What are the symptoms of a vitamin D deficiency?

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Vitamin D is important for health. Some of its roles in the body include:

• helping with the absorption of calcium
• maintaining healthy bones
• regulating genes and cell growth
• preventing rickets and osteoporosis
• modulating the immune system

Vitamin D is naturally present in very few foods, and often in amounts too low to help a person meet their daily recommended intake. In response, manufacturers fortify several foods with the vitamin.

According to a 2020 review, 50% of the worldwide population has insufficient levels of vitamin D. In the United States, 35% of adults have the deficiency.

The prevalence of vitamin D deficiency is highest among older adults, people with obesity, and people in hospitals and other care facilities.

Many people with vitamin D deficiency have no symptoms. However, the deficiency can cause the following issues.

Frequent infections or illnesses

Vitamin D helps support the immune system — it plays a role in regulating immune function and inhibiting inflammatory reactions.

It can also help prevent infections in the upper respiratory tract.

Fatigue and muscle weakness

Because vitamin D is key to bone health, an insufficient amount can cause bone and muscle weakness, which can lead to fatigue.

Researchers behind a 2014 study that included 174 participants with fatigue found that taking supplementary vitamin D for 5 weeks significantly improved fatigue symptoms.

Bone and joint pain

Vitamin D can increase bone mass and prevent bone loss. If someone has bone and joint pain, it may indicate a vitamin D deficiency.

Joint pain could also result from issues such as rheumatoid arthritis. A 2012 study linked vitamin D deficiency with an increased risk of developing the condition.

Fractures

Adequate vitamin D in the body helps maintain bone strength by supporting the absorption of calcium.

According to the National Osteoporosis Foundation, this is particularly important for females after menopause, which can cause bone density to decrease and the risk of osteoporosis to increase.

If someone has a fracture, the doctor might test their vitamin D level, depending on the person’s age and health history.

Depression

The authors of a 2019 review have found that lower levels of vitamin D may increase the risk of depression.

There are vitamin D receptors in the brain, and the research indicates that the vitamin has a protective anti-inflammatory effect.

As a result, the scientists conclude, a person with very low vitamin D levels and depression may benefit from taking a supplement of the vitamin.

Slow wound healing

If wounds take longer than usual to heal, it might be a sign of low vitamin D levels.

Results of an in vitro study suggest that vitamin D plays an important role in wound healing because it regulates growth factors and other compounds that form new tissue.

Another study has found that people with leg ulcers were more likely to have vitamin D deficiencies. Those who took 50,000 international units (IU) of vitamin D every week for 2 months experienced better wound healing, the researchers observed.

The deficiency can develop at an early age. In response, U.S. health authorities mandate that infant formula is fortified with 40–100 IU/100 kilocalories of vitamin D.

Symptoms of a vitamin D deficiency in children include:

• irritability
• lethargy
• bone pain or fractures
• deformities of the teeth
• developmental delays

A vitamin D deficiency can lead to further health issues.

Rickets

Rickets develops from a vitamin D deficiency, and it is rare in the U.S.

The condition tends to occur in babies and preschool-age children, though it can arise in older kids. It affects the development of the bones, wrists, knees, and joints in the ribs, and it can cause bowing of the legs.

Doctors treat rickets with vitamin D supplements and by ensuring that there is enough calcium in the diet.

Cardiovascular disease

According to 2013 research, there is a connection between vitamin D levels and the risk of cardiovascular disease. This may be because vitamin D protects the heart and combats inflammation.

An older review found that low vitamin D levels are linked to other conditions that increase the risk of developing cardiovascular disease — conditions such as hypertension and metabolic syndrome.

Autoimmune disease

Vitamin D is a natural immune modulator, and research suggests that low levels of the vitamin may be connected to autoimmune diseases, including:

• type 1 diabetes
• multiple sclerosis
• rheumatoid arthritis
• Crohn’s disease

The National Institute for Health and Care Management have the following guidelines for doctors about managing vitamin D deficiencies:

• Recommend treatment if a person’s vitamin D level is under 25 nanomoles per liter (nmol/l).
• Recommend treatment if the level is 25–50 nmol/l, and there are other indications of the deficiency.
• If the level is adequate (above 50 nmol/l), give advice about how to prevent the deficiency.

Adults with vitamin D deficiency require 6,000 IU of vitamin D-3 every day for 8 weeks or 50,000 IU weekly for 8 weeks.

When a blood test shows that the person’s level of vitamin D has adequately increased, the doctor may recommend a 2,000 IU daily maintenance dosage.

They may also suggest a calcium supplement and give other dietary and lifestyle advice.

Food sources

It can help to ensure that the diet includes plenty of vitamin D. Below are some foods that contain high levels of the vitamin:

Supplements

Supplements and fortified foods contain vitamins D-2 or D-3.

Manufacturers use fungi and yeasts to manufacture D-2, and this form is suitable for people on a vegan diet. They use lanolin from sheep wool to produce D-3.

Research indicates that at higher doses, vitamin D-2 is less potent than D-3.

Anyone experiencing symptoms of vitamin D deficiency should speak to a doctor.

Many people have no symptoms but can find out if they have adequate levels with a simple blood test.

Vitamin D deficiency is common, and people may not realize that they have it.

Anyone with symptoms of the deficiency should see a doctor. Also, it is important to consult a healthcare provider before taking supplements that would exceed the recommended daily intake.