Vitamin D Deficiency

Despite being called a vitamin, vitamin D actually acts as a hormone within the body. Vitamin D impacts full body health and almost every cell in the human body has a vitamin D receptor.[1] It is estimated that about 3% of the human genome is regulated by the vitamin D endocrine system and over 1000 genes in the human body are impacted. 

Natural sources of vitamin D

There are very few food sources of vitamin D.  Natural food sources of vitamin D include oily fish, red meat, liver, and egg yolks. Sometimes foods such as cereal, milk, and juice are fortified with vitamin D in order to increase intake from food sources. However, these foods contain very low amounts of vitamin D and are not sufficient for maintaining health and preventing deficiency on their own. 

Vitamin D production naturally occurs in the body when ultraviolet B (UVB) light hits the skin and converts a specialized cholesterol to pre-vitamin D3. Pre-vitamin D3 is converted to vitamin D3 in the skin and transferred to the blood stream over the course of several days. After arriving in the liver, vitamin D requires two metabolic conversions to become calcitriol, the active form of vitamin D. Finally, calcitriol binds to vitamin D receptors in almost every cell throughout the body. This process is regulated by the body and bioavailability is managed by several internal control mechanisms that boost efficiencies when vitamin D levels are low and reduce them when levels are high to prevent toxicity. 

Signs and symptoms of vitamin D deficiency

Having low levels of vitamin D can cause a variety of symptoms. Vitamin D is most well-known for the role it plays in bone health. Vitamin D is crucial for supporting strong, healthy bones by allowing the body to absorb calcium. Having a deficiency in vitamin D can cause joint and bone pain, bone loss, weakening of the bones, and numbness. Vitamin D deficiency can also cause muscle pain and weakness. In addition to supporting bone health, vitamin D’s role in calcium absorption and inflammation helps maintain healthy teeth and gums. Vitamin D deficiency has been shown to increase risk of tooth decay and gum disease. 

Fatigue and getting sick often can also be consequences of vitamin D deficiency. Many studies have shown that vitamin D impacts the immune system. A systematic review of 25 randomized controlled trials concluded that vitamin D supplementation significantly reduced the risk of acute respiratory tract infection.[2] Click here to read more about how vitamin D may impact COVID-19.

Low levels of vitamin D can also impact the body in more subtle ways. Weight gain has been linked to vitamin D deficiency, as well as headaches in some cases. For some people, vitamin D deficiency can cause skin conditions such as red, dry, itchy skin. Vitamin D deficiency can cause rashes, acne, and slow healing of wounds in the skin. Supplementation and treatment with vitamin D have been shown to improve skin conditions such as eczema and psoriasis.

Vitamin D deficiency can also impact mood and mental health. Several published reviews indicate that vitamin D plays a role in the pathogenesis of mental health disorders and particularly mood disorders. Click here to read more about the impact of vitamin D on mental health.  

If you think you may have low levels of vitamin D, ask your doctor to perform a blood test to check for vitamin D deficiency.

Is low vitamin D common?

Having low levels of vitamin D is incredibly common, and many people don’t even recognize they have a vitamin D deficiency. It is estimated that approximately 70% of the global population has insufficient or deficient levels of vitamin D.[3,4]

There are a variety reasons why vitamin D deficiency is so common. Since vitamin D is not found in many food sources, our main source of vitamin D is the sun. The problem however is our current modern lifestyle does not allow us to get enough sun exposure to stay healthy. As we have developed into a largely indoor society, we venture less frequently into the sun. We now spend the majority of our days working and playing indoors. When we do get outside, we cover ourselves with protective clothing or sunscreen in an effort to prevent skin cancer and premature skin aging. Additionally, in order to get vitamin D from the sun, we must expose our skin to direct sunlight when atmospheric and geographic conditions are absolutely perfect. Many factors limit our ability to make vitamin D from sunlight, including latitude, season, time of day, cloud cover, altitude, and pollution.  

Vitamin D deficiency versus insufficiency

Among the medical community, vitamin D deficiency is usually defined as a serum 25-hydroxyvitamin D level of less than 20 ng/mL (50 nmol/L), and insufficiency is defined as a serum 25-hydroxyvitamin D level of 20 to 30 ng/mL (50 to 75 nmol/L). Above 30 ng/mL is usually considered sufficient.[5] 

Is vitamin D deficiency dangerous?

A large body of scientific research suggests that vitamin D deficiency can effect risk and outcome of a wide variety of health conditions. Research has linked vitamin D deficiency to increased risk of many diseases including osteoporosis, cancer, heart disease, diabetes, MS, psoriasis, asthma, rheumatoid arthritis, depression, hypertension, and COVID-19.  

Can vitamin D deficiency cause hair loss?

Vitamin D deficiency can cause hair loss in some cases. Research has shown that vitamin D plays a role in stimulating new and old hair follicles. When you don’t have enough vitamin D, it can cause hair growth to be stunted. Vitamin D has also been linked to the autoimmune condition, Alopecia areata, which causes hair to fall out in clumps.[6]

Can vitamin D deficiency cause anemia?

