ADVANCED NUTRITIONAL CONCEPTS
This chapter is designed for those who want additional information on some of the materials presented in the first seven chapters. For many of you, this information is over and above what you need to know to feed the ABC way. For those of you want this level of information, the concepts and research to be covered here include:
1. An introduction to the chemistry of fats for dogs.
2. Do wild prey animals produce different fats than domesticated animals?
3. Dogs and carbohydrates.
4. Kidneys and high protein diets.
5. Pet food math.
An introduction to the chemistry of fats for dogs
As discussed throughout the book, the issue of fats in a dog’s diet— both the amount and balance—is important and not well understood by most dog owners. Fortunately, by following the recommendations in the previous chapters, it’s easy to improve the fat balance and add defended-from-oxidation DHA and other essential fats, whether you’re feeding dry, frozen, or homemade foods. If you want to know why I have made those recommendations, this section is for you. Follow me on this short journey into the chemistry of fats for dogs. It’s exciting, because recent science shows that we can really help our dogs be smarter and healthier by improving the balance of fats we feed them.
The chemistry of fatty acids
The fats in our food consist primarily of fatty acids, which are chains of one to twenty-four carbon atoms with hydrogen atoms attached. In chemistry-speak, it looks a little like this: C-C-C-C-C-C-C-C-C-C-C-C, a 12-carbon saturated (all single bonds) fatty acid. All the carbon atoms, except the ones at each end of the chain, have hydrogen atoms attached all around then; the carbon atoms are saturated with hydrogen.
How the carbon atoms are attached to each other and the number of carbon atoms in the chain determines the type of fat and the properties of the fat. The carbon atoms can be attached to each other with single bonds, sharing one electron, or with double bonds, sharing two electrons. In chemistry-speak, it looks like this: C-C-C-C-C-C-C-C-C-C=C-C-C-C-C-C, a 16-carbon monounsaturated (mono = one double bond) fatty acid. Single bonds are more stable than double bonds; it’s easier to share one electron than two. Fatty acids with only single bonds, saturated fats, are more stable—less likely to go rancid—than those with one or more double bonds, the monounsaturated and polyunsaturated fats.
There are three broad categories of fatty acids: saturated fatty acids (SFAs) with no double bonds; monounsaturated fatty acids (MU-FAs) with one double bond; and polyunsaturated fatty acids (PU-FAs) with more than one double bond. No fat is totally saturated or unsaturated. Almost all natural fat sources contain SFAs, MUFAs, and PUFAs, as shown in Table 8.2. Natural fats may contain 50 to 60 different fatty acids. For instance, cow’s milk has at least 60 different fatty acids and most fish contain 50 or more different types of fat.
Saturated fatty acids
Saturated fatty acids have no double bonds; adjacent carbon atoms share only one electron. This is a stable relationship, and therefore saturated fats, like coconut oil and beef fat, do not readily oxidize and have long shelf lives. There are many types of saturated fats, depending upon how many carbon atoms are attached. The shorter the saturated fat (the fewer the number of carbon atoms), the more readily it burns, and the more easily the dog can digest it. Coconut oil is rich in short chain saturated fats, and animal fats are rich in the longer saturated fats.
Saturated fats provide favor and energy, and assist in the absorption of fat-soluble vitamins. Some of the short-chain (2–6 carbon atoms) saturated fats are reported to have anti-microbial properties—which may help prevent some bacterial and viral diseases. Saturated fats are required in cell membranes. Too much saturated fat (which I define as more than 20 g/1,000 kcal or more than 20 grams per day for a 45-pound pet dog) can lead to health problems, including reducing the dog’s ability to learn and remember.
Almost all fat-containing foods have some saturated fats. As long as there is enough fat in the diet, there’s usually enough saturated fat.
