Vitamin D is both a nutrient we eat and a hormone produced by the body. It's a fat soluble vitamin that has long been known to help the body retain calcium and phosphorus, which is crucial for bone formation. Laboratory studies have also demonstrated that vitamin D plays a significant role in supporting a healthy immune function.
Vitamin D and Sunlight
Vitamin D is produced naturally in the skin by exposure to sunlight. During the winter months when sun exposure is limited, and people stay inside more due to the cold, many people can have insufficient levels of vitamin D. In addition, people with darker skin tend to have lower blood levels of vitamin D because the pigment melanin acts as a shade, reducing the production of vitamin D.
The daily amount of vitamin D required to maintain healthy bones and normal calcium metabolism is set out by the RDA (Recommended Dietary Allowance). The minimum vitamin D requirement might not be met by a lot of people for various reasons.
- RDA: The Recommended Dietary Allowance for adults 19 years and older is 600 IU (15 mcg) daily for men and women, and for adults >70 years it is 800 IU (20 mcg) daily.
- UL: The Tolerable Upper Intake Level is the maximum daily intake unlikely to cause harmful effects on health. The UL for vitamin D for adults and children ages 9+ is 4,000 IU (100 mcg). Studies have shown higher levels up to 10,000 IU (250 mcg) daily have no adverse effects. Consult your doctor for more information.
Vitamin D and Healthy Immune Function
In addition to its positive effects on calcium and strengthening bones, various studies have shown that vitamin D has an important impact on immune cells. Vitamin D is involved in immunity through several mechanisms and plays a role in regulating both the innate and adaptive immune response in the body.* The innate immune system is the body’s non-specific, first line of defense against foreign pathogens. Vitamin D impacts immune health by interacting with vitamin D receptors on innate immune cells throughout the body.*
Food Sources for Vitamin D
The majority of foods do not naturally contain vitamin D, but some have been fortified with it. For most of us, the best way to obtain sufficient vitamin D is through a supplement because it's difficult to eat enough on your own. Fat fish flesh and fish liver oils are the best sources. Egg yolks, cheeses and beef liver are also found to have small amounts. Some mushrooms contain vitamin D; in addition, due to the fact that they have intentionally been exposed to a high amount of UV light, certain commercially available mushrooms are also carrying higher levels of Vitamin D2. Vitamin D can be found in these sources:
- Cod liver oil
- Tuna fish
- Orange juice fortified with vitamin D
- Dairy and plant milks fortified with vitamin D
- Beef liver
- Egg yolk
- Fortified cereals
- vitamin D supplements
Differences Between Vitamin D Supplements
Vitamin D supplements are available in two forms: vitamin D2 and vitamin D3. Both are also naturally occurring forms that are produced in the presence of the sun’s ultraviolet-B (UVB) rays, hence its nickname, “the sunshine vitamin.” The human body produces vitamin D3 by itself and it is present in animal foods. A meta-analysis of randomized controlled trials found that D3 supplements tended to raise blood concentrations of the vitamin more and sustained those levels longer than D2.*
Benefits of Vitamin D3
Nature's Lab Vitamin D3 Plus is a great way to increase your daily intake of this important nutrient needed for healthy joints, calcium absorption and immune function.* Vitamin D3 is the most active form of vitamin D and helps support healthy calcium levels in the blood and bones and also supports immune health.* Vitamin D plays a role in activating the immune system's T-cells, which are responsible for identifying and defending the body against harmful organisms, to promote immune system health.*
Vitamin D. The Nutrition Source. (2023, March 7). https://www.hsph.harvard.edu/nutritionsource/vitamin-d/
Aranow, C. (2011, August). Vitamin D and the immune system. Journal of investigative medicine : the official publication of the American Federation for Clinical Research. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3166406/
The role of vitamin D in the immune system. SOLIUS® Medical Light Therapy. https://www.solius.com/vitamin-d-immune-system