#308 - AMA #61: Sun exposure, sunscreen, and skin health: relationship between sun exposure and skin cancer, vitamin D production, and photoaging, how to choose a sunscreen, and more - Peter Attia (2024)

In this “Ask Me Anything” (AMA) episode, Peter delves into two topics that have generated a lot of questions over the years: skin cancer and sunscreen. He begins by exploring the basics of UV radiation, discussing its effects on vitamin D conversion, photoaging, and its role in skin cancer. He examines various skin types, discussing their implications for sun exposure and vitamin D levels, as well as how to determine where you fall on the skin type scale. He then delves into the various types of skin cancer, with a particular emphasis on melanoma, exploring its complex relationship with UV exposure and other contributing risk factors. Additionally, he covers tanning beds, the importance of early skin cancer detection through regular skin checks, and the often confusing topic of sunscreen. He explains how sunscreen affects UV radiation and skin cancer risk, what SPF levels to choose, the differences between organic and mineral sunscreens, and what to consider when selecting the best sunscreen for your needs.

If you’re not a subscriber and listening on a podcast player, you’ll only be able to hear a preview of the AMA. If you’re a subscriber, you can now listen to this full episode on your private RSS feed or on our website at the AMA #61 show notes page. If you are not a subscriber, you can learn more about the subscriber benefits here.

We discuss:

• The impact of UV radiation on the skin [2:00];
• Understanding solar UV: from the electromagnetic spectrum to skin health [3:45];
• The role of sunlight in vitamin D production [8:30];
• Factors contributing to vitamin D deficiency: insufficient UV exposure, magnesium levels, and more [9:45];
• Sun exposure needs for different skin types, and the limitations of current studies in defining vitamin D deficiency [12:45];
• The acute and long-term effects of excessive UV exposure: sunburn, photoaging, and the increased risk of skin cancer [15:30];
• Types of skin cancer and associations with UV exposure [17:45];
• The complex relationship between melanoma and UV exposure [22:15];
• Why UV exposure alone doesn’t necessarily explain the risk for melanoma [25:15];
• Other risk factors for melanoma [29:15];
• Tanning beds and skin cancer risk [34:45];
• Balancing sun exposure: benefits and risks [38:15];
• Tattoos and sun exposure [40:30];
• The importance of regular skin checks, dermatologists, and emerging technologies showing promise for early detection of cancer [41:45];
• Self-skin checks: what to look for [46:30];
• Prevalence of skin cancer and the importance of early detection [49:30];
• Summary of the major risk factors for melanoma [54:15];
• The role of sunscreen in reducing skin cancer risk [55:45];
• How sunscreen works, the differences between chemical and mineral sunscreens, an explanation of SPF, and more [58:30];
• How to determine the appropriate sunscreen SPF to use based on the UV index [1:04:45];
• Choosing the right sunscreen for your individual needs [1:07:00];
• The impact of water and perspiration on sunscreen effectiveness [1:12:00];
• Chemical vs. mineral sunscreens: safety concerns and recommendations [1:14:00];
• Concerns about hormone effects from chemical sunscreens [1:19:15];
• Sunscreen summary: skin types, key considerations, recommended brands, and more [1:23:15]; and
• More.

§

The impact of UV radiation on the skin [2:00]

Today’s AMA topics:

• Focus on skin cancer and sunscreen
• There has been a high volume of questions and prevalent confusion about these topics
• The team dedicated months of work to study these topics

For the discussion on skin cancer

• Peter talks about the importance of understanding the impact of UV radiation on the skin
• Part of that will be about the key aspects of UV radiation including…
  • A brief explanation of UV radiation.
  • And the three main impacts of UV radiation:
    • 1) Vitamin D Conversion: How UV light facilitates the production of vitamin D in the skin.
    • 2) Photoaging: The effect of ultraviolet light on skin aging.
    • 3) Role in Skin Cancer: How UV radiation contributes to the development of different skin cancers

Understanding solar UV: from the electromagnetic spectrum to skin health [3:45]

When we say solar UV, what are we referring to?

Figure 1. Sources: NPR. Power Electronic Tips, Office of the Surgeon General (US); 2014

Electromagnetic Spectrum Overview: What is happening when wavelengths across an electromagnetic spectrum change in size?

Different types of waves explained:

• Sound Waves: Longer wavelengths can bend around corners, making them audible even when the source is not in direct sight.
• Light Waves: Shorter wavelengths are visible to the human eye but cannot bend around corners like sound waves.
• Visible Light Spectrum
  • The visible spectrum of light ranges from 400 to 700 nanometers.
  • This range represents only a small part of the entire electromagnetic spectrum, including everything from red light to blue light.
• Ultraviolet Light
  • Ultraviolet light exists from about 100 to 400 nanometers, just below the visible light spectrum.

More about ultraviolet light—it is divided into three types:

• UVA: 315 to 400 nanometers.
• UVB: 280 to 315 nanometers.
• UVC: 100 to 280 nanometers.

Characteristics of Ultraviolet Light

• Shorter wavelengths contain more energy.
• Common misconceptions about microwaves:
  • Microwaves have longer wavelengths than visible light.
  • Visible light is more energetic than microwaves, so standing next to a microwave is not more dangerous than exposure to visible light.

Ultraviolet A, B, and C

• UVA: Longest wavelength, lower energy, penetrates deeper into the skin, contributing to aging and long-term skin damage.
• UVB: Shorter wavelength, higher energy, responsible for sunburn and crucial for vitamin D conversion in the skin.
• UVC: Shortest wavelength, highest energy, but does not reach Earth’s surface due to atmospheric absorption, so it is not a concern for skin exposure.

Relevance of UVA and UVB: UVA and UVB are the primary types of UV radiation that reach Earth’s surface.

• UVA:
  • Broader band (315 to 400 nanometers).
  • Accounts for 95% of UV radiation exposure.
  • Penetrates deeper into the skin but is less ionizing.
• UVB:
  • Narrower band (280 to 315 nanometers).
  • Accounts for 5% of UV radiation exposure.
  • Higher energy, causes sunburn, and aids in vitamin D conversion.

Conclusion of UV Radiation Explanation

• UV light, visible light, and other forms of energy differ significantly.
• UVA and UVB have specific impacts on skin health, with UVA penetrating deeper and contributing to aging, while UVB causes sunburn and helps in vitamin D synthesis.

The role of sunlight in vitamin D production [8:30]

{end of show notes preview}