Understanding nutrition research is like trying to hit a pinata blindfolded- but with no pinata in the room. Even intelligent people can fall in the trap of cherry-picking unmeaningful studies to support a preconceived idea. Understanding a studies place among the hierarchy of evidence is an important skill to your nutrition toolkit.
This blog will investigate the limitations and strengths of extrapolating nutrition research from animals to practical human recommendations.
Animal Studies are Important for Research
These types of studies are key to the development of nutrition research. Performing studies on humans require strict compliance with ethical parameters. This excludes many of the new or unsafe trials to cell-based and animal studies. These studies are not subject to the same level of ethical requirements and generally are cheaper to perform than human trials. Additionally, they can be more effectively controlled and therefore more sensitive to any potential changes.
Once a concept becomes clear, researchers can then use this information to determine if it is worth testing in human trials.
Animal Outcomes ≠ Human Outcomes
As mentioned previously, animal studies tend to be a lot more controlled than human trials. When looking for an effect, researchers will often use super-doses of a substrate. Any change from these studies can easily be miss-interpreted and cause food alarmism.
For example… There is a notion that artificial sweeteners alter the gut microbiome. Much of this came from a study by Suez and colleagues. These researchers compiled animal data looking at the effect of high doses of saccharin on the intestinal microbiome.
Ultimately, they concluded that these doses negatively affected the microbiome of animals which lead to glucose intolerance.
This study is perfect for those already biased towards artificial sweeteners to support their worries. However, the available research does not support this claim when looked at in humans.
Additionally, understanding how this fit’s in the context of an entire diet is important. To match the dose Suez and colleagues found to be high in humans, an individual would have to consume 12 sugarine sweetener tablets per day.
Same Same, But Different
Some animals have very similar physiology to humans. Although, if it’s not obvious by looking, animals and humans are still different.
One of the key differences in commonly studied animals, such as rats, are basal metabolic rate and ability to maintain homeostasis under stress. This is referred to as metabolic stability which describes a cells ability to maintain homeostasis under stress.
When adjusted for weight, the metabolic rate of rats is seven times faster than human. They also have a weak capacity to maintain cellular homeostasis when their system is stressed. Due to this, their response in a studies treatment may be significantly more pronounced or unique to rats.
Human’s have a low metabolic rate (adjusted for weight) and high capacity to maintain homeostasis. As such, any outcome that has been seen in rats, particularly in disease and longevity, may not be present in humans due to our adaptive capabilities.
Differences In Metabolic Pathways
The differences in metabolic pathways are also apparent across humans and rats. The belief that sugar, particularly fructose, consumption inherently leads to fat-gain partly stems from extrapolated rat-based research.
What anti-sugar diehards forget to mention, or likely are unaware themselves, is that rat’s have ten-times the capacity in converting carbohydrates to fat (de novo lipogenesis) compared to humans.
Ultimately, this allows rats to convert carbohydrates to fat, at much lower doses than what can occur in humans. This knowledge demonstrates the little merit that anti-sugar claims have that use animal studies for the bases of their argument.
Wrapping it Up
Animal studies are still a fundamental component of research. However, understanding the limitations of these studies in nutrition and disease research is key to providing objective evidence-based knowledge.
