We are not talking about this today.
Rather, we are discussing this. (And its relevance to your dog’s food and health).
What is a Maillard Reaction?
In this first essay of our series, “The Maillard Papers“, let’s begin by defining exactly what the Maillard Reaction is (and why should dog owners should care).
The Maillard Reaction is named for the French scientist Louis Camille Maillard who, in the early 1900’s, was attempting to produce synthetic meat protein in his laboratory. The glop that he ended up creating looked nothing at all like meat, but it did have a very distinctive meaty aroma and flavor – that of charred meat (or burnt toast – another type of Maillard reaction).
The compounds that produced these smells and flavors were eventually referred to as Maillard end products. They comprise a diverse group of cross linked molecules formed by the binding of simple sugars (glucose, fructose, galactose) with the amino group of certain amino acids in proteins, most commonly lysine and arginine. The formation of Maillard end products can, at the very least, lead to decreased availability of the essential amino acid lysine in the food’s protein. This is especially important in pet foods because the loss of available lysine can result in its deficiency in foods that are purported to be “complete and balanced”. Nutritionally, this has the potential to be a serious problem (see “How Reactive is Your Lysine” for details).
There is also a separate health concern related to Maillard compounds.
Advanced Glycation End Products (AGEs)
Maillard end products are not stable molecules. Once formed, they spontaneously rearrange and result in more chemically stable compounds – Advanced Glycation End Products (or AGEs). These compounds ultimately give rise to melanoidins, which are the pigments that impart the brown coloring in heat-processed foods. More importantly though, the accumulation of AGEs in the body has been found to influence the development of several types of chronic inflammatory diseases (1). This is true for both humans and several other species. For our purposes, we will focus on the science that is available regarding dogs and AGEs.
Food Processing and AGEs
The chemical reactions that lead to the formation of AGEs occur most rapidly under conditions of prolonged heat (cooking, extrusion) and in the presence of simple (reducing) sugars. In today’s modern world, a variety of thermal food processing techniques are used to improve the safety, nutritional value, shelf-life and taste of foods. In human foods, this has led to increased production (and subsequently consumption) of AGEs. Foods with the highest levels include fried and broiled meats and fish (with fried bacon being extremely high), processed cheeses, tub margarine and mayonnaise. By comparison, foods that contain very low concentrations of AGEs are fresh fruits and vegetables. While roasting vegetables increases AGEs somewhat, concentrations are still orders of magnitude lower than those found in processed meats.
In dog foods, the process of rendering to produce animal-protein meals along with the high heat treatments that are used during extrusion and canning are associated with increased production of AGEs (2). Although there are fewer studies of AGEs in pet foods compared with those of human foods, we do have some published data. Starting around 2012, Charlotte van Rooijen, a researcher at Wageningen University in The Netherlands, conducted a series of studies of the Maillard reaction and AGEs in pet foods as her PhD dissertation topic. These studies served to stimulate increased interest in AGEs, pet foods and health among other companion animal nutritionists and researchers (3).
AGEs in Commercial Dog Foods
The van Rooijen studies provided new insight into the levels of AGEs in commercially produced dog foods (3). Here are a few of her findings:
- On average, the concentrations of AGEs in commercial pet foods are similar to concentrations found in highly processed human foods (such as fast food burgers, french fries and margarines).
- Levels in dog foods are usually higher in canned foods than in extruded foods, but there is a great deal of overlap between food categories. Ultimately, the quality of starting ingredients plus processing temperatures and processing quality control influence the AGE concentrations found in a final product.
- Last, and possibly most importantly, when average intake per day of certain AGEs in dogs were compared with those of humans consuming a Western diet…….dogs consumed over 122 times more of one compound (called hydroxymethylfurfural or HMF) compared to humans. The implications of these differences will be explored more in the following essays in this series.
Impact on Canine Health?
If we know that the processing of commercial dog foods results in relatively high concentrations of Maillard endproducts and subsequently AGEs in foods, the next question is to ask whether or not these compounds, when consumed at these levels, are relevant to our dogs’ long-term health. As we will see in the following essays in this series, several researchers are examining AGE levels in dogs’ bodies, how the types of foods that are fed influence these levels, and what this may signify for our dogs’ health.
- Gill V, Kumar V, Singh K, Kumar A, Kim J. Advanced Glycation End Products (AGEs) may be a striking link between modern diet and health (Review Paper). Biochemicals 2019; 9:888-904.
- Teodorowicz M, Hendriks WH, Wichers HJ, Savelkoul HFJ. Immunomodulation by processed animal feed: The role of Maillard reaction products and Advanced Glycation End Products (AGEs). Frontiers in Immunology 2018; 9:2008; doi: 10:3389/fimmuno.2018.02088.
- van Rooijen C, Bosch G, van der Poel AFB, Wierenga PA, Alexander L, Hendriks WH. The Maillard reaction and pet food processing: Effects on nutritive value and pet health. Nutrition Research Reviews 2013; 26:130-148.