Share thisMost all of us are aware that certain dietary choices can increase or decrease the likelihood of developing certain diseases. Our diets can also change our metabolism as well the levels of circulating factors (hormones, lipids, etc.) which may be markers for disease risk. What is often overlooked is the fact that these concepts also apply to laboratory animals, making diet a critical part of study design.
Like humans, the animal’s phenotype, ranging the full spectrum from good health to a disease state, is the result of the interaction between their genes and their environment. Since the genetic makeup of the animal is fixed, manipulating their phenotype generally means making subtle or drastic changes in their environment, which include diet, housing, and ambient temperature. For good and ill, environmental modifications can happen easily and sometimes occur without researchers’ knowledge, leaving them scratching their heads and wondering why previous results were not repeated under what they thought were identical study conditions. Hence, control over environmental conditions is important to minimizing data variability.
Nutritional science research during the 20th century has shown that diet is a powerful environmental tool capable of changing the phenotype of an animal. Diet-induced disease models rely on diet to drive the desired phenotype. Examples include diet-induced obesity, diabetes, dyslipidemia, hepatosteatosis, atherosclerosis, and hypertension, to name a few. Diet also plays an extremely important role even when it is not being used purposefully to develop a disease state. For one, diets fed during pregnancy and lactation can have long-term effects on the phenotype of the offspring. Additionally, diets fed during a toxicology study can affect how the test compound manifests its toxicological effects. Hence, conclusions drawn about the toxicology of a compound may vary depending on the type of diet fed during the study.
We Are All Nutritionists
Given the importance of diet on outcome, how should scientists make choices about what to feed? First, they should realize that since they are feeding an animal some type of diet, they should add “nutritional scientist” to their job description. It is now up to them to embrace this new title (or not). And, as all nutritional scientists know, it is in their best interest to be involved with and cognizant of the choice of diet fed to their research animals, as this may save innumerable headaches down the road. Secondly, they should know that while there is no perfect diet, some have real advantages over others.
Report, Repeat, Modify
When choosing a diet, one should ask three questions: Can I report it (can I tell others exactly what my animals were fed)? Can I repeat it (is there diet variability and will I be able to get the same results next year)? Can I modify it (as my hypotheses change, can I easily change the dietary components while keeping it otherwise matched to previous diets)? The answer should be “yes” to all three.