Life in plastic, it's (not) fantastic

A (hopefully) more nuanced discussion of microplastics

Top of the morning, sapien. Welcome to Common Sense Medicine, where I try and keep you up to date on the latest and greatest in longevity science.

I talked about my hip injury in the past few issues and what I’m doing to rehab it, but apparently it wasn’t enough to do it just 2-3x a week, and it was getting worse. It’s still not too bad, but I think it was worth to pause my exercise routine over it because it was getting to the point where it was affecting me at rest. We will see how I can rehab it for running the half marathon over time, but I believe it’s largely about strengthening the muscles which I said I would. I’m pausing, trying to reorient to daily rehab, and moving onwards with daily rehab at this point to see if that is making a difference.

I think this is an issue which I’m probably going to enlist some medical help with as well. In my opinion, when you have a MSK injury like this one, it’s usually soreness or a tweak which can be fixed. When the injury continues > 1 month, then it’s time to investigate for causes which may not be on your radar. Most times when thinking about MSK injuries, it’s more about “what can you do without pain” versus “let’s get you cured.” When thinking about things that will move the needle, it’s very personalized owing to the fact that injuries like hip impingement is based on your own anatomy.

I’m on my autopsy rotation these few months, so I literally see dead people and help do their autopsies. I feel like it’s an educational experience because not that many people in their lives get to see the complete nature of the human body after medical school, especially those which have different organ situs than normal. Something else I’ve been thinking about is the long-term effects of diet, specifically microplastics. Let’s get into the newsletter and I can explain more.

THE WEEKLY DOSE

I see dead people (with plastic in their brain)

I’ve been around Twitter, and my newsfeed has a bunch of “biohackers” who spew random things about hormone health, exercise, methylene blue, everything under the sun. I usually read all of what they have to say, whether I agree with it or not, just to give myself ideas about what I want to cover in this newsletter. I also read the traditional medicine folk argue until they’re blue in the face against them, bringing up evidence of the contrary.

I try to look up if there’s any articles around that topic before I dive deeper into each topic, so I can build up my views in a more nuanced way usually instead of kowtowing always to an expert authority. So when I saw this study in Nature Medicine, I was surprised, largely because this has been a fringe talking point and the most traditional medicine physicians dismissed it as a fringe talking point:

Most of the usual suspects on X have gotten tested, and found that they should completely rehaul their life from getting reverse osmosis filters, to storing their food in glass containers, and getting rid of plastic cutting boards.

Bryan Johnson has touted his ‘microplastics testing kit’ to lower your risk of getting it in our gonads and our brain, Huberman has his own tools and techniques which have shown to lower the risk of accumulating microplastics due to their risk on our fertility and our health. There is no causal link of microplastics and any disease, however, there is a lot of correlative data which may indicate that curtailing our plastic exposure may be good for us.

Nihart et al. ran their own version of a correlative study, focusing particularly on the correlation of microplastics and brains with dementia, investigating whether there was any association between the level of micro and nanoplastics (MNP) and other influencing factors.¹ Let’s dive deeper.

What did they do?

The investigators took samples from decedents’ (people who died) brain, liver, and kidney using a forensic pathologist who gave them samples from the University of New Mexico medical examiner office. Due to the condition approval, they only got some of the demographic information (i.e., age, sex, race/ethnicity, cause of death, and date of death), which were consistent across cohorts with confirmed dementia and those without dementia. While they used organs from University of New Mexico’s Office of the Medical Invesigator (OMI), they also received organs from the East Coast as well to remove bias.

They used Pyrolysis Gas Chromatography-Mass Spectrometry (PY-GC/MS) to identify and quantify microplastics in tissue samples while minimizing plastic contamination. Brain, liver, and kidney tissues were dissected with stainless steel instruments on glass surfaces, weighed to approximately 500 mg, and digested in 10% potassium hydroxide (KOH) at 40°C for 3-5 days.

After full digestion, the samples were ultracentrifuged at 100,000 x g for 4 hours in polycarbonate tubes, and the resulting pellet was washed with ethanol, dried, and a ~1 mg portion was analyzed. The samples were pyrolyzed at 600°C in an EGA/PY-3030D pyrolysis unit, thermally decomposing the polymers into characteristic pyrolysis products, which were carried by helium gas into an Agilent 8890 GC/5975 MS system for separation and mass spectrometric analysis.

The mass spectrometer ionized the pyrolysis products and measured their mass-to-charge (m/z) ratios, and the resulting spectra were analyzed using F-Search MPs software, which matched the detected peaks to a reference library of known polymer pyrolysis products, identifying twelve target polymers, including polyethylene (PE), polypropylene (PP), polystyrene (PS), and polyvinyl chloride (PVC). A calibration curve using a microplastic-CaCO3 standard at five different weights was created, with only curves having an R² > 0.98 considered valid.

Quality control measures included analyzing plastic components of labware and reagents separately to rule out contamination, confirming that the plastic composition of the experimental materials did not significantly contribute to the detected microplastics in the tissue samples.

