Protein 101

The facts about protein – this is a re-print of an old article I did for my yahoogroup, in it’s heyday..but the facts are solid and we have an entry point for going deeper into  exploration on the topic.The core components of a healthy and balanced home made diet are the total energy, based of course on nutrients that provide energy – protein, carbohydrate, and fat. We’ve done a   lot on carbs – let’s take a look at protein.
First in a series. 🙂

Section One
This section tells you how proteins play a big role in regulating metabolism, transporting essential materials around the body and defending your dog against disease. So first – what ARE proteins?
Proteins are the essential parts of all living cells and they have many important functions. For one thing, they help build cell structures and muscle fibre. As you are probably aware, it is very important to eat enough protein so your tissues can grow and repair themselves properly. But you may not realise that proteins also play a big role in other bodily functions, such as: regulating metabolism (as enzymes and some hormones); transporting essential materials around the body; and defending the body against disease. Protein is also a source of energy in the diet and will give the same amount of energy as its equivalent weight in carbohydrate. What all this means for you as the owner of a dog, and the person who feeds him, is that you need to be aware of your dog’s protein requirements. In this section, we’ll go over the basic facts about protein, and then talk about how they apply to looking after your dog.

 

What are proteins? Which amino acids are essential?

Essential and non-essential amino acids for dogs

What happens to proteins in the body

The quality of protein from different sources

Why dogs need protein

When dogs need extra protein

The signs of protein deficiency How disease affects a dog’s protein needs

 

 

 

What are proteins? Proteins are large molecules made up of long chains of constituent units called the amino acids. Only about 20 amino acids are commonly found in proteins. But hundreds or thousands of these amino acids may be arranged in any combination to give an almost infinite variety of naturally occurring proteins, each with its own characteristic properties. Like carbohydrates and fats, proteins contain carbon, hydrogen and oxygen. Among these nutrients, the element that makes proteins unique is nitrogen, a constituent of all the amino acids. This is why nutritionists often refer to “nitrogen balance” when they assess the protein status of the body. Two of the amino acids contain sulphur, which means this element is also found in many proteins. Which amino acids are essential? Amino acids may be classified as either essential (indispensable) or non-essential (dispensable). The body cannot produce enough essential amino acids, so they must be supplied in the diet. Non-essential amino acids are equally important as components of body proteins. They can, however, be made from excesses of certain other dietary amino acids, or from other dietary sources of nitrogen. In dogs, 10 of the amino acids are essential to their diet.

Essential and non-essential amino acids for dogs

Essential Amino Acids 

Arginine

Histidine

Isoleucine

Leucine

Lysine

Methionine

Phenylalanine

Threonine

Tryptophan

Valine

 

 Notes: 1. Although classified as non-essential, cystine and tyrosine can supply about 50% of the requirement for methionine and phenylalanine, respectively

2. Methionine and cystine are the sulphur-containing amino acids.

 

What happens to proteins in the body

Proteins in the diet are ultimately broken down into various amino acids by the action of enzymes in the digestive tract. Shorter chains of amino acids are referred to as peptides, so the sequence goes like this: Proteins —–> long-chain peptides —–> short-chain peptides —–> amino acids This process begins in the stomach and continues in the small intestine, where the products of digestion are absorbed across the gut wall into the blood. Amino acids are then transported around the body;cells that need amino acids will remove them from the blood. Any surplus amino acids are processed, mainly in the liver, to remove nitrogen from the molecule. The nitrogen is converted to ammonia, which may be turned into new amino acids or converted to urea and excreted in the urine by the kidneys. Free ammonia is highly toxic, and urea is one of the few safe forms in which nitrogen can be eliminated from the body. The remainder of the amino acid molecule is used as a source of energy, or stored as fat.

