Vitamin d sources and benefits

Vitamin D


Vitamin D is a fat-soluble vitamin. Fat-soluble vitamins are stored in the body’s fatty tissue.

Alternative Names

Cholecalciferol; Vitamin D3; Ergocalciferol; Vitamin D2


Vitamin D helps the body absorb calcium. Calcium and phosphate are two minerals that you must have for normal bone formation.

In childhood, your body uses these minerals to produce bones. If you do not get enough calcium, or if your body does not absorb enough calcium from your diet, bone production and bone tissues may suffer.

Vitamin D deficiency can lead to osteoporosis in adults or rickets in children.

Food Sources

The body makes vitamin D when the skin is directly exposed to the sun. That is why it is often called the “sunshine” vitamin. Most people meet at least some of their vitamin D needs this way.

Very few foods naturally contain vitamin D. As a result, many foods are fortified with vitamin D. Fortified means that vitamins have been added to the food.

Fatty fish (such as tuna, salmon, and mackerel) are among the best sources of vitamin D.

Beef liver, cheese, and egg yolks provide small amounts.

Mushrooms provide some vitamin D. Some mushrooms you buy in the store have higher vitamin D content because they have been exposed to ultraviolet light.

Most milk in the United States is fortified with 400 IU vitamin D per quart. Most of the time, foods made from milk, such as cheese and ice cream, are not fortified.

Vitamin D is added to many breakfast cereals. It is also added to some brands of soy beverages, orange juice, yogurt, and margarine. Check the nutrition fact panel on the food label.


It can be hard to get enough vitamin D from food sources alone. As a result, some people may need to take a vitamin D supplement. Vitamin D found in supplements and fortified foods comes in two different forms:

  • D2 (ergocalciferol)
  • D3 (cholecalciferol)

Follow a diet that provides the proper amount of calcium and vitamin D. Your provider may recommend higher doses of vitamin D if you have risk factors for osteoporosis or a low level of this vitamin.

Side Effects

Too much vitamin D can make the intestines absorb too much calcium. This may cause high levels of calcium in the blood. High blood calcium can lead to:

  • Calcium deposits in soft tissues such as the heart and lungs
  • Confusion and disorientation
  • Damage to the kidneys
  • Kidney stones
  • Nausea, vomiting, constipation, poor appetite, weakness, and weight loss


Some experts have suggested that a few minutes of sunlight directly on the skin of your face, arms, back, or legs (without sunscreen) every day can produce the body’s requirement of vitamin D. However, the amount of vitamin D produced by sunlight exposure can vary greatly from person to person.

  • People who do not live in sunny places may not make enough vitamin D within a limited time in the sun. Cloudy days, shade, and having dark-colored skin also cut down on the amount of vitamin D the skin makes.
  • Because exposure to sunlight is a risk for skin cancer, exposure for more than a few minutes without sunscreen is not recommended.

The best measure of your vitamin D status is to look at blood levels of a form known as 25-hydroxyvitamin D. Blood levels are described either as nanograms per milliliter (ng/mL) or nanomoles per liter (nmol/L), where 0.4 ng/mL = 1 nmol/L.

Levels below 30 nmol/L (12 ng/mL) are too low for bone or overall health, and levels above 125 nmol/L (50 ng/mL) are probably too high. Levels of 50 nmol/L or above (20 ng/mL or above) are enough for most people.

The Recommended Dietary Allowance (RDA) for vitamins reflects how much of each vitamin most people should get on a daily basis.

  • The RDA for vitamins may be used as goals for each person.
  • How much of each vitamin you need depends on your age and gender. Other factors, such as pregnancy and your health, are also important.

Infants (adequate intake of vitamin D)

  • 0 to 6 months: 400 IU (10 micrograms per day)
  • 7 to 12 months: 400 IU (10 mcg/day)


  • 1 to 3 years: 600 IU (15 mcg/day)
  • 4 to 8 years: 600 IU (15 mcg/day)

Older children and adults

  • 9 to 70 years: 600 IU (15 mcg/day)
  • Adults over 70 years: 800 IU (20 mcg/day)
  • Pregnancy and breastfeeding: 600 IU (15 mcg/day)

The National Osteoporosis Foundation (NOF) recommends a higher dose for people age 50 and older, 800 to 1,000 IU of vitamin D daily. Ask your health care provider which amount is best for you.