Monounsaturated fatty acids
Monounsaturated fatty acids have one double bond; they are therefore more prone to going rancid than saturated fats. If packaged and handled well, they are shelf stable for several months or more, especially if they contain antioxidants. Most plant and animal fats contain MUFAs. Olive oil, avocado, nuts, and bone marrow having especially high MUFAs content. Monounsaturated fatty acids are also found in the cell membranes of plants and animals—their fluidity helps keep animals’ arteries supple. Some reports indicate that too many MUFAs may interfere with the functions of the essential polyunsaturated fats. The ancestral diet contained 15–25 g/1,000 kcal of MUFAs and I think that is a wise target.
Polyunsaturated fatty acids
Polyunsaturated fatty acids have more than one double bond. Sharing two electrons (double bonds) is not a stable relationship; an oxygen atom can come along and take an electron, which oxidizes the fat. That’s why polyunsaturated fats go rancid quickly when exposed to air and light, unless protected by a variety of antioxidants. The more double bonds (DHA has six) in a fatty acid, the more prone it is to rancidity.
Where the first double bond is determines the properties of the fat and whether it is an omega-6 or omega-3 fat, the two primary types of PUFAs. Because humans and dogs cannot make a double bond after the third carbon atom—omega-3 fatty acids (abbreviated n-3), and omega-6 fatty acids (n-6)—it is therefore essential for dogs (and humans) to obtain these fatty acids from the diet; these are the essential fatty acids, or EFAs. It is important that there are proper amounts of total PUFAs (5–15 g/1,000 kcal), the omega-6 and omega-3s are balanced in the range of 2:1 to 6:1, and that a complete range of n-6s and n-3s are included in the diet.
Omega-6 fatty acids
The four primary omega-6 fats are linoleic acid (LA), gamma linoleic acid (GLA), conjugated linolenic acid (CLA), and arachidonic acid (AA). LA is the simplest and most stable, and is used within the body primarily to make the longer chain omega-6 fatty acids, such as arachidonic acid. Depending upon its health and other factors, a dog can convert 18-carbon LA to GLA, CLA, and then to 20-carbon AA, the primary fat in the brain. It takes energy and special enzymes to make this conversion, so a dog under stress can have difficulties producing sufficient quantities of these “conditionally essential” (essential during times of high stress or growth) fatty acids. Lack of LA in the diet will cause the dog’s coat to fall out, make the dog sluggish, or eventually kill the dog. Lack of AA, GLA, and CLA in the diet has more subtle effects; lack of AA, a brain fat, in a puppy’s diets can produce a “dumber” adult dog. On the other hand, too much LA and AA can cause inflammation throughout the dog’s body, and can crowd out the use of DHA in the dog’s brain, again producing a dumber dog.
Omega-3 fatty acids
The three primary omega-3 fatty acids are ALA, EPA, and DHA. The simplest omega-3 is ALA (alpha linolenic acid), which we get from flaxseed, chia, hempseed, walnuts, and other plants. Humans and dogs use ALA primarily for the raw ingredients to make EPA and DHA, which are essential for optimal body, brain, and eye health. Most dogs can convert some (0.1–15%) of the 18-carbon ALA to the 20-carbon EPA and then to the 22-carbon DHA, but recent studies show that some dogs (including older dogs, young puppies, and adult dogs under stress) can’t convert enough ALA to DHA to meet their needs and therefore need a dietary source of DHA, usually from fish or fish oils. Many dog foods contain ALA, which is less expensive and more stable than DHA, and tout their “omega-3s,” but it’s not the same: to be at their best physically and mentally, dogs need to consume defended-from-oxidation DHA.
The misleading omega-6 to omega-3 ratio
Many researchers recommend an omega-6 to -3 ratio of 2:1 to 7:1. Responding to consumer demands, many dog food manufacturers list the omega-6/-3 ratio on their packages or websites. A good omega-6 to omega-3 ratio, though, does not mean that the fats are balanced and complete.
