Most dogs now dine on some type of genetically modified (GM) food, often in the form of corn and soy in their kibble. As these ingredients increasingly enter the food supply, we have one more reason to wonder if our shopping choices might be harming our pets.

More animal feeding studies are needed, experts say, and a recent long-term, peer-reviewed report points out why. It found that a diet of GM corn and soy led to higher rates of severe stomach inflammation in pigs, which are physiologically similar to dogs.

Robert Silver, DVM, a Boulder, Colo., holistic vet, tackled the issue earlier this year when he presented his paper, “Genetically Modified Food and Its Impact on Pet Health” at the American Holistic Veterinary Medical Association conference in Kansas City, Mo. Why did he choose this controversial topic, one that few vets even acknowledge?

Silver—a pioneer in the field of holistic veterinary medical practice—says he was inspired by a seminar he attended in Boulder on GM foods and human health. The speakers included Don Huber, a Purdue University professor, and activist Jeffrey Smith, who discussed problems, including reproductive difficulties, that have occurred in livestock fed GM crops.

“I found this seminar mind-opening,” says Silver, the lone vet in attendance. “I had always believed the PR about GM foods—that they are going to feed the world and are a good outcome of our genetic technology.”

The Food and Drug Administration, which regulates the safety of GM crops consumed by humans and animals, considers most GM plants “substantially equivalent” to traditional plants and “generally recognized as safe.” Their regulation involves a voluntary consultation process with the developer before products are brought to market.

Smith, founder of the Institute for Responsible Technology, disagrees. On its website (responsibletechnology.org), he warns that “nearly all GM crops are described as ‘pesticide plants.’ They either tolerate doses of weed killer, such as Roundup, or produce an insecticide called Bt-toxin. In both cases, the added toxin—weed killer or bug killer—is found inside the corn or soybeans we consume.”

Silver says that while “allergies, GI problems, increased risk of cancer, neurodegenerative conditions” and other ills could all be, in part, related to GM foods, “there is no objective evidence of this yet” in dogs. “However, all vets will agree that there has been an uptick in [these diseases] in the past 10 to 20 years.” The advent of GM foods in the 1990s “fits into this timing of disease increases,” he says.

His presentation referred to studies that raise doubt about the safety of biotech crops, such as one reported in 1996 in the New England Journal of Medicine, which found that genes inserted into crops can carry with them allergenic properties.

Silver says that genetic modification introduces foreign proteins that may encourage allergies, and the widely planted Bt corn, which makes its own insecticide, “could possibly cause leaky gut, the gateway to chronic disease.” Corn is a major component of most commercial pet foods. “The big problem with commercial foods is that they are manufactured at high temperatures and pressures,” which alters them and makes them “potentially more allergenic.” And commercial foods contain industrial ingredients that are “more likely to contain GM and herbicide contaminants.”

A study published last year found that GM crops engineered to withstand the toxic herbicide Roundup must now be doused with even more herbicide, since weeds have also developed resistance to it. Residues of these chemicals on crops can find their way into pet food.

A 2013 study published in the science journal Entropy reports that the heavy use of Roundup could be linked to Parkinson’s, autism, infertility and cancers. It goes on to report that residues of Roundup in food can interact with, and enhance, the damaging effects of other environmental toxins. “Negative impact on the body is insidious and manifests slowly over time as inflammation damages cellular systems throughout the body,” the study’s researchers say.

According to Silver, heightened sensitivity to dietary ingredients “is probably what we are seeing with GM foods. It is of concern that this may be driving the increase in GI problems in pets.” Although gluten probably does account for some problems with grain consumption, “I think that grain-free diets, if they are also soy free and contain protein from animals not fed GM crops, can help many dogs, due to being GM free—and not due to some allergy or gluten issue.”

To a holistic doctor, food is medicine, and Silver strongly recommends home meal preparation from individually sourced ingredients to avoid feeding GM ingredients, especially to pets who have other health problems. “I am truly a holistic practitioner in that I believe an ounce of prevention is worth a pound of cure.”

References
Carman, J., et al. 2013. A long-term toxicology study on pigs fed combined genetically modified (GM) soy and GM maize diet. Journal of Organic Systems 8 (1): 38–54.

Benbrook, C.M. 2012. Impacts of genetically engineered crops on pesticide use in the U.S.—the first 16 years. Environmental Sciences Europe 24: 24.

Ordlee, J., et al. 1996. Identification of a Brazil-nut allergen in transgenic soybeans. The New England Journal of Medicine 334: 688–692.

Samsel, A., and S. Seneff. 2013. Glyphosate’s suppression of cytochrome P450 enzymes and amino acid biosynthesis by the gut microbiome: Pathways to modern diseases. Entropy 15 (4): 1416–1463.

