Vitamin D is an important nutrient. It regulates the amount of calcium and phosphorus and affects several systems within your body. While other vitamins have to be introduced into the body, your skin can synthesize vitamin D from cholesterol when exposed to sunlight. Hence the name Sunshine vitamin.

Even though this seems like an easy way to keep your vitamin levels up, catching sunlight while in a car or by a window at work isn’t as beneficial as you might think. This is because of glass blocks out ultraviolet B rays that are essential for the synthesis of vitamin D.


Vitamin D is a fat-soluble vitamin that exists in various forms including D1, D2, D3. However, vitamin D3 (cholecalciferol) and vitamin D2 (ergocalciferol) are the most important for humans.

Unlike the name suggests, vitamin D is a hormone and is responsible for proper bone structure, cellular growth, and improved immunity.

Deficiency of Vitamin D

Even though your body can synthesize vitamin D; deficiency is more prevalent than you may think.

Vitamin D deficiency occurs when intake is significantly lower than the recommended levels. This can be caused by:

  1.  Limited exposure to the sun
  2. Insufficient absorption of vitamin D from the digestive tract.

It’s estimated that about 1 billion people worldwide have low levels of the vitamin in their blood

According to a 2011 study, 41.6% of adults in the US are deficient. The most affected groups being Hispanics and African-Americans populations at 69.2% and 82.1% respectively.


The most accurate way to measure how much vitamin D is in your body is the 25-hydroxy vitamin D blood test.

Results often vary depending on your age and sex. There may be slight differences from lab to lab depending on the type of testing method used.

Results can be categorized as follows:

  • Deficiency: less than 30 nmol/L (12 ng/mL)
  • Potential deficiency: between 30 nmol/L (12 ng/mL) and 50 nmol/L (20 ng/mL)
  • Normal levels: between 50 nmol/L (20 ng/mL) and 125 nmol/L (50 ng/mL)
  • High levels: higher than 125 nmol/L (50 ng/mL)


There are numerous reasons why people develop vitamin D deficiency. They include:

1. Age

As you age your skin is unable to synthesize vitamin D effectively which is responsible for the absorption and regulation of calcium. Calcium is important for proper bone strength.

Most elderly people develop osteoporosis because they spend more time indoors and have limited intake of vitamin D.

2. Being overweight or obese

Obesity does not impede the skin’s ability to synthesize vitamin D. However, a large amount of subcutaneous fat can slow down the transfer of the vitamin into the system.

Additionally, obese or overweight individuals who have had gastric bypass surgery may require vitamin D supplements in the future to prevent deficiency. This is because part of the small intestine (duodenum), which is responsible for the absorption of vitamin D has been bypassed. So, the absorption of vitamin D from fat stores into the system may not be compensated overtime.

Source: UCLA Health.

3. Inadequate diet

People who follow a strict vegan diet are at risk of experiencing a deficiency. This is because vitamin D is mostly found in animal-based products such as fish, fish oil, eggs, and dairy. To get the right amount of vitamin D intake you need to include these foods in your diet. However, if you’re experiencing any difficulties you could use supplements instead.

4. Dark skin

Darker skin generally has more melanin pigmentation. Dark skin has a great ability to block out ultraviolet rays. Sadly, this reduces the skin’s ability to synthesize vitamin D.

5. Staying indoors

People who spend a lot of time at home or have jobs that limit sun exposure don’t get adequate amounts of vitamin D.

6. Living far from the equator 

Areas far from the Equator have very little sun all year round. This is likely to affect how much vitamin D people living in this location get overtime. People who live near the equator and spend a lot of time outdoors are less likely to be deficient.


The daily recommended dosage of vitamin D is reliant on your age. Vitamin D intake is measured in micrograms (mcg) or international units (IU). The National Institute of Health recommends the following dosage.

  • Infants 0–12 months: 400 IU (10 mcg).
  • Children 1–18 years: 600 IU (15 mcg).
  • Adults up to 70 years: 600 IU (15 mcg).
  • Adults over 70 years: 800 IU (20 mcg).
  • Pregnant or lactating women: 600 IU (15 mcg).

