The Powerful Health Benefits of Vitamin D

Woman with her eyes closed and her arms stretched out to her sides smiling and basking in the sun.
  • Vitamin D is an essential nutrient found in foods like fortified milk and cereals, and fatty fish and eggs.

  • The body produces vitamin D on the skin when it is exposed to the sun’s ultraviolet B (UVB) light.

  • Although research into the benefits of vitamin D is somewhat limited, it's widely believed to have a significant impact on bone health, the immune system, and even depression.

Often referred to as the ‘sunshine vitamin’, vitamin D is an essential nutrient that the body needs to perform various functions.

Some of its most important roles in the body include supporting immune function, aiding calcium absorption, and fighting inflammation.

For many years, scientists have been researching the various health benefits of vitamin D and how it supports overall health and well-being.

Exploring the many benefits of vitamin D, and how it works can help you ensure your levels of this nutrient are adequate.

What is Vitamin D?

Unlike other nutrients, vitamin D is produced in the body when the skin is exposed to sunlight. Sunlight converts a chemical in the skin into an active form of the vitamin called calciferol.

Vitamin D can also be found naturally in some foods, including:

  • Fortified milk

  • Plant-based milk alternatives like soy, almond, and oat milk

  • Fortified cereals

  • Fatty fish like anchovies, herring, salmon, and sardines

  • Eggs

  • Beef liver

  • Orange juice

The body can also receive this essential nutrient through vitamin D supplementation, which involves taking dietary supplements that contain the nutrient.

Vitamin D is fat-soluble, meaning it is stored in the liver and other fatty tissues in the body. The vitamin is only secreted from these tissues when the body needs it.

A glass of milk, fatty fish, cheese, eggs and other foods that are rich in vitamin D on a counter.

What are adequate vitamin D levels?

According to the National Institutes of Health (NIH), the amount of vitamin D you need each day depends on your age and if you are pregnant or breastfeeding.

Below are the daily recommended amounts in international units (IU), which is the measurement of a quantity in substances such as vitamins or hormones.

Age Group

Amount of vitamin D in international units (IU)

Children up to the age of 12 months old

400 IU

Children between one and 13 years old

600 IU

Teens between 14 and 18 years old

600 IU

Adults 19 to 70 years old

600 IU

People over 71 years old

800 IU

Pregnant and breastfeeding women

600 IU

The only way to know if you have enough vitamin D in your body is through a blood test conducted by a health care provider. It is typically measured by nanograms per milliliter (ng/mL).

The NIH says levels of 20 ng/mL are adequate for most people for bone and overall health.

Levels below 12 ng/mL might result in weakened bones and affect your health. And levels above 50 ng/mL mean your vitamin D levels are too high and might cause health problems.

What is a Vitamin D Deficiency?

When you have a vitamin D deficiency, its levels in your body are too low. Poor bone health is the main problem associated with low vitamin D levels.

Key Point: Symptoms of a Vitamin D Deficiency

According to the NIH, the following health problems could be symptoms of a vitamin D deficiency:

  • Fatigue
  • Body aches and pains
  • Stress fractures in the bones
  • Depression
  • Hair loss
  • Muscle weakness
  • Loss of appetite
  • Falling ill regularly

Who should take vitamin D supplements?

People with an increased risk of a vitamin D deficiency may benefit from a supplement containing this nutrient.

Research suggests that many people do not get enough vitamin D from sunlight and food alone. In fact, women rarely get more than 200 IU per day, and men less than 160 IU per day. This may mean that a vitamin D supplement is necessary.

However, it is essential to consult a health care professional before taking supplemental vitamin D, as it is possible to take too much of it. This is called vitamin D toxicity.

Symptoms of vitamin D toxicity include:

  • Nausea and vomiting

  • Poor appetite

  • Weight loss

  • Constipation

  • Weakness

  • Confusion

  • Heart problems

  • Kidney stones or kidney damage

Key Point: How to Get Enough Vitamin D from Sunlight

It is recommended that people spend between 20 to 30 minutes in the sun each day.

Exposing your arms and legs to midday sun is most effective and can help you absorb more vitamin D.

What are the Main Benefits of Vitamin D?

Most of the current research available on the benefits of vitamin D is based on results found in animals or limited groups of people.

With these limitations in mind, scientists do have some knowledge about this vitamin's benefits.

Healthy bones and teeth

One of the most vital roles vitamin D plays in the human body is that it promotes calcium absorption in the gut.

