Doctors say the ideal form of vitamin D comes from the skin when it absorbs sunlight. A dietitian expert weighs-in on the effectiveness on vitamin supplements.

SEATTLE — As Pacific Northwesterners go deeper into the “big dark,” some may wonder about their vitamin D levels. 

“It’s so unique because it’s the one vitamin that we actually get from the sun, literally the reaction that the sun has on our skin, which is unique. No other vitamin is like that,” said Judy Simon, a registered clinical dietitian at UW Medicine.

When our skin absorbs UV rays, it makes vitamin D, and this version of vitamin D made from sunshine is exceptional. 

“It lowers blood pressure and can reduce rates of cardiovascular disease,” Simon said. 

That reaction comes from sunlight triggering the release of nitric oxide in our skin, according to Simon. 

But as the days grow darker sooner during these fall and winter months, many turn to vitamin D supplements to boost levels.

But are they as effective as catching some rays?

Simon said supplements are effective and adds, it might depend on the type of supplement you take.

“First of all, it’s best that it’s in an oil form rather than a gummy or maybe a solid in oil form is best. Eating it with a meal, even your largest meal, and having some fat at the meal has shown to have the most impact on raising your vitamin D level,” Simon said.

By oil form, Simon said the kind in soft gel capsules.

As for what vitamin D does for people exactly, it’s basically — everything.

“Every cell in our body has vitamin D receptors, and we need vitamin D to optimize our metabolism for bone building, for metabolic health,” Simon said.

Historically, people supplemented vitamin D from food sources like cod liver oil or fish stock.

It’s naturally found in salmon, with smaller amounts in egg yolk, fortified dairy and even mushrooms when exposed to UV light.

But Simon said it’s challenging to get enough from diet alone and symptoms of deficiency may not be apparent at all.

She says a good first step to figure this out is talking with your primary care doctor.

“Many people won’t know they’re deficient unless they get that baseline,” Simon said.