Sunday 27 January 2008

Low Magnesium Cat Food

I refer in this short article to two sources, Elizabeth Hodgkin's book "Your Cat" and an article.

Elizabeth says that the increase in urinary tract disease and the increase in use of dry cat food are linked (she calls dry cat food "dry kibble" as it is based on starch to make the manufacturing process work). I have written on this already. The manufacturers came to realize that there was a problem and took steps. I think we are talking about the late 1990s here but could be wrong. The steps they took according to Elizabeth were incorrect.

Anyway, they concluded from their research that the levels in magnesium in commercial cat foods was a contributing cause of UTI (urinary tract infection). They figured this out on the basis that the crystals (urine crystals forming in the urinary tract) were made up of a magnesium salt. The argument was that high levels of magnesium resulted in the magnesium crystallizing in the tract.

The answer then was to manufacture low magnesium cat food. Hills manufacture Prescription Diet s/d for example. Drs Carlson and Giffin (Cat Owner's Home Veterinary Handbook) say that cats fed on this food exclusively will cease to show signs of FUS within 5-7 days. They say that to completely dissolve struvite stones (urinary tract crystalline stones caused by an infection setting of a chemical reaction in the urea) takes about 1-2 months on the diet. However this is not meant to be a permanent or long term diet.

Urine in cats who eat dry cat food has an alkaline pH and magnesium crystals form in alkaline urine. So they also made the food more acid. This worked to an extent but Elizabeth argues it caused some new problems. The answer should have been to take steps to make food that more accurately replicated the natural diet of a cat that feeds on high protein food.

One problem with dry foods is that they are dry and cats do not make up this deficiency in intake of water by drinking more water. This makes the urine more concentrated leading to crystal formation.

So, where does that leave us? First I don't know how you tell what "low in magnesium" means. All you can do is compare the levels on the cat food packets and pick the lowest level (but it still may be too high for a cat). But better still it seems to me is to create a diet for your cat that as near as possible mimics her wild cat diet. The nearest we can get to that with commercial cat food (as opposed to home made cat food) is wet cat food, plus say some fish (I microwave frozen Coley and add water) and to choose the wet cat food with the lowest magnesium levels.

The author Franny Syufy had a problem with one of her cats that was magnesium related. She says and I fully agree, that the ingredients on cat food packaging is confusing. When you read the ingredients it basically shocks. Most of the contents are water ("moisture") then there's vegetable matter....

Update: does a low magnesium cat food affect the incidence of heart disease?

The manufacturers proudly put on the boxes phases like "Rabbit and Carrots". When did you last see a cat eat carrots?

Photo copyright and by dusdin


  1. My lovely boy has recently died.
    He ate all dry food, Purina One for Sterile Cats, and became blocked. With being blocked came nasty bacterial infections that wouldn't go away despite being treated with antibiotics (one of the being the all powerful Imipenem).
    A few days before he passed away we learnt he was FIV positive, even though his first lab test came negative.

    I can't stop wondering that if i had provided him with wet food, even if in a 50/50 basis, he wouldn't get blocked and thus, not get the bacterial infection.

    It's a pity most veterinarians still proclaim the virtues of dry food, and yes, it seems more practical, but my advice is that, if you wish to let your cats eat dry food when you're at work, at least feed them the wet one before going to work and after arriving, so that there's enough water in them to fully produce the right amount of urine.

  2. Hi, thanks for the comment. Yes, vets do promote dry cat food. There are probably commercial reasons behind it. Frankly I think vets are sometimes (not always) too profit orientated, which distorts their judgment.

    I am very sorry to hear of your cat's death.

  3. Thank you for your support, and also for writing a post on this subject... People need to know about this, to get as much info as they can. It could save many, many lives.

    Thanks again.

  4. I am so sorry to hear about your cat. I have 4 cats and I would no way just feed my cats dry food, I give them can and dry daily. I could never understand why vets would recommend an all dry diet.Again, Im sorry you lost your precious cat.

  5. I feed my cats either cooked boneless chicken or stewing beef mixed in with their canned cat food and then some dried food at night. It keeps their quality protein much higher than just commercial food. The old cat has small amounts of cream a few times a week and that's done wonders for his arthritis.

    1. I think you are doing a good job, Nice mix. Well thought out. I give my cat a bit of dried for occasional grazing at night. But 90% of his diet is the best quality wet cat food I can get. One problem is that he prefers low quality cat food! Must have been raised on it. He is a rescue cat so I don't know his past.


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