Vitamin D Deficiency: Signs, Causes, and Treatment

Known as the “sunshine vitamin,” vitamin D is a fat-soluble vitamin that is involved in many essential body processes and functions.

This vitamin is produced in the body with the help of ultraviolet rays from sunlight. Vitamin D affects your health in many ways, including boosting the immune system, reducing inflammation, promoting cell growth, and supporting neuromuscular functions.

Vitamin D is primarily known for supporting calcium metabolism. It plays a crucial role in the absorption of calcium from food and supplements, which allows the body to maintain healthy bones cells.

It also plays a key role in the prevention and treatment of health issues, such as type 1 and type 2 diabetes, hypertension, glucose intolerance, and multiple sclerosis and other autoimmune diseases.

There are two major forms of vitamin D, namely, vitamin D₂ or ergocalciferol, and vitamin D₃ or cholecalciferol.

The D₂ form of the vitamin is obtained when we eat fortified foods, plant foods, and supplements. The D₃ form is found in dietary sources and is also internally manufactured by the body when the skin is exposed to ultraviolet B (UVB) rays of the sun.

Vitamin D synthesis in the body is a complex process. It begins when the skin is exposed to sunlight and absorbs the invisible UVB part of the light spectrum. The vitamin D is processed by the liver and then the kidneys and converted into a form that the body can use.

Vitamin D₃ is a “prohormone” as it helps to increase the levels of other “feel-good” hormones in the brain, particularly the neurochemicals called dopamine and serotonin.

Besides fortified foods and supplements, animal foods such as fatty fish, cod liver oil, eggs, and liver are abundantly supplied with this vital nutrient. These foods can help increase your body’s level of vitamin D, in the absence of adequate sun exposure.

When you do not get enough sunlight or if you do not eat foods rich in vitamin D, you are at a higher risk of suffering from vitamin D deficiency. Additionally, your body may be unable to absorb or metabolize the vitamin D obtained from food, leaving you at risk of vitamin deficiency.

What Causes Vitamin D Deficiency?

The following are some of the most common contributing factors to developing a vitamin D deficiency:

Lack of Sun Exposure

Your body synthesizes its own vitamin D from cholesterol, but it requires the skin to be exposed to sunlight for the process to successfully take place.

Thus, people who do not spend enough time in the sun are likely to have low vitamin D levels in the body. If you happen to reside in the northern latitudes where the sun is usually at a low angle for most of the year and the days are shorter, you will have very little access to direct sunlight.

Similarly, if you spend little to no time outside or are employed at a job that requires you to stay indoors, insufficient exposure to the sun’s UVB rays will reduce your body’s ability to manufacture vitamin D.

Living in Highly Polluted Areas

Even if the sun shines brightly on your part of the world and you venture out often, the carbon particulates present in an excessively polluted environment tend to absorb or scatter some of the sun’s rays and prevent the sunlight from reaching you in all its intensity.

Excessive Sun Protection

If you are in the habit of using copious amounts of sunscreen that block out the ultraviolet radiation from the sun completely or wear sun-protective clothing whenever you step out, your skin will lack the necessary means to generate vitamin D on its own.

Melanin

The color of your skin depends on the pigment substance called melanin, which competes with another skin component that is responsible for stimulating vitamin D production. Both these substances require UVB rays to perform their respective functions.

Dark-skinned individuals who have higher melanin generally need more UVB exposure than light-skinned people to produce the same amount of vitamin D.

Ambient Skin Temperature

If your skin is warm, such as during hot, sunny summers, it will absorb the UVB rays of the sun more readily than cool or cold skin.

Kidney or Liver Diseases

The health of your kidneys and liver has a direct bearing on vitamin D metabolism and absorption in the body. People with impaired kidneys or liver generally have a hard time converting vitamin D into its bioactive form.

Digestive Issues

The vitamin D consumed as part of your diet or through supplementation is partially absorbed by the small intestine.

Digestive factors such as the gastric, pancreatic, and bile secretions as well as the integrity of the intestinal wall influence the absorption of vitamin D.

Certain disorders that affect your gut health and digestion such as celiac disease, Crohn’s disease, chronic pancreatitis, and cystic fibrosis can cause inadequate absorption of vitamin D.