A study by researchers at the University of Missouri finds that eating canned dog food may increase a pet’s exposure to the endocrine-disrupting chemical, Bisphenol A (BPA).

While the study was short-term, the results were “very revealing,” says investigator Dr. Cheryl Rosenfeld, an associate professor of biomedical sciences in the MU College of Veterinary Medicine. Fourteen healthy pets were switched from their usual diet of kibble to canned food. Could a two-week menu change raise the dogs’ BPA levels?

It did, three-fold, and that could really be an issue for dogs that eat the same diet every day.

Over 300 studies have linked BPA to health problems from reproductive disorders to cancer, and now research is shedding light on how people and animals are exposed to the plastic-hardening chemical. While the FDA has reviewed the studies, they still consider BPA “safe at the current levels occurring in foods.”

By measuring BPA’s escape from packaging, scientists are narrowing the focus. One study settled the debate over whether BPA—banned in baby bottles but used in many other items—seeps from metal can linings and taints human foods. (It does). 

And in August, a long-term study in the UK found a sharp decline in canine fertility associated with exposure to other endocrine-disrupting chemicals. The researchers considered food packaging a possible source, finding the chemicals in a range of dry and wet foods.

Some plastic dog toys have also been found to leach the chemical. A study at Texas Tech by environmental toxicologists Phil Smith and Kimberly Wooten found that BPA and phthalates leached from plastic bumpers into dishes filled with artificial dog saliva.

Wooten, who wasn’t involved in the present study, says that while it isn’t clear if dog health is being harmed long-term, “it’s still important information to have since there’s so little data on canine exposure to these types of chemicals.” She knows of no other studies that have looked at the effects of a specific BPA source on the concentrations in the blood.

“I’d say a 3-fold increase suggests that for dogs that eat canned food, their diet is the most important contributor to their total BPA levels.”  

The current study highlights another concern; with the pet food industry being held by about five companies, it seems commercial foods aren’t as diverse as packaging suggests. Of the two (unnamed) brands in the study, one was declared “BPA-free” by the manufacturer.

So, skip the can and spare your dog? It turned out, the dogs already had a small amount of BPA circulating in their blood, shown by initial baseline samples. The researchers then analyzed both the cans and the food for BPA. They also checked for any disturbances in gut bacteria and metabolic changes.

Although one of the diets was presumed to be BPA-free, feeding either brand for two weeks resulted in a three-fold increase of BPA levels in the animals. At the same time, the dogs showed gut microbiome and metabolic changes, with potential health consequences. Increased BPA may also reduce one bacterium known to metabolize BPA and related environmental chemicals, according to the study.

Bagged kibble might also contain BPA, since the dogs had some BPA in their blood before the study, possibly from their dry diets.

“This is the point that it is not clear,” Rosenfeld says. “It could be that the food already contains BPA. However, we saw minimal levels when the dogs were on kibble.” In some cases, very low amounts can lead to equally if not greater harmful effects as high doses, she says. The greatest concerns may be at the low and high doses.

“The doses we found in the dogs after being on canned food though were comparable to what has been linked to health problems in humans and rodents,” a list that includes diabetes and obesity, among others.

If the dogs continued to eat the canned food, would BPA keep building up in their bodies?

“We did not see what would happen if we took the dogs off the canned food or kept them on it longer,” Rosenfeld says. “These are definite follow-up studies.” Ideally, based on the results of this one, she says they would pursue long term studies to test BPA concentrations after long term feeding of canned food, examining the dogs for metabolic disorders—such as obesity and diabetes—and neurological ones, using MRI and behavioral testing.

In a previous rodent study, they did find that the longer mice were on a diet containing BPA, even though it was being metabolized, it would start accumulating in their system so that greater amounts would persist over time, she says.

In humans and primates, BPA is excreted through urine. “It is not clear how it is cleared in dogs.”

While BPA affects the reproductive system, Rosenfeld says they did not find any gender differences in this initial study—“but we would need to test more dogs to confirm.”

The main concern about the gut microbiome changes is that they have been linked with various diseases, including neurological, metabolic, immunological, gastrointestinal, and possibly even cancer, she says. “Thus, by affecting the gut microbiome, BPA could induce such secondary effects.”

Unfortunately, a supposedly safe substitute for BPA, BPS, didn’t fulfill its goal. Rosenfeld says that in rodents and fish, BPS has already been shown to lead to similar health concerns as BPA. Their study didn’t test BPS in the cans. “It is not clear if some dog foods are using this substitute,” she says.

“By feeding fresh food, dry food, and minimizing canned food, it will reduce exposure to BPA and BPS.”

This is a very easy method to make yogurt. All you need is a slow cooker, milk, a live-active yogurt starter (either from a previous batch, or a store bought plain yogurt), and, a cooking thermometer (that is optional).