Vitamin D toxicity almost always occurs from using too many supplements. The safe upper limit for vitamin D is:

One microgram of cholecalciferol (D3) is the same as 40 IU of vitamin D.


Salwen MJ. Vitamins and trace elements. In: McPherson RA, Pincus MR, eds. Henry’s Clinical Diagnosis and Management by Laboratory Methods. 23rd ed. St Louis, MO: Elsevier; 2017:chap 26.

How to Soak Up in Vitamin D This Winter

Has the cold, long winter got you itching for some sunshine? With shorter days and less sunlight, getting enough of the “sunshine vitamin”, or vitamin D, can prove to be a challenge. Especially in the wintertime, it can be hard for us to get adequate amounts of the nutrient from the sun. So how exactly can we make sure we’re getting enough vitamin D in the winter? In fact, there’s actually other sources of the vitamin and ways to measure if you’re getting enough.

Before we get into it, what exactly is vitamin D? It’s an important nutrient that helps regulate your calcium and phosphorus levels, two minerals that are essential for your bone health. It’s even thought to be linked to Alzheimer’s disease and the cold and flu. Different age groups require different amounts of the nutrient. Those in between 1 to 70 years of age are recommended to have 600 IU (15 micrograms) per day.¹ Infants under 12 months of age need 400 IU (10 micrograms) per day while those over 70 years old require 800 IU (20 micrograms) per day. Besides exposing your skin to sunlight, which can be scarce in the winter, you can also get vitamin D from dietary sources. There are certain foods that contain fair amounts of the vitamin, including fatty fishes, like salmon, tuna, and sardines, and eggs. In many countries, it’s also added to milk, and some yogurts, orange juices, and breakfast cereals. By tracking what you eat, you can roughly calculate how much vitamin D you’re getting from dietary sources. In many cases, it may be hard to get the recommended amount of the vitamin through food alone. You could also consider taking vitamin D supplements. These may exist as supplements of their own or as multivitamins, and are available at pharmacies. There are also vitamin drops that are available for infants.

If you’re worried about whether you’re getting enough vitamin D or not, you also have the option to take a blood test. The 25-hydroxyvitamin D test is the standard way to monitor vitamin D levels and reflects the amount of vitamin D your skin produces from the sun and how much you consume from foods and supplements. If you want to find out your exact levels, you should speak to your doctor about getting a blood test. In addition, the QSun app is a free app that helps you stay safe in the sun while maintaining a healthy vitamin D status. An upcoming feature is a vitamin D manager that helps you manage your vitamin D intake. With the app, you’ll be able to track how much of the vitamin you get from the sun, dietary sources, and supplements. You’ll also be able to see if you’re getting enough of the nutrient and how much you need to meet your daily goals, as well as track your long-term progress. You can download the app first for iOS or Android, and stay on the lookout for the new update!

  1. National Institutes of Health. (2016). Vitamin D. Retrieved February 1st, 2018

What Does Vitamin D Do?

Vitamin D helps your child build strong bones and prevent rickets. Rickets is a condition of softening of the bones that can occur in growing children.

When Does My Child Need Vitamin D? And How Much?

All children need vitamin D beginning shortly after birth.

  • Children younger than 12 months old need 400 IUalert iconof vitamin D each day.
  • Children 12 to 24 months old need 600 IU of vitamin D each day.

Did You Know?

Fortified cow’s milk is not recommended for children younger than 12 months old.

It may put your baby at risk for intestinal bleeding. It also has too many proteins and minerals for your infant’s kidneys to handle and does not have the right amount of nutrients your infant needs.

How Can I Make Sure My Child is Getting Enough Vitamin D?

Did You Know?

