Vitamin D or the Sunshine Vitamin: How Much Sun Exposure Do I Need to Produce It?

Despite its name, "vitamin" D is, in fact, a hormone, and a potent one at that. Vitamin D is a pluripotent hormone with receptors found in almost every cell and tissue of the human body, regulating up to 200 genes.

The reason you may have heard of this as the "sunshine vitamin" is because it primarily synthesizes from cholesterol when the skin is exposed to sunlight.

Vitamin D, mainly produced by the skin and activated in the kidneys, helps control the concentration of calcium in the blood and is crucial for strong bone development.

Activated vitamin D increases the amount of calcium the intestines can absorb from ingested food into the bloodstream and prevents the loss of calcium in the kidneys. It also modifies the activity of bone cells, playing a key role in the formation of new bone in both children and adults.

Therefore, its deficiency is linked to:

1. Osteomalacia (adults): Higher doses of vitamin D can help prevent osteoporosis, falls, and fractures in older adults.
2. Rickets (children): Vitamin D deficiency in children is characterized by delayed growth and soft, weak, and deformed long bones that bend and arch under their weight when they start walking.

Additionally, vitamin D deficiency has been associated with various health benefits, indicating a wide range of potential functions. However, studies reporting on vitamin D benefits still need cautious interpretation, as the benefits are not fully proven.

For instance, it plays a significant role in the prevention of different diseases such as:

1. Infection Prevention: Some studies link vitamin D deficiency to more severe respiratory infections, including COVID-19, due to its role in immune system function.
2. Cancer Prevention: Vitamin D may help prevent cancer. A study noted that 1,100 IU per day, along with calcium, significantly reduced the risk of cancer in a considerable percentage of patients.
3. Metabolic Diseases: It plays an indirect but important role in carbohydrate and lipid metabolism, as reflected in its association with type 2 diabetes, metabolic syndrome, insulin secretion, insulin resistance, polycystic ovary syndrome, and obesity.
4. Cardiovascular Risk: This includes dysfunction of endothelial cells, accelerating atherosclerosis, hypertension, or abnormal coagulation, ultimately leading to a higher risk of cardiovascular events.
5. Dementia: Vitamin D deficiency increases the risk of developing dementia.
6. Chronic Pain: Various studies suggest a relationship between vitamin D deficiency and chronic pain.

Certainly, vitamin D likely plays a role in many more biological processes that are still unknown. To date, scientific and epidemiological studies are needed to consolidate information from initial studies and establish all the postulated benefits of vitamin D.

You can obtain vitamin D from:

1. Sun Exposure
2. Foods containing vitamin D
3. Supplements

Except for fatty fish livers, very few foods naturally contain vitamin D, and the primary source of vitamin D comes from skin exposure to sunlight through ultraviolet type B (UVB) rays. The liver and kidneys convert vitamin D (produced in the skin and absorbed in the diet) into the active hormone called calcitriol or 1,25(OH)2D. This is the active, steroid-hormonal form of vitamin D.

Calcitriol interacts with the vitamin D receptor, found in almost every cell in the body. When the active form of vitamin D binds to this receptor, it activates or deactivates genes, causing changes in cells. This explains why vitamin D has so many functions in our bodies.

Vitamin D3 is photochemically produced from 7-dehydrocholesterol in the skin through sunlight exposure, specifically UVB radiation. The amount of UVB synthesized follows a daily cycle, with peak intensity at noon and a significant decrease at the beginning and end of the day.

Additionally, this type of solar radiation also contributes the most to skin cancer development, making it crucial to know how much time we should expose ourselves to it.

It's essential to note that light exposure through windows is insufficient because glass almost completely blocks UVB light.

Lastly, it's important to know that tanning beds (UVA rays) play no role in vitamin D production, as it's the UVB rays that synthesize this vitamin.

The required dose of UVB reaching the body surface area (BSA) to maintain an optimal vitamin D state is not definitively known. However, available scientific evidence suggests that synthesis occurs with low doses of UVB rays.