The quality of proteins from different sources

When you’re choosing food for your dog, you need to consider (among many factors) the quality of the protein it contains. Quality in this case starts with digestibility and amino acid composition. The amino acid profile of a food reflects which of the 20 amino acids it contains; the highest quality proteins contain the highest levels and best balance of the essential amino acids. These highest quality proteins are found in the food young animals eat: eggs and milk. Next come animal tissues such as meat and fish, and then vegetable and cereal proteins. Vegetable and cereal proteins generally have much lower levels of the essential amino acids, and need to be mixed with other protein sources to provide a diet that includes adequate overall protein quality. Still, this is a generalisation, and there are some vegetable protein sources, such as soya protein concentrate, that have a high digestibility and a reasonably good amino acid profile.(not that I’m recommending soy, just a bit of information).  How digestible a protein is shows how much of the protein an animal eats is actually absorbed across the intestinal wall, into the body and then available for a variety of uses. For dogs, the digestibility of protein varies from around 70% for some vegetable proteins, to between 90% and 95% for egg and milk proteins. In general, dogs can digest proteins of animal origin more efficiently than most vegetable proteins. But there can be a considerable overlap, depending on the protein source and the way the food is prepared. This doesn’t mean dogs should be fed entirely on milk and eggs! In fact, some dogs may not tolerate dairy products very well because they may not be able to digest large amounts of lactose, the sugar in milk. The key factor here is proper mixing of different protein sources to provide a well-balanced, digestible diet- if possible. If your dog doesn’t tolerate mixed proteins, you can try feeding them separately, at different meals – or maybe do with a singe source and supplement accordingly.

 

 

Why dogs need protein

Animals need protein in their diet to satisfy two needs: A).. to provide the essential amino acids that their own tissues can’t make, and B).. to provide nitrogen for making non-essential amino acids and other nitrogen-containing compounds. Some protein is lost from the body every day, even in adult dogs. All dogs have a continuous need for dietary protein to replace the protein they lose during the natural turnover of skin, nails, hair and other body tissues, and in secretions; some of the products of protein breakdown are also excreted in the urine. Also, about 1% of body protein is broken down and re-synthesized every day. But this can’t happen if the body isn’t taking in enough protein, because the supply of some essential amino acids will be limited. And if a dog isn’t taking in enough overall energy, protein synthesis may be compromised, because some released amino acids will be used as an energy source. This will trigger some signs of protein deficiency.It’s important to meet, but not significantly exceed, daily requirements.

 

When dogs need extra protein

Dogs need extra protein when they’re growing, pregnant, or lactating, and when their bodies need to repair damaged tissue. During these critical times, protein quality and digestibility are most important. Growing puppies need greater levels of protein in their diet so new tissues can grow and for normal maintenance. But the minimum protein requirements vary widely according to breed differences, environmental factors, and variations in the dietary source of protein. People often mistakenly believe that large amounts of extra protein will help a growing puppy develop condition and muscle. Unfortunately, this isn’t the case, since any surplus protein a dog consumes is simply converted to energy. Excessive energy intake in growing dogs can lead to problems such as fat deposits and obesity in small breeds and skeletal developmental abnormalities in large breeds.Growth diets should always be formulated by someone with both training and experience in these all-important calculations.

The signs of protein deficiency

Protein deficiency, resulting from either insufficient dietary protein or from a shortage of particular essential amino acids, can lead to generalised weight loss in adult dogs and poor growth in puppies, and to muscle wastage. Other signs include a depressed appetite, rough and dull hair coat, increased susceptibility to disease and, in some cases, edema (retention of fluid).

How disease affects a dog’s protein needs

Dogs that are stressed, through injury or disease, often have greater than normal protein requirements. Unless your vet tells you otherwise, a diet for your dog under these conditions should contain enough protein to support normal growth. But there are certain medical conditions where some restriction of dietary protein may be beneficial. In dogs with developed kidney failure, the kidneys become less efficient in eliminating the toxic products of protein breakdown. By restricting the protein intake, and by using only high-quality proteins, the breakdown of non-essential protein is limited, and toxic waste production is produced. Many of the clinical signs of kidney failure can be improved by feeding your dog a diet with a reduced level of protein, but high-quality protein. You may individually adjust the level of protein according to the severity of your dog’s condition. Furthermore, protein restriction may not be necessary in early cases of kidney failure(although we do start mineral restriction at the first signs). . Similarly, dogs with liver disease may have difficulty processing the nitrogen waste products of protein breakdown. They may benefit from a moderate restriction of their dietary protein. The liver, though, has a great capacity to regenerate and the protein content of the diet should be high enough to support growth of the organ during the critical period of repair. So you need to balance carefully the level of protein in your dog’s diet according to his needs. Changing the source, but not the level, of dietary protein may also be a good idea in managing some cases of food allergy in dogs. Although this condition isn’t common, some animals do develop an allergic response to certain proteins or other ingredients in their diet. In dogs, the proteins most commonly implicated in food allergy are cow’s milk, beef and chicken–alone or in combination. The aim in managing this condition is to find out what the offending ingredient is, and remove it, in all its forms, from the diet. You then need to feed a balanced diet, using one (or a very limited number of) alternative source(s) of protein.

