Research Rudiments Part I: Animal Studies
Understanding the pro’s, con’s, and utility of animal research
I recently posted an in-depth review of research regarding artificial sweetener consumption and weight management, in which different studies presented different findings depending upon their design.
Specifically, data from rodent and observational studies showed that artificial sweetener consumption is detrimental to weight management, while data from randomized-controlled trials suggested the opposite conclusion.
Addressing each of these study types’ limitations and strengths, I explained why I felt the randomized-controlled trials likely pointed in the most accurate direction on this front.
But, while writing that post, I decided that the topic of understanding and comparing different study designs is important enough to double-tap and explain further. As an old mentor of mine would put it, these are the types of concepts that, “take you from the freshman to the JV level,” in terms of reading scientific research, in my opinion.
So, here and in a couple of posts to follow, I’ll break down the basics of the main categories of research studies, their key features and subtypes, and their pertinent strengths and limitations.
We’ll kick things off with animal studies.
Pro’s of Animal Research
I imagine the name animal research is fairly self-explanatory–conducting experiments involving animals as the subjects; however, I suspect it’s less obvious why we would conduct this type of research and what we can draw from it.
One useful aspect of animal research lies in the numbers, in that, by utilizing animals, researchers have easier and greater access to subjects in comparison to when they use humans. This includes the ease of finding subjects for studies in general as well as finding enough total subjects.
Additionally, researchers can leverage the fact that some animals have significantly shorter lifespans than humans and easily conduct a series of experiments lasting the full length of their animal subjects’ lives.
For example, Caenorhabditis elegans–commonly known as C. elegans–a nematode worm with an average lifespan of 18-20 days, is classically used for longevity research. (I) While it is infeasible to conduct a controlled experiment on a human across the entirety of their lifespan, organisms like C. elegans make this a common reality.
Animal research also allows for extremely high control, in that, as I alluded to in the last paragraph, we can isolate animals in a lab and dictate everything they do and are exposed to. Furthermore, we can precisely record everything they do and are exposed to.
This is possible with humans, to an extent, such as when human subjects live within a research facility for the duration of a given study, but only for very short periods of time.
Lastly, researchers utilize animal models to test circumstances they deem too risky or unethical to use on humans. For example, animal models are commonly used to test whether an intervention–like a drug or food product–is safe prior to implementing that intervention in human studies. Similarly, some animal research entails genetically inducing a disease in the animals to assess its pathology, timeline, or responsiveness to given treatments.
Con’s of Animal Research
Now, this type of research does have downsides. First and foremost, since these animals have different physiology than humans, we cannot assume that we will show the same results these animal subjects show.
With that said, we do share some physiological features with certain animals, allowing us to advance our hypotheses by researching those animals. For example, pigs and humans have similar gastrointestinal (GI) tracts, making pig models particularly useful for conducting experiments centered on the GI tract. (II)
On the contrary, we can run into trouble if we attempt to draw conclusions in an area where humans fundamentally differ from the subject animal. As I mentioned in a recent post, one such example is that rodents tend to drastically overeat in ad-libitum feeding conditions (i.e. unlimited food conditions) compared to humans. For this reason, in my opinion, it is reasonable to heed results from rodent feeding studies with a hint of skepticism.
In addition to physiological differences, animals also differ behaviorally. For example, we can ask humans whether they felt they were overeating due to hunger, cravings, boredom, or other reasons; however, it’s difficult to deduce why an animal overeats in a study.
So, though they offer the benefit of more continuous and precise measurements, animal studies can fall short when it comes to interpreting the causes of results.
Notably, animal studies typically take place in laboratory settings, rather than free-living conditions or in the given animals’ natural habitats. So, we cannot conclude with certainty whether these studies’ results are confounded by the, “unnatural,” experimental settings.
For instance, in theory, if we took rodents and isolated them so that they did not have access to sunlight or the ability to interact and mate with other rodents, we may confound the results of hormonal measurements.
Another example I heard from Dr. Peter Attia is that rodent longevity studies underestimate the importance of strength, muscle mass, and bone health in humans because the rodents aren’t exposed to accidental fall injuries in their laboratory environment.
Though these types of injuries don’t come into play in these rodent studies, they are prevalent and important when it comes to considering healthy aging in humans. This is something to consider when interpreting these types of study results, for example when deciding whether it’s better to consume more or less protein for longevity purposes.
Conclusions
So, much like any other study category or design, animal models offer certain advantages–such as running tests across the entirety of the subjects’ lifespans or testing novel drugs. However, they also have their limitations, like their lack of specificity to humans, difficulty ascertaining behavioral cause and effect, and use of “unnatural” laboratory settings.
For these reasons, animal models are typically used as stepping stones to further hypotheses and provide direction for more human-specific research. In Part II of the Research Rudiments Series we’ll move on to this human-specific research, starting with observational studies.
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