Vitamin D deficiency affects almost 50% of the global population. It is a significant issue since a lack of this nutrient is associated with various medical conditions.
This article explains the symptoms and causes of vitamin D deficiency, plus how to prevent and treat it. Read on for our complete guide.
Symptoms of Vitamin D Deficiency
To understand how vitamin D deficiency affects the body, we need to summarize this nutrient’s functions.
Vitamin D plays a fundamental role in maintaining the body’s calcium and phosphate levels. These minerals are essential for healthy bones. Therefore, a lack of vitamin D can negatively impact the skeleton. It leads to thin, soft, weak, and misshapen bones, causing rickets in children and osteomalacia in adults.
The symptoms of these diseases include:
- Skeletal deformities
- Increased risk of fractures
- Dental problems
- Poor growth and development in children
However, vitamin D deficiency symptoms do not only involve the bones. Vitamin D receptors exist throughout many of the body’s tissues. The nutrient affects inflammation, the cell cycle, immune function, and glucose metabolism. Therefore, scientists have linked deficiencies with a wide range of conditions, including:
- Some forms of cancer
- Cardiovascular disease
- High blood pressure
- Multiple sclerosis
Unfortunately, though, there is currently not enough evidence that vitamin D supplementation can effectively treat these issues.
Clinical Signs of Vitamin D Deficiency
Doctors can also see the signs of low vitamin D on a blood test. They use a reading known as serum 25(OH)D to determine a patient’s vitamin D status.
The abbreviation 25(OH)D stands for 25-hydroxyvitamin D, also known as calcidiol. It is one of two forms of vitamin D that the body produces from food and sunlight. The other is 1,25(OH)2D (1,25-hydroxyvitamin D or calcitriol).
By looking at a patient’s 25(OH)D levels, doctors can identify deficiencies early.
The 25(OH)D form of vitamin D remains in the body for longer than 1,25(OH)2D. Therefore, it is a more reliable marker of deficiency. It is measured in nanomoles per liter (nmol/L) or nanograms per milliliter (ng/mL).
By looking at a patient’s 25(OH)D levels, doctors can identify deficiencies early and prescribe treatment before serious symptoms occur.
What Is a Normal Vitamin D Level?
The chart below explains how doctors typically classify vitamin D levels:
Vitamin D Level (nmol/L)
Vitamin D Level (ng/mL)
Vitamin D Status
Severe deficiency with risk of rickets or osteomalacia
Generally inadequate for bone health and general wellbeing
50 or above
20 or above
Generally adequate for bone health and general wellbeing
125 or above
50 or above
Risk of adverse effects, especially if over 150nmol/L (60ng/mL)
What Causes Vitamin D Deficiency?
Unlike many other nutrients, it is challenging to get enough vitamin D from our diets. Our bodies make most of this vitamin when we expose our skin to the sun. For this reason, some have nicknamed vitamin D “The Sunshine Vitamin.”
When the sun’s ultraviolet B (UVB) rays hit the skin, our cells convert cholesterol into vitamin D. However, this form of the nutrient is not bioactive. First, the liver and kidneys must process it to make it usable. The same is true of vitamin D from food sources. Therefore, people with liver or kidney disorders may have difficulty producing enough vitamin D.
Older people are also more likely to become deficient because the skin becomes less able to synthesize vitamin D with age. People with dark skin are also at higher risk than those with lighter skin. Darker-skinned individuals have more of the pigment melanin. It absorbs UVB rays and means more sunlight is necessary to make adequate vitamin D.
Other groups of individuals who may be at risk of deficiency include:
- Children who are solely breastfed for a long time
- People who spend lots of time indoors
- People who cover most of their skin with clothing
- Vegetarians and vegans
- People with conditions that reduce fat absorption (vitamin D is fat-soluble)
- People who are obese or have undergone bariatric surgery
Certain medications can also affect vitamin D metabolism, including cholesterol drugs, anti-seizure drugs, AIDS/HIV treatments, and more. However, a lack of sunlight and an inadequate diet remain the most common causes of vitamin D deficiency.
Vitamin D Deficiency Treatment
Individuals can improve their vitamin D levels in several ways:
Getting sufficient UVB exposure is crucial. However, it is vital to balance this against the risks of excessive sun exposure. For most individuals, 5–30 minutes of sun exposure daily or twice weekly is enough. However, the precise amount will depend upon various factors, including skin type, location, and time of year.
It is essential to go outside to synthesize vitamin D, as windows can block UVB rays. The best time to do this is between 10 am and 4 pm, although it is essential to be cautious and avoid sunburn.
Vitamin D Food Sources
It is also possible to top up vitamin D with certain foods. The best dietary sources are oily fish (salmon, mackerel, sardines, etc.) and fish liver oils. There are smaller amounts of vitamin D in the following foods:
- Beef liver
- Egg yolks
- Fortified milk, cereals, yogurt, or margarine
Mushrooms are one of the best vegetarian vitamin D sources. Like humans, they can make vitamin D using sunlight. However, most store-bought varieties grow in the dark. Therefore, they contain relatively low levels of vitamin D. The good news is that placing them in a sunny spot for 15–120 minutes before cooking can significantly increase their vitamin D levels.
Vitamin D Supplements
People who are unable to get enough vitamin D naturally can take a daily supplement. They are available in two forms, D2 (ergocalciferol) and D3 (cholecalciferol). These compounds have a slight difference in their chemical structure, but the body can absorb both of them well.
Many people will benefit from supplementation, but it is possible to consume too much vitamin D.
Many people will benefit from supplementation, but it is possible to consume too much vitamin D. Side effects include:
- Poor appetite
- Muscle weakness
- Neurological or psychiatric symptoms
- Excessive urination
- Thirst and dehydration
- Kidney stones
In extreme cases, vitamin D toxicity could cause kidney failure, irregular heartbeat, and even death.
Therefore, it is essential to monitor one’s intake, especially if using multiple supplements. For example, someone taking a fish oil supplement in addition to a multivitamin might be getting too much vitamin D.
The recommended daily intakes for vitamin D are listed below:
Recommended Daily Vitamin D Intake
71 years and older
Bottom Line on Vitamin D Deficiency
Lack of vitamin D can cause numerous health problems. The most common are bone disorders, such as rickets and osteomalacia. However, vitamin D deficiency has been linked with a range of other physical and psychological conditions.
The most common causes of deficiency are a lack of sunlight and an inadequate diet. Supplementation is an effective treatment, although individuals should not consume more than 800IU of vitamin D daily.
Anyone who suspects they may be vitamin D deficient should seek advice from their physician. They will be able to run the appropriate tests and recommend the most effective treatment.