Soybean Use for Canine Nutrition

In an overview written by the American Cancer Society: “In laboratory studies, animal studies, and research looking at groups of people and what they eat, certain chemical components of soy have been linked to a lower risk of breast and prostate cancer. Randomized clinical trials are needed to understand how these findings apply to cancer prevention in humans. Most studies that have shown benefit have used whole soy protein rather than soy components and extracts.

Soybean products are promoted for their protective properties against breast, prostate, colon, and lung cancer. The effects of soy are thought by some to be due to substances called isoflavones, although other substances may also contribute. Isoflavones are sometimes called plant estrogens or phytoestrogens because they mimic (although weakly) estrogen that is produced in humans and animals. Genistein, daidzein, and glycitein are isoflavones that are present in small amounts in other foods but are most abundant in soy.

As a protein source, soybean products are promoted as a healthier alternative to meat and as an aid to weight loss. Soy products are also used to lower cholesterol and blood pressure, and to relieve symptoms of menopause and osteoporosis. Soy protein in a diet low in saturated fat and cholesterol is also promoted as a method to help reduce the risk of heart disease.”

Veterinary research and medicine: As researchers attempt to find cures and treatments of cancers in humans, the information “creeps” over to veterinary research and medicine, attempting to treat health problems in dogs. The use of soy proteins to treat small animal disorders is speculative, and any potential benefits are being extrapolated from the potential benefits to humans.
The use in treating small animal disorders has been discussed in material written by: Steve Marsden, DVM ND MSOM LAc DiplCH AHG, Shawn Messonnier, DVM and Cheryl Yuill, DVM, MSc, CVH. Specifically:
•    Treatment of estrogen-sensitive conditions (benign enlargement of the prostate gland and urinary incontinence).
•    Diabetes treatment.
•    Cancer

Research of soy use in dog food: A recent study published in the Journal of Animal Science, March 25, 2014 conducted by P& G Pet Care and the University of Guelph, Department of Animal and Poultry Science, Guelph, Ontario, Canada, to: “evaluate the effect of increasing the inclusion of soybean meal (SBM) in an adult dog food on body composition, hematological, biochemical blood analyses, and total tract nutrient digestibility. Nutritionally complete and balanced diets were formulated with commercial-grade SBM (48% CP) to replace 0, 10, 20, or 30% of the protein provided by dried chicken protein resulting in final SBM inclusion of 0, 6.0, 11.5, and 17.0% (as-fed basis), respectively.” The implied results of the testing occurring over a 6 month period: “from these results that the partial replacement of dried chicken protein with SBM in a nutritionally complete and balanced diet does not compromise the nutritional status and long-term health of adult dogs.”

As written by the National Research Council: “Soybean is considered a nondigestible carbohydrate or oligosaccharide. Oligosaccharides are components of fiber found in plants that are fermentable. They are specifically Galactooligosaccharides (GOS) capable of increasing the number of beneficial bacteria in the colon, while simultaneously reducing the population of harmful bacteria. They are resistant to hydrolytic digestion in the small intestine, and are fermented in the lower gastrointestinal tract of dogs. As oligosaccharides pass through the small intestine, they are fermented by microbes in the colon and excreted as short-chain fatty acids (SCFAs) (mainly acetate, propionate, and butyrate) The Nutrient Requirements of Dogs and Cats, 2006, p.60, (Roediger, 1980; Roberfroid, 1993). Butyrate is the preferred energy substrate for canine colonocytes, The Nutrient Requirements of Dogs and Cats, 2006, p.67, (Drackley and Beaulieu, 1998), and likely plays a key role in normal colonocyte function, including cell proliferation, differentiation, and metabolism, The Nutrient Requirements of Dogs and Cats, 2006, p.67, (Sakata 1987; Scheppach et al., 1992).”

Soybean—Research as an endocrine disruptor: Research scientists Daniel Doerge and Daniel Sheehan provide critical information relative to the issue. The research has been published in: VOLUME 110, SUPPLEMENT 3, JUNE 2002, pp 349-353, Environmental Health Perspectives.

