Vitamin D: What’s the Right Level?

Decoding Vitamin D: Striving for Optimal Levels

Vitamin D is a crucial nutrient that is essential for humans to maintain strong bones and teeth. It plays an important role in our overall health and wellbeing. This vitamin is unique, as it can be synthesized by the body as well as obtained from dietary sources. Vitamin D is a fat-soluble vitamin that can be stored in the body. In this article, we will explore the definition and importance of Vitamin D, along with a brief history of its research.

Vitamin D is a group of fat-soluble vitamins that includes Vitamin D2 and Vitamin D3. The primary source of Vitamin D is sunlight. When the skin is exposed to sunlight, it can produce Vitamin D3. Vitamin D can also be obtained from dietary sources like fatty fish, egg yolks, and fortified foods like milk, orange juice, and cereals.

The importance of Vitamin D cannot be overstated. It assists in the absorption of calcium and phosphorus, which is required for building and maintaining strong bones and teeth. Vitamin D also plays a key role in the immune system, neuromuscular function, and reduction in inflammation. Studies have shown that adequate levels of Vitamin D can reduce the risk of several health conditions, including osteoporosis, cardiovascular disease, and cancer.

Vitamin D research has a rich history. In the early 1900s, scientists noticed that children who lived in cities with less exposure to sunlight were more prone to developing rickets, a disease that causes soft and weak bones. In the 1920s, researchers discovered that exposure to UV light could cure rickets. Vitamin D was later discovered, and it was found to be essential for preventing and treating rickets.

In subsequent years, researchers learned more about Vitamin D, and it became apparent that it was linked to many other health conditions. Today, Vitamin D deficiency is a common problem among people of all ages, leading to a wide range of health problems. In the following sections, we will delve deeper into the importance of maintaining optimal levels of this vital nutrient.

How the Body Gets Vitamin D

Sun Exposure

One of the primary ways the body gets Vitamin D is through sun exposure. When ultraviolet B (UVB) rays from the sun penetrate the skin, they activate a form of cholesterol called 7-dehydrocholesterol, which is found in the skin's lower layers. This process leads to the production of Vitamin D3, which is then metabolized by the liver and kidneys to create the active form of Vitamin D that the body can use. However, it's important to note that the amount of Vitamin D produced from sun exposure can vary widely depending on several factors such as the time of day, cloud cover, and geographic location. Moreover, excessive exposure to sun rays could damage the skin and lead to skin cancer.

UVB Rays

UVB rays are the most effective for activating 7-dehydrocholesterol, and they are present in sunlight during peak hours of the day (between 10 a.m. and 3 p.m.). However, UVB rays don't penetrate glass very well, so sun exposure while inside a car or building won't produce enough Vitamin D to meet the body's needs.

Skin Color

Skin color is also a significant factor in sun exposure's effectiveness how much Vitamin D skin produces in response to sunlight. Darker skin produces less Vitamin D than lighter skin, primarily because the higher melanin content in darker skin acts as a natural sunscreen, reducing the skin's ability to produce Vitamin D.


Vitamin D can also be obtained through diet by consuming foods that are rich in it such as fatty fish such as salmon, herring and mackerel. In addition, some cereals, dairy products (organic milk, cheese, yogurt) and orange juice are fortified with Vitamin D.

Food sources of Vitamin D

Vitamin D-rich foods include salmon, tuna, mackerel, egg yolks, and fortified foods like milk, orange juice, and cereals.


Diet alone can make it difficult to meet the daily requirements of Vitamin D, and in some cases, supplements are needed to get proper amounts. Vitamin D supplements come in two forms, D2 and D3. While D2 is found primarily in plants, D3 is derived from animal sources, including fish oil and sheep's wool. Vitamin D supplements are available without a prescription and are affordable for most people. Nevertheless, consult your doctor before taking supplements to make sure you don't exceed the recommended daily dose.

Overall, getting Vitamin D through sun exposure and a healthy diet can help maintain optimal levels of this essential nutrient. Additional supplementation may be required for certain conditions or to make up for a deficiency.

Recommended and Optimal Vitamin D Levels

Recommended Levels according to different organizations

For Vitamin D levels, different organizations have different recommended levels, and it varies depending on factors like age, health status, and geographic location.

The most widely recognized recommendations for Vitamin D levels are as follows:

  • The Institute of Medicine(AKA the National Academy of Medicine) recommends a Vitamin D level of 20 nanograms per milliliter(ng/mL) for healthy individuals, including infants, children, and adults up to 70 years old.
  • The Endocrine Society suggests higher levels of Vitamin D, at least 30 ng/mL for a “Optimal Bone Health” level for most individuals.

Optimal Levels for different groups

Optimal Vitamin D levels for different groups vary widely based on health status, age, and other factors. Here are some optimal levels for a few demographics:

  • Pregnant women: Optimal levels for pregnant women should be at least 30-60 ng/mL of Vitamin D to support healthy fetal development and prevent maternal osteoporosis.
  • Children: For children, the American Academy of Pediatrics suggests maintaining a Vitamin D level of 20-30 ng/mL to promote bone health and other health benefits.
  • Elderly: Older adults are more likely to have Vitamin D deficiency due to decreased sun exposure and skin thickness. Therefore, for people above age 70, the Endocrine Society suggests an optimal level of 30-50 ng/mL of Vitamin D to help reduce the risk of falls and fractures.