Fortified cow’s milk is not recommended for children younger than 12 months old.

It may put your baby at risk for intestinal bleeding. It also has too many proteins and minerals for your infant’s kidneys to handle and does not have the right amount of nutrients your infant needs.

For babies who are receiving any breast milk:

  • Breast milk usually does not provide all the vitamin D a baby needs, so breastfed babies will need a supplemental source. Talk to your child’s doctor or nurse about giving your child over-the-counter vitamin D drops. These drops contain enough vitamin D (400 IU each day).

For babies who are receiving infant formula:

  • The amount of infant formula your child drinks per day can depend on your child’s age.
  • 32 ounces of standard infant formula per day contains 400 IU of vitamin D. If your baby is drinking less than this amount per day, he or she may need a vitamin D supplement.
  • Talk with your child’s doctor or nurse if you would like help making sure your child is getting enough vitamin D from the infant formula you use.

For children who have started eating solid foods:

Did You Know?

Fortified cow’s milk is a great source of vitamin D for children over 12 months old.

Most cow’s milk sold in stores is fortified with vitamin D. Talk to your child’s doctor or nurse about vitamin D at your child’s next check-up.

Make sure your child’s diet has foods with vitamin D. Some examples of foods with vitamin D include:

  • Some fishexternal icon (for example, salmon or light canned tuna).
  • Eggs.
  • Vitamin D-fortifiedalert iconproducts like cow’s milk (for children 12 months and older), yogurt, cereals, and some juices.

Vitamin D supplements are another way to help children get enough vitamin D every day. Talk with your doctor or nurse about vitamin D at your child’s next check-up if you have questions.

Learn more about vitamin D and sunlight for your baby.

For more information on vitamin D, check out the American Academy of Pediatrics Vitamin D Recommendationexternal icon.

Did You Know?

Fortified cow’s milk is a great source of vitamin D for children over 12 months old.

Most cow’s milk sold in stores is fortified with vitamin D. Talk to your child’s doctor or nurse about vitamin D at your child’s next check-up.

Top of Page

Which foods contain vitamin D?

Surprisingly few foods contain vitamin D — unless it’s added to the food. That’s because your body is built to get vitamin D through your skin (from sunlight) rather than through your mouth (by food). But once your body has enough, it doesn’t matter whether you got it through your skin or through your stomach.

There are three vitamin D super foods:

  • Salmon (especially wild-caught)
  • Mackerel (especially wild-caught; eat up to 12 ounces a week of a variety of fish and shellfish that are low in mercury)
  • Mushrooms exposed to ultraviolet light to increase vitamin D

Other food sources of vitamin D include:

  • Cod liver oil (warning: cod liver oil is rich in vitamin A; too much may be bad for you)
  • Tuna canned in water
  • Sardines canned in oil
  • Milk or yogurt — regardless of whether it’s whole, nonfat, or reduced fat — fortified with vitamin D
  • Beef or calf liver
  • Egg yolks
  • Cheese

Nearly all milk in the U.S. is fortified with vitamin D. So are many brands of orange juice, yogurt, margarine, and ready-to-eat breakfast cereals.

Next: How much vitamin D do I need?

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Vitamin D is an essential fat-soluble vitamin that promotes good bone health by maintaining the body’s calcium pool. It maintains the body’s calcium pool by helping the body absorb calcium and by regulating the amount of calcium in the body’s blood levels. Adequate levels of Vitamin D are also said to help with immunity, decrease the risk of cardiovascular disease and lower the risk of some cancers.


The biggest and primary source of Vitamin D is the sun, as our skin makes Vitamin D when it is exposed to UV-B rays. Some foods naturally contain Vitamin D, including fatty fish (i.e. Salmon, Herring, Mackerel) and Shitake Mushrooms. Other Vitamin D food sources are fortified with the vitamin, such as milk, cereals and yogurt. But no food sources (natural or fortified) contain adequate enough amounts of the Vitamin D. As a result, most people need to take a multivitamin (Women’s One-A-Day Multivitamin tablets have 800 IU’s) or a Vitamin D Supplement to ensure that their body is receiving enough Vitamin D on a daily basis. Your doctor will let you know which type/strength of multivitamin or supplement is best for you.


