Dr. Heidi Yellen is a name you will encounter again and again when you begin exploring the fascinating subject of fabric frequencies and the possible relationship between the materials we wear and our well-being.
I certainly did.
One article led to another. Then another. Before long, I was reading claims about linen, wool, cotton, silk and synthetic fabrics that made me look at the clothes in my own closet a little differently. And many of those kept leading back to the same name: Dr. Heidi Yellen.
So who was she, what did she reportedly study, and why are people still talking about her work more than two decades later?
I went looking for the story behind those numbers and here’s what I found:
Dr. Heidi Yellen and the Question That Still Has People Talking.
The work most frequently attributed to Dr. Yellen dates to approximately 2003 and centers on measuring what have been described as the energetic characteristics or “signature frequencies” of different fabrics.
The basic idea behind the work is certainly intriguing. Could the materials we put against our bodies every day have energetic properties of their own? And if they do, could those differences have an effect on us?
Those questions helped create what has become a surprisingly widespread discussion about the frequency of clothing.
Today you’ll find Dr. Yellen’s name mentioned on websites devoted to natural fabrics, wellness, sustainable clothing and other subjects involving the materials we bring into our lives.
But there’s an interesting wrinkle to this story: Where Is Dr. Yellen’s Research Paper? This is something I think you deserve to know!
The fabric-frequency numbers attributed to Dr. Yellen have been repeated for more than two decades, but documentation of the original research has not been found. Nor have I been able to locate the original study as a conventional peer-reviewed scientific paper that allows us to examine the complete methodology and results for ourselves.
That doesn’t make the subject uninteresting. Actually, it made me even more curious:
- Where did these specific numbers come from?
- What was being measured?
- Why have the numbers continued to circulate for more than twenty years?
Instead of pretending we have every answer, let’s follow the trail we do have.
The Fabric Measurements Attributed to Dr. Heidi Yellen
Accounts of Dr. Yellen’s work commonly report that a healthy human body was assigned a measurement of approximately 100.
Then come the fabrics. The measurements most often repeated are:
- Linen — 5,000
- Wool — 5,000
- Organic Cotton — 100
- Conventional Cotton — approximately 70
- Silk — approximately 10–15
- Rayon, Polyester and other Synthetics — generally reported at the low end, often around 10–15
Now you can see why these numbers attracted attention! If the healthy human body is represented by approximately 100 and linen and wool are represented by 5,000, that is enough of a difference to make almost anybody ask: “What in the world is going on here?”
That’s exactly the kind of question that can send you down a very interesting rabbit hole.
What Was Dr. Yellen Actually Measuring?
This is where I found one of the most interesting pieces of the story.
In a 2012 email attributed to Dr. Yellen, she described how the fabric measurements had been made. According to her account, a technician named Ivanne Farr used a digital instrument called an Ag-Environ machine, designed by Bob Graham, whom Yellen described as a retired Texas A&M professor.
Yellen said the instrument had originally been developed to analyze what Graham called the “signature frequencies” of agricultural products and help determine appropriate times for harvesting.
That gives us more information about where the familiar fabric numbers came from—but it also creates another question: Exactly what do those numbers represent?
Over the years, websites repeating Yellen’s work have described the measurements in different ways. Some call them frequencies and attach units such as Hz to the numbers. Others describe them using different terminology, including angstroms.
Those measurements are not interchangeable.
That’s why, on this page, I’m giving you the numerical measurements commonly attributed to Dr. Yellen without attaching a scientific unit that I cannot reliably verify.
The mystery isn’t quite solved, but at least now we know a little more about where the story began.
Why Linen Became the Star of the Story
If one fabric became particularly associated with Dr. Yellen’s work, it was linen.
Linen is commonly reported at 5,000, dramatically higher than the approximately 100 attributed to the healthy human body.
And linen already had quite a résumé before anybody started discussing its frequency.
It is one of humanity’s oldest textiles. It breathes well, absorbs moisture and is remarkably durable. Linen has been used throughout history for clothing, bedding, bandages and many other practical purposes.
Its long history has also helped give linen a modern reputation in some natural-living circles as a kind of “healer cloth.”
Suddenly, an ancient natural fabric has a very modern mystery attached to it.
Wool Brought an Ancient Question Into the Conversation.
If you’d like to explore linen and some of the other fabrics in greater detail, go HERE to discover The Frequency of Clothing.
Wool is also commonly assigned the remarkable measurement of 5,000 in accounts of Dr. Yellen’s work.