 

 

 

 ADDITION TO THE ORIGINAL ARTICLE

on January 15, 2009 A member asks: “I can understand why no one wants to say what the upper limit of Protein is but I’m surprised that no one knows what the lower limit should be. Why is there such a mystery about how much Protein is enough?”

There is absolutely no mystery about this, the 2006 NRC Guidelines state it clearly:

Minimal requirement = 2.62 grams per kilogram BW ( to the power 0.75)

Recommended Allowance = 3.28 grams per kilogram (to the power 0.75)

Safe Upper Limit = NONE

Protein requirements are also influenced by various factors such as the dog’s overall condition, the digestibility of the food source, activity level and others. In general, when I formulate a diet for a healthy dog, I use 2 – 3 times the recommended allowance. So let’s take a look at an example. My 75 lb dog. First, take the weight in kilograms – so 34.01 kgs. Next, we take this number to the power of 0.75 – easily done on one’s computer calculator: we get the number 14.08. This is the number that will represent my dog in all calculations from here on in, his metabolic weight. To now find his “requirement” – let’s say, his RA or recommended allowance, all we need to do is multiply his number – 14.08 – by the RA – 3.28.

Here’s what we get: 46.182. That’s the recommended gram weight of total protein for the day. If I were to put this strictly into practice, I would end up with a percentage of total protein probably around 15% I am guessing. So let’s have a peek and see. I’ve formulated a diet for Daniel that contains only 46 grams of protein per day. I will also use the RA for total fat, which in this case would be 27 grams. His caloric needs are 1840 per day, so if I devise a very simple diet of brown rice, coconut oil and turkey, and stick strictly to the RA for fat and protein,I would get percentages like this:

Distribution of calories:

Protein: 11.3 %

Fat: 15.6 %

Carbohydrate: 73 %

I would also be feeding this:

1. Turkey, Dark Meat w/skin, boneless, roasted, diced 0.33 of: 1 cup, diced (46.2g)

2. Grain, Rice, Brown, ckd 7 of: 1 cup, cooked, hot (1365.0g)

3. Oil, Coconut 1 of: 1 tbsp (13.5g)

 

That’s right – SEVEN cups of brown rice, and a third of a cup of turkey. This diet technically meets the RA for protein and fat. Of course it doesn’t take into consideration fatty or amino acid levels or vitamins and minerals, this is an exercise to show how there is so much confusion between percentages and actual gram content. I often develop  diets for  dogs  with liver issues where the protein percentage is in the midteens but the gram content is actually over the RA. Vets will want a higher level based on percentage but after we speak they understood that percentages are not the whole story. They tell us how much of a given nutrient the diet contains – RELATIVE to other energy nutrients. In actual practise, I use much – MUCH higher levels of protein and fat in my own dog’s diet as well as professional cases. It’s not in any way optimal to feed a 75 pound dog 1/3 of a cup of meat and 7 cups of rice per day. When we look at the recipe above we also will see that no less than 34 of the 46 grams of total protein come from the rice. So if we were to use more sweet potato than rice we could actually inch up the turkey a bit…. but the poor dog who has to eat so much carb and so little protein! Let’s not forget that from mouth to tail, dogs are carnivores, and derive most quality nutrients from animal sources. I have long defended the use of fiber in the canine diet, because I am not so much interested in what wolves do or don’t eat  – on a practical level, at any rate – but in what type of diet is absolutely optimal for the individual dog I’m working with. This always means some fiber, although the type and amount will vary. But all that said, animal products – protein and fats – should form the mainstay of a healthy dog’s diet. This menu I used above as an example is lower than what I’d use for dogs with liver disease,by far – yet it meets the NRC Guidelines for requirements.