The recommended level of Vitamin D intake increases with age as the skin’s ability to make Vitamin D decreases along with the body’s kidney and liver function. Current Vitamin D intake recommendations are as follows: 200 IU/day for ages 0-50, 400 IU/day for ages 51-70 and 600 IU/day for people over 70 years of age. These numbers are expected to increase, as it is believed that the recommended current intake levels are too low to achieve adequate Vitamin D levels in the body. In fact, it is estimated that people need up to an additional 2,000 IU’s of Vitamin D per day to achieve adequate Vitamin D levels depending on the time of year, exposure to the sun and a person’s skin tone.


Any person having a Vitamin D level of under 30 ng/mL is considered to have an insufficient level of Vitamin D in their body; Anyone having a Vitamin D level of less than 21 ng/mL is considered deficient. Vitamin D deficiency is more commonly seen in the winter and spring seasons as the sun’s rays are not as strong during these months, thus making it harder for the skin to make Vitamin D. Vitamin D deficiency is also more commonly found in person’s with darker skin tones, as the additional pigment in their skin makes it harder for the sun’s rays to penetrate the skin and make Vitamin D. Other deficiency factors include the use of sunscreen, air pollution, smoking, obesity, distance from the equator, mal-absorption of Vitamin D by the body, renal and liver disease and some medications.

Some of the effects of Vitamin D deficiency include the development of soft bones, which can lead to Rickets (along with poor diet), osteoporosis, muscle weakness, seizures, an increased risk of developing autoimmune diseases, such as muscular sclerosis, and a higher risk of developing some cancers (not yet conclusive).


There is not much risk associated with the intake of too much Vitamin D. The biggest side effect is the possibility of developing kidney stones.


Proper treatment for low Vitamin D levels depends on how deficient in Vitamin D a person is. For people with Vitamin D levels below 21 ng/mL, a treatment plan of Vitamin D3 50,000 IU supplements three times a week for one month is normally prescribed. After the month, Vitamin D levels will be re-checked to monitor increases in the Vitamin D levels. People with Vitamin D levels below 30 ng/mL are normally placed on a treatment plan of Vitamin D3 1,000 IU supplements 2-3 times a day for three months. After three months the Vitamin D levels are re-checked to monitor increases in the body’s Vitamin D levels. Once a person’s body reaches an adequate level of Vitamin D (over 30 ng/mL), that person will begin taking a Vitamin D3 1,000 IU supplement once per day to maintain healthy Vitamin D levels. Vitamin D3 1,000 IU supplements can be found over-the-counter at any pharmacy or store that sells pharmaceutical items. Vitamin D3 50,000 IU supplements are available by prescription only. If you are placed on a treatment plan that requires you to take Vitamin D3 50,000 IU supplements, your doctor will provide a prescription for the supplements to be picked up at the pharmacy of your choice.

Everything you need to know about Vitamin D

Why is vitamin D important?

Although vitamin D is called a “vitamin” (i.e., a required nutrient obtained from the diet), it is not truly a vitamin. It acts more like a hormone since the body can synthesize it from cholesterol after the skin is exposed to UVB rays from the sun. Vitamin D is estimated to be involved in the regulation of up to 2000 genes—that’s a lot of input into the critical processes happening in every cell throughout the entire body!3,4 Consequently, this vital nutrient has been linked to almost every health condition under the sun, from bone and muscle health, to brain health, pregnancy, immune activity, cardiovascular functions and more. In contrast, vitamin D deficiency can lead to significant health consequences, and it’s estimated that 42% of American adults are deficient.1,5 Below are some of the many aspects of health which vitamin D has been shown to impact.