Anemia is a condition where your blood doesn’t have enough healthy red blood cells to carry adequate oxygen around the body. Some studies have found an association between vitamin D deficiency and risk of anemia. It is proposed that vitamin D’s role in managing inflammation and antimicrobial peptides allows it to impact anemia. By down regulating pro-inflammatory cytokines, vitamin D may be able to increase iron availability and production of red blood cells.[7] 

Does vitamin D deficiency cause insomnia?

Vitamin D deficiency has been correlated to fatigue, sleeping less and poor sleep quality. A 2018 meta-analysis concluded that vitamin D deficiency is associated with a higher risk of sleep disorders.[8] Vitamin D also plays a role in regulating inflammation. Low levels of vitamin D can increase inflammation in the airways, which can increase chances of sleep apnea and disturbed sleep. 

Does vitamin D deficiency cause dizziness?

Vitamin D deficiency on its own usually does not cause dizziness but, increasing vitamin D level has been shown to help with some medical conditions that cause dizziness. Vertigo is a condition that is characterized by dizzy spells, feeling off balanced or like you are spinning, and nausea. Having a vitamin D deficiency may increase risk of vertigo and studies have shown that increasing vitamin D level can decrease recurrence of symptoms. [9]

Is vitamin D deficiency hereditary?

If a woman has a vitamin D deficiency during pregnancy, her baby can be born with a low vitamin D level. Furthermore, if a breastfeeding mother has a vitamin D deficiency, her child will not receive enough vitamin D through breastmilk alone. Research suggests that vitamin D status of a mother during pregnancy can impact a variety of health outcomes for her child in the future. Children who have low vitamin D levels during infancy and early childhood are at increased risk of rickets, a condition where the bones become soft. For these reasons it’s especially important that an expecting mother keep her vitamin D level sufficient during and after pregnancy.[10]

Vitamin D is also believed to play a role in supporting healthy pregnancies. Studies have shown that women with sufficient levels of vitamin D are more likely to become pregnant. Additionally, it’s been shown that having a vitamin D deficiency increases risk of miscarriage.[11]

Some studies have found that vitamin D deficiency may have a genetic component. One such study found 4 different genes variants that could impact an individual’s risk of being vitamin D deficient.[12]

Is low vitamin D a sign of cancer?

Scientific research suggests a correlation between insufficient vitamin D and increased risk of cancer. Studies have shown that many cancer patients have a vitamin D deficiency or insufficiency. Increasing vitamin D levels has been shown to decrease incidence of multiple forms of cancer and improve survival rates.[13] More clinical trials are needed to determine if vitamin D supplementation can play a role in the prevention and treatment of cancer. 

Is vitamin D deficiency curable?

Vitamin D deficiency is curable and there are multiple treatment methods to remedy vitamin D deficiency from home. Certain sources of vitamin D may be better for treating vitamin D deficiency than others.

There are multiple different forms of oral treatment medication for vitamin D deficiency. Vitamin D oral supplements can be found at most drug stores in pill, liquid, or spray form and come as either vitamin D2 (ergocalciferol) or vitamin D3 (cholecalciferol). Vitamin D3 is usually found in animal sources and is what is formed in your skin upon exposure to UVB light. Vitamin D2 is usually found in plant sources and fortified foods. Most doctors recommend taking vitamin D3 as it is more effective at raising blood levels of vitamin D and improving vitamin D status.[14] 

Treatment guidelines for low vitamin D vary greatly between different medical authorities. The Institute of Medicine’s (IOM) recommended dietary allowance is 600 International Units (IU) per day. Many vitamin D researchers disagree with this recommendation and say that the IOM’s recommended allowance isn’t enough to prevent deficiency or support bone health. Generally, 4,000 IU or less per day is considered safe, as long as your blood values are being monitored.

It is important to avoid excessive doses of oral vitamin D. If vitamin D intake is too high, it can cause elevated blood calcium levels and potentially dangerous consequences. Taking too high a dose of oral supplements to treat vitamin D deficiency can result in diarrhea, constipation, and stomach pain. If you have or digestive distress, excessive thirst, or frequent urination when treating vitamin D deficiency with oral supplements, you should contact your doctor as these may be signs of elevated calcium levels and vitamin D toxicity.  

Obtaining vitamin D from light may be the best way to treat vitamin D deficiency. Unlike with oral supplements, you cannot overdose on vitamin D3 produced by your skin. If you have enough vitamin D, your body will simply produce less. Using light for making vitamin D allows your body to self-regulate vitamin D production and make as much as it needs to stay healthy, without any risk of overdose or toxicity.

Another downside of oral vitamin D supplements is that they are actually not effective for a surprisingly large number of people. Millions of people have a fat malabsorption condition (cystic fibrosis, Crohn’s disease, celiac, liver disease, etc.) that prevents them from absorbing fat soluble vitamin D supplements, yet their bodies can successfully produce significant amounts of vitamin D from UVB light.

During the summer months you can make vitamin D from the sun by going outdoors and exposing your skin to the sun between 10am-4pm. In northern climates, getting vitamin D from the sun in the winter is not possible. Between November and March, the angle of the sun prevents the majority of ultraviolet B (UVB) light from getting through the atmosphere, and therefore from reaching our skin to stimulate vitamin D production.