Evaluating foods and diets based upon a listed omega-6/-3 ratio is often not helpful for two reasons.49 First, a “perfect ratio” of omega-6/-3 of 3:1 is not a balanced fat diet for dogs if all the omega-3s are ALA from plant sources and do not include a source of defended-from-oxidation DHA. Second, the amounts of omega-6s and -3s are equally important as the ratio of omega-6s/-3s. As you can see in the Table 8.1 below, some diets (in this case 93% lean beef) have good omega-6/-3 ratios, but do not have enough omega-6s to meet minimum requirements, and therefore are not healthy. Similarly, some diets have good ratios, but contain too many PUFAs. Too few or too many omega-6s and -3s, even in the ideal ratio, may contribute to health problems, including premature aging.50
Table 8.1 93% lean beef, good ratio, but insufficient amounts of LA and ALA, g/1000 kcal
*does not meet standards
Table 8.2 Fatty acid content of various oils
PUFAs are fragile. Increased consumption of PUFAs, especially DHA, EPA and AA, is healthful only if the fats are well defended-from-oxidation, before and after the dog consumes them.
One of the most important lessons I learned about formulating dog foods was: what can oxidize will oxidize. Many years ago I developed a freeze-dried “raw” food. Freeze drying removes the moisture in a food at low temperatures, thereby preserving most of the nutrients. I packaged the product in a high-barrier-to-oxygen foil bag, and included an oxygen scavenger (one of the small packets often found in vitamin jars) in the bag to absorb the oxygen left in the bag after packaging. Theoretically, I should have had a stable product, with a shelf life of at least one year. But when I tested the product every month for oxidizing fats, I found a steadily deteriorating product. The fats—probably EPA and DHA—were becoming rancid. The defenses against oxidation I utilized were not sufficient. It’s not just the DHA and EPA in the food that will oxidize; these fats in the dog’s cells can oxidize as well. I define defended fats as those having enough defenses against oxidation to protect the fats before and after ingestion.
Before ingestion, the fats need physical defenses such as eggshells, nutshells, fish scales, and opaque glass packages, and antioxidant protection to prevent them from going rancid. After ingestion, the fats must be protected by sufficient amounts of a variety of anti-oxidants obtained from the diet, including vitamin E and carotenes. Without sufficient antioxidant protection, for example, the DHA in the cell membranes of the dog’s eyes may oxidize, and the dog may lose vision as she ages.
Do wild prey animals produce different fats than domesticated animals?
Hypothesis: Domesticated prey animals, even if they are fed the same food, will not have the same types of fat as wild prey animals because they don’t need the same types of fats.
A wild animal needs to hear and see well, think and move quickly in order to survive. It needs significant amounts of DHA, a very fluid fat, to do these tasks well. Generally speaking, areas of the body that require rapid movement contain DHA (a hummingbird’s wings are rich in DHA, for example). I suspect that wild prey animals will convert more of the ALA they consume (from grasses) to DHA than domesticated animals that have no need for rapid movement or alertness.
It’s expensive—in terms of energy and nutrients—for an animal to convert ALA to DHA and then store the DHA. The domesticated pasture-fed animal has no need to convert the ALA it eats to DHA, so it probably won’t make as much DHA as the wild animal. Why waste the energy converting ALA to DHA when it’s not needed? DHA requires greater protection against oxidation than ALA, putting a further strain on the animal. When it comes to storing fat, saturated fats are much more stable.
A pasture-raised ruminant, with little need to think and move quickly, would probably store as much fat as possible as stable, saturated fats, and use much of the polyunsaturated fats it consumes for what minimal energy needs it has. The wild animal, with a greater need for the polyunsaturated fats, probably converts more of the saturated fats to energy. Fed the same foods (different quantities based upon activity levels), domesticated prey animals would therefore have more saturated fats, and a higher percentage of their polyunsaturated fats will be short-chain fats than with wild prey animals, who would have a higher percentage of long-chain polyunsaturated fats, particularly DHA.
Dogs and carbohydrates
Do dogs need carbohydrates? No, dogs do not need carbohydrates, as long as they are eating a high protein diet. All the leading canine nutrition textbooks, quoted below, agree. But that does not mean all dogs should not consume carbohydrates. Carbohydrates provide a significantly less expensive source of energy than protein and most fats. While, in a perfect world, I’d prefer for dogs to eat low carbohydrate diets, in the real world it is often essential for dogs to consume considerable amounts of carbohydrates to reduce the cost of the dog food for the dog’s owner, and the cost of producing meat on the environment.
