Vitamin D

Vitamin D
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A human body produces vitamin D in response to sun exposure. A person can also increase their vitamin D intake through certain foods or supplements.

Vitamin D is essential for a variety of reasons, including maintaining healthy bones and teeth. It can also protect against a range of diseases and conditions, such as type 1 diabetes.

Despite its name, vitamin D is not a vitamin but a prohormone or precursor to a hormone.

Vitamins are foods that the body cannot create and therefore one must consume it in the diet. However, the body can produce vitamin D.

In this article, we look at the benefits of vitamin D, what happens to the body when people do not get enough, and how to increase vitamin D intake.


Vitamin D has multiple roles in the body. It helps with:

  • Promoting healthy bones and teeth
  • Supporting immune, brain and nervous system health
  • Regulating insulin levels and supporting diabetes management
  • Supporting lung function and cardiovascular health
  • Affect the expression of genes involved in cancer development

Read on to learn more about these roles:

Healthy bones

Vitamin D plays an important role in regulating calcium in the blood and maintaining phosphorus levels. These factors are vital for maintaining healthy bones.

People need vitamin D to allow the intestines to stimulate and absorb calcium and to restore calcium that the kidneys would otherwise secrete.

Vitamin D deficiency in children can cause rickets, which causes a severe distorted appearance due to the softening of the bones.

Similarly, in adults, vitamin D deficiency manifests itself as osteomalacia or bone softening. Osteomalacia causes poor bone density and muscle weakness.

Vitamin D deficiency can also occur as osteoporosis, in which more than 53 million people in the United States either seek treatment or face an increased risk.

Reduced flu risk

A 2018 review suggested that current research found vitamin D in some studies to have a protective effect against the flu virus.

However, the authors also looked at other studies where vitamin D did not have this effect on flu and flu risk.

Therefore, more research needs to be done to confirm the protective effect of vitamin D on the flu.

Healthy babies

Vitamin D deficiency is linked to high blood pressure in children. A 2018 study found a possible link between low vitamin D levels and stiffness in children’s artery walls.

The American Academy of Allergy Asthma and Immunology (AAAAI) suggests that the evidence points to a link between low vitamin D exposure and an increased risk of allergic sensitivity.

One example is children who live closer to the equator and have lower rates of allergy hospitalization and also less prescription for epinephrine autoinjectors. They’re also less likely to have a peanut allergy.

AAAAI also highlights a study of egg intake in Australia. Eggs are a common source of early vitamin D. Children who started eating eggs after 6 months were more likely to develop a food allergy than children aged 4-6 months.

Also, vitamin D may increase the anti-inflammatory effects of glucocorticoids. This benefit makes it potentially useful as a supportive therapy for people with steroid resistant asthma.

Healthy pregnancy

A 2019 review suggests that pregnant women with vitamin D deficiency may have a higher risk of developing preeclampsia and giving birth prematurely.

Doctors also associate poor vitamin D status with gestational diabetes and bacterial vaginosis in pregnant women.

It is also important to note that in a 2013 study, researchers linked high vitamin D levels during pregnancy to an increased risk of food allergies in the child in the first 2 years of life.

Although the body can create vitamin D, deficiency can occur for many reasons.

Skin type: Darker skin and sunscreen, for example, reduce the body’s ability to absorb ultraviolet radiation B (UVB) rays from the sun. Absorption of sunlight is essential for the skin to produce vitamin D.

Sunscreen: A sunscreen with a sun protection factor (SPF) of 30 can reduce the body’s ability to synthesize the vitamin by 95% or more. Covering the skin with clothing can also inhibit vitamin D production.

Geographical location: People living in northern latitudes or areas of high pollution, working night shifts, or connected to home should aim to consume vitamin D from food sources whenever possible.

Breastfeeding: Babies who are exclusively breastfed need a vitamin D supplement, especially if they have dark skin or have minimal sun exposure. The American Academy of Pediatrics recommends that all breastfed babies receive 400 international units (IU) of oral vitamin D per day.

Although people can take vitamin D supplements, it is best to get any vitamin or mineral from natural sources whenever possible.

The symptoms of deficiency

Symptoms of vitamin D deficiency can include:

  • Regular illness or infection
  • Tiredness
  • Bone and back pain
  • Low mood
  • Impaired wound healing
  • Hair loss
  • Muscle pain

If vitamin D deficiency continues for a long time, it can cause complications such as:

  • Cardiovascular conditions
  • Autoimmune problems
  • Neurological diseases
  • Infections
  • Pregnancy complications
  • Some cancers, especially breast, prostate and colon.

Vitamin D sources

Getting enough sunlight is the best way to help the body produce enough vitamin D. Abundant food sources for vitamin D include:

  • Fatty fish such as salmon, mackerel, and tuna
  • Egg yolk
  • Cheese
  • Beef liver
  • Mushrooms
  • Fortified milk
  • Fortified cereals and juice
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