Vitamin D consistently takes the MVP when it comes to vitamins—it’s involved in everything from bone and immune health to muscle function, hormones, and glucose regulation.
But if you’re someone who excludes animal-based foods from your diet and lives in a climate where you don’t have year-round access to the sun, keeping your levels up can be a challenge.
If you’ve been sitting outside on an overcast day only to come inside and find you’re burned, you’ve experienced first-hand what we’re talking about. If you’ve been under the impression that a bright sunny day is needed to pump up your vitamin D levels, we have news for you—it’s not.
Just like you can get burned on a cloudy day, the UV rays from the sun penetrate through clouds, and you can still get your share of vitamin D, sun or not.
In this article, we’ll break down the top reasons why you need vitamin D and how to get enough—even if it’s cloudy.
What Is Vitamin D And Why Do We Need It?
Although categorized as a fat-soluble vitamin, vitamin D is a hormone. Vitamin D is one of the few nutrients that the body can synthesize through exposure to UVB rays.
It plays critical roles in maintaining optimal health and is required to develop, grow, and maintain a healthy skeleton from birth until death, among many other functions.
Vitamin D exerts many of its biological functions via regulating gene transcription through the vitamin D receptor (VDR), and it’s suggested that vitamin D directly or indirectly controls anywhere from 200 to 2,000 genes 1.
Nearly every cell in the human body contains a vitamin D receptor (VDR). While the classic actions of vitamin D are on calcium and phosphorus metabolism, it also plays a role in other body systems and functions, including:
- Gastrointestinal tract
- Immune system
- Cardiovascular system
- Pancreas
- Muscles
- Brain
- Cell cycle regulation
- Insulin production
Because vitamin D can cross the blood-brain barrier, it exhibits profound influences on brain function, though its exact role is unclear. But low vitamin D levels have been linked to various consequences, with the most profound impact on bone health.
Insufficient vitamin D, less than 15% of dietary calcium, and roughly 60% of phosphorus are absorbed 2. However, optimal vitamin D levels boost calcium and phosphorus absorption by up to 40% and 80%, respectively.
Can You Get Vitamin D On A Cloudy Day?
Yes—whether you’re having a rainy day or dead in the middle of winter, it is possible to reap the mood-boosting, immune-supporting benefits of vitamin D on a cloudy day.
While the amounts produced will be lower than what your body would synthesize in full, direct sunlight, UVB rays from the sun can penetrate through clouds to reach your skin.
That said, how much reaches your skin depends on what kind of clouds are present. Heavy cloud cover can block most UV rays; thin or broken clouds allow passage of UV rays; puffy, fair-weather clouds deflect rays and can increase the amount of UV radiation reaching the ground.
Specifically, the U.S. National Weather Service and Environmental Protection Agency figure 89% transmission of UV rays for scattered clouds, 73% for broken clouds, and 32% for overcast conditions. So, can you still get vitamin D on a cloudy day? Absolutely.
But for people who live in a climate where winter rolls in, a lack of sun exposure leads to a high rate of seasonal affective disorder (SAD)—recurrent depressive episodes typically experienced during winter 3.
Several plausible mechanisms exist behind seasonal affective disorders, but studies show that many people who experience SAD have low vitamin D levels 4.
How To Get Vitamin D
As you may have guessed, there’s one place where you can get an unlimited source of vitamin D: the sun. When exposed to the sun, UVB rays penetrate the skin and trigger the conversion of provitamin D3 to pre-vitamin D3, which can isomerize to vitamin D3 or be photolyzed to two other compounds 5.
Once formed, vitamin D3 enters the systemic circulation and is metabolized into 25-hydroxyvitamin D3 and 1,25-dihydroxyvitamin D3 (1,25-[OH]2-D3)—the active form that exhibits the classical functions of vitamin D.
UVB rays from the sun are strongest between 10 am and 3 pm in the spring, summer, and fall. While supplemental vitamin D is effective for increasing serum levels, studies show that vitamin D produced in the skin may last twice as long in the bloodstream compared to dietary or supplemental vitamin D 2.
However, several factors interfere with the skin’s ability to produce vitamin D, including skin pigmentation, aging, and sunscreen use.
If you aren’t keen on sweating under the sun, there are other places to get vitamin D:
- Oily cold-water fish (salmon, sardines, mackerel, herring)
- Cod liver oil
- Egg yolks
- Tuna
- Fortified foods (milk, orange juice, cereals)
Alternatively, opt for a multi that includes it—like Performance Lab NutriGenesis Multi. While you may be inclined to forego the supplements, NutriGenesis technology is unique to Performance Lab.
It uses nature-identical vitamins and minerals complexed with cofactors to enhance absorption and utilization. So, you know what you’re getting is working.
And if you want further support, why not throw in Performance Lab PL-Immune—a dynamic probiotic and antioxidant stack that activates five types of immune cells to store frontline defenses fast and bolster your body’s natural immune function for robust long-range health.
References
- Hossein-nezhad A, Holick MF. Vitamin D for health: a global perspective. Mayo Clin Proc. 2013;88(7):720-755.
- Nair R, Maseeh A. Vitamin D: The “sunshine” vitamin. J Pharmacol Pharmacother. 2012;3(2):118-126.
- Kurlansik SL, Ibay AD. Seasonal affective disorder. Am Fam Physician. 2012;86(11):1037-1041.
- Penckofer S, Kouba J, Byrn M, Estwing Ferrans C. Vitamin D and depression: where is all the sunshine?. Issues Ment Health Nurs. 2010;31(6):385-393.
- Holick MF, Smith E, Pincus S. Skin as the site of vitamin D synthesis and target tissue for 1,25-dihydroxyvitamin D3. Use of calcitriol (1,25-dihydroxyvitamin D3) for treatment of psoriasis. Arch Dermatol. 1987;123(12):1677-1683a.