Steps:

1. Pour one to two quarts of milk (low fat or whole) into a slow cooker, cover the pot. Turn the heat on medium or high. Heat the milk slowly, it needs to get to reach at least 180 degrees (30 mins. to an hour or longer). Stir a few times while it is heating, make sure it doesn’t stick to the bottom of the pot and that it doesn’t boil.

2. Turn the slow cooker off, uncover and unplug it and let the milk cool down to 110 degrees, this too can take 30 mins. to an hour or even longer.

3. While the heated milk is cooling off, take the starter out of the refrigerator. If you are using a quart of milk use a tablespoon of the starter, if you are using two quarts, use 2 tablespoons.

4. Once the milk has cooled to 110 degrees, ladle a small amount (1/3 of a cup or so) into a small bowl or measuring cup with the starter, then stir or whisk. Make sure you incorporate all of it, and then slowly add that mixture back into the crock pot, stirring thoroughly.

5. With the crock pot turned off, replace the lid, and wrap the pot with two or more towels. Make sure you do NOT disturb the pot; yogurt prefers a very still environment to go through the fermentation process. The low heat that was generated in Step 1, is sufficient for this process. This process can take 6 to 8 hours.

6. If you are making Greek style yogurt, carefully transfer or pour the yogurt into the EuroCuisine strainer (or use cheesecloth) and refrigerate at least 4 hours. If you are making regular style yogurt, you can put the yogurt in mason/glass jars, and refrigerate at least 4 hours or overnight. If you are making Greek style yogurt, you will place the “finished” yogurt in glass jars, preserving the whey.

Yet another sure fire way to make yogurt is using a dehydrator. Following the same cooking steps in the “heating pad” method of heating the milk, cooling it, and inoculating it with a yogurt starter, the next step is to pour the milk into glass jars, cover each with a lid (the plastic mason jar lids work well) and place them on the bottom shelf of a dehydrator, first removing the other shelves. Many dehydrators have a temperature setting for yogurt. Place the cover back on the dehydrator and incubate for 8 to 10 hours at 115 degrees (or following the setting on your dehydrator). Similar to the other methods, after the yogurt has set, refrigerate at least 4 hours. You will be amazed at how different (thicker) the yogurt becomes after it has been refrigerated.

If you are making Greek style yogurt, strained it either using cheese cloth in a strainer or the Euro Cuisine GY50 Greek Yogurt Maker method, first in the refrigerator, and then putting it into jars. Yogurt keeps for about a week.

Whey is the by-product of the yogurt making process, especially when you strain yogurt to produce a thicker, i.e. Greek style product. Whey protein is considered a complete protein and contains all 9 essential amino acids and is low in lactose content, so do not throw this precious liquid away! If you do not use it within a week or so, you can freeze it for later use.

Here are some of the endless ideas for using whey protein:

• For making smoothies (2 g of protein in one cup)

• In baking muffins, pancakes, breads, dog treats.

• Soaking beans or lentils (great to add to your dog’s meals)

• Use as a “topping” for your dog’s food. *

• As a substitute for buttermilk in recipes.

• Use in salad dressings (it is as acidic as a citric juice).

• Protein Shake

Making A Super Protein Shake For Dogs

One of my favorite uses for whey is to make a super protein “shake” for the dogs, that I mix into their meals or as a mid afternoon “slurp” snack. I was recently introduced to “nutrient extraction” super-blender appliances, such Nutribullet and Ninja. They make blending delicious and nutritious drinks and sauces so easy. For the dogs’ nutri-blasts, I use a handful of whatever leafy green vegetable, kale, spinach or chard, we have on hand, a few blueberries, a mix of goji berries, hemp and chia seeds, whey, and, for extra thickness, a tablespoon or so of yogurt—you can also add pulverized egg shells for more calcium. The Nutribullet grinds and mixes all these ingredients up in less than a couple of minutes. The dogs simply love it. If I have some cooked sweet potato, I add that too. The ingredient mixes are endless, plus it makes digesting vegetables easier for a dog’s digestive tract too.

For more information about the other possible health benefits of whey protein, see dogcancer.net.au

Keeping dogs healthy is important to us so we’ve created new calorie requirement estimator and food counter apps. We are hoping that these web-apps will come in handy for you to try your hand in cooking for your dogs. You can make all the meals for your dogs, or simply add home cooked meals as a supplement to the manufactured food.