That becomes particularly interesting because of an ancient Biblical instruction:
Deuteronomy 22:11: “You shall not wear cloth of wool and linen mixed together.”
That instruction was written thousands of years before anyone had the technology we have today for studying the properties of fabrics.
The Bible doesn’t explain in this passage why wool and linen were not to be worn together.
I did have a possible explanation : Linen and wool have very different properties. We often think of linen as a cool, breathable fabric, while wool provides insulation and helps retain warmth. Could those very different characteristics have had something to do with the instruction?
I don’t know. That’s simply my own thought.
And now, centuries later, we have another curious piece to add to the story: the measurements attributed to Dr. Yellen place both linen and wool at 5,000.
Does that explain the Biblical instruction?
We don’t know.
But does it make the connection interesting?
You bet it does.
It’s one of those little discoveries that makes you keep reading when you were supposed to be doing something else.
Then There’s Organic Cotton.
Organic cotton is another fascinating part of the story because its reported measurement is approximately 100—the same number commonly attributed to the healthy human body.
Conventional cotton, on the other hand, is generally reported at approximately 70.
If two versions of what we casually call “cotton” received different reported measurements, what accounted for the difference?
I don’t know.
And without the complete original methodology, I don’t think we should pretend to know.
But now I’m reading the tag.
And sometimes that’s exactly what good information does. It gets us to start noticing things we never paid much attention to before.
What About Silk and Synthetic Fabrics?
The lower end of the reported measurements is just as interesting.
Silk is often listed around 10–15, along with rayon and several synthetic materials such as polyester, acrylic and nylon.
That surprises many people, particularly when it comes to silk, because we tend to think of silk as a luxurious natural material.
I wouldn’t use these reported measurements alone to decide whether a particular fabric is “good” or “bad.”
But they certainly give us another reason to become curious about what our clothing is made from.
We spend hours every day surrounded by fabrics—shirts, pants, pajamas, sheets, towels, blankets and upholstery.
Maybe reading that little fabric-content label isn’t such a silly idea after all.
Did Dr. Yellen Actually Test Hemp?
Here’s another interesting discovery.
The Hemp frequently appears today on lists of supposedly high-frequency natural fabrics alongside linen and wool.
But I haven’t found reliable documentation showing that hemp was actually included in Dr. Yellen’s original fabric measurements.
That’s worth mentioning because information has a funny way of changing as it travels.
One person writes something. Another person repeats it. Someone adds a detail. Twenty years later, everybody assumes the added detail was part of the original story.
Hemp may indeed have interesting properties as a natural textile. But unless we can verify that Dr. Yellen or someone else tested it, I’m not going to put a Dr. Yellen measurement beside it.
That’s simply keeping our story straight.
Why Does Dr. Heidi Yellen’s Work Still Matter?
More than two decades after the research attributed to her, people are still talking about it.
Why?
I think part of the answer is that the subject touches something we’re becoming increasingly aware of:
Our environment matters.
We think about what’s in our food. We read labels on supplements. We pay more attention to chemicals in household products. We think about the air we breathe and the water we drink.
So perhaps it isn’t so strange that people are also beginning to ask questions about the fabrics touching our bodies for hours every day:
- Your clothing.
- Your sheets.
- Your towels.
- Your blankets.
- Even the upholstery you’re sitting on while you read this.
Once the question enters your head, it’s rather difficult to get it out.
Don’t Take My Word for It—Get Curious.
That’s really what I hope this page accomplishes.
I don’t need you to leave here believing every number ever attributed to Dr. Yellen.
I’d much rather have you leave wondering:
- What are my clothes made from?
- Would I like to include more natural fibers in some of the things I buy?
- Why were linen and wool given such extraordinarily high reported measurements?
- What else surrounds my body every day that I’ve simply never thought about?
Those questions are the doorway.
And they’re exactly the kinds of questions we’ll continue exploring.
Take the Next Step Into The Frequency of Clothing.
We’ve concentrated here on Dr. Heidi Yellen and the research attributed to her.
Now let’s have some fun with what those ideas could mean in everyday life.
We’ll look more closely at linen, wool, organic cotton, silk and synthetic fabrics. We’ll talk about reading clothing labels.
We’ll even wander through a desert marketplace. There’s a camel involved.
Don’t ask!
When you’re ready to continue exploring, click HERE to take the next step into The Frequency of Clothing.
The important thing is to keep learning, keep asking questions and keep paying attention to what surrounds you.
Because sometimes something as ordinary as the shirt on your back can open the door to a subject you never knew you wanted to explore.