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July 1, 2024 • 22min
#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
The Peter Attia Drive
In this "Ask Me Anything" (AMA) episode, Dr. Peter Attia and his co-host Nick Feldman dive deep into two interconnected topics that generate many questions from listeners: skin cancer and sunscreen. They explore the fundamentals of UV radiation, its effects on vitamin D production and skin health, different skin types and their implications for sun exposure, various forms of skin cancer with a focus on melanoma, and the often confusing topic of sunscreen including how it works and what to look for when choosing one.
#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
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Key Takeaways
- UV radiation impacts the skin in three main ways: vitamin D conversion, photoaging, and skin cancer risk
- UVA and UVB are the two types of UV radiation that reach the Earth's surface and impact skin:
- UVA (95% of UV radiation) penetrates deeper but has less energy
- UVB (5% of UV radiation) is higher energy and responsible for sunburn and vitamin D production
- Vitamin D production from sunlight depends on many factors including skin type, location, time of day, and exposed skin surface area
- Darker skin tones require more sun exposure to produce adequate vitamin D levels compared to lighter skin tones
- Excessive UV exposure can lead to sunburn, photoaging, and increased skin cancer risk
- The three main types of skin cancer associated with UV exposure are: basal cell carcinoma, squamous cell carcinoma, and melanoma
- Melanoma has a complex relationship with UV exposure - intermittent intense exposure may be more risky than chronic exposure
- Regular skin checks and early detection are crucial for catching and treating skin cancers early
- Sunscreen helps protect against UV damage but proper application and reapplication is key
- Both mineral and chemical sunscreens can be effective when used correctly
Introduction
In this "Ask Me Anything" (AMA) episode, Dr. Peter Attia and his co-host Nick Feldman dive deep into two interconnected topics that generate many questions from listeners: skin cancer and sunscreen. They explore the fundamentals of UV radiation, its effects on vitamin D production and skin health, different skin types and their implications for sun exposure, various forms of skin cancer with a focus on melanoma, and the often confusing topic of sunscreen including how it works and what to look for when choosing one.
Topics Discussed
Understanding UV Radiation and Its Impact on Skin (02:42)
Dr. Attia begins by explaining the electromagnetic spectrum and where UV radiation fits:
- UV radiation occupies wavelengths just below visible light (100-400 nm)
- Shorter wavelengths contain more energy
- UV radiation is divided into UVA, UVB, and UVC
- Only UVA and UVB reach Earth's surface and impact skin
He outlines the key differences between UVA and UVB:
- UVA: 95% of UV radiation, longer wavelength, penetrates deeper into skin
- UVB: 5% of UV radiation, shorter wavelength but higher energy, responsible for sunburn and vitamin D production
UV Radiation and Vitamin D Production (09:22)
Dr. Attia explains how UV radiation, specifically UVB, helps produce vitamin D in the skin:
- UVB converts vitamin D2 or pre-vitamin D3 into vitamin D3
- Process requires both UVB radiation and body heat
- Vitamin D3 from sunlight is chemically identical to supplements or food sources
He discusses factors affecting vitamin D levels:
- Amount of sun exposure
- Adipose tissue (more fat tissue can sequester more vitamin D)
- Skin tone (darker skin requires more sun exposure for vitamin D production)
- Magnesium levels (low magnesium can impede vitamin D metabolism)
Skin Types and Sun Exposure Needs (13:06)
Dr. Attia introduces the Fitzpatrick scale for classifying skin types:
- Type 1: Very pale, burns easily, doesn't tan
- Type 2: White skin, burns easily, tans minimally
- Type 3: White skin, may burn, tans easily
- Type 4: Light brown/olive skin, rarely burns, tans easily
- Type 5: Brown skin, rarely burns, tans easily
- Type 6: Black skin, unlikely to burn, darkens with sun exposure
He notes that lighter skin types (1-3) may need as little as 9 minutes of midday sun exposure to produce adequate vitamin D, while darker skin types may need 3-4 times that amount. However, he cautions that the study defining "adequate" used a very low threshold for vitamin D levels.
