☀️ Sunscreen, Sunlight & Vitamin D: Are You Blocking More Than Rays?

Every year around fall, I start hearing the same question from clients:
“If sunscreen blocks UV rays, does that mean I’m blocking my vitamin D?”

It’s a great question — and the answer isn’t as simple as you might think.

As a pharmacist and gut health coach, I love when curiosity meets science. Let’s explore what really happens between your sunscreen, your skin, and your body’s ability to make the sunshine vitamin that supports everything from immunity to gut health.

🌞 How Vitamin D Is Made in Your Skin

Vitamin D isn’t technically a vitamin — it’s a hormone precursor your body makes from sunlight.

When UVB rays hit your skin, they interact with a molecule called 7-dehydrocholesterol, transforming it into vitamin D₃ (cholecalciferol).
That vitamin D₃ then travels through your bloodstream to your liver and kidneys, where it’s converted into its active form — calcitriol (1,25-dihydroxyvitamin D).

This active form plays a crucial role in:

• Strengthening bones and muscle function

• Regulating immune responses

• Supporting gut barrier integrity and microbiome balance

In short: UVB is the spark that starts the entire process.

🧴 What Broad-Spectrum Sunscreen Really Blocks

Modern sunscreens are designed to be broad-spectrum, meaning they protect your skin from both UVA and UVB rays.

Here’s what that means:

• UVA rays penetrate deeper into the skin, contributing to aging and oxidative stress.

• UVB rays cause sunburn and are the same rays that trigger vitamin D production.

So theoretically, yes — if you apply sunscreen perfectly and evenly, you’re blocking much of the UVB light that activates vitamin D in your skin.

But that’s not the whole story.

🔬 What the Research Actually Shows

In controlled lab studies, applying sunscreen thickly can prevent vitamin D synthesis.

However, real-world evidence tells a different story:

• Most people apply far less sunscreen than recommended and often miss spots.

• Even with SPF protection, some UVB rays still reach the skin.

• A 2019 systematic review found little evidence that sunscreen use reduces vitamin D levels in real-life settings (PubMed ID: 30945275).

In fact, people who use sunscreen regularly often have normal vitamin D levels — especially those who spend time outdoors, eat vitamin D–rich foods, or take supplements.

So while sunscreen can reduce UVB exposure in theory, it doesn’t typically cause vitamin D deficiency on its own.

🌿 The Gut-Health Connection

Vitamin D plays a surprisingly powerful role in gut wellness.

Research shows it helps:

• Maintain the gut barrier, reducing intestinal permeability (“leaky gut”)

• Regulate immune tolerance, helping calm inflammation

• Support the microbiome, influencing diversity and balance of gut bacteria

Low vitamin D levels are linked with increased digestive symptoms, fatigue, and mood changes — particularly in women over 40 or those managing IBS, perimenopause, or autoimmune tendencies.

That’s why vitamin D isn’t just about bones — it’s also about balance from the inside out.

🌤️ Finding the Balance: Skin Protection &

Vitamin D

You don’t have to choose between protecting your skin and making vitamin D.
Here’s how to achieve both:

• ☀️ Enjoy short, safe sun exposure — about 10–15 minutes on uncovered skin a few times per week.

• 🧴 Use broad-spectrum sunscreen when outdoors for longer periods to prevent burns and skin damage.

• 🥗 Add vitamin D-rich foods like salmon, eggs, and fortified milk alternatives.

• 💊 Supplement wisely, especially during fall and winter months or if you live in northern latitudes.

The key is balance — not fear.

💛 Time to Check Your Levels

As daylight fades and sunscreen remains part of your daily routine, this is the perfect time to audit your vitamin D status.

Your body’s needs depend on your age, lifestyle, skin tone, and overall health — especially if you’re managing digestive symptoms or hormonal transitions.

That’s why I created the Vitamin D Audit — a quick, personalized assessment to help you:
✅ Identify your unique vitamin D needs
✅ Understand the link between your vitamin D and gut health
✅ Receive science-backed recommendations to support bone, immune, and digestive wellness

📋 Ready to find your balance?
➡️ Book your Vitamin D Audit today and get your personalized recommendations before October 31.
message me “D Audit” at wellnessbymarica@bell.net or go to Instagram @gutwellnessbymarica

🧠 References:

1. Young AR et al. Br J Dermatol. 2019;181(5):1052–1059.

2. Neale RE et al. J Invest Dermatol. 2019;139(1):146–152.

3. Holick MF. J Clin Endocrinol Metab. 1988;64(6):1165–1171.

4. Wang TT et al. J Steroid Biochem Mol Biol. 2019;188:145–152.