Vitamin D

Medically reviewed by Debra Sullivan, Ph.D., MSN, R.N., CNE, COI — Written by Megan Ware, RDN, L.D. On November 7, 2019

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A human body produces vi-ta-min D as a response to sun exposure. A person can also boost their vi-ta-min D intake through certain foods or supplements.

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

Despite its name, vi-ta-min D is not a vitamin, but a prohormone, or precursor of a hormone.

Vitamins are nutrients that the body toàn thân cannot create, and so a person must consume them in the diet. However, the body can produce vitamin D.

In this article, we look at the benefits of vitamin D, what happens lớn the body when people vày not get enough, and how to boost vi-ta-min D intake.


Share on PinterestDuring sun exposure, a person’s body produces vitamin D.
Vitamin D has multiple roles in the body. It assists in:

promoting healthy bones và teethsupporting immune, brain, & nervous system healthsupporting lung function và cardiovascular health

Read on to find out about these roles in more detail:

1. Healthy bones

Vitamin D plays a significant role in the regulation of calcium & maintenance of phosphorus levels in the blood. These factors are vital for maintaining healthy bones.

People need vi-ta-min D lớn allow the intestines to stimulate và absorb calcium và reclaim calcium that the kidneys would otherwise excrete.

Vitamin D deficiency in children can cause rickets, which leads lớn a severely bowlegged appearance due lớn the softening of the bones.

Similarly, in adults, vi-ta-min D deficiency manifests as osteomalacia, or softening of the bones. Osteomalacia results in poor bone density và muscular weakness.

A vi-ta-min D deficiency can also present as osteoporosis, for which over 53 million people in the United States either seek treatment or face an increased risk.

2. Reduced risk of flu

A 2018 reviews of existing research suggested that some studies had found that vitamin D had a protective effect against the influenza virus.

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

Further research is, therefore, necessary khổng lồ confirm the protective effect of vi-ta-min D on the flu.

3. Healthy infants

Vitamin D deficiency has link to high blood pressure in children. One 2018 study found a possible connection between low vi-ta-min D levels and stiffness in the arterial walls of children.

The American Academy of Allergy Asthma và Immunology (AAAAI) suggest that evidence points to a connection between low vitamin D exposure and an increased risk of allergic sensitization.

An example of this is children who live closer to the equator & have lower rates of admission to lớn hospital for allergies plus fewer prescriptions of epinephrine autoinjectors. They are also less likely lớn have a peanut allergy.

The AAAAI also highlight an Australian study of egg intake. Eggs are a common early source of vitamin D. The children who started eating eggs after 6 months were more likely lớn develop food allergies than children who started between 4–6 months of age.

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

4. Healthy pregnancy

A 2019 đánh giá suggests that pregnant women who are deficient in vitamin D may have a greater risk of developing preeclampsia và giving birth preterm.

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

It is also important to lưu ý that in a 2013 study, researchers associated high vi-ta-min D levels during pregnancy with an increased risk of food allergy in the child during the first 2 years of life.

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


Skin type: Darker skin, for example, và sunscreen, reduce the body’s ability to absorb the ultraviolet radiation B (UVB) rays from the sun. Absorbing sunlight is essential for the skin khổng lồ produce vi-ta-min D.

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

Geographical location: People who live in northern latitudes or areas of high pollution, work night shifts, or are homebound should aim lớn consume vitamin D from food sources whenever possible.

Breastfeeding: Infants who exclusively breastfeed need a vitamin D supplement, especially if they have dark skin or have minimal sun exposure. The American Academy of Pediatrics recommend that all breastfed infants receive 400 international units (IU) per day of oral vi-ta-min D.

Supplement drops for babies are available online.

Although people can take vi-ta-min D supplements, it is best to obtain any vitamins or minerals through natural sources wherever possible.

Read more on vitamin D deficiency.


Symptoms of vi-ta-min D deficiency may include:

regular sickness or infectionlow moodimpaired wound healingmuscle pain

If vitamin D deficiency continues for long periods, it may result in complications, such as:

cardiovascular conditionsautoimmune problemsneurological diseasesinfectionspregnancy complicationscertain cancers, especially breast, prostate, & colon.

People can measure vitamin D intake in micrograms (mcg) or international units (IU). One microgram of vitamin D is equal to lớn 40 IU.

The recommended daily intakes of vi-ta-min D are as follows:

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

Sensible sun exposure on bare skin for 5–10 minutes, 2–3 times per week, allows most people to produce sufficient vitamin D. However, vitamin D breaks down quite quickly, meaning that stores can run low, especially in winter.

The upper limit that healthcare professionals recommend for vi-ta-min D is 4,000 IU per day for an adult. However, the National Institutes of Health (NIH) say that vi-ta-min D toxicity is unlikely at intakes under 10,000 IU per day.

Excessive consumption of vi-ta-min D can lead to lớn over calcification of bones and the hardening of blood vessels, kidney, lung, và heart tissues.

The most common symptoms of excessive vitamin D include headache & nausea. However, too much vitamin D can also lead to lớn the following:

loss of appetitea metallic tastevomiting

Excess vitamin D usually occurs from taking too many supplements. It is best to lớn get vi-ta-min D from natural sources.

If someone is taking supplements, they should choose their brand carefully, as the FDA vày not monitor the safety or purity of supplements.

There is a selection of vitamin D supplements available for purchase online.

It is the total diet and eating pattern that is most important in disease prevention & good health. It is better khổng lồ eat a diet with a variety of nutrients than to lớn concentrate on one nutrient as the key khổng lồ good health.