Vitamin D benefits and the consequences of deficiency

When many people think about vitamin D, they likely think about their bones. Vitamin D is known for helping to balance minerals like calcium, phosphorus, sodium, and magnesium for healthy bone formation and mineralization.6 Although vitamin D plays a significant role in skeletal health, its benefits go well beyond bone health to all parts of the body. Because of the abundant presence of these minerals, along with vitamin D receptors in the body, vitamin D’s benefits are vast, directly and indirectly influencing countless physiological functions.7 For example, vitamin D can act as an antioxidant, regulate immune activity, support cardiovascular health, modulate blood sugar balance, regulate neurotransmitter synthesis and more.

Vitamin D from food, supplementation, or sun exposure, is originally in an inactive form. It must shuttle first through the liver, to become 25(OH) vitamin D, and then to the kidney, to become biologically active 1,25(OH)2 vitamin D. Once biologically active, vitamin D travels to organs throughout the body. Because vitamin D receptors are found in most organs in the body (e.g. intestines, pancreas, kidney, lungs, thyroid, etc.), vitamin D affects their health and functions. Below are some of the organ systems that benefit from vitamin D, and the negative consequences of vitamin D deficiency in select health conditions.7

Vitamin D and musculoskeletal health

Vitamin D supports the normal structure and function of bones and muscles. Historically, the consequences of chronic vitamin D deficiency have been on full display in cases of rickets, a skeletal disorder that results in weakening and distortion of bone growth in children without food sources of vitamin D and low sun exposure.3 Vitamin D deficiency also affects adults, as evidenced by an increased risk in certain types of fractures and forms of muscles weakness.3,8

Vitamin D and brain and nervous system

Vitamin D substantially affects the brain and nervous systems. Studies have shown that supplemental vitamin D may enhance mood during the winter season when vitamin D synthesis from the sun is extremely low.9,10 In addition, research suggests that low vitamin D levels may be associated with increased sleepiness and sleep difficulties.11,12

Vitamin D and pregnancy

Growing evidence also supports the benefits of vitamin D during pregnancy. Recent studies have found that during pregnancy, vitamin D may reduce the risk of many pregnancy complications.13–18 For more information about the role of vitamin D during pregnancy check out “The Importance of Vitamin D During Pregnancy”.

Vitamin D and immunity and respiration

Since vitamin D plays a role in regulating the immune system, it may also have a positive influence on immune-related conditions such as acute and chronic respiratory complications and may help to diminish their symptoms when they occur.3 For example, adequate amounts of vitamin D during childhood and adulthood have been shown to decrease the risk of the exacerbation of chronic respiratory issues and their symptoms.18,19 Studies have also shown that pregnant women taking 4,400 IU of vitamin D per day may reduce the risk of respiratory issues in their newborn to three-year-old children, compared to pregnant women who took just 400 IU per day.20 Self-reported incidences of seasonal respiratory complications have shown to be significantly lower in women taking 800 IU per day compared to placebo.21,22 For more information check out “Don’t Forget Vitamin D this Cold and Flu Season”.

Vitamin D and cardiovascular health

In addition to the respiratory system, research shows that vitamin D plays a role in the health of the cardiovascular system as well, helping to reduce the risk of various complications of the heart and blood vessels.23,24 For example, researchers reported that daily vitamin D supplementation using a wide range of doses (i.e. 600 IU, 2,000 IU, 4,000 IU) decreased stiffness of specific blood vessels after only eight weeks, compared to placebo. Even more compelling, the influence of vitamin D was observed in a dose-response relationship, meaning that as more vitamin D was taken, more improvement in blood vessel structure was observed.25

Vitamin D and metabolism

Vitamin D is involved in numerous metabolic processes throughout the body, with research showing that vitamin D can positively influence blood sugar imbalances and metabolic complications.26–29 Obesity is a significant risk factor for many metabolic and cardiovascular imbalances. Research suggests that the prevalence of vitamin D deficiency may be higher among people with obesity (and to a lesser degree in people who are overweight) and those with blood-sugar imbalances.30 Importantly, the association between vitamin D and metabolic complications may be dose-dependent—the better one’s vitamin D status, the lower the risk of many of these imbalances.

Sources and forms of vitamin D

Vitamin D