Abstract: Goitrogenic and Estrogenic Activity of Soy Isoflavones Daniel R. Doerge1 and Daniel M. Sheehan2
1Division of Biochemical Toxicology, National Center for Toxicological Research, Jefferson, Arkansas, USA; 2Daniel M. Sheehan and Associates, Little Rock, Arkansas, USA
Soy is known to produce estrogenic isoflavones. Here, we briefly review the evidence for binding of isoflavones to the estrogen receptor, in vivo estrogenicity and developmental toxicity, and estrogen developmental carcinogenesis in rats. Genistein, the major soy isoflavone, also has a frank estrogenic effect in women. We then focus on evidence from animal and human studies suggesting a link between soy consumption and goiter, an activity independent of estrogenicity. Iodine deficiency greatly increases soy antithyroid effects, whereas iodine supplementation is protective. Thus, soy effects on the thyroid involve the critical relationship between iodine status and thyroid function. In rats consuming genistein-fortified diets, genistein was measured in the thyroid at levels that produced dose-dependent and significant inactivation of rat and human thyroid peroxidase (TPO) in vitro. Furthermore, rat TPO activity was dose-dependently reduced by up to 80%. Although these effects are clear and reproducible, other measures of thyroid function in vivo (serum levels of triiodothyronine, thyroxine, and thyroid-stimulating hormone; thyroid weight; and thyroid histopathology) were all normal. Additional factors appear necessary for soy to cause overt thyroid toxicity. These clearly include iodine deficiency but may also include additional soy components, other defects of hormone synthesis, or additional goitrogenic dietary factors. Although safety testing of natural products, including soy products, is not required, the possibility that widely consumed soy products may cause harm in the human population via either or both estrogenic and goitrogenic activities is of concern. Rigorous, high-quality experimental and human research into soy toxicity is the best way to address these concerns. Similar studies in wildlife populations are also appropriate.

Soybean—Research as a trypsin inhibitor: Research science enables us to understand that anti-nutritional factors associated with vegetables occur in nature to protect the seed prior to germination. Seed germination occurs over three stages and it is in the third stage of germination that the inactivation of the digestive inhibiting enzymes occurs. Nature provides this process for seed to protect against ingestion by animals prior to germination.

From this knowledge there is an understanding that vegetable seed structures are not 100% consistent between seed type and location used, and therefore there is discussion among research scientists that suggest the levels of digestive inhibiting enzymes is not consistent among seed due to genetic changes or modification.

There remains a significant dispute as the percent of reduction of the level of digestive inhibiting enzyme trypsin once soybean undergoes the stress of the manufacturing process.

•    Although nondigestible in the small intestine (almost always misunderstood for being negative), soybean is a fermentable fiber source from which the substrate butyrate is excreted by the fermentation process in the colon, Butyrate becomes the food for the cells lining the colon, providing for improved gastrointestinal tract health in dogs.
•    Soy protein is being studied and considered for use in treating small animal disorders such as: cancer, diabetes, and incontinence.
•    Improper diet formulation causing insufficient levels of dietary iron combined with the use of soy as a replacement for meat protein in the formulation may adversely affect thyroid function.
•    Research suggests that the alteration of the physical properties of soybean begins the process of counteracting the digestive inhibiting enzyme trypsin…To what extent is disputed.

The wealth of information on the internet is mixed between research science and interpretation. Research science is very beneficial as long as the intent of the research is not predisposed to manipulate testing for desired outcomes. Human interaction in analytics drives results to prove theories and assumptions, and often conclusions become misleading which then becomes “factual” as known by those individuals seeking that outcome.

“Day-in and day-out” we are exposed to information touted as “fact” when the actual fact about the “fact” is that the “fact” is only factual to what you know to be the truth. What you know to be the truth may be different from the next person. A most common example of this is the witnessing of an event. Each person exposed to the event has a different truth of the facts of the event. This is known as the “human factor.”

So then…what about soybean and where lies the truth? The truth may be that some of the benefits of soy may be overshadowed by the overuse of soy. Overuse as nature did not intend! Overuse to save money in the manufacturing of dog food. Skimping on nutrition for our dogs where nature did not intend is detrimental to their long-term health.

Alan Anderson,  February 2015