To start working out the amount of protein to use (we’ll get to sources later) find your dog’s protein RA first, then in a home made diet, go 2-3 times above that in grams. You have a huge range of fat to play with, and what works best will often be a matter of some trial and error (and sources,  many dogs can take the same amount of fat if it’s fish based and higher in Omega3 than they can from beef or lamb, or who actually tolerate coconut oil better than animal-fats; it’s really very individual with fat, but that’s another topic). I know this was lengthy and detailed and may be hard to follow if you aren’t used to thinking in numbers. And it is very superficial nutrition –  foundational might be a better word -but extremely important nonetheless. The calories your dog eats, and how those calories are divided between fat, protein and carbohydrate are foundational to how you develop a home made diet, that’s the first step. You will eventually need to think about things like fatty and amino acids, food sources and anti nutrients, biological value – it does get complex. But in terms of protein, there is no safe upper limit – on paper at least. This doesn’t mean that feeding a huge amount of animal protein is advisable; in some cases it can even be dangerous. But there is no need to fear a healthy level of varied animal protein in a normal dog’s diet. In fact, it’s one critical component of an optimal, personalized, health-supportive diet.

 

Zinc

Since this sub-category is “Nutrients A-Z” – and since I am always going on about zinc, I thought we might start with a short entry on the role, requirements and optimal sources of zinc in the canine diet.

In contrast to the never-ending tomes I compose on energy nutrients, I’m going to strive to be succinct in these entries – shall we see how I do with that goal?

DESCRIPTION

ZINC is the second must abundant trace mineral in the body, after iron. It is an essential nutrient that must be ingested dietarily. Zinc is present throughout the body in low concentration, but in most tissues. It performs multiple critical functions and must be supplied at adequate levels consistently or deficiency states will result, from mild to severe. Zinc is essential but should not be taken in high doses or even moderately elevated doses over a long period of time. It is one of the nutrients most commonly underfed in home made diets, raw or cooked.

FUNCTIONS

Zinc’s functions in the body can be divided into three categories; these are Catalytic, Structural, and Regulatory.

1) Catalytic – Zinc is known to act as either a catalyst or a cofactor in  200 enzymes – these in turn are involved in carbohydrate and protein metabolism, cell replication and wound healing.

2) Structural – Zinc plays an essential role in the structure and function of biological membranes and proteins; when cell membranes lose zinc they become more vulnerable to oxidative stress and suffer functional impairment.

3) Regulatory – Zinc is also needed for “stabilization of DNA and RNA ( NRC, Nutrient Requirements of Dogs, 2006 pg. 173)  functioning as a cofactor in the synthesis of both. Zinc “finger proteins” regulate gene expression “acting as  transcription factors (binding to DNA and influencing the transcription of specific genes). Zinc also plays a role in cell signaling and has been found to influence hormone release and nerve impulse transmission.” Linus Pauling Institute page on zinc here

In plain language – zinc plays a role in immune function , protein synthesis , wound healing , DNA synthesis, and cell division. Zinc also supports normal growth and development  for your growing dog.. A daily intake of zinc is required to maintain a steady state because the body has no specialized zinc storage system.

REQUIREMENTS

For humans, the RDA for adults for zinc is 15 mgs daily.

For dogs, whose sizes range from  teacup to Great Dane, a little more calculation is involved.

The National Research Council  has provided us with an Adequate Intake/Recommended Allowance for dietary zinc for dogs.  It is 2.0 mgs/ KGbw/0.75.  What this means is; to figure out what an individual dog should take in, we first need to take the body weight in kilograms to the power of 0.75 – this  number is  used to calculate all dietary requirements, including energy. With zinc, the number we arrive at is multiplied by 2.0. So let’s look at a 50 pound dog, once again;

Pounds = 50, so kgs = 22.68 kilograms

Now take that number to the power of 0.75 – using the Microsoft calculator on your computer, set to Scientific, that function looks like this: x^y

Now you have the “magic number” – 10.39

Next,multiply this number by 2.0 and you have 20.78 mgs – let’s say, 21 mgs daily. So a fifty pound dog requires MORE daily zinc than a 150 pound human does. In a weekly batch for a fifty pound dog – which is what I often recommend and what I do myself much of the time – that’s 147 mgs. Depending on the fiber content of the diet, we might want to go a little bit higher than that. But let’s look at the 21 mgs a day – if our fifty pound dog is not very active, and eating 1200 calories a day, coming from turkey, beef liver, brown rice, and sardines, we might end up with about half that amount. Although the foods are fresh, home prepared and healthy, carbs low and glutenfree – the recipe is still seriously low in zinc.  Over time, immune system issues, skin issues, other problems arise that – chances are – your vet, even holistic vet, may not diagnose.

The moral of this story is don’t depend on food alone for adequate levels of zinc. If you’re doing a home made diet, you need to supplement.  Do the math, and supplement accordingly. Why go to all the work of shopping cooking measuring and feeding home made diet, only to shortchange your dog on one of  the essentials?

