What's The Best Way To Get Vitamin D: The Skin Or The Gut? We Investigate

Did you know that clinical vitamin D insufficiency persists in almost half (41%1) of the population? This is a problem because vitamin D plays a critical role in several functions in the body, from bone health to thyroid function. We need vitamin D to thrive, which raises the question: How do we increase our vitamin D levels?

Vitamin D can be consumed via a few food sources or supplementation, or synthesized in the skin via ultraviolet radiation. 

This is where the controversies arise. It's challenging to get enough vitamin D via food alone, given how few sources there are. And while sunlight can help increase natural vitamin D levels in the body, UV radiation is notorious for triggering skin cancers, damage, and premature aging, which means folks are stuck in a tricky place.

Here's the thing: You can get vitamin D from sunlight, but for many, sun exposure alone is often not enough to provide all the vitamin D that your body needs. 

For example, location often plays a role: Research8 suggests that if you live above or below a certain latitude (33 degrees, specifically), you'll be unable to produce vitamin D from sunlight during the winter months.

Environmental factors can also influence your skin's ability to create vitamin D. For example, air pollution8 and particulate matter have been shown to interfere with vitamin D production. 

And skin tone plays a role in the body's ability to produce enough vitamin D. Larger amounts of melanin9 in the skin affect the skin's ability to produce vitamin D from UV rays; people with darker skin tones need longer exposure to the sun (up to two hours a day) to produce adequate vitamin D levels. Of course, this is often not possible. 

And even when individuals have met the sunlight requirements to obtain adequate vitamin D, it's still not always enough, notes Hu. In fact, she says, research has found that individuals who spend all day in the sun without sunblock can still be vitamin D deficient10.

According to Hu, "It's much safer and more reliable to take a vitamin D [supplement] than go in the sun, get sunburned, and potentially [get] skin cancer because of that fear of vitamin D deficiency." 

One study even pitted supplementation and sunshine against each other, finding that those who took a modest level of oral vitamin D supplementation (1,000 IU of D3 taken daily) experienced an increase in vitamin D blood levels. Participants who chose to rely on sunlight exposure, on the other hand, had no significant increase.

"There are also a lot of other studies supporting that our skin's capacity to convert vitamin D from sun exposure declines over age12, but our GI absorption stays relatively stable," Hu explains. Meaning, older adults experience a reduced capacity to produce vitamin D313 from UVB radiation.

And as we noted, you can try to consume vitamin D through whole foods like fatty fish, liver, red meat, milk, and some mushrooms, but eating enough to reach sufficiency can be challenging.