Do you ever notice that some of your pants and shirts have more static cling than others? If you look at clothing or fabric labels you will find polyester listed more often than not. What exactly is polyester? Why does it create static, and what does static electricity do to our bodies? We recently dug into the literature on polyester fabrics and have made a move away from wearing clothes and buying products made with polyester. The science is far from conclusive, but for us, it was enough to make a change.
Making the change is harder than it sounds because many of the cotton fabrics available today are made with blends that include polyester. To make our lives easier, we’re accepting blends that have at least 90% cotton. It’s even more difficult to find dog products made from natural fabrics, so Joelle has started making the dogs’ winter clothes at home (beds next!). Today we want to highlight our reasons and share some of the research and anecdotes that we found interesting. Before that we have an announcement:
We might run out of books!
The number of pre-sales for The Dog’s Table is much greater than our publisher anticipated. They had to reprint already. But that second reprint wasn’t enough and now they are planning for a third reprint. There is a real possibility that we run out of books during the holidays. If you haven’t purchased yours already, we highly recommend that you do. First, it ensures that you can get copies for yourself and as gifts on release date. Second it shows the publisher how many more people want it, so they can actually print enough.
The book turned out better than we had hoped. It’s not just cute and fun, it’s also the most well-researched book in this space EVER. We demystify making dog food, cover dog nutrition in-depth, and make feeding simple. There are easy recipes that have 5 ingredients and take 5 minutes of prep time. There are recipes for puppies, seniors, weight loss and even special recipes for athlete and working dogs (working dogs and athletes have drastically different requirements). Of course we also included fancy meals for special occasions. Go preorder today!
What is polyester?
Polyester is typically made from PET (polyethylene terephthalate) the same material that is used to make soda bottles and mylar balloons. It’s simply plastic that’s spun into thread and woven into fabrics. It’s durable, wrinkle-resistant and wicks sweat. It can be extremely soft, like in fluffy dog beds and silky-smooth activewear. It’s also much cheaper to make than natural fabrics.
However, there are drawbacks. Polyester is less breathable than natural fibers so it can trap odors and moisture. As mentioned above, it’s also more prone to static (more on this below). Also, because polyester is just plastic, it sheds microplastics into the air when worn and also into the environment when washed. According to one study, 43% microplastics from indoor dust came from textiles.
What does the research say on plastics?
Microplastics are a recent hot topic. Because plastics are used everywhere and for everything, we end up eating a lot of it. This is surprising to many. With any surprising finding, there are also a lot of sensationalized headlines and misinterpreted data. One such headline was about how much plastic we consume weekly. The report, from the WWF/University of Newcastle, claimed that an average person eats about a credit card sized amount of plastic each week, but this claim was later debunked due to faulty methodology (more on this below).
There is evidence of microplastics in human tissues, from the lungs to kidneys and even in brain and reproductive organs. Because the brain and reproductive organs have special barriers that reduce exposure to environmental toxins, evidence of plastic deposits there is particularly concerning. Alzheimer patients, who often have degraded blood-brain barriers, tend to accumulate lots of plastics in their brains.
Plastics in tissue is associated with a number of health issues from hormonal disruption to heart disease, cancer and infertility. According to a study published in The New England Journal of Medicine, patients with microplastics embedded in the plaque in their hearts were 4.5-times more likely to have a heart attack.
Why are polyester clothes concerning?
Aside from the exposure to microplastics, polyester is believed by some researchers to create a charge from static electricity that can impact our health in surprising ways. First is the affect on the skin. Some people may have immune responses to the electrical charge that can cause itching and allergic reactions. But most concerning is the potential to affect hormones and reproductive organs. According to one small study in female dogs, polyester underpants reduced progesterone levels and inhibited conception. Five months after the underpants were removed, progesterone levels returned to normal and the dogs were able to conceive.
The science is far from definitive as most of the studies examining this phenomenon are small. There were studies in the 1990s conducted on humans that showed similar results, but the studies were also small and used unnatural garments. However, because there are several studies that show polyester garments effecting hormones and fertility, coupled with the fact that polyester creates the highest electrostatic charge buildup of any fabric, this is enough evidence for us to make a change.
Electrostatic charge of a garment is due to the properties of that material. For example lower moisture retention, like with polyester, is associated with higher friction. Also, polyester sheds lots of electrons while cotton and wool shed the least. Friction plus electron shedding creates static electricity. For this reason, we prefer cotton and wool, especially for those garments very close to skin. We also use cotton for our pups’ clothes. It’s just more comfortable.
Comparing scientific studies
We often talk about the importance of high-quality studies. But how do we define high-quality? What makes one study bad and another good? Though there are many factors, we simplify quality into two basic criteria. The first criteria is how researchers set up the study. We previously discussed the hierarchy of studies, which ranks meta-analyses, RCTs (randomized controlled trials), population studies, and single case studies. How researchers get their data, and how much data there is, makes one type of study stronger evidence than another. Researchers can measure things themselves, they can ask subjects to fill out questionnaires, or they can look at many other studies and draw conclusions about an entire topics (meta-analyses).
The second basic criteria is how well the study is conducted under that set up. What choices did the researchers make? Did researchers clearly define success? Or did they make a change after they conducted the study? How did they analyze the data? How did they choose to include or exclude data when unexpected situations occurred?
Since meta-analyses summarize many studies, they are often considered to be the strongest evidence, but the methods are where researchers often make mistakes. Mistakes in meta-analyses are often about which studies to include. For example if a researcher doing a meta-analysis includes low-quality studies then the conclusions of the meta-analysis are suspect, even though it is highest in the hierarchy of studies.
Examining how well the researchers conducted their study takes a lot more work and knowledge. Most influencers, and unfortunately many researchers, don’t read past the summary (called an abstract). Yet, the methods section of each paper is actually the most important. For example in our previous post about supplements we pointed out how the researchers didn’t wash fur samples in their study. We believe that to be a mistake, but it was only apparent after comparing the methods of several other papers.
It’s not always straight forward. Great research needs both to be set up correctly and then executed correctly. The only way to get familiar with these methods is to read a lot of studies and even better if you can run some experiments yourself (even just simple ones).
That’s it for this week. Enjoy the fall weather and stay cozy!
All the best,
Joelle and R.A.