DEFICIENCY

“Canine and Feline Nutrition:A Resource for Companion Animal Professionals” lists the following signs of zinc deficiency in dogs:

– growth retardation in pups

– anorexia

-testicular atrophy, impaired reproductive function

– immune system dysfunction

– conjunctivitis, skin lesions

In dogs and cats, skin and hair coat changes are usually the first clinical signs of zinc deficiency; these signs have been described as dull, coarse hair coat and skin lesions that show parakeratosis and hyperkeratinization*” (Canine and Feline Nutrition, pg. 48) This is of interest to me as a nutritionist, as I see so many cases of poor coat where the owner immediately started to supplement fatty acids (which may or mat not be in need of supplementation). In either case, if the poor coat is related to zinc deficiency, fish oils will no help it. Adding supplemental zinc to recommended levels, or putting the dog on a diet formulated with AAFCo or NRC levels and ensuring they eat adequate amounts of it, will. Note there are many causes of poor coat, but fatty acids always seem to be what owners – and vets – will go to first.

Parakeratosis: dry, flaking, scaly skin

Hyperkeratinization: a disorder of the cells lining the inside of a hair follicle. It is the normal function of these cells to detach or slough off  from the skin lining at normal intervals. The dead cells are then forced out of the follicle (primarily by the growing hair). However, in hyperkeratinization, this process is interrupted and a number of these dead skin cells do not leave the follicle because of an excess of keratin, a natural protein found in the skin. This excess of keratin,  results in an increased adherence/bonding of dead skin cells together. This cohesion of cells will block or “cap” the hair follicle (leading to keratosis pilaris) or clog the oil duct (leading to acne).

EXCESS

The NRC Guidelines states that “zinc is a relatively nontoxic substance and dietary deficiencies are much more likely to occur than are excesses” (NRC pg 175) Clinical signs of (rare) zinc toxicity, usually from ingestion of metallic objects, include acute gastroenteretis, hemolytic anemia and lethargy.  However, it is still important to monitor zinc levels due to it’s interactions with other minerals, especially copper, iron and calcium. More on this in Nutrient Interactions (below). It is worth noting that the current trend to amping up zinc for humans during a cold or other infection is no substitute for maintaining good zinc levels all year round!  Strong immune function depends regular levels of zinc  more than sudden, sweeping “therapeutic” doses.

Although this is related to humans, it may be of interest here as well. Acute toxicity has been reported:

Isolated outbreaks of acute zinc toxicity have occurred as a result of the consumption of food or beverages contaminated with zinc released from galvanized containers. Signs of acute zinc toxicity are abdominal pain, diarrhea, nausea, and vomiting. Single doses of 225 to 450 mg of zinc usually induce vomiting. Milder  GI distress has been reported at doses of 50 to 150 mg/day of supplemental zinc. Metal fume fever has been reported after the inhalation of zinc oxide fumes. Specifically, profuse sweating, weakness, and rapid breathing may develop within eight hours of zinc oxide inhalation and persist 12-24 hours after exposure is terminated.”

Linus Pauling Institute, page on zinc

The major complication of less extreme, longterm overdose is copper deficiency.


FOOD SOURCES

By far the highest concentration of zinc in food is found in oysters; most of us, however,  are not going to include these in our dog’s daily diets, although I have known some who tried (and there are other problems associated with daily feeding of fish and seafood, which I’ll be going into in detail in the section on protein). More reasonable sources for the average home feeder include:

Beef– 5 ounces of lean, cooked brisket has almost 10 mgs

Pork– 5 ounces lean cooked pork loin – 3.5 mgs

Turkey–  5 ounces darkmeat with skin, cooked, 5.6 mgs

Lamb– 5 ounces  lean leg, cooked – 5.8 mgs

Liver, beef and calves: Beef liver is a good source with 4.5 mgs per 3 ounces of cooked weight, but calves liver has almost twice that amount with 8 mgs  pre 3 oz serving. beef liver is higher in copper though – again almost twice the level – so decide what you need most and add accordingly.