Moderate amounts (up to one-third by weight of the recipe) of high protein, mineral rich carbohydrates such as sweet potatoes, yams, and low gluten grains such as oats and rice, are healthy for most adult dogs, as long as the fats in the recipe are balanced and the meats lean. In Appendix A, I present four high protein, low-and-balanced fat, moderate-carbohydrate content recipes, developed in conjunction with Mary Straus, originally published in the Whole Dog Journal.
While some raw food “purists” may object to feeding any carbohydrates to dogs, I pose the following question:
Q. Which is healthier—very high levels of fats, or moderate levels of carbohydrates from nutrient rich foods, such as sweet potatoes?
A. I think a strong argument can be made that moderate levels of carbohydrates from nutrient rich sources are healthier for most adult dogs than diets high in saturated fats (typical raw beef products) or polyunsaturated fats (typical chicken products).
Here are comments from four of the leading textbooks about the role of carbohydrates in dog foods:
Canine and Feline Nutrition (co-authored by two scientists from Iams): “The fact that dogs and cats do not require carbohydrate is immaterial because the nutrient content of most commercial foods include (carbohydrates).”51
Small Animal Clinical Nutrition IV, published by the founder of Science Diet: “Dogs and cats do not have an absolute dietary requirement for carbohydrates in the same way that essential amino acids or fatty acids must be provided…. From a practical sense, the answer to this question is of little importance because there are carbohydrates in most food ingredients used in commercially prepared dog foods.”52
The Waltham Book of Companion Animal Nutrition: “There is no known minimum dietary requirement for carbohydrate…”53
Nutrient Requirements of Dogs and Cats, from the National Research Council of the National Academies (NRC), 2006, states that even pregnant and lactating bitches do not need a dietary source of carbohydrate as long as they have a high protein diet.54
Is Carbohydrate a Dirty Word?
You won’t find carbohydrates listed on your dog food bag even though almost all dog foods consist of at least some carbs. In the guaranteed analysis, required on every dog food or treat sold in the U.S., you’ll find water, protein, fat, and fiber. The word “carbohydrate” is almost never mentioned. Fiber is an indigestible carbohydrate—it is primarily plant cell walls resistant to digestion.
Members of the Association of American Feed Control Officials (AAFCO) regulate pet foods, including treats and supplements, on a state-by-state basis. Manufacturers must send labels of all the pet foods they sell to the association member in each state, who then reviews the label and issues a license to allow sale of that product in the state. Most members follow the model regulations as designated by AAFCO. If a label does not follow AAFCO regulations, the state regulator may decide not to license the product. If the product is sold without a license, the regulator can go into a store and remove the product, which is not a good thing to happen to a pet food manufacturer. Therefore, most pet food companies play by AAFCO’s rules (the more powerful companies help make the rules).
AAFCO guidelines, as published in the Official Publication of the Association of American Feed Control Officials, discourage the use of the word “carbohydrate” anywhere on a pet food label. Here are the exact words:
“…carbohydrate guarantees are no longer considered as necessary or meaningful for purchaser information, therefore, their future use is discouraged.”55
Technical manuals are not regulated by AAFCO, but one can still rarely find “carbohydrate” mentioned, whether the manual is written for veterinarians or dog guardians. For example, in a publication for veterinarians, Applied Clinical Nutrition of the Dog and Cat, A Guide to Waltham Veterinary Diets, the word “carbohydrate” is not even mentioned in the 44-page technical discussion of their Veterinary Canine Calorie Control Diet and Canine Restricted Protein Diets. Waltham lists protein, fat, ash, crude fiber content and 12 minerals, 11 vitamins, 11 amino acids, but not carbohydrates. 56
Kidneys and high protein diets
There are many myths in the world of dog foods. One of them is that high protein diets damage the kidneys of dogs. Mary Straus, writing for the Whole Dog Journal, responds to this myth:
Research done on dogs has now proved that protein does not damage kidneys, and feeding a lower protein diet does not protect them. In fact, senior dogs fed high protein diets live longer and are healthier than those that are fed low protein diets, even when one kidney has been removed. Studies conducted at the University of Georgia in the 1990s demonstrated that feeding protein levels of 34 percent [on a dry matter basis]to older dogs with chronic kidney failure and dogs with only one kidney caused no ill effects.