Without enough calcium and phosphate, the body can’t grow or maintain strong, healthy bones and teeth.

Vitamin D can prevent bones from becoming brittle, which could lead to fractures and breaks. It also protects against diseases like osteoporosis in older adults.

Research suggests that inadequate calcium absorption could lead to joint pain and early-onset osteoarthritis.

One study found that vitamin D may help lower the risk of tooth decay, cavities, and gum disease because it helps the body absorb calcium.

Little boy smiling and showing off his muscles.

Improved brain function

Studies have shown that vitamin D may affect brain functioning. This is likely because there are vitamin D receptors throughout the brain and spinal cord.

Vitamin D may play a role in the synthesis of neurotransmitters in the brain and the growth and repair of nerves.

Also, vitamin D might help to protect the neurons in the brain by reducing inflammation, which may improve brain function.

Research indicates that a vitamin D deficiency may increase the risk of developing dementia in some people.

Another study found that vitamin D may help to clear amyloid plaque in the brain, which is known for its link with Alzheimer’s disease.

Strengthening the immune system

Another important role vitamin D plays in the body is maintaining and strengthening the immune system.

It does so by stimulating T-cell production, which can encourage an immune response to viruses and bacteria.

Research has also found that vitamin D deficiencies may lead to acute respiratory tract infections — such as tonsillitis and laryngitis.

Also, studies suggest that vitamin D helps prevent the development of certain autoimmune diseases by strengthening immune function.

Although more research is needed on this particular benefit, trials show autoimmune diseases that may be prevented by vitamin D include diabetes, asthma, and rheumatoid arthritis.

Cancer prevention

There is increasing evidence pointing to how vitamin D may help reduce the risk of developing cancer in some people.

One scientific review found that vitamin D may reduce colon, ovarian, prostate, and breast cancer risk.

This is potentially due to how vitamin D helps cells to repair and regenerate in the body. This may prevent or decrease the growth of cancerous tumors and stimulate dead cells that have been damaged due to cancer.

It might also decrease the formation of blood vessels in cancerous tumors.

An improved mood

Seasonal affective disorder (SAD) is a mental health condition characterized by depression that occurs at the same time each year, usually when there is less sunlight.

The NIH states that a person’s vitamin D status may play a role in developing SAD.

The body produces less vitamin D when there is less ultraviolet light, which may affect the levels of serotonin in the brain. Serotonin is a hormone in the body that regulates mood.

One study recently found that vitamin D supplementation may help reduce the depressive symptoms associated with SAD.

Woman standing on a balcony looking at the sun.

Aided weight loss

Although research into the weight loss benefits of vitamin D is limited, this nutrient may help people shed pounds.

Research has found that people who were overweight or obese, lost weight when they took a combination of vitamin D and calcium supplements.

However, it’s worth noting that participants also combined these supplements with a calorie-restricted diet.

Lowers blood pressure and reduces the risk of heart disease

One of the known markers of cardiovascular disease is high blood pressure, also known as hypertension. A study found that vitamin D deficiencies can cause high blood pressure and even organ damage as a result.

The researchers found that vitamin D supplementation may be an effective treatment for hypertension, which could reduce the risk of heart disease.

Other than high blood pressure, an increasing amount of research has found that vitamin D may help reduce:

  • Heart disease

  • Congestive heart failure

  • Stroke

  • Heart attack

  • Arterial disease

What are the Differences Between the Different D Vitamins?

Research suggests that each form of vitamin D has different effects on the body. The vitamin D family includes D2 and D3, known as ergocalciferol and cholecalciferol.

The key difference between the two molecules is that D3 is a fat-soluble vitamin that is naturally produced by the body through sunlight exposure.

On the other hand, D2 is mostly derived from plants and fortified foods.

Where Can I Learn More About Vitamin D Benefits?

If you suspect you have a vitamin D deficiency, it's important to consult with a medical professional. With LifeMD, an online board-certified physician can provide you with an accurate diagnosis and advice on taking vitamin D supplements. Book a telehealth appointment today.

Dr. Asunta Moduthagam

Dr. Moduthagam has been a family medicine physician since 2011. She loves working with patients to help them reach an optimal state of well-being. She’s dedicated to thoughtful, compassionate care and is committed to being her patients’ best advocate.

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This article is intended for informational purposes only and should not be considered medical advice. Consult a healthcare professional or call a doctor in the case of a medical emergency.

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