Other foods contribute to the total zinc content, but less so, and much of the zinc in foods like rice and lentils is offset by phytate. I consider turkey, beef, lamb and pork among the best choices for dietary zinc, for dogs. For interests sake, here’s a few more foods high in zinc (we can have some, too!) Each 100gram serving of the foods below contains:

Pumpkin seeds- 7.5 mgs

Ginger root-6.8

Pecans- 4.5

Brazil Nuts- 4.2

Oatmeal, cooked – 3.2s

Split peas, cooked – 4.2

Buckwheat, cooked – 2.5

Check the zinc content of your dog’s food at http://www.nutritiondata.com and always remember that any  single food you use will have other nutrients too, so analyze your full recipe, and supplement according to what is missing or low. Copper is often low as well, so balance it all out carefully. 🙂



DRUG INTERACTIONS

Something we as dog lovers should be area of is zinc’s potential effect on some antibiotics – as much as we hate to give them, they are occasional necessities, and even life savers. Zinc supplementation may decrease absorption of some antibiotics, so do give them away from food or discuss with your vet. There is no need, if making a balanced home made diet, to leave the zinc out during a round of antibiotics. This applies to supplemental zinc added above and beyond the RA, such as one might use during infection or therapeutically to reduce copper levels. Not a huge concern, but something to be aware of.

Some types of diuretic, especially used longterm, may increase need for dietary zinc. Again – please discuss with your veterinarian.

ANTIBIOTIC INTERACTIONS

  • Ciprofloxacin (Cipro)
  • Levofloxacin (Levaquin)
  • Ofloxacin (Floxin)
  • Moxifloxacin (Avelox)
  • Norfloxacin (Noroxin)
  • Gatifloxacin (Tequin)
  • Tetracycline
  • Minocycline (Minocin)
  • Demeclocycline (Declomycin)

However, doxycycline (Vibramycin) does not seem to interact with zinc.

Cisplatin (Platinol-AQ) — This drug, used for chemotherapy to treat some types of cancers, may cause more zinc to be excreted in the urine. If your dog is undergoing chemotherapy, do not give additional zincwithout talking to your oncologist.

Deferoxamine (Desferal) — This medication, used to remove excess iron from the blood, also increases the amount of zinc that is lost in urine.

Immunosuppressant medications — Since zinc may make the immune system stronger, it should not be taken with corticosteroids (such a prednisone), cyclosporine, or other medications intended to suppress the immune system.

Nonsteroidal anti-inflammatory drugs (NSAIDs) — Zinc interacts with NSAIDs and could reduce the absorption and effectiveness of these medications.

Penicillamine — This medication, used to treat Wilson’s disease (where excess copper builds up in the brain, liver, kidney, and eyes) and rheumatoid arthritis, decreases the levels of zinc in the blood.

Thiazide diuretics (water pills) — This class of medications lowers the amount of zinc in the blood by increasing the amount of zinc that is passed in  urine.  These include

  • Chlorothiazide (Diuril)
  • Hydrochlorothiazide
  • Chlorthalidone (Hygroton)
  • Indapamide (Lozol)
  • Metolozone (Zaroxolyn)
  • Polythiazide (Renese)
  • Quinethazone (Hydromox)
  • Trichlormethiazide (Metahydrin, Naqua, Diurese)




NUTRIENT INTERACTIONS

Zinc, as has been mentioned interacts with copper, iron and calcium, and is adversely affected by high dietary phytate. There are other less wellknown interactions, especially the connection with Vitamin A –  we could go into much detail about all of them but at the very least I to touch on them here . For those who think that all this calculating of numbers and percentages and so on is unnecessary micromanagement, read on. The mineral levels are critically important, and become even more so for a growing dog or one under stress or dealing with illness. Zinc is affected by, and can also affect, many other essential nutrients – goog reason to find the right levels for your own homefed dog, and stick with them.

PHYTATE

Dietary phytate reduces the absorption of zinc, and if excess presence is combined with overly high levels of calcium,  a deficiency scenario can develop, even when adequate levels of zinc are provided in the diet.  Phytate – as discussed in the carbohydrate thread, is a chemical found in many plants, and has both benefits and undesirable aspects. Whenever a food rich in phytate comprises a significant part of the diet, steps should be taken to reduce it, as in pre-soaking and overcooking brown rice. In some cases elevated minerals may be added, but this is an individual call and not all dogs can or should have mineral elevation to compensate for phytate. The ideal solution is to feed controlled amounts of foods with phytate, and keep minerals in the RA range. Brown rice and lentils, while beneficial foods for the dog in reasonable quantities, contain significant levels of phytate;cooking does reduce it significantly.

