0.5%, you are not going to
find a complete commercial food with phosphorus below this level, but you may be able to find a food in the table which has a low
level of phosphorus which your cat will eat. The table lists foods in order of
phosphorus content so you can clearly see which foods might be worth
considering.
In order to keep
your cat eating, you may have to have a less ambitious goal, at least to start
with, of, say, feeding a food with less than 0.75% or less than 1%
phosphorus.
But your ultimate
goal should be to feed the lowest phosphorus food that your cat will eat.
Whichever food you
opt for, always introduce a new food gradually (mix it with the food you've
been using previously and gradually increase the percentage of the new food) so
as to reduce the risk of tummy upsets.
If you are not
feeding a therapeutic kidney food, you will probably have to give your cat a
phosphorus binder. Please read the
Phosphorus Binders page for more information.
Protein
The need for
reduced
protein for CKD cats is much debated, and may not be necessary for cats
in the early stages of CKD. See
Nutritional Requirements for more information.
However,
since BUN levels are influenced by diet, it does often help the cat feel
better if you restrict protein intake, particularly as the CKD progresses and
BUN rises.
Most therapeutic
kidney diets have protein levels of between 28 and 35%.
When choosing a
commercial food from the lists, I would not only look at the
phosphorus level but also consider the protein level. That is to say, if for
example I have two foods with the same phosphorus level to choose from and my
cat will eat both of them, and one food has 32% protein while the other has
50% protein, I would normally choose the lower protein food.
Ohio State University College of Veterinary Medicine has stated that protein
should never be reduced to less than 20% of calories. According to
Small Animal Clinical Nutrition — 6th Edition,
Chapter 37, Chronic Kidney Disease
(2019) Davenport D & Kirpensteijn J (Eds.) Mark Morris Institute, this is around 24% on a
dry matter analysis basis.
Personally I would try to
feed a food with a protein level of 35% on a dry matter analysis basis, or
as close to this as you can get.
Sodium
Since CKD cats are
prone to high blood pressure, it is generally advisable to try to feed a food
low in sodium.
In fact, one study,
Effects of sodium chloride on selected parameters in
cats (2006) Kirk CA, Jewell DE, Lowry SR Veterinary
Therapeutics: Research in Applied Veterinary Medicine7(4)
pp333-346 found that there was actually no change in blood pressure in the
CKD cats in this study, but levels of BUN, creatinine and phosphorus were
higher in the cats eating a high sodium diet compared to those eating a low
sodium diet.
The sodium content of therapeutic kidney diets varies widely. The
minimum level permitted by AAFCO is 0.2%. It is unlikely that you need to go
much higher than this.
As with protein, I
would factor this into choosing a food. If for example I have two foods with
the same phosphorus level and a similar protein level to choose from and my
cat will eat both of them, and one food has 0.3% sodium while the other has 1%
sodium, I would normally choose the lower sodium food.
Fat
As with protein, cats need relatively high levels of fat compared to a human
or dog.
Fat does not result in a lot of waste products like protein, so processing
it is not a strain on the kidneys. In fact, in most CKD prescription foods,
the fat content is increased to compensate for the reduced protein levels.
Therefore a diet relatively high in fat can help an older cat to maintain
his/her weight while placing less strain on the kidneys.
In other words, if you have a choice of two similar foods and you wish to
maintain or even increase your cat's weight, it is probably better to choose
the food with the higher fat content.
Sources of Data
I have spent hours
contacting the various brands to obtain the correct information, and I
have then crunched the numbers where necessary.
These analyses have
been compiled in good faith from the information provided to me by the
brands. I have obtained the data from their websites or in writing in order
to avoid any misunderstandings. The data may not necessarily match the
information on the cans, which show maximum values for moisture and phosphorus
rather than actual values.
Unfortunately food
formulations can change without warning, and therefore I cannot guarantee that
the data are still accurate; no responsibility can be accepted. Several of the
brands have asked me to emphasise that their non-therapeutic kidney
diets are not intended for CKD cats.
For those juggling
more than one health condition, the tables also includes some data for other
therapeutic diets.
Although I don't recommend feeding
raw foods to CKD cats, since I know some people may already be feeding
them, data for these foods are included.
Please see the
sidebar on the left or
Cat Food Data
Overview for links to the wet and dry food data tables, plus brand contact
details and my opinion of their levels of helpfulness.
TREATING YOUR CAT WITHOUT VETERINARY ADVICE CAN BE
EXTREMELY DANGEROUS.
I have
tried very hard to ensure that the information provided in this website is
accurate, but I am NOT a vet, just an ordinary person who has lived
through CKD with three cats. This website is for educational purposes
only, and is not intended to be used to diagnose or treat any cat. Before
trying any of the treatments described herein, you MUST consult a
qualified veterinarian and obtain professional advice on the correct
regimen for your cat and his or her particular requirements; and you
should only use any treatments described here with the full knowledge and
approval of your vet. No responsibility can be accepted.
If your cat
appears to be in pain or distress, do not waste time on the internet,
contact your vet immediately.
This site was
created using Microsoft software, and therefore it is best viewed in
Internet Explorer. I know it doesn't always display too well in other
browsers, but I'm not an IT expert so I'm afraid I don't know how to
change that. I would love it to display perfectly everywhere, but my focus
is on making the information available. When I get time, I'll try to
improve how it displays in other browsers.
This site is a labour of love, from which I do not make
a penny. Please do not steal from me by taking credit for my work.
If you wish to
link to this site, please feel free to do so. Please make it clear that
this is a link and not your own work. I would appreciate being informed of
your link.