Lack of Vitamin D Intake Through Your Diet

Even though the body is more than capable of producing its own vitamin D in response to the skin being exposed to sunlight, the nutrient can also be supplemented through your diet.

People with a vitamin D deficiency are generally recommended to eat more of foods that are naturally rich in vitamin D such as eggs, beef liver, oysters, shrimp, and fish like salmon, tuna, mackerel, and cod, as well as foods that are fortified with the vitamin.

Increasing Age

Your ability to produce vitamin D efficiently may decrease with advancing age. The skin of older people has lower levels of the substance that UVB light converts into vitamin D.

Additionally, your kidneys become less efficient at converting vitamin D into its active form, calcitriol, as you become older.

Obesity

People with a body mass index greater than 30 have been found to have low bioavailability of vitamin D in the body.

Fat cells tend to extract the vitamin D from the blood, interfering with its release into the circulation. As a result, people who have excessive fat and are overweight release less vitamin D into the circulation, paving the way for a vitamin D deficiency.

How Much Vitamin D Do I Need?

Health organizations worldwide do not have a consensus with regard to the optimum daily intake of vitamin D. An individual’s daily vitamin D requirement depends upon a number of factors, such as:

• Age
• Skin tone
• Climate
• Weather-related sun exposure
• Diet
• Weight
• Ethnicity
• Activity level
• Metabolic health

Therefore, it is always advisable to consult your doctor about appropriate vitamin D intake goals for your particular case.

As per The Institute of Medicine (IOM), the normal blood levels of vitamin D stand at 20 nanograms per milliliter (or 50 nanomoles per liter). The organization goes on to recommend 600 to 800 IUs (international units) of vitamin D per day for those with negligible exposure to the sun.^[1]

The age-wise recommended dietary intake of vitamin D in international units (IU) is as follows:

• Infants below the age of one: 400 IU
• Children between the ages of 1 and 13 years: 600 IU
• Adolescents between the ages of 14 and 18 years: 600 IU
• Adults between 19 and 70 years of age: 600 IU
• Adults who are 71 years of age or older: 800 IU
• Pregnant and breastfeeding women: 600 IU

It is generally safe for infants below the age of 9 to take as much as 1,000 IUs per day, while the tolerable upper limit for people aged 9 years or older is set at 4,000 IUs per day. Do not take more than 4000 IUs without checking with your healthcare provider about how much you need.^[2]

How are Vitamin D Levels Measured?

The standard test for measuring your body’s vitamin D levels is the 25-hydroxy vitamin D blood test. The normal range for healthy individuals is 20 nanograms/milliliter (ng/ml) to 50 ng/ml. If your level is found to be below 12 ng/mL, that would suggest that your body has a vitamin D deficiency.^[2]

How to Tell if Your Body is Running Low on Vitamin D

If you are deficient in vitamin D, your body may not be able to function properly and you may experience the following signs and symptoms.

1. Impaired Immunity

The most important sign of low vitamin D is weak or impaired immunity, causing you to more easily pick up illnesses.

Vitamin D supports the proper functioning of the T cells that build immunity to help your body fight foreign, invading organisms.

A 2011 study published in the Journal of Investigative Medicine highlights that vitamin D helps modulate the innate and adaptive immune responses and its deficiency is associated with increased autoimmunity and increased susceptibility to infections.^[3]

2. Bone Pain

Vitamin D is important for bone, cartilage, and muscle function. An inadequate amount of vitamin D in the body can cause general muscle pain, muscle cramps, and chronic joint pain.^[4][5]

When vitamin D is low, calcium does not reach your skeletal system, contributing to bone pains.

In fact, its deficiency is also associated with diseases such as multiple sclerosis, rheumatoid arthritis, osteoarthritis, chronic fatigue syndrome, and fibromyalgia. All these health issues have a common symptom – joint pain.

3. Tiredness and Fatigue

Your body needs vitamin D for energy. If you are constantly tired without any apparent reason, it may be wise to get your vitamin D level checked.

A low vitamin D level leads to fat accumulation. This, in turn, lowers your metabolic rate and makes you less energetic.