The Recommended Dietary Allowance for adults between the age of 19 years to 10 years is 600 IU. However, if you are past 70 years of age you need 800 IU daily.

The maximum daily intake that your body can handle without the unnecessary side effects is 4,000 IU for both adults and children over the age of 9 years. This limit is known as the Tolerable Upper Intake Level.

Exposure to the sun for 5–10 minutes, 2–3 times per week, allows your skin to synthesize sufficient amounts of vitamin D. However, risk factors such as your age, weight, or skin color also determine whether or not you need to get more exposure or additional supplements.


As mentioned earlier vitamin D deficiency can be subtle. It’s easy for you to miss any signs of the deficiency even when they take a significant toll on your day-to-day life. Below is a list of signs and symptoms that show vitamin D deficiency.

1. Chronic back pain

According to the American Association of Neurological Surgeons between 75% to 85% of Americans experience back pain at some point in their lives. Vitamin D is responsible for the absorption and maintenance of calcium levels in the body. Calcium is important for proper bone health your bones hold 99% of the total calcium in your body.

Studies have shown a correlation between low levels of vitamin D and chronic lower back pain. Taking supplements is likely to relieve the condition and improve musculoskeletal strength.

Vitamin D deficiency is associated with back pain amongst premenopausal women. Studies have shown that deficiency can be associated with lumbar disc degeneration in the lumbosacral region resulting in back pain.

2. Bones loss (Osteoporosis)

As earlier mentioned, vitamin D plays a crucial role in the absorption and regulation of calcium. Calcium is important for proper bone health. Most people diagnosed with bone loss assume that they need more calcium. Your calcium intake may be good, but without the proper levels of vitamin D calcium will not be absorbed as required.

When your bones lose minerals such as calcium you develop low mineral density. This puts you at risk of getting fractures.

The National Osteoporosis Foundation recommends the below daily calcium and vitamin D intake depending on your age and sex.

Daily calcium intake.

Daily vitamin D Intake

According to the National Institute of health 53 million Americans are at risk of developing osteoporosis. Even though there are many reasons behind the development of osteoporosis, adequate vitamin D intake is a good strategy for protecting bone mass and reducing fracture risk.

3. Rickets and Osteomalacia

Children with vitamin D deficiency are at risk of developing rickets. Signs of rickets may include:

  • Slow bone growth
  • Bowed or curved legs
  • Dental cavities and irregularities
  • Wide joints in the elbows and wrists
  • Muscle weakness
  • Soft bones that break easily or cause deformities
  • bone pain or tenderness
  • Large forehead or abdomen
  • Unusually shaped ribs and breastbone

This condition can affect any child who doesn’t get enough levels of vitamin D. However, it is more prevalent in:

  • Dark-skinned children,
  • Children born prematurely
  • Children taking medication that interferes with vitamin D

In its severe form rickets can cause cramps, heart problems, seizures, breathing difficulties, and lifelong disability.

In adults, this condition is known as Osteomalacia, which is the softening of Bone. This condition results in poor bone density and muscular weakness.

Both these conditions can be treated by increasing exposure to the sun, making proper dietary adjustments, or taking vitamin D supplements.

4. Depression

Vitamin D plays a role in brain function. Therefore, low levels of the nutrient could result in depression or mental illness. Studies have shown that low levels of vitamin D increase the chances of depression among older people.

Vitamin D receptors can be found in the brain; specifically, parts that are involved in the physiology of depression. These include the prefrontal cortex, hippocampus, hypothalamus, thalamus, and Substantia nigra.

According to Psychology Today, The active form of vitamin D known as calcitriol activates an enzyme known as tyrosine hydroxylase. This enzyme is responsible for the synthesis of dopamine, epinephrine, and norepinephrine. Disturbance of both dopamine and norepinephrine play a major role in causing depression.