Effects of Excessive UV Exposure (16:12)
Dr. Attia outlines the potential negative effects of too much UV exposure:
- Sunburn: Acute, painful skin damage
- Photoaging: Premature aging of skin, including wrinkles and sagging
- Increased skin cancer risk: The most serious long-term concern
He shares a striking example of photoaging from a truck driver with asymmetric sun exposure over many years, highlighting the visible difference in skin aging between the more and less exposed sides of his face.
Types of Skin Cancer and UV Associations (18:30)
Dr. Attia discusses the three main types of skin cancer associated with UV exposure:
- Basal cell carcinoma (BCC): Most common, slow-growing, rarely metastasizes
- Squamous cell carcinoma (SCC): Second most common, can be more aggressive than BCC
- Melanoma: Least common but most dangerous, can metastasize rapidly
He notes that while all three are associated with UV exposure, the relationship is most straightforward for BCC and SCC. Melanoma has a more complex relationship with UV exposure.
Melanoma and UV Exposure (22:15)
Dr. Attia delves into the nuanced relationship between melanoma and UV exposure:
- Intermittent intense sun exposure may be more risky than chronic exposure
- Childhood sunburns are a significant risk factor
- UV exposure alone doesn't fully explain melanoma risk
- Other factors like genetics and immune function play a role
He emphasizes that while UV exposure is a risk factor, it's not the only one, and melanoma can occur in areas not typically exposed to sun.
Other Risk Factors for Melanoma (29:15)
Dr. Attia outlines additional risk factors for melanoma:
- Family history of melanoma
- Personal history of other skin cancers
- Fair skin, light hair, and light eyes
- Presence of atypical moles
- Weakened immune system
- Age (risk increases with age)
Tanning Beds and Skin Cancer Risk (34:45)
Dr. Attia discusses the risks associated with tanning beds:
- Emit primarily UVA radiation, which penetrates deeper into skin
- Associated with increased risk of all skin cancer types, especially melanoma
- Particularly risky for young people
He strongly advises against using tanning beds for any reason.
Importance of Skin Checks and Early Detection (41:45)
Dr. Attia emphasizes the importance of regular skin checks:
- Recommends annual full-body skin exams by a dermatologist
- Discusses emerging technologies for early skin cancer detection
- Encourages self-checks between professional exams
He provides guidance on what to look for during self-checks, including the "ABCDE" criteria for suspicious moles:
- Asymmetry
- Border irregularity
- Color variations
- Diameter larger than 6mm
- Evolving or changing over time
Sunscreen: How It Works and What to Look For (55:45)
Dr. Attia explains how sunscreen works to protect against UV damage:
- Two main types: chemical (organic) and mineral (inorganic) sunscreens
- Chemical sunscreens absorb UV radiation and convert it to heat
- Mineral sunscreens reflect and scatter UV radiation
He discusses key factors to consider when choosing a sunscreen:
- SPF (Sun Protection Factor): Measures protection against UVB
- Broad-spectrum protection: Covers both UVA and UVB
- Water resistance: Important for swimming or sweating
- Application and reapplication: Crucial for effectiveness
Chemical vs. Mineral Sunscreens: Safety and Recommendations (1:14:00)
Dr. Attia compares chemical and mineral sunscreens:
- Chemical sunscreens:
- More cosmetically elegant, easier to apply
- Some concerns about systemic absorption and potential hormone effects
- Mineral sunscreens:
- Generally considered safer, especially for sensitive skin
- Can leave a white cast on skin
- Main ingredients are zinc oxide and titanium dioxide
He notes that both types can be effective when used correctly, and the best sunscreen is one that you'll use consistently.
Conclusion
Dr. Attia concludes by emphasizing the importance of a balanced approach to sun exposure and skin protection. While some sun exposure is beneficial for vitamin D production and overall health, excessive UV radiation can lead to premature aging and increased skin cancer risk. Regular skin checks, early detection, and proper use of sunscreen are crucial for maintaining skin health and preventing skin cancer. He encourages listeners to be mindful of their individual skin type and risk factors, and to consult with a dermatologist for personalized advice on sun protection and skin cancer prevention.