A 2014 study published in the North American Journal of Medical Sciences suggests that by correcting your low vitamin D, you can significantly reduce the severity of fatigue symptoms.^[6]

4. Mood Swings

A deficiency of the sunshine vitamin can also lead to sudden mood swings. Vitamin D aids in the production of serotonin, the brain hormone associated with mood elevation and happiness. Increased serotonin can also help lessen the impact of stress and prevent or treat mild depression.^[7]

A deficiency of vitamin D may also relate to other affective disorders, such as seasonal affective disorder (SAD), premenstrual syndrome, and fibromyalgia.

Studies have found that some people suffer from mild depression during the winter months, known as SAD, mainly due to lack of sun exposure.^[8]

5. Psoriasis

Vitamin D deficiency can also contribute to psoriasis, an autoimmune skin disorder.

According to the National Psoriasis Foundation, appropriate sun exposure helps slow down the rate of growth and shedding of skin cells.^[9]

A 2013 study published in Dermato-Endocrinology suggests that autoimmunity has been associated with vitamin D deficiency and resistance.^[10]

This pilot study also concluded that high-dose vitamin D₃ therapy might be effective and safe for patients with vitiligo and psoriasis.

If you are diagnosed with psoriasis, get your vitamin D levels checked and ask your doctor about taking a daily dose of fermented cod liver oil.

6. Digestive Problems

When you suffer from a gastrointestinal condition, your body may not be able to absorb this fat-soluble vitamin. This can lead to a low vitamin D level in the body.

These gastrointestinal conditions may include Crohn’s, celiac, and non-celiac gluten sensitivity, and inflammatory bowel disease.

Vitamin D receptors are present on the cells in the digestive tract and immune system, where vitamin D can bind to these receptors and help your body function properly.

A 2011 study published in Therapeutic Advances in Gastroenterology showed a link between low vitamin D and gastrointestinal diseases as well as inflammatory bowel disease and colorectal cancer.^[11]

7. Excessive Sweating

A low level of vitamin D in the body also causes excessive sweating, especially on the head. Also, excessive sweating in newborn babies due to neuromuscular irritability is an early symptom of vitamin D deficiency.^[12]

Excessive sweating on the head can be a key symptom of rickets, a form of vitamin D₃ deficiency that affects bone development in children.^[13]

Vitamin D regulates the concentration of minerals and your body’s fluid balance, which helps regulate your body temperature.

8. High Blood Pressure

If you have high blood pressure, also known as hypertension, it may indicate a low vitamin D level in your body. Vitamin D suppresses the enzymatic process that can constrict the arteries and lead to high blood pressure.

In addition, vitamin D helps improve blood circulation throughout the body, which is essential for your heart to function properly. This helps reduce the risk of heart attacks, heart failure, strokes, and other problems.

A 2013 study published in Hypertension suggests that 3 months of oral vitamin D₃ supplementation on an unselected population of African-Americans showed a significant reduction in systolic pressure. However, more research is required in this field.^[14]

9. Overweight or Obesity

If you are obese, there is a high chance of developing vitamin D deficiency.

A 2013 study led by the Institute of Child Health at University College London suggests that obesity leads to vitamin D deficiency.^[15]

Researchers found that a 10% rise in body mass index (BMI) causes a 4% drop in concentrations of vitamin D in the body.

In addition, high muscle mass and low body fat also lead to vitamin D deficiency.

What are the Treatment Options for Vitamin D Deficiency?

If you are diagnosed with low levels of vitamin D, the standard treatment to overcome the deficit usually involves the following three strategies:

• Take a vitamin D supplement: Your doctor may prescribe you a supplement or multivitamin to make up for the lack of vitamin D in your body. Although there are over-the-counter options available, it’s best to confer with your doctor before starting any such supplement. The doctor will determine the appropriate dosage for your individual case, taking into account all the necessary factors.
• Get this vitamin from dietary sources: Increase your consumption of foods that are naturally rich in vitamin D such as cod liver oil, tuna, salmon, and mackerel. Other dietary sources that contain relatively lower amounts of vitamin D but can benefit your health nevertheless include beef liver, cheese, and egg yolks. Lastly, dairy products and certain cereals come fortified with vitamin D and can help meet your daily recommended intake of this nutrient.
• Go out in the sun more often: Soaking in the early morning sun for 10 to 15 minutes without sunscreen helps boost your vitamin D levels naturally. While people with a vitamin D deficiency are generally advised to increase their daily exposure to natural sunlight, there can be certain risk factors worth considering. If you happen to have generally sensitive skin, are prone to sunburn, have a history of skin cancer, or have a pale complexion, excessive sun exposure might end up doing more harm than good in your particular case. To avoid any unforeseen complications or adverse side effects, you must consult with your healthcare provider about the adequacy of this treatment tactic for your case.

