The Tenpenny Files with Dr. William Supple Jr.

What Did 50 Years of Fearing the Sun Do to Our Health?

For more than half a century, Americans have been warned about the dangers of the sun. Stay out of it. Cover up. Wear sunscreen. Protect your skin. Somewhere along the way, avoiding sunlight became synonymous with protecting our health.

But what if there is another side to that story that we haven’t been paying enough attention to?

Dr. William Supple Jr. is a neuroscientist who has spent decades studying vitamin D, and he believes what he calls the “sun scare” may have created consequences that extend far beyond weak bones. His new book, The Sunlight Solution: Reclaiming Vitamin D, Reversing the Chronic Disease Epidemic, and Making America Healthy Again, challenges us to look at what happened as we moved indoors, covered our skin and dramatically reduced one of the primary ways the human body produces vitamin D.

Bill’s interest in this didn’t begin as an academic exercise. Nearly 40 years ago, while he was in graduate school at Dartmouth, he developed psoriasis. He noticed something strange: when he went to Florida, it cleared. When summer arrived, it cleared. That observation sent a neuroscientist down a completely different research path and eventually led to the questions at the center of this book.

Why does virtually every cell in the body have a vitamin D receptor? Why does the amount of vitamin D our skin can produce decline as we age? Why are people living in northern climates unable to make adequate vitamin D from the sun during portions of the year? And if vitamin D is involved in regulating immune function and inflammation, why do we still tend to talk about it primarily in terms of bones?

This is where the conversation gets really interesting.

Bill connects vitamin D status to chronic inflammation and begins walking through the implications he believes that may have for cardiovascular disease, brain health, Alzheimer’s disease, muscle strength, aging, autoimmune conditions and other chronic illnesses. We also get into an area I didn’t expect to spend as much time on: athletes and concussions. Bill explains why someone can look incredibly fit and still be vitamin D deficient, and why he believes vitamin D status may influence the brain’s inflammatory response following a traumatic injury.

Then we get to older adults. We talk constantly about osteoporosis and broken hips, but Bill raises a different question: Why did that person fall in the first place? His discussion of vitamin D receptors in muscle, fast-twitch muscle fibers, strength and the ability to catch yourself when you lose your balance gives you a completely different way of thinking about aging and fall risk.

And then there’s sunscreen.

Bill devoted an entire chapter of The Sunlight Solution to a deliberately provocative question: “Is Sunscreen the New Margarine?” We talk about why he chose that comparison, his concerns about chemical sunscreen ingredients, what happens to vitamin D production when UVB is blocked, and why he believes our relationship with sunlight needs to be reconsidered. His argument isn’t that burning your skin is healthy. His question is whether decades of treating sunlight itself as something to fear created another problem that received far less attention.

As I went through The Sunlight Solution, I kept coming back to questions I wanted Bill to answer directly, and I’m guessing you’ll have many of the same ones. How much vitamin D do we actually need? Can you take too much? Why isn’t vitamin D routinely checked during pregnancy? What happens as we get older and our skin becomes less efficient at making it? Why are so many athletes deficient? What about vitamin K? And after everything we’ve been told about protecting ourselves from the sun, what are we supposed to make of sunscreen?

That’s why I want you to watch this interview before you decide that you already know enough about vitamin D. Bill’s answers take this well beyond the usual conversation about taking a supplement for your bones. When he starts explaining the connections he sees to inflammation, the brain, cardiovascular disease, muscle strength, falls, Alzheimer’s disease and even concussion, you begin to understand just how much of the vitamin D story most of us have never been taught.

Then get the book.

I really do think The Sunlight Solution belongs in your health library. There is so much packed into it, but Bill has written it in a way that makes it very easy to use. If cardiovascular disease is your concern, go there. If it’s psoriasis, brain health, aging, fertility or muscle loss, go to that chapter. You can pick it up because you have a specific question today and come back six months from now because you’re looking for something completely different.

And there are things I wanted Bill to explain that become much more interesting when you hear them directly from him. Why does he call the last 50 years the “sun scare”? Why does he believe chronic vitamin D deficiency has consequences that extend so far beyond bone health? What does vitamin D have to do with the inflammatory response after a concussion? Why does he say that with older adults we shouldn’t just be talking about the broken hip, but asking why they fell? And what led him to title an entire chapter “Is Sunscreen the New Margarine?”

Those are the questions we get into here. The research behind them, and the connections to individual health conditions, are waiting for you in the book.

So watch this conversation with Dr. William Supple Jr. first. I think you’ll understand very quickly why I recommend The Sunlight Solution, and why this isn’t a book I would read once and put away. It’s one I would keep within reach.

Meet our Guest

Dr. William F. Supple Jr. is a neuroscientist, researcher, educator and author whose career has included research into the brain mechanisms involved in learning, memory and emotion.

He earned his bachelor’s degree from Marist College and his Ph.D. from Dartmouth College, where his research contributed to understanding the role of the brainstem and cerebellum in behavior. He later taught brain-behavior sciences and developed a sports psychology course at the University of Vermont.

His interest in vitamin D became personal decades ago when he developed psoriasis and noticed that his symptoms changed dramatically with seasonal and geographic differences in sun exposure. That observation eventually led to years of research into sunlight, vitamin D and the role he believes vitamin D status plays across multiple systems of the body.

His 2026 book, The Sunlight Solution: Reclaiming Vitamin D, Reversing the Chronic Disease Epidemic, and Making America Healthy Again, examines the history of sun avoidance, vitamin D deficiency and the scientific literature connecting vitamin D with immune regulation, inflammation, brain health, cardiovascular health, muscle function, aging and chronic disease.

Website

Book: https://amzn.to/4fyp9iW