Is raw pet food healthier than heat-treated pet food?
This review summarizes current research by Dr. Heidi Junger on the effects of heat on nutrients in food. [This article, like all content on this website, is protected by copyright; if you want to use all or part of this content, please contact us first; if approved, please give explicit credit to Onesta Organics.]
Many pet owners know that raw foods are available for their cat, dog, rodent, or other non-human companion. Some pet guardians feel very strongly that raw food is the healthiest food available for pets and, accordingly, provide their dog or cat plenty of raw meaty bones, organ meats, or raw, whole food-based organic treats. Moreover, increasing numbers of holistic veterinarians have become convinced that raw food provides the healthiest diet for pets.
Cats and dogs, like all other animals, evolved with raw foods. The wild ancestors of our pets were shaped by natural selection; the strongest individuals were the most likely to pass their genes along to future generations. In contrast, most domestic cats and dogs were bred by humans for particular functional or structural traits without little or no consideration for the health of future generations. This is why many of today's pets suffer from congenital disorders. Certainly, some skeptics may argue that, while raw foods were critical to the survival of our pets's distant ancestors, today' s heat-treated foods provide ample nutrition for modern dogs and cats. They may sincerely believe that cooking improves digestibility and makes foods safer for cats and dogs. Nevertheless, ample research suggests that a well-rounded raw diet provides the best insurance for a pets's health, particularly if that pet has a congenital disorder.
Decades ago, Edward Howell described feeding trials in which cats were fed either cooked or raw foods. His data showed that cats on the raw food diet were generally healthier and had more, and healthier, offspring than cats on the cooked food diet. Many proponents of raw pet foods are familiar with Howell's studies and have concluded that raw foods are healthier than heat-processed foods. Nevertheless, opponents of raw pet foods clamor for 'indisputable facts' and additional research data showing that raw pet food is indeed healthier than heat-treated food. Given the oft-repeated claims that cooked foods are healthier, easier to digest, and safer, their skepticism seems warranted. These pet guardians don't just want promises and anecdotal evidence; they really want hard facts. Although the research exists, unfortunately, only a few people have the time, access, or opportunity to find it. Published experimental data clearly show that all nutrients are affected by excessive heat. Here are just a select handful of conclusions from studies I found that show conclusively that heat damages nutrients in food to such a great degree that the food becomes downright unhealthy:
How heat affects food nutrients - Research review
[See references at bottom of page]
High heat destroys vitamins, antioxidants, enzymes, and reduces mineral bioavailability
It has been clearly demonstrated that every high heat process, including pasteurization, decreases antioxidant properties and causes loss of most enzymes and many vitamins (particularly A, E, C, B(1), and folic acid) (4a,7,8,10,17). Pasteurization is also known to decrease ascorbic acid (vitamin C), total phenols, and anthocyanins (1,9).
High heat causes gelatinization and fragmentation of starch and carbohydrates, and denatures proteins:
High heat causes most prominently starch gelatinization and irreversible protein denaturation (proteins are very unstable at high heat, just consider how fast egg white changes its consistency).
When exposed to heat, proteins, starches, and non-starch polysaccharides can fragment, creating reactive molecules that may form new linkages not found in nature. Even brief blanching causes leaching of minerals from foods (4a). Furthermore, heat processing causes molecular alterations of the fibers present in food (12).
Heat decreases protein digestibility, loss of amino acids, and reduces mineral bioavailability as well as growth of animal, reduces bioavailability of amino acids and protein digestibility:
Cows milk protein (serum protein bovine serum albumin) is denatured at a temperature of 85 degree C (185F) (15). Heat treatment of proteins (lactablumin, soy protein isolate) at 75 degrees C (167F) causes formation of unnatural amino acid derivates that may produce adverse and drastic effects on growth, protein digestibility, protein quality, and mineral bioavailability and utilization in rats. At the same time, cysteine, lysine, threonine, and serine are lost in heat processed food (4b,14).
High heat causes copper deficiency, and reduces bioavailability and levels of amino acids, reduces protein digestibility:
Excessive heat treatment of infant formulas induces copper deficiency in infant rhesus monkeys (5). Heat treatment of infant formula and milk causes not only deficient copper plasma levels and reduced bioavailability of amino acids and lysine levels (6), but also strong protein-protein and protein-lipid interactions (4). These interactions increase with increasing processing temperature which supports the notion that heat impairs protein digestibility. Damage to food proteins are also explained by complex biochemical reactions between proteins and carbohydrates and oxidation (2).
Heat causes the formation of anti-nutritional factors which reduce protein digestibility:
Another study shows that anti-nutritional factors (e.g., oxidized amino acids, D-amino acids, unnatural amino acid derivatives) are formed during heat processing of casein, lactalbumin, soy protein isolate, and wheat proteins. These factors have been shown to be poorly digestible (less than 40%) and their presence significantly reduced protein digestibility in rats and pigs (11).
Heat denatures proteins and induces formation of potentially carcinogenic compounds in fish and meat:
Cooking of meat of fish not only causes denaturation of proteins and formation of anti-nutritional factors, but can also induce formation of potentially carcinogenic compounds (3).
Digestibility of starch and protein was most improved by raw food processes:
An in vitro (i.e., test tube) study shows that pressure cooking, dehulling, germinating, and soaking all improved starch and protein digestibility of beans. However, the most effective improvement in digestibility of starch and protein was brought about by germination, followed by dehulling, and soaking (a method we employ here at Onesta Organics) (16).
