Everything You Need to Know About Vitamin D

In an era where indoor lifestyles and office-centric work environments have become the norm, a silent health concern looms large: vitamin D deficiency. Vitamin D is crucial for bone health, immune function, and overall well-being. 

However, modern lifestyles that keep us indoors don't lend themselves to getting enough sun for sufficient vitamin D production. As a result, experts estimate that nearly 50 percent of Americans aren't getting enough vitamin D.

Despite its significance, questions remain: How much is enough? Can supplements effectively address a deficiency? Is there a benefit to taking more than the recommended amount?

The answers to these questions remain a topic of research and debate among researchers and doctors.

Vitamin D, also known as calciferol, is a fat-soluble vitamin essential for various body functions. Colloquially known as the "sunshine vitamin," our bodies make vitamin D when our skin is exposed to sunlight — a built-in production system that hints at just how essential vitamin D is for our health

​​Vitamin D regulates calcium and phosphorus levels in the blood. These two essential minerals then go on to build strong bones and carry out myriad other bodily functions.

Even with adequate vitamin D, we only absorb between 30 and 40 percent of the calcium from food; without enough vitamin D, that number drops to only 10 or 15 percent.

Vitamin D is fat-soluble, meaning it's absorbed with dietary fats and stored in fat tissue and the liver, ready for release when our body signals the need.

Over a century ago, researchers uncovered the role of vitamin D in bone health; the initial breakthrough found that vitamin D could cure rickets — a debilitating bone disease in children.

This discovery led to the fortification of staple foods like milk and orange juice that we see in grocery stores today.

Vitamin D deficiency can have similar effects on adults by causing a condition called osteomalacia, where bones do not mineralize properly, making them more susceptible to breaks and fractures.

Read More: Are You Getting Enough Phosphorus for Healthy Bones and Teeth?

While our bodies can produce it through sun exposure, there are several other sources to ensure adequate intake, especially in situations where sun exposure is limited. Here's a look at the best sources:

Certain foods are natural sources of vitamin D, including fatty fish like salmon and mackerel, fish liver oils, and small amounts in beef liver, cheese, and egg yolks.

Sun exposure is a primary natural source of vitamin D. When your skin is exposed to sunlight, it produces vitamin D naturally.

Fruits generally contain minimal vitamin D, but fortified orange juice can be a source.

Like fruits, most vegetables are not significant sources of vitamin D, but fortified products like certain plant-based milks can provide it.

Vitamin D supplements are available for those who have limited sun exposure or dietary intake of Vitamin D.

Read More: What Foods Have Vitamin D?

The range for vitamin D levels, as measured in the blood, is typically expressed in nanograms per milliliter (ng/mL) or nanomoles per liter (nmol/L). The optimal range for vitamin D is considered between 25 and 80 ng/mL. 

Ranges can vary slightly depending on the laboratory and the method used for testing, but generally, the accepted ranges are as follows:

• Severe Deficiency: Less than 10ng/mL. This range could be associated with osteomalacia or rickets.

• Mild Deficiency: Between 10 and 24 ng/mL. This level may be associated with secondary hyperparathyroidism and/or osteoporosis.

• Optimal: Between 25 and 80 ng/mL. 

• Possibly Toxic: Greater than 80 ng/mL. 

Read More: Here’s Why You May Want To Take Vitamin D and Magnesium Together

While many individuals with low vitamin D might not display clear symptoms, there are subtle signs that can indicate a potential shortfall. These can include:

• Pain in bones

• Joint discomfort (Arthralgias)

• Muscle aches (Myalgias)

• Tiredness

• Twitching of muscles (fasciculations)

• Lack of strength

Read More: 15 Signs of Vitamin D Deficiency

Various physical and lifestyle elements can hinder the body's production and absorption of vitamin D. Several factors can limit sun exposure, reducing the amount of sunlight your skin receives. These factors can be environmental, personal or related to health and age:

• Being homebound

• Residing in polluted areas

• Working night shifts

• Having a darker skin complexion

• Aging

Vitamin D deficiency may lead to weakened immune function and increased susceptibility to infections. Experts have sought to decode the link between vitamin D and immune health in recent years.