What did they find?

First, they found that there were more plastics in the brain in 2024 versus 2016 (p < 0.05), and they were more abundant than the microplastics found in the kidney and the liver. Liver samples also had more microplastics in 2024 versus 2016, but kidneys did not (p < 0.0001).

This analysis was a bit suspect because they ran multiple tests on the data until they got a significant result — in the first portion, they tried comparing each organ in 2016 to 2024, and they found nothing (see Supplementary Table 4,5). When they transformed the data to lognormality, they could have come to a wrong conclusion about the data.

This is also frustrating because they then go onto cite the significance was due to a two-way ANOVA test, which assumes normality (checks out why they had made this transformation).

However, they could have used a generalized estimating equation or another equation which doesn’t assume normality.²

They also found that the most widespread microplastic in the brain was polyethylene (PE), which made up approximately 75% of the brain’s MNP by volume on average. They added two more variables to make their analysis robust: (1) they tried to see whether this affected people not just in New Mexico but also in the east coast to see geographic variance, and (2) they tried to see how dementia patients differed from those without dementia.

For the former group, they were able to find brains from the east coast which died earlier than those in New Mexico — but they were able to make a linear regression of their plastic concentration, which increased over time (p < 0.0001, R^2 value = 0.3982).

Furthermore, dementia patients included 6 with Alzheimer’s Disease, 3 with vascular dementia, and 3 unknown diagnosis from the New Mexico OMI patients. The brains compared to brains without dementia, and they found that they were significantly higher than those without dementia (p < 0.0001)

They also found that the particles found in the brain and liver were not just microplastics, but nanoplastics (<1 micrometer wide), using transmission electron microscopy. Part of the way they did this was that they observed the size and shape of the particles and compared it to other publications which used TEM in animal studies (mussel fishes in this case), because they can’t tell the composition of the material when looking at it on TEM.

The authors hypothesized that the distribution of the plastics was dependent on the absorption of lipids (which is how they ended up in the brain preferentially). In the case of the liver and kidney, they didn’t see as much of an accumulation, so they speculated that this was due to the relative lack of lipids in those organs and the low probability that plastics were in the vascular compartment.

They found that age is not correlated to the accumulation of microplastics, which suggests that plastic accumulation is independent of cumulative exposure over time (p = 0.89). But, they did find that there was an increasing plastic concentration over time (see above graph).

The investigators also admitted that Pyrolysis GC-MS is not an accepted method by the research community for measuring in vivo concentrations of plastics, however, they noted the consistency across both sites that they were running this study in measuring plastics. They also admitted that they could have overestimated the plastic content since it looks so similar to lipids, and the KOH might have not totally dissolved all of the organic material. They could have also underestimated the nanoplastic level, based on the limits of TEM.

What does this mean practically?

There are a few takeaways from this study. First, it’s true that we don’t know much about the effects of microplastics on our health. They could be harmful, or they could be helpful. However, it’s not a fringe talking point to be concerned that they’re accumulating in our bodies. They’re not causing dementia, but maybe people who are predisposed to dementia are more likely to have more accumulation of plastics in their brain.

Part of the reason that there is an increase in plastics in decedent’s brains is that there’s plastic everywhere—even in the air and rain. However, I don’t think it changes my life too much to start using more stainless steel appliances and pans, and buying more stainless steel spoons and forks. I also don’t mind that my water bottle is metal, and that I’m more focused on being more mindful about my choice of food (i.e., avoiding canned foods, etc.)

I think I’m not changing my behaviors just because of this paper, but I think that the correlative data about microplastics are pretty convincing that there is some association of plastic accumulation in our body. I think that it isn’t a bad idea to focus on mindful changes which can help us avoid it as much as possible. I’m not saying I’m dropping $1,300 on a new reverse osmosis filter, but I think the benefit of choosing not to have plastic is helpful in moderation.

THE PRESCRIPTION

Q1 2025: Hypertrophy Cycle Progress

The upshot: With all of the rehab, I’ve actually been losing weight. I haven’t focused on lifting weights as much, and not really focusing on the diet. 2 steps forward, 1 step back. However, we’re not stopping moving forward, as I said last week. Here’s to next week pushing it back up to 156 lbs. and getting in the weight room at the gym more consistently.

REMEMBER, IT’S JUST COMMON SENSE.

Thanks so much for reading! Let me know what you thought by replying to this email.

See you next week,

Shree (@shree_nadkarni)

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The information provided here is not medical advice. This does not constitute a doctor patient relationship and this content is intended for entertainment, informational, and educational purposes only. Always consult with a doctor before starting new supplementation protocols.

1. Nihart AJ, Garcia MA, El Hayek E, et al. Bioaccumulation of microplastics in decedent human brains. Nat Med. Published online February 3, 2025:1-6. doi:10.1038/s41591-024-03453-1

2. I’m not a biostatistician and may be making claims outside of my wheelhouse. Maybe this is technically sound and I’m just harping about things that wouldn’t make a difference in this case.