One of the current issues on the topic of phytoestrogens in dog food is proving to be quite confusing. With the endless speculation amongst the internet one can see why dog food buyers are so concerned about which way to turn.
The question about phytoestrogen in dog food and its potential affect in fertility was recently asked by a German Shepherd breeder. Shannon Winkler from ‘Brashawin German Shepherds’ who has been feeding Performadog for quite a few years and asked Bill our nutritionist the complex question of how to solve this dilemma.
Firstly, thank you for answering my previous question on allergies; this information blew my mind and opened up a whole new way of thinking when it comes to feeding. I would love to discuss phytoestrogen and the good and bad of its involvements in dog foods. Some seem to have high amounts of ingredients such as Flax Seed, Soybeans etc. Some studies I have recently read have shown that phytoestrogen can have negative impacts on the reproductive system.
Just how much of those ingredients would a dog need to consume for it to have adverse effects on the reproduction system?
Hope you can help shed some light on this and look forward to your informative answer to the dog world”.
Thanks for your terrific question, you really know how to ask the curly ones!
In straightforward terms, there is no definitive research to show that phytoestrogen affects fertility in dogs. In fact, there is precious little information relating to the effects of phytoestrogen in any species, including humankind. There is a suggestion from a 2006 review that some phytoestrogen may reduce the likelihood of breast cancer in woman. Still, the balance of the available literature suggests there is no ill-effect on fertility in mice, rats and dairy cows. However, a 2013 study in cows fed high levels of phytoestrogen suggested this did affect fertility. There are also warnings concerning grazing ewes and lambs on pastures containing high levels of phytoestrogen-rich species of sub-clover. I vividly remember grazing trials in the early 1960s where wethers (de-sexed male sheep) started lactating after continued grazing of Yarloop sub-clover. I would hasten to add that clovers such as Yarloop contain particularly high levels of phytoestrogen and to recreate this effect would be similar to dining exclusively on a diet of soybean and flaxseed.
In all aspects of nutrition, the key to good health and performance is very much to do with maintaining the correct balance of both ingredients and essential nutrients in the food. Much of the discussion regarding possible adverse effects on canine fertility from phytoestrogen appears to have mirrored the rise in popularity of grain-free diets. The connection here is concerning the widespread practice of replacing grains with legumes in an attempt to satisfy the requirement for carbohydrate in the food, not to mention the move towards vegetarian and vegan foods. Unfortunately, the increase in popularity of grain-free foods has also been linked with a steep rise in the number of reported cases of dilated cardiomyopathy (DCM) in dogs. Does this mean we can conclude that phytoestrogen causes DCM?
I think not!
But this type of reasoning, based purely on circumstantial evidence, tends to be the stuff of wild rumour and innuendo across chat sites and the internet. A more measured response is to look closely at the standard of the foods in question and to see if there is a common factor that could cause problems such as infertility, or disorders like DCM. All of the research we have conducted suggests there is no single factor behind the disorder unless of course, it was a bus that ran over the dog! Without a doubt, the underlying problem always comes back to diet design and the balance therein.
What all this means is that the balance of essential nutrients is only a part of the balanced nutrition scenario. Of equal importance is the balance of ingredients used in the delivery of those nutrients. After all, each ingredient has its good points and its bad points; there is no such thing as the perfect ingredient. And it is these ingredients that feed the microbial population in the gut. When you consider there are roughly 150 times more genes contained in the microbial gene pool in the gut as there are in the gene pool of the body of the dog, it’s easy to see why poorly arranged or inappropriate ingredients can cause unpredictable results in the animal. It is the unintended consequences of poor diet design that appears to be the elephant in the room, not the presence of a level of phytoestrogen that is contributed from a correctly balanced supply of appropriate ingredients.