Resources:

1. IOM Updates Guidance on Vitamin D, Calcium. AAFP Home. https://www.aafp.org/news/health-of-the-public/20101201iomrpt-vitdcal.html. Published December 1, 2010.
2. Ferrari HB-, Willett W. Comment on the IOM Vitamin D and Calcium Recommendations. The Nutrition Source. https://www.hsph.harvard.edu/nutritionsource/2010/12/25/comment-on-the-iom-vitamin-d-and-calcium-recommendations/. Published January 8, 2019.
3. Aranow C. 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/. Published August 2011.
4. Yilmaz R, Ozkayit S. Vitamin D Deficiency and Chronic Widespread Pain. European Medical Journal. https://www.emjreviews.com/rheumatology/article/vitamin-d-deficiency-and-chronic-widespread-pain/. Published January 2, 2018.
5. Elbossaty WF. Mineralization of Bones in Osteoporosis and Osteomalacia. Annals of Clinical and Laboratory Research. http://www.aclr.com.es/clinical-research/mineralization-of-bones-in-osteoporosis-and-osteomalacia.php?aid=21384. Published November 27, 2017.
6. Roy S, Sherman A, Monari-Sparks MJ, Schweiker O, Hunter K. Correction of Low Vitamin D Improves Fatigue: Effect of Correction of Low Vitamin D in Fatigue Study (EViDiF Study). North American journal of medical sciences. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4158648/. Published August 2014.
7. Bertone-Johnson ER, Hankinson SE, Bendich A. Calcium and Vitamin D Intake and Risk of Incident Premenstrual Syndrome. Archives of Internal Medicine. https://jamanetwork.com/journals/jamainternalmedicine/fullarticle/486599. Published June 13, 2005.
8. Nepps P. Vitamin D and Mood Disorders. Journal of Lancaster General Health. http://www.jlgh.org/Past-Issues/Volume-1—Issue-3/Vitamin-D-And-Mood-Disorders.aspx. Published 2006.
9. National Psoriasis Foundation. https://www.psoriasis.org/about-psoriasis/treatments/phototherapy.
10. Finamor DC, Sinigaglia-Coimbra R, Neves LCM, et al. A pilot study assessing the effect of prolonged administration of high daily doses of vitamin D on the clinical course of vitiligo and psoriasis. Dermato-endocrinology. https://www.ncbi.nlm.nih.gov/pubmed/24494059. Published January 1, 2013.
11. Raman M, Milestone AN, Walters JRF, Hart AL, Ghosh S. Vitamin D, and gastrointestinal diseases: inflammatory bowel disease and colorectal cancer. Therapeutic advances in gastroenterology. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3036961/. Published January 2011.
12. Sahay M, Sahay R. Rickets-vitamin D deficiency and dependency. Indian Journal of Endocrinology and Metabolism. http://www.ijem.in/article.asp?issn=2230-8210;year=2012;volume=16;issue=2;spage=164;epage=176;aulast=Sahay. Published 2012.
13. Soliman AT, Dabbagh ME-, Adel A. Clinical Responses to a Mega-dose of Vitamin D3 in Infants and Toddlers With Vitamin D Deficiency Rickets. Journal of Tropical Pediatrics. https://academic.oup.com/tropej/article/56/1/19/1659276. Published June 7, 2009.
14. Forman JP, Scott JB, Ng K, et al. Effect of vitamin D supplementation on blood pressure in blacks. Hypertension. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3775458/. Published April 2013.
15. Obesity leads to vitamin D deficiency. UCL News. https://www.ucl.ac.uk/news/2013/feb/obesity-leads-vitamin-d-deficiency. Published November 15, 2018.