Seasonal affective disorder (SAD) has also been linked to low levels of vitamin D. Patients show symptoms of depression during the winter seasons when there is little sunlight making it harder for your body to synthesize adequate amounts of vitamin D. When levels of vitamin D in the brain change, they affect serotonin levels consequently affecting your mood. Serotonin is a neurotransmitter that regulates our moods, sleep, appetite, and more.

It’s a good idea to make foods rich in vitamin D or supplements to help regulate your mood during winter.

5. Poor health

Constantly getting the flu may be an indication that you are vitamin D deficient. This vitamin has been linked to healthier immune systems. It keeps the immune system strong and allows it to fight off viruses and bacteria.

A recent study run by the National Center for Biotechnology Information concluded that supplementing individuals who suffer from Autoimmune diseases with vitamin D has a positive effect on their immunity.

In the past, Vitamin D was used in the treatment of infections such as tuberculosis before the discovery of effective antibiotics. Back then tuberculosis treatment included prolonged exposure to the sun. This was thought to directly kill tuberculosis.

Cod liver oil, a rich source of vitamin D has also been used as a treatment for tuberculosis and increased protection from infections like colds, bronchitis, and pneumonia.

Recent studies conducted by the National Center for Biotechnology Information have also demonstrated that when administered vitamin D has led to a 42% decrease in cases of influenza infection.

6. Fatigue and tiredness

Fatigue can be described as a feeling of tiredness and lack of energy. It interferes with the quality of your social, family, and work life. It is estimated that 37 % of the USA workforce suffers from fatigue. Although it is twice as common in women as men it is not associated with age or occupation.

There are numerous causes of fatigue, sadly vitamin D deficiency is often overlooked during diagnosis. However, it plays a leading role when it comes to tiredness and exhaustion.

Fatigue can be associated with reduced efficiency of the mitochondria, better known as the powerhouse of the cell. By combining both glucose and oxygen the mitochondria can make an energy-rich molecule known as ATP. This molecule exists in a form that can be used easily by the cell. To make the ATP molecule the mitochondria uses phosphocreatine as a ready energy source. But like all energy sources, the phosphocreatine gets low. The ability to replenish this energy source after muscle contraction is a great way to measure mitochondrial efficiency. Vitamin D helps reduce recovery time hence increasing mitochondrial efficiency.

In a recent study about 72% of patients who reported feeling fatigue had a vitamin D deficiency. Once their vitamin levels were normalized their fatigue scores improved drastically.

7. Slow wound healing 

If wounds take longer than usual to heal, it might be a sign of low vitamin D levels. Vitamin D promotes the creation of cathelicidin. This is an antimicrobial peptide that helps your immune system fight off infections.

Once your skin is hurt you will require large amounts of vitamin D to promote healing. Test tube studies have shown that it increases the formation of compounds that aid in the formation of new tissue. If you exhibit a slow rate of healing after surgery or injury you may need to pump up your vitamin D levels.

In recent years Vitamin D has been shown to help in cases of vascular diseases by promoting angiogenesis (the formation of new blood vessels) and inhibiting inflammation.

It has also been found to influence healing among diabetic patients. Diabetic patients with foot infections and severe vitamin D deficiency are more likely to suffer from inflammation. This can jeopardize healing.

8. Muscle and joint pain

Vitamin D is essential for proper bone and muscle function. Its anti-inflammatory properties provide relief to muscle and joint aches.

research paper from 2012 points out that low levels of vitamin D deficiency could be a risk factor for inflammatory diseases such as Rheumatoid arthritis or increase its severity. Rheumatoid arthritis is a chronic inflammatory condition that affects the joints

Individuals with Rheumatoid arthritis are at higher risk of getting osteoporotic fractures and experience greater joint pain.

Clinical therapy is often ineffective when it comes to chronic muscle pain. Some types of muscle-skeletal pain such as fibromyalgia are not associated with vitamin D deficiency.

Some studies illustrate that vitamin D can relieve chronic muscle pain. The studies remain controversial given the limitations of human clinical studies. However, Symptoms similar to those of humans during early vitamin D deficiency such as muscle sensitivity have been replicated in rodents.

More studies are being conducted in a bid to link vitamin D deficiency with muscle pain. But it’s always a good idea to make sure that you have the recommended levels. After all, better safe than sorry.

