Do phthalates (plastics) cause insulin resistance?
“Phthalates are found ubiquitously in plastics, among other common day to day utilities, and it does have a good amount, although not an infallible amount, of evidence stacked pointing toward phthalates having a detrimental impact on insulin sensitivity (driving the body to be more insulin resistant, diabetic). Phthalates enact these effects, partly, through reduced insulin receptor levels on the cells.”
I was listening to a podcast wherein a researcher, Dr. Shanna Swan, was discussing the effect a molecule known as a phthalate has on testosterone, insulin resistance, and more health metrics. Now, phthalates are ubiquitous in plastics, but many other common items, as well, so I’ll discuss some of the ways to avoid phthalates. So, my curiosity piqued, I decided to do a bit of investigating of my own. Below, I’ll detail a few of the discoveries I made on the role phthalates have on insulin resistance. In the future, I will cover how phthalates also affect other health metrics, but for now let’s focus on insulin resistance – I analyzed 3 studies to come to these conclusions.
1. Do phthalates (plastics) cause insulin resistance?
I started out by focusing my attention on associative studies – meaning, studies that find the connection between one factor and another factor, without controlling for other variables. In this instance, one factor is phthalates, and the other factor is insulin resistance. So, looking at the first study, the researchers measured urinary phthalates across a sample of thousands of people and looked for a connection between phthalates and insulin resistance. What we see [Figure 2] is that greater insulin resistance was associated with more phthalates in the urine. However, as I mentioned, this is merely correlational – so, the researchers don’t control for other factors, therefor we can’t assume phthalates are the cause of the rising insulin resistance. For that, we need to bring in two more studies.
Now, to be intellectually honest, we should acknowledge that the following data I’ll be sharing is based on two animal studies [Figure 1]. Unfortunately, there are no studies (up to this point) looking at an intervention of phthalates in humans, so with the available evidence, we have to make do.
The available evidence indicates that with an exposure of phthalates to various animals, they develop insulin resistance, independent of anything else. We can see that illustrated, as mice exposed to phthalates see an increase in their insulin resistance measures, known as HOMA-IR [Figure 3]. So, this data, plus the associative data, indicates strongly, although not with 100% certainty, that phthalates impair insulin sensitivity (elevate insulin resistance risk).
2. How do phthalates cause insulin resistance?
Here, we return to the direct application of phthalates to animals and the researchers indicate a series of effects that occur. First, phthalates seem to have differing effects, depending on the tissue experimented on. So, the data we have isn’t all encompassing, but one of the mechanisms is known to be through reducing the available insulin receptor levels. So, even if insulin levels are elevated post food consumption, there are fewer receptors to accept said increase in insulin, making the overall tissue insensitive to insulin [Figure 4].
Not only are there fewer insulin receptors, but even if the insulin signal is translated to within the cell, the cell has fewer of the molecules that propagate that signal further. One of these key molecules is called Akt – which is a master molecule that controls multiple mechanisms, not least of which being insulin sensitivity.
But, as I mentioned, while these show some of the mechanisms, these are unlikely to be the only ones.
So, big picture – what’s the take away here?
Phthalates are found ubiquitously in plastics, among other common day to day utilities, and it does have a good amount, although not an infallible amount, of evidence stacked pointing toward phthalates having a detrimental impact on insulin sensitivity (driving the body to be more insulin resistant, diabetic). Phthalates enact these effects, partly, through reduced insulin receptor levels on the cells. If you want to unlock this full article, have access to all my other articles, as well as have access to seminars on this topic and to ask me related questions, consider joining the Physionic Insiders, here: https://bit.ly/PhysionicInsiders Answered for the Physionic Insiders: 3. How do you avoid phthalate negative effects?