The first thing to do is to confirm or calculate how many kilocalories your dog requires to be fed on a daily basis (Daily Energy Requirement or DER). The total calorie requirement should be divided by the number of meals (usually 2) fed to your dog daily. All treats and snacks also need to be accounted for and their calories should be subtracted from the total that will be provided in their meals. It is always recommended that before making changes to a dog’s current diet you discuss this plan with your veterinarian. Do keep in mind that there are a number of different approaches that are used to calculate a dog’s caloric needs so while our app calculates your dog’s DER, there are other formulas with slightly different results (we have included a chart that uses another popular measurement, the Maintenance Energy Requirement, that you can also follow.)

Screenshot of Bark's DER Calculator

Do keep in mind that these calculations are really only estimates. Also, it is important to note that every dog is truly an individual, and their current weight, activity level, age, intact or neuter, physiological condition and other factors must also be considered. No matter what formula you use, the best way to judge a feeding plan’s efficacy is by simply keeping track of any weight loss or gain, and adjusting accordingly. And again, it is good to consult with your vet before making any changes to a dog’s diet.

Ingredient Calculations:

When calculating the calories for ingredients, there are a variety of sources that can be used. I decided to do compute calculations in ounces to make it simpler for myself, and others to use. The ingredients we have included in our chart are the most common ones found in home cooked meals. If there are ingredients missing you can use any of the online calorie sources that we have noted under the chart to add those to your list.

A digital kitchen scale is definitely the easiest when to know how much any ingredient weighs—you need to measure the actual weight, not the volume (such standard measuring cups measure).

When using the slow cooker approach to making dog meals, you will also need to factor in the weight of the water you use in cooking the meals. So if you use 6 cups of water, or 48 ounces, that weight will need to be added to the total weight of the ingredients, to get an accurate calculation how many calories there are in one ounce of the food. Most slow cooker meals are around 20 to 35 calories per ounce.

Supplementation:

As Dr. Greg Martinez has noted in his slow cooker recipe, you will need to provide supplementation to most diets (especially those that do not incorporate any manufactured food). Common supplements include calcium (or bone meal) about 1 tsp per pound of food, Vitamin E (2 IU per pound of dog daily), and either sardines in water (one-quarter to one tin twice weekly) or one to three 1,200 mg fish oil capsules daily (Dose is based on 10 to 30 mg/pound of DHA and EPA).

In my investigations into home cooking for your pet I have used a variety of excellent sources that you might also like to consult. Here is a sampling of the books, websites, and services:

Starting with Dr. Richard Pitcairn’s classic Complete Guide to Natural Health for Dogs & Cats. His was one of the first guides to home cooking and the ingredient charts are extremely helpful, especially detailing the amount of water to use per dry ingredient, and the cooked yields.

Home-Prepared Dog & Cat Diets by Patricia Schenck, DVM, PhD contains many different diet plans, and the special medical conditions that they cover.

Monica Segal offers nutritional consultations and menu planning, that can also include supplementing a kibble based diet. She is the author of 9Kitchen and Your Dog’s Diet. monicasegal.com

Rebecca Remillard, DVM, Veterinary Nutritional Consultations. She as been providing consultations for 20 years. She provides customized recipes for healthy pets, and nutritional consultations for pets with medical conditions. She works directly with pet guardians and with their vets. petdiets.com

Sean Delaney’s Balance It is also a veterinarian nutritional consulting service. His site offers many interesting recipes and diet plans. Balanceit.com, go to the “free balanceit ez tab” to build your own recipes and to understand their nutrient composition. balanceit.com

Mary Straus’ website dogaware.com is a good resource for sample diets (both raw and cooked) and supplements for home prepared meals, as well as general health related topics. dogaware.com

For recipes books:

Dr. Becker’s Real Food for Healthy Dogs & Cats by Beth Taylor and Karen Shaw Becker, DVM has an emphasis on ancestral diets, but a lot of valuable information. drkarenbecker.com

Dinner Pawsible by Cathy Alinovi, DVM and Susan Thixton. Has over 60 recipes that will inspire you and entice your pets. drcathyvet.com

Dr. Greg’s Dog Dish Diet by Greg Martinez, DVM will get you started on the slow cooking approach to cooking for your pets. Be sure to watch his youtube channel too, so you can get some great cooking pointers.

Rick Woodford has provided an invaluable service with both his Feed Your Best Friend Better and his new Chow recipe books. His recipes can be used to supplement a kibble or canned food diet or provide healthy menu choices on their own. dogfooddude.com

Other Sources and Textbooks:

Dog Food Logic: Making Smart Decisions for Your Dog in an Age of Too Many Choices (Dogwise) by Linda Case

Applied Veterinary Clinical Nutrition Edited by Andrea J. Fascetti and Sean J. Delaney

Small Animal Clinical Nutrition, 4th Edition by Michael Hand, DVM, Craig Thatcher, DVM, Rebecca Remillard, DVM and Philip Roudebush, DVM.

Nutrient Requirements of Dogs and Cats National Research Council.