Now, a growing body of research hints at a potential relationship between long-term vitamin D deficiencies and the onset of autoimmune conditions like diabetes and rheumatoid arthritis. Yet, more research is needed to confirm these links. 

Read More: What Do Scientists Know About Vitamin D and Cancer?

Taking vitamin D supplements, when directed by a healthcare professional, may be a good option for addressing deficiency or insufficiency to avoid serious health problems. There are two main types of vitamin D: vitamin D2 and vitamin D3.

Vitamin D2 (Ergocalciferol) is derived from plant sources and is often used in prescription supplements. It can also be found in fortified foods. While vitamin D2 can raise blood levels of vitamin D, it is generally considered less effective at maintaining adequate levels compared to vitamin D3.

Vitamin D3 (Cholecalciferol) is naturally synthesized in the skin when exposed to sunlight. It is also available as a supplement and is typically more effective at raising and maintaining blood levels of vitamin D. Vitamin D3 supplements are widely available over-the-counter and are often preferred.

Both vitamin D2 and vitamin D3 can be used to correct deficiencies when prescribed by a healthcare provider. However, vitamin D3 is generally preferred for supplementation due to its greater efficacy in maintaining adequate vitamin D levels. Be sure to consult with your healthcare provider to find out which vitamin D supplement to use. 

Read More: Should You Take a Vitamin D Supplement?

While rare, consuming excessive amounts of vitamin D can pose health risks. Excessive vitamin D intake from supplements can lead to calcium buildup in the blood.

This condition can trigger a range of unpleasant symptoms, including nausea, vomiting, weakness and frequent urination. Experts note that reaching hazardous levels is generally difficult despite these potential side effects. Symptoms of vitamin D toxicity are most likely to occur with a daily intake of at least 10,000 IU (250 mcg), according to the Institute of Medicine. Your body naturally regulates vitamin D, eliminating excess amounts to maintain balance.

The Food and Drug Administration (FDA) recommends a daily allowance of 400 International Units (IU) of vitamin D. But some studies suggest that adults may need at least 800 IU to protect against bone fractures. However, these are general guidelines. The amount of vitamin D an individual needs can vary based on several factors, including age, skin color, geographic location, and overall health. 

The importance of the sunshine vitamin is undeniable, impacting our bones and maybe even our immune systems. Ensuring you get enough, whether through sun exposure, diet or supplements, is essential while still being cautious of not overdoing it.

Read More: What Is the Correct Dosage of Vitamin D for Adults?

Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:

• Nutrition Research. Prevalence and Correlates of Vitamin D Deficiency in US Adults. 

• Harvard School of Public Health. Vitamin D.

• Current Rheumatology Reports. Calcium and Vitamin D: Skeletal and Extraskeletal Health. 

• BoneKEy reports. Rickets before the discovery of vitamin D.

• National Institutes of Health: Office of Dietary Supplements. Vitamin D Fact Sheet for Consumers.

• Mayo Clinic. Vitamin D Deficiency in Adults: When to Test and How to Treat

• National Library of Medicine. Vitamin D Deficiency

• Cureus. Benefits and Risks of Sun Exposure to Maintain Adequate Vitamin D Levels

• Geriatric Orthopaedic Surgery & Rehabilitation. Is Supplementation of Vitamin D Beneficial for Fracture Healing? A Short Review of the Literature

• National Institutes of Health. Vitamin D: Fact Sheet for Consumers

• International Journal of Molecular Sciences. An Update on the Effects of Vitamin D on the Immune System and Autoimmune Diseases

• Biochem J. Vitamin D deficiency and diabetes

• Qatar Medical Journal. Effectiveness of Vitamin D2 Compared With Vitamin D3 

• Healthline. Vitamin D2 vs. D3: What’s the Difference?

• Mayo Clinic. What Is Vitamin D Toxicity? Should I Be Worried About Taking Supplements?

• Frontiers in Endocrinology. Vitamin D Toxicity-A Clinical Perspective