The 15-Minute Vitamin D Trick Hiding in Your Mushroom Basket

A simple “sun tan” for mushrooms that can boost Vitamin D — and yes, it still counts after cooking. I kid you not.

I learned something new this week from our nutritionist, Linda Kilworth — and I’ll be honest… if I’d heard it anywhere else, I probably would’ve raised an eyebrow.

You can naturally boost the Vitamin D in regular store-bought mushrooms by giving them just 15 minutes in the midday sun.
No special gear. No fancy steps. Just a tray, a timer, and a patch of sunshine.

It’s one of those rare nutrition tips that’s actually:

• easy to do
• costs nothing
• and can become a simple weekly habit

Why this works (the simple version)

Mushrooms contain a natural compound called ergosterol. When mushrooms are exposed to UV light, that compound converts into Vitamin D₂ (the plant-based form of Vitamin D).

Same concept as humans and sunshine — different biology, same “light does the job” idea.

And here’s the best part: once the Vitamin D is created, it stays elevated in the fridge for about a week — and it still holds up after cooking.

How to “tan” your mushrooms (15 minutes)

You’ll need: mushrooms, a plate or tray, sunshine, a timer.

1. Lay mushrooms out on a tray
   Whole or sliced both work — but sliced gives more surface area.
2. Gills up
   If you’ve sliced them, you’ll see the gills clearly. If they’re whole, just sit them so the underside is getting light.
3. Midday sun for 15 minutes
   Think between 10am and 3pm, when UV is strongest.
4. Back into the fridge
   Then cook them exactly how you normally would.

Chef’s note: Set a timer. This is a quick “boost and back inside” trick — not a sunbake.

Does it still count after cooking?

Yes. You can roast them, pan-fry them, toss them through pasta, stir them into sauces — they’ll still carry that Vitamin D benefit through the cooking process.

Short on time (or no sunshine)?

Look for packs labelled Vitamin D enriched (some mushrooms are UV-treated after harvesting).

Same idea — they’ve just done the “tanning” step for you.

Easy ways to use your “tanned” mushrooms

• fold into omelettes or scrambled eggs
• roast on a tray with olive oil, garlic, herbs
• toss through pasta sauce, stir-fries, soups
• add to a steak side, risotto, or a warm salad
• build into a veg-heavy side dish (hello fibre + flavour)

Basically: cook them the way you already do — you’ve just made them work harder first.

Final thought from Chef Ian

This is exactly the kind of tip I love sharing — simple, evidence-based, and achievable.

No guilt. No overhaul. Just a tiny habit that stacks up over time.

And if you want the bigger picture around vitamins/minerals (and what matters most as we age), Linda’s blog is the perfect companion read:
“Essential Vitamins & Minerals” → link here
Please note: this one is behind the Chef’s Table member paywall.

Chef Ian