Newsletter #301

This week, we’d like to revisit the subject of perfluoroalkyl and polyfluoroalkyl substances (PFAS). PFAS are chemicals that are commonly found in food packaging, due to their ability to resist water, oil, and grease. These substances tend to hang around in the environment, and have been shown to build up in animal tissues (which is why they’re sometimes referred to as “forever chemicals”).

These properties have raised concerns about their potential long-term effects on human health, especially as they’ve grown in prevalence. We know, for example, that higher plasma levels of PFAS are associated with higher risk of developing hypertension, as well as diabetes.

A new longitudinal study gives us a clearer picture of potential sources of PFAS in the diet. This analysis is worth a closer look because it involves multiple blood samples over time, which enables us to see how certain foods or beverages might go on to affect PFAS levels upon follow up. It also revealed one surprising source of PFAS that a lot of you (including me) probably consume regularly.

(Finally, before we dive into this, you might be wondering what can be done about PFAS, given their propensity to accumulate in our bodies. Believe it or not, donating blood or plasma can help. One study found that donating plasma resulted in a 30% reduction in the body burden of PFAS after one year!)

Researchers at the Keck School of Medicine at USC analyzed data from two different cohorts: One was the Southern California Children’s Health Study (CHS), a group of 123 young adults residing in close proximity to the university. In addition, the research team looked at 604 participants in the National Health and Nutrition Examination Study (NHANES), a nationally representative sample designed to monitor the health and nutritional status of people around the US.

Participants in both groups provided detailed information about their food and beverage intake, as well as how frequently they consumed food prepared at home, versus at restaurants. Furthermore, subjects gave blood samples, which were analyzed for various types of PFAS. Importantly, in the CHS group, blood was drawn at baseline, and again at a followup appointment four years later. In this way, the researchers could pinpoint how items in the diet might be associated with subsequent levels of chemicals floating in the bloodstream of the participants in these studies.

So what did their analysis reveal? Let’s start with what I would consider to be the least surprising finding: Higher intake of fast food was robustly linked to higher levels of PFAS.

This makes a ton of sense. Lab studies that examine various forms of fast food packaging generally find signs of PFAS, and this is particularly true for materials that are designed to be in contact with food, like grease-resistant wrappers. Items from non-fast food restaurants were also pegged as potential sources, but had less consistent associations.

In contrast, higher intake of food prepared at home was associated with lower levels of PFAS, across both cohorts. This lines up with a prior analysis of cross-sectional data, which found significantly lower serum levels of PFAS in people who ate more food prepared at home.

When the researchers zeroed in on individual foods and beverages and how they were related to serum PFAS, most of the major offenders were the sorts of things that you expect to see on a list like this – hot dogs, processed meat, chips, bottled water, etc.

Basically, stuff that most of you probably limit already.

But one item jumps off the page, and deserves more attention. Tea.

According to the authors, “The strongest positive associations were observed with tea and pork intake.”

In CHS subjects, a 1-serving increment of tea was associated with 24.8% higher PFHxS, 16.17% higher PFHpS, and 12.6% higher PFNA. Similar associations emerged from the NHANES data.

Since a lot of us are avid tea consumers, and we tend to think of tea as being a healthy beverage, I want to dig a little deeper into this association and what might be driving it.

My first instinct would be to wonder if the apparent association with tea is actually due to contaminated tap water, which is unfortunately a significant problem in parts of the US. But if we look up at that heatmap diagram, we see that higher intake of tap water was negatively correlated with blood levels of PFAS at follow up, so that’s probably not it.

What about various additives that people typically like to pour in tea? Same thing — milk and sugar were associated with lower PFAS. (Sugar, weirdly, had the strongest negative association with PFAS of any single item.)

So if it’s not coming from the water that it’s being brewed in, and it’s not coming from stuff being added afterwards, it must be from the tea itself. Or rather, their packaging. You see, tea bags are generally made of paper, and we tend to see PFAS in paper products. In fact, tea may be an especially potent source of PFAS because of the brewing process, since we know that heat exposure dramatically escalates the leaching of PFAS.

It’s tempting to blame the manufacturers of our favorite teas, but they may not even be aware of this problem. The growing ubiquity of these chemicals, as well as their remarkable persistence in the environment, could cause PFAS to appear in paper products like tea bags unintentionally.

Until regulations are put in place to more strictly limit PFAS, your best bet here is probably to stick to loose leaf tea, and rely upon a metal infuser or French press.

In terms of style, these two men could hardly be more different, but apparently they were good buddies, and spent a great deal of time out drinking together in Paris in the 1920s.

Joyce, in particular, seems to have been a belligerent drunk, eager to pick fights but ill equipped to finish them (he was described by contemporaries as “wispy” and “unmuscled”).

Realizing his limitations, he would then retreat behind his more formidable friend, crying, “Deal with him, Hemingway. Deal with him.”

The major advantage of single-use tea bags, of course, is convenience. So if you’re looking to switch to loose leaf tea, you’ll want to find a method that is as easy as possible to use, which is why I selected this steel infuser. It’s designed to be simple to load and unload, as well as clean up, and the super-fine mesh won’t let any tea leaves escape into your drink.

Since we’re on the subject of daily environmental exposures, we thought we would highlight our How-to Guide to Indoor Air Quality.

The EPA has estimated that concentrations of certain recognized air pollutants can be 2-5 times higher in indoor environments than outdoors, due to compromised dilution capacity in enclosed spaces. Beyond the long-term health implications, there is some intriguing evidence suggesting that clearing such pollutants could make us smarter and more productive. For example, installing air filters at schools has been shown to improve exam scores in students, and study participants in “Green” buildings, with excellent ventilation, perform better on tests of higher-order cognitive function.

This guide will show you how to test indoor air quality, and support maintenance of better air quality in your indoor spaces, for a healthier body and mind.

Wishing you the best,

https://mailchi.mp/humanos.me/newsletter-301