These same studies did raise the issue of whether low-protein diets may cause harm. The mortality rate was greater for the dogs fed 18 percent protein than for the ones fed 34 percent protein. Another study done on dogs with only one kidney showed that protein levels up to 44 percent of the diet had no harmful effect on the remaining kidney.”57
You can find the full article, with references, at www.dogaware.com.
Pet food math
The basic math concept for analyzing any pet food is:
fat + protein + carbohydrate = 100% of calories
Most of us, including when we look at food labels on human food, tend to focus on the gross amount of fat, protein, and carbohydrates contained in the food we eat or feed our dogs. The best way to analyze any food is the way professional food scientists and formulators do—by looking at where the calories come from. In other words, they analyze foods on a caloric basis, and that’s how I have analyzed the recipes in this book.
So given this perspective, it is not always easy to answer a question like “How much protein is in the dog food you feed?” The “guaranteed analyses” on bags of dog food do not tell you the most important information: the percentage of calories from protein and the grams of protein per 1,000 kcal. What I am going to show you in this section is how to take the guaranteed analysis information and calculate the protein, fat, and carbohydrate content on a “dry matter” (DM), percentage of calories and grams of nutrients on a per 1,000 kcal basis.
Guaranteed analyses: protein, fat, carbohydrate content.
All dog food and treat packages are required to include a guaranteed analysis, listing protein and fat as minimums, and fiber and moisture as maximums on an “as fed” basis. The guaranteed analyses are not complete, though, since they do not list the carbohydrate content of the food. This is important information—carbohydrate content is required on all human food labels—but pet food regulations do not allow the word “carbohydrate” on the label. So we need to calculate carbohydrates, and, fortunately, it’s easy.
All dog foods consist of protein, fat, moisture, ash, and carbohydrate. The total of these components equals 100%. Ash is what’s leftover if one cooks the food at very high temperatures; it is generally the mineral content of the food. Fiber is the part of the plant material that the dog cannot digest; it’s considered to be a carbohydrate.
Carbohydrates, while not essential nutrients, are used in most dry dog foods as an inexpensive (relative to meat) source of calories.
Calculating carbohydrate content
Here is a typical guaranteed analysis for an adult dry food:
Keep in mind that the protein and fat figures are minimums only; few companies understate protein, but some may understate fat. Ash is usually not listed. Typical ash content of a dry food is in the 4 to 8% range, and we’ll use 6% in our calculations. Even though fiber is a carbohydrate, we will subtract the fiber when calculating total digestible carbohydrate content because fiber provides no calories.
The FDA defines how to calculate carbohydrate: Subtract the weight of crude protein, total fat, moisture, and ash from the total weight (“wet weight”) of the sample of food.58
Therefore, in our example, we calculate the carbohydrate content like this:
Carbohydrate contents= 100% — 26% — 15% — 10% — 6% = 43%.
In this example, carbohydrates include fiber. Subtract the fiber (4%) and the digestible carbohydrate content is 39%.
Comparing protein content of dry and canned or wet foods
To compare dry with wet foods, you must subtract the water content from the food content. Water, though absolutely essential, provides no calories, minerals, or vitamins. What remains after you remove the water is the dry matter (DM)—protein, fat, carbohydrate (including fiber), and ash. A DM analysis tells us the percentage of the DM that is protein, fat, and carbohydrate, and allows us to make more accurate comparisons between various types of foods.
The label of a typical canned dog food states:
Which has more protein, the dry food at 26% protein, or the canned food at 10% protein? Let’s find out.