The effect of heat on proteins might have been best summarized in a review by Swedish researchers, in which it is stated that reduced protein digestibility is primarily associated with excessive heat (18).
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As you can see, data from several research studies strongly suggest that heat treatment of foods affects almost all nutrients, both qualitatively and quantitatively, as well as causes impaired protein and starch digestibility. The results of these studies show clearly that raw pet foods, with which our pets evolved, are much healthier options than heat-treated foods that contain not only fewer, but even unhealthy, nutrients.
It's truly disturbing to me, as a raw pet food manufacturer and animal lover, that some competitors continually deceive their customers shamelessly, and time and again, get away with such deception. One company continues to market its cat and dog foods as 'dehydrated raw' even though, on their own website, they have recently admitted (albeit on a difficult-to-find webpage) that they use heat-treated (or steamed) meats, eggs and fish in their 'dehydrated raw' foods. They explain that this is a measure to provide foods that are safe and free of bacterial contamination. They either don't know that raw feeders expect the meat, fish, eggs, etc. they give their pets to be, well, raw, or they simply ignore this fact. Even though some raw feeders may cook the plant ingredients in their dog's or cat's food, they always keep meat, fish, and eggs raw. The very same company also seems to be ignorant of the fact that, unlike the human digestive system, the digestive systems of both cats and dogs are relatively resistant to, and tolerant of, bacteria from foods. In addition, they seem to place little confidence in either the sanitary state of the human food facility that produces their products or the quality of their own ingredients. On this latter point, their concern may actually be justified, since they don't use certified organic meats or eggs (which are much less likely to be contaminated than their non-organic counterparts) and they can't really determine how sanitary the contract manufacturing facility is (note that human food manufacturing sites are usually only expected once in a decade, whereas USDA certified organic pet food factories are inspected at least once a year).
Unfortunately, some retailers knowingly sell such 'half-baked,' so-called 'raw' pet foods for profit's sake. Nevertheless, I'm confident that the time will come when all pet foods are regulated. Widely enforced regulations and tight oversight, which now only apply to USDA certified organic pet foods, will eliminate such egregious deceptions. Not only do deceptive claims and poor food production practices hamper the success of the legitimate raw food movement, they also contribute to unnecessary illnesses in pets whose unsuspecting guardians purchase deceptively marketed pet foods with the best of intentions.
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Raw pet food - Healthier pets?
Are cats, dogs, or other animals that eat raw food diets healthier than those that eat processed foods? Apparently, according to some holistic veterinarians and many pet guardians—especially in cases where the raw food diet is adjusted to the needs of the individual animal. A diet can best be modified to a pet's needs with the help of an experienced veterinarian, who can evaluate the food composition that would provide the greatest benefit to that pet. Moreover, raw pet foods don't generally contain ingredients which have been implicated in common ailments in today's pets. For example, raw diets seldom contain the refined grains that are known to contribute to dog or cat obesity, diabetes, inflammation or allergens such as soy. At present, no double-blind trials have been published which show conclusively that raw diets can control chronic medical conditions. However, the omission of problem ingredients in most raw food diets, as well as the benefits of raw nutrients, certainly suggest that raw diets are healthier than heat-treated diets. In addition, a number of veterinarians have reported that individualized raw diets can prevent a number of conditions, including bladder stones, feline lower urinary tract disease, frequent ear infections, and intermittent vomiting or diarrhea.
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Raw pet food - Safety
Raw foods spoil rapidly if not refrigerated or frozen. Spoiling of raw foods can entail the growth of bacteria that may either have contaminated the food before purchase or were unwittingly added to the food by the consumer. To avoid foodborne illnesses, it is therefore very important to store and handle raw pet foods with special care. Store raw pet foods in the freezer or refrigerator in a sealed container. Avoid excess exposure to air, which may harbor a wide variety of microorganisms. Prevent cross contamination, i.e., to avoid contamination of the packaged food through your hands, don't touch the inside of a raw food container. So, in the case of our dry raw treats, we recommend that you pour out the amount that you are going to feed at any given time instead of repeatedly reaching into the bag. Furthermore, in the case of dehydrated raw foods, avoid exposure to humidity, which encourages growth of bacteria and fungi. To protect yourself, wash your hands following any contact with animals, raw foods, food and water bowls, or feces. Properly clean and sanitize all food and water bowls to avoid growth of microbes.
It needs to be mentioned that the latest pet food product recalls due to bacterial contamination affected products that were heat-treated. This shows that cooking, baking, or steaming of food doesn't prevent all contamination.
In general, it is not recommended to feed raw diets in households with young children, elderly persons, or immunosuppressed individuals. However, we think that this recommendation should only be followed if there is danger of contamination.
Since we wrote this, we saw a competitor use our 'recommendation sentence' from above, but they turned it around to explain why they use cooked meats and fish in their dehydrated dog and cat foods which they still market as 'raw.' They explain that they steam animal-based ingredients 'to protect the young, elderly and immonosuppressed animals.'
Unfortunately, this competitor obviously didn't understand what we meant. 1. We clearly refer to the humans in a household. Humans have a different digestive tract and physiology than dogs and cats. 2. Dogs, cats, and other species of animals, of all ages, and especially sick animals will benefit from healthy raw pet food (but ask a qualified veterinarian to get a professional opinion for your particular pet). 3. Even if the competitor would be right assuming that steaming of meats and fish *would* be beneficial for particular animal groups, did they never hear that plants can also be contaminated and cause sickness? Sometimes it scares me how little some competitors seem to know, and or how they try to keep having it both ways, in order to sell cooked pet foods as 'raw.'
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