Overall, the recommended and optimal Vitamin D levels depend on several factors like age, health status, and geographic location. People should regularly monitor their Vitamin D levels and intake to ensure that they are staying within the recommended range. Consulting a doctor, before taking Vitamin D supplements is always recommended to ensure any underlying health conditions or adverse effects are taken into account.

Risks and Consequences of Vitamin D Deficiency

Vitamin D is essential for maintaining good health. Its deficiency increases the risk of various diseases and health issues. Below, we will explore some of the severe consequences of Vitamin D deficiency.

Symptoms of Vitamin D Deficiency

Some common symptoms of Vitamin D deficiency include:

  • Fatigue and general weakness
  • Muscle pain and weakness
  • Depression and anxiety
  • Bone fragility
  • Slow healing of wounds
  • Hair loss


Vitamin D helps the body to absorb calcium, which is essential for bone health. When someone suffers from Vitamin D deficiency, the body cannot absorb enough calcium, which may lead to decreased bone mineral density, which significantly increases the risk of fractures over time. In severe cases, Vitamin D deficiency can result in osteoporosis.

Cardiovascular Disease

Vitamin D deficiency can lead to cardiovascular disease due to its association with high blood pressure, heart failure, and heart attacks. Studies show that Vitamin D reduces inflammation and improves blood vessel function, which are essential in preventing cardiovascular disease.


Vitamin D deficiency has been linked to increased risk of some cancers, including breast, colon, and prostate cancer. One study showed that higher levels of Vitamin D intake lowered the risk of colon cancer by 32% among women.

Rheumatoid Arthritis

Vitamin D deficiency is a significant risk factor for rheumatoid arthritis development. Adequate Vitamin D levels have been shown to reduce inflammation and pain, leading to better quality of life for people living with rheumatoid arthritis.


In conclusion, Vitamin D is crucial for overall health and wellbeing. Vitamin D deficiency can lead to many severe and chronic health problems such as osteoporosis, cardiovascular disease, cancer, rheumatoid arthritis, and more. Maintaining optimal levels of Vitamin D is vital to prevent these health issues.

How to Increase Vitamin D Levels

Vitamin D is essential in maintaining good health, and maintaining optimal levels of Vitamin D is vital in preventing health problems associated with Vitamin D deficiency. Here are some ways to increase your Vitamin D levels:

Sunlight Exposure

Sunlight exposure is an efficient way to increase Vitamin D levels naturally. Spending just a few minutes in the sun every day can go a long way. Here are some tips to maximize your sunlight exposure:

  • Expose your skin to the sun between 10 a.m. and 2 p.m.
  • Exposing your face, arms, hands, or legs to the sun increases the absorption of Vitamin D.
  • The more skin you expose, the more Vitamin D is produced. However, avoid excessive sun exposure, as it can lead to sunburns and skin cancer.
  • Wearing minimal clothing, such as shorts and T-shirts, can help optimize Vitamin D production.


While sunlight exposure is the most efficient way to increase Vitamin D levels, it is not always practical or possible. Therefore, incorporating foods that are rich in Vitamin D is crucial. Some of the best food sources of Vitamin D include:

  • Fish – salmon, mackerel, and tuna
  • Egg yolks
  • Fortified foods – milk, orange juice, and cereal
  • Cheese

Ensure that you are consuming an adequate amount of Vitamin D from your diet. If you do not consume enough Vitamin D through your diet, consider taking supplements.


Supplements are a convenient way to increase Vitamin D levels. Consider taking supplements if your diet is low in Vitamin D or if you live in places with limited sunlight. Vitamin D supplements come in various forms, such as soft gels or tablets. Consult with your healthcare provider to determine if taking supplements is appropriate for you and to determine the appropriate dosage for your individual needs.


Increasing Vitamin D levels is necessary to maintain optimal health. Incorporating sunlight exposure, consuming foods rich in Vitamin D, and taking supplements are essential in increasing Vitamin D levels. By utilizing these methods, individuals can reap the benefits of optimal Vitamin D levels, which include improved bone health, reduced risk of chronic diseases, strong immune function, and an overall feeling of well-being.


Maintaining appropriate Vitamin D levels is essential for overall health and well-being. Vitamin D is responsible for the absorption of calcium that is necessary for the proper functioning of the body. Inadequate Vitamin D levels can lead to health problems, including osteoporosis, cardiovascular disease, and cancer, to mention a few.

It is essential to seek medical advice if deficiencies persist. A physician can assess individual risk factors and determine the appropriate measures to take to ensure healthy Vitamin D levels. Simple blood tests can help determine the current level of Vitamin D in the body.

A call to action is essential to increase awareness of Vitamin D deficiency. It is necessary to spread the word that Vitamin D deficiency is a prevalent health problem and that simple measures can be taken to resolve it. Some initiatives to spread awareness about Vitamin D deficiency include:

  • Screening campaigns in communities, schools, and other public places
  • Sponsoring research on associations between Vitamin D deficiency and chronic diseases
  • Providing educational resources on Vitamin D and its benefits
  • Partnering with health professionals organizations to incorporate Vitamin D testing in routine patient checkups.

Overall, maintaining healthy Vitamin D levels is essential, and each individual must take appropriate measures to ensure optimal levels. Seeking medical advice and taking action to spread awareness are two essential aspects of this process.

William H. McDaniel, MD

Dr. Robert H. Shmerling is the former clinical chief of the division of rheumatology at Beth Israel Deaconess Medical Center (BIDMC), and is a current member of the corresponding faculty in medicine at Harvard Medical School.

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