I love it, I avoid it, and my vitamin D level is proof neither approach is quite right.

I love the sun. I'd lay out all day in high school, and I'd still do it today if I had the time.

But somewhere along the way, the fear of skin cancer and wrinkles got to me. So now I do what most doctors do: practice avoidance. Shade. SPF 50. Cover up. Even in 90-degree NYC summer weather, I spend most of my day indoors or covered — like most of us do now, sunny climate or not.

Which is probably part of why my vitamin D came back low. Turns out I'm in good company: almost 90% of American adults are below what's considered an optimal level — not "deficient" by the old textbook cutoff, but below where you actually feel and function best (GrassrootsHealth NHANES analysis).

We've spent 20 years being told the sun is the enemy. For skin cancer and photoaging, some of that's true. But we're not that different from plants — we need light to run our biology, not just to tan. Turns out sunlight moves the needle on mood, blood pressure, sleep, and even immune function — all separate from vitamin D entirely.

This week: what sun exposure actually does for you beyond vitamin D, why total avoidance has its own cost, and how to get enough without frying your skin.

Get 15–20 minutes of midday sun on bare arms and legs most days — more skin exposed means less time needed, and it's the single biggest vitamin D lever most people aren't pulling.

Sunscreen goes on after that window, not before — mineral, not chemical, not aerosol.

❌ The old assumption: Any time outside counts as "getting sun."

✅ The new reality: Vitamin D synthesis depends on skin surface area exposed and time in strong sun — not just being outdoors. Modeling of summer sun at latitudes comparable to most of the US shows that with roughly a third of your skin exposed — arms, legs, face, think shorts and a T-shirt, not a business suit — about 5–10 minutes of midday sun several times a week is enough to maintain an already-healthy vitamin D level (Photochemistry and Photobiology, 2024). That's maintenance, not correction. 

Building up from a deficient level takes longer, and face and hands alone — which is what most "I get sun" actually means — expose maybe 5–10% of your skin. That's a fraction of what these studies assume.

❝ If you're only exposing your face and hands, you're getting a fraction of the sun exposure most vitamin D research assumes.

☀️ Sunlight does more than make vitamin D. Strip out the vitamin D angle entirely and sunlight is still doing important work for your health:

🚪 Most of us are indoors almost all day. Even in sunny states, Americans spend the vast majority of daylight hours indoors, in a car, or covered up. Add daily sunscreen and long sleeves, and you get genuine light deprivation dressed up as sun protection.

⚖️ The real tradeoff: cancer, aging, and total avoidance all carry risk.

 Cumulative UV exposure drives up to 80% of visible facial aging — wrinkles, sagging, sunspots — and raises skin cancer risk with repeated burns (Clinical, Cosmetic and Investigational Dermatology, 2013). 

But total avoidance has a cost too: in a 20-year Swedish cohort of nearly 30,000 women, those who avoided the sun had roughly double the mortality rate of the highest sun-exposure group, and lived 0.6–2.1 fewer years — a magnitude of risk the researchers compared to smoking (Journal of Internal Medicine, 2016). That same high-exposure group did have more skin cancer. The answer isn't "more sun, always" — it's brief, unprotected exposure without burning, then covering up or applying sunscreen for the rest of the day.

1️⃣ Get 15–20 minutes of midday sun with real skin exposed, most days. Arms, legs, and face — not just hands through a car window. Late morning to early afternoon, before you'd start to burn. In winter or at northern latitudes, you'll need more time, or a vitamin D3 supplement to make up the gap.

2️⃣ Reapply mineral sunscreen once your window is up. Zinc oxide or titanium dioxide only — skip oxybenzone, octinoxate, and other chemical filters tied to hormone disruption.

3️⃣ Know your actual vitamin D number. Don't estimate based on how much time you spend outside — get 25(OH)D tested. In my practice, this is one of the first labs I run on anyone who's fatigued, low mood, or getting sick often.

4️⃣ Watch for bemotrizinol, the FDA's newest sunscreen filter. Approved in June 2026 — the first new sunscreen active ingredient allowed in the US in 25 years.

The goal: get enough real sunlight to run your biology — without burning, without spraying benzene on your skin, and without pretending five minutes in the car counts.

I was a lifeguard in high school. I spent hours baking in the sun, and my friends and I were competitive about who was the most tan. I loved turning a golden brown. Some olive skin gene from an ancestor somewhere really had my back.

I rarely miss those days, but when I do, it's not just the tanning I miss — it's the pace. Hanging out with my friends all afternoon by the pool feels very far away.

These days I find myself in perpetual motion. Work, email, social media, social engagements, parenting, cleaning, errands, writing — even meditating becomes just another task. There is rarely a waking hour where I have nothing to do, and if there is, I manage to fill it within minutes with an activity, a task, or an obligation.

When did it become normal to always be on the run?

I prescribe my patients one waking hour a day of relaxation, to turn on the parasympathetic nervous system and stimulate the body's natural rest, digest, relax, and heal response. The body can clean up dead and damaged cells, clean out brain plaques, reset the immune system, and heal the gut — if given a fighting chance to do so in a state of peace. In the spirit of practicing what I preach, I've been spending evenings in the warm weather lately reading and meditating on my roof, listening to the city around me, aware of my nervous system wanting to keep firing on all cylinders, and watching it fight the downtime.

A key component of practicing longevity for me is giving up the need to do everything myself — to be the driver of the bus or the keeper of the pace. In this case, I'm trusting my body to keep me young and well by letting it do what it inherently knows how to do, when given the opportunity. Longevity isn't always about what we do — it's also about what we allow to happen for us, when we slow down enough to let it.

If you read this and realized you genuinely don't know your vitamin D number, that's worth fixing before you guess your way through another summer. Parsley's longevity labs test vitamin D alongside the other markers that actually predict how you're aging — and you can pair it with a clinical visit to build a real plan around what you find, sun, supplements, or both.

Book your labs + consult here →

Stay strong, stay curious, and breathe,

Robin

As always, this newsletter is for informational and educational purposes only and is not intended as medical advice. Always consult your healthcare provider before making any health decisions or changes to your treatment plan.