Step 1. Calculate the total dry matter in both foods by subtracting the percentage moisture from 100%.
Canned food, with 75% moisture, has 25% total dry matter (100% — 75%). If the can is 12 oz, 25% of the can, or 3 oz., is dry. The rest is moisture. Dry food, with 10% moisture, has 90% dry matter.
Step 2. Divide the listed protein percentage by the dry matter percentage.
Listed protein: 10%. Divide 10% by 25% = 40% protein DM.
Listed protein: 26%. Divide 26% by 90% = 29% protein DM.
The canned food has more protein than the dry food, even though the listed protein of the dry food is much higher. Protein is 40% of the dry matter of a typical canned food (listing 10%) and 29% of the dry matter of the dry food (listing 26%).
You can calculate the fat and carbohydrate content in the same manner. Table 8.3 compares the macronutrient content of the dry and canned foods above on dry matter basis. The carbohydrate content is the digestible portion only (total carbohydrate less fiber).
Table 8.3 Macronutrient content, dry matter basis
Calculating percentage of calories
A better picture of the overall balance of the diet emerges when the actual percentage of calories from each nutrient is known. Human nutritionists almost always think in terms of the percentage of our calories that we get from fat. It is important information for pet foods as well.
Fat provides 8.5 to 9 kcal of metabolizable energy (the amount of usable energy obtained from the food by the dog) per gram, more than twice as much as carbohydrates and protein, which provide 3.5 to 4 kcal/gram, depending on the quality of the food. Human-quality foods are generally more digestible than pet quality foods, therefore they contain more energy. When calculating calories for human foods, food scientists use Atwater factors: 9 kcal/g of fat and 4 kcal/g of protein and carbohydrate. For animal foods, AAFCO requires that caloric content be calculated using modified Atwater factors: 8.5 kcal/g of fat, and 3.5 kcal/g of protein and carbohydrate because the ingredients are less digestible. In this book, I assumed all ingredients were human grade, and therefore all calculations used Atwater factors.
To determine the percentage of the calories from fat, protein, and carbohydrate multiply the “as fed” or listed percentage of protein and carbohydrate (less fiber) by 4; multiply the as fed fat content by 9; add the numbers together, and then take the percentage that each macronutrient provides. Here’s an example, this time using a typical frozen raw food.
Analysis on the bag reads:
We’ll estimate ash at 1.5% (about 6% on a dry matter basis), which is typical for raw beef and lamb diets; chicken based foods usually have a 2–3% ash content (Table 8.4).
Table 8.4 Commercial frozen raw diet, caloric contribution calculations
63% of the calories in this food are from fat, making this a very high-fat food, certainly when compared with dry foods and the ancestral diet. Even though this is a raw, meat-based food, with 36% of the calories from protein, it contains less protein than some of the high protein dry foods, as shown in Table 2.1 in Chapter 2.
Calculating amount of nutrients per 1,000 kcal.
As a food formulator, I analyze food on an amount of nutrient per 1,000 kcal basis. This is the AAFCO required method of analyzing high caloric content diets, which all meat-based diets are. A 45-pound dog will consume about 1,000 kcal per day.
It’s easy to calculate amounts on a 1,000 kcal basis. In Table 8.4 above, we see that there are 1.44 kilocalories per gram of food, as fed. That means that there are 694 grams of food per 1,000 kcal (1000 kcal/1.44 kcal/g = 694 g).
To calculate the grams of protein and fat, multiply the “as fed” or listed percentage by 694 grams. 13% of 694 grams is 90, i.e., there are 90 grams of protein per 1,000 kcal. 10% of 694 is 69, i.e., there are 69 grams of fat per 1,000 kcal. If you have a typical 45-pound dog and fed this food, your dog would consume 90 grams of protein and 69 grams of fat. Table 8.5 compares the fat and protein content of various foods, including the recipes presented in Chapter 6.
Table 8.5 Grams of fat and protein per 1000 kcal, various foods