9. Heart disease

According to John Hopkins Medicine, Vitamin D deficiency puts you at risk of developing peripheral arterial disease, strokes, and congestive heart failure. You can also develop cardiovascular diseases such as high blood pressure and diabetes among others.

As mentioned earlier, vitamin D has anti-inflammatory properties that regulate immune and inflammatory cells that often cause cardiovascular disease. In addition to this, the vitamin keeps your arteries flexible and relaxed, controlling blood pressure.

There are conflicting reports on the efficiency of vitamin D in the prevention of heart disease. While low vitamin levels are a risk factor when it comes to heart disease, it is not clear if vitamin D can help prevent heart attacks, stroke, or cardiovascular disease. Or if it can work on people who already have a problem. We only hope that the growing body of knowledge helps bring clarity sooner rather than later.

10. Cavities

Dental health problems aren’t often categorized as serious yet they affect our daily lives. Dental caries and gum pathology are often associated with chronic health problems such as dementia, Alzheimer’s, and heart disease. It is possible that the mercury filling used in fillings is a contributing factor.

Some clinical trials have suggested that high levels of vitamin D can help prevent decay and cavities. Vitamin D calcium and phosphorus are all required for the formation of healthy teeth and gums.

Introducing Vitamin D in children is especially beneficial, it has been seen to:

  • Improved tooth development
  • Improve the formation of dentin
  • Provide topical protection like fluoride
  • Change the components of saliva that enhance enamel strength

Studies have also shown that increasing vitamin D intake during pregnancy can give children a fighting chance against tooth caries in the future. However, studies suggest that using a vitamin D supplement is no longer effective past the age of 13, especially for girls. This has been attributed to an increase in subcutaneous fat. Seeing as the vitamin is fat-soluble its effectiveness is adversely affected.


It’s often rare for vitamin D to build up to toxic levels but when it does its effects can be severe. You can develop toxic levels if you take high dosage supplements over time. This is why it’s so important to constantly monitor your vitamin D levels.

You should note that toxic levels only occur as a result of taking supplements and not through exposure to sunlight or taking vitamin D rich foods.

Effects include:

1. Hypercalcemia

Vitamin D promotes the absorption of calcium from the intestine. Due to this relationship, an increase in Vitamin D can lead to too much calcium.

Hypercalcemia refers to excess calcium in the blood. This often occurs when you have more than 10,4000 ng/mL of calcium in your blood. It can lead to the release of calcium from the bones to the bloodstream.

Source: VitaminDWiki

Too much calcium in the blood can lead to:

  • Diarrhea and constipation
  • Loss of appetite
  • Joint and muscle pain
  • High blood pressure
  • Headaches
  • nausea and vomiting
  • Muscle weakness
  • Exhaustion
  • Metallic taste in the mouth

2. Kidney damage

This often occurs when an individual has taken over 3,600,000 IU within 3 months. When calcium is in excess within your bloodstream it can bind with phosphorus to form crystals. When deposited within organs, these crystals can cause organ damage.

The kidney is vulnerable to these calcium deposits since it acts as a filter. These deposits can cause nephrocalcinosis which results in kidney damage or even kidney failure.

Symptoms of nephrocalcinosis include:

  • Nausea and vomiting
  • severe pain in the stomach, back, groin area, or testicles.
  • Fever and chills

3. Irregular heartbeat and heart attack

As earlier mentioned, large amounts of calcium and phosphate can combine to form crystal deposits. These deposits can cause plaques in the valves or arteries of the heart thereby interfering with its functioning. This results in irregular heartbeats.

Heart complications related to vitamin D toxicity include:

  • High blood pressure
  • Irregular heartbeat,
  • Exhaustion
  • Pain when exercising
  • Chest pain


Vitamin D is essential for your bodies. Taking regular tests to determine your vitamin levels can help you prevent serious long-term consequences.

Even though your body actively synthesizes vitamin D ensure that your diet includes foods that are high in vitamin content. If not, take regular supplements.

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