COPPER
High zinc intake adversely affects copper status and absorption; many home made diets are marginally to seriously low in copper to begin with. The optimal ratio between zinc and copper is 10:1. If zinc is elevated for any reason, copper levels should be raised too. The exception to this is of course, copper-storage disease, in which high levels of zinc are used therapeutically to chelate (bind to and remove) copper from the body. Often home made diets are low in copper as well, so either add copper-rich foods like beef liver when adding zinc, or supplement with both, to ensure  copper levels stay optimal, too.

CALCIUM and IRON: Both of these minerals can impair the absorption of zinc, even when adequately represented in the diet, if they are overfed. I often see home made diets which are not only low in zinc but very high in calcium and iron ( this is the classic RMB scenario where beef is the main protein source).  Be sure to check the required levels of both calcium and iron, and make sure they are not excessive, or you can still experience  the many issues associated with even mild zinc deficiency. It can take years to show up, so prevention is key.

VITAMIN A

Zinc and vitamin A interact  as well, although this has not been as well studied in the dog as in humans.. Zinc is a component of retinol-binding protein,which is necessary to  carry vitamin A in the blood. Zinc is also required for the enzyme that converts retinol (vitamin A) to retinal.Retinal s necessary for the synthesis a protein called  rhodopsin, present in the eye; this protein is needed for the eye to adapt to the dark properly. Low levels of zinc is associated with decreased release of vitamin A from the liver, which may contribute to symptoms of night blindness .



ON SUPPLEMENTATION:

Zinc supplements are available in a number of forms; citrate, picolinate and gluconate are all popular versions.

The inorganic forms of zinc found in multivitamins are usually not absorbed very well  in human studies; zinc is most bioavailable when it is bound to a ligand/chelator (such as EDTA), amino acid (such as histidine) or organic acid (such as citrate) . Zinc methionine is an exception, with studies showing it to have low bioavailability equal to that of the inorganic forms chloride and proprionate, and it is hypothesized that the bond is not strong enough to survive the upper GI tract . Zinc picolinate is one of the most bioavailable forms .

Chelated” means connected with another molecule. These include organic acids such as  picolinic acid, orotic acid, citric acid and gluconic acid.These are the forms of zinc I use and recommend in my diets. No inorganics – sulfate and oxide. Zinc methionine has the above-mentioned controversy about it, so I stick to the gluconate, citrate and picolinate forms

It’s good to know that zinc oxide, often used in cheaper commercial dogfoods, is not considered a highly bioavailable form at all and should be avoided. I see a number of foods now that are trying to appear “premium” and are in fact, better than some f the truly abominable products, but still cutting corners where consumers aren’t likely to notice. Minerals in oxide form is a big red flag.  I prefer not to use sulfate, but stick with the chelated forms.


ETCETERA

  1. In humans many factors can increase the need for zinc – but many, such as alcohol consumption, do not apply to dogs. There may be a need for extra zinc in dogs with kidney disease, pancreatitis, IBD (Inflammatory Bowel Disease) any type of infection, diabetes, liver disease, EPI (exocrine pancreatic insufficiency) or who are on a vegetarian diet.
  2. Dogs who require a high fiber diet, such as those with pancreatitis, should have zinc given separate from meals if at all possible.
  3. Zinc malabsorption occurs in several breeds of dogs, notably the Alaskan Malamute, Siberian Husky, Great Dane and Doberman Pinscher. The syndrome usually shows up at about a year old and manifests frequently with quite severe dermatological symptoms; Owners almost always will take the dog to the vet at this point and oral supplementation resolves the issue, although much higher amounts of zinc are used than for dogs with normal absorption capacity. More on this issue here

TAKEWAY MESSAGE

If you are feeding a home made diet unsupplemented with zinc, chances are your dog is in need of some.  Run your recipe through nutritiondata.com and check the amounts against his requirement, as explained above. Low zinc can contribute to skin and coat problems, if your dog has any poor coat or skin issue, evaluate dietary zinc as part of your strategy.

Don’t stress, but take this one to heart. Its all too often overlooked as something that “variety” will take care of – and trust me, it won’t.


RESOURCES

Canine and Feline Nutrition, A Resource for Companion Animal Professionals

Nutrient Requirements of Dogs, National Research Council, 2006

Encyclopedia of Nutritional Supplements, Michael T. Murray

Linus Pauling Institute