Supplements Vs Sunshine: Which Is The Superior Source Of Vitamin D?

February 25, 2023

Despite its key role in bone, muscle, and immune health, half of the U.S. population is not getting the vitamin D it needs to support whole-body health.* To be specific, 29% of American adults are deficient in vitamin D, while 41% are insufficient1.

Consuming enough vitamin D from food alone is absurdly difficult. Very few foods have any—much less high amounts of—vitamin D (and even those are negligible), which is why 93% of U.S. adults2 aren’t even consuming 400 I.U. of D daily from food alone. We’re left with two sources to get the D we need: the sun and supplementation. So which one is the better option? Researchers came to a clear answer.

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A 2021 study conducted in Korea put these two methods of getting vitamin D to the test. Vitamin-D-deficient participants were given the choice between sunlight exposure and a modest level of oral vitamin D supplementation (1,000 I.U. of D3 taken daily, to be exact). 

Serum 25(OH)D levels (i.e., the blood biomarker for vitamin D status) were evaluated at the beginning and end of the three-month study to document changes. The sunlight exposure group had no significant increase in average serum 25(OH)D levels, while the oral supplementation group saw an average serum increase of 11 ng/ml at the end of the three months. 

In other words, vitamin D levels increased in participants that took 1,000 I.U. of vitamin D3, while those exposed to the sun experienced no significant changes. This confirmed what mindbodygreen has known all along: Vitamin D supplementation is the most effective and efficient method of raising vitamin D to levels of sufficiency.* 

Nutrition scientist Ashley Jordan Ferira, Ph.D., RDN, shared these additional insights: “This study is valuable for two reasons. First, it demonstrates the efficacy of vitamin D supplementation in positively affecting vitamin D status. Second, it confirms the pharmacokinetic research-backed phenomenon that predicts 1,000 I.U. of vitamin D3 will move the 25(OH)D “needle” by about 10 ng/ml in normal-weight adults. That predictable math is the reason why we actually need much more vitamin D, around 5,000 I.U. or more, to achieve and maintain vitamin D sufficiency throughout life.”*

With the many factors that affect our exposure to sunshine and ability to convert it into this essential vitamin—such as geographic location, season, climate, UV levels, pollution, clothing, sunscreen, age, and skin tone—we simply can’t rely on sunlight when it comes to getting enough vitamin D.

Even if we all lived in the perfect conditions for vitamin D sufficiency, the majority of us work indoors and aren’t exposed to the sun for most of the day. (And cumulative sun exposure throughout life comes with its own set of risks.) The science is conclusive: vitamin D supplementation is the way to go.

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While it’s clear vitamin D supplementation is an effective way to promote sufficient D levels, there are a lot of inefficient supplements out there that might not do the trick due to their subpotent or ineffective formulas. As Ferira expounded, this study confirms that taking 1,000 I.U. is the rule-of-thumb to raise vitamin D serum levels approximately 10 ng/ml in healthy adults. That’s why we recommend an even higher daily dose of 5,000 I.U. for adults (3,000 I.U. at the absolute minimum to avoid clinical insufficiency cutoff of 30 ng/ml). 

As far as form and function go, it’s important to take D3 (which is two to three times more effective than D2) with a healthy source of fat.* Vitamin D is a fat-soluble vitamin, which means taking your supplement with a meal that includes a dose of fat—or better yet, choosing a supplement with built-in healthy fat—is an effective and smart way to maximize D’s bioavailability.* (Bonus points if your supplement of choice is also clean and sustainable—i.e., it uses high-quality, organic, and plant-based ingredients from premium sources.)