Vitamin D is widely regarded as one of the most important vitamins for helping you keep your body in tip-top shape. The funny thing is – it isn’t a vitamin at all. Vitamin D is actually a hormone since our skin can synthesize it from sunshine. Like other hormones, this synthesized substance heads straight for the bloodstream where it can begin to circulate throughout the body.
Although vitamin D is primarily known for enhancing calcium and phosphorus uptake to support strong bones, the list of this amazing hormone’s benefits would stretch for miles if we tried to write them all down. But, just for fun, here are a few:
- Vitamin D can actually bind to hormone receptors, thereby influencing over 200 genes connected to disease expression. One team of Canadian researchers found 2,776 binding sites for the vitamin D receptor along the length of the genome
- In the small intestines, vitamin D turns on genes that encode proteins, and tell them to uptake calcium to support healthy bones and joints. Once enough calcium is absorbed, the production of vitamin D shuts off.
- Vitamin D is important for gut health because it helps maintain the integrity of the gut lining and soothes irritation.
- Vitamin D also plays a key role in maintaining a balanced immune response by helping regulate inflammation, limiting cytokine production, increasing antimicrobial peptides, and activating macrophages.
Fast Facts: Vitamin D3 is favored over D2 for supplementation because research has shown that D3 levels remain elevated for longer after entering the blood stream. While both will raise blood levels initially, D2 leaves the bloodstream much faster, leaving the body depleted.
Could Pollution Hurt Bone Health?
One of the earliest manifestations of vitamin D deficiency noted was the development of rickets, a defective mineralization or calcification of the bones that can lead to things like fractures and deformities. During the Industrial Revolution of the 1800s, cases of rickets skyrocketed. Eventually, scientists attributed the increase to pollution, which blocked out sunlight. As a result, city populations weren’t getting enough sun exposure and their bodies couldn’t synthesize adequate levels of vitamin D.
Vitamin D has a pretty interesting history, huh?
How Sun Synthesis Works
Consider this: If you stand outside in Corvallis, Oregon in mid August and have medium-toned skin, it’ll take you about eight minutes to synthesize 1000IU of vitamin D. If the same person steps outside in mid December, it’ll take at least 24 hours, yes, HOURS, to synthesize 1000IU. Several factors influence the amount of time it takes to synthesize vitamin D, one of the most salient being skin color. The darker the pigment of a person’s skin, the more melanin it contains, which acts as a natural sunscreen. Your latitude, as well as your age (the older you get the less cholesterol in your skin, which is a substrate of vitamin D), also affects vitamin D absorption.
Fast Facts: The body can actually store vitamin D for later use. For instance, if you’re out in the sun for several hours one day, but you don’t catch any rays for a few days after that, your body can tap into its stores to fuel vital biological processes.
Sun & Supplements Reign Supreme as Best Vitamin D Sources
The Linus Pauling Institute suggests that people over the age of 18 should aim for about 1,500-2,000IU of vitamin D3 per day. While that might be a decently easy feat during the summer, sunlight is much scarcerin the winter months as the days get shorter and the skies get cloudier.
Unfortunately, diet is not a very good source of vitamin D; Fruits and vegetables contain little to none of this essential hormone, and even the typical food sources, like salmon, cod liver oil, and mushrooms, are actually quite low in vitamin D. That’s why leading researchers suggest supplementing with vitamin D, especially during the winter.
Fast Facts: 1 billion people worldwide have insufficient vitamin D levels, while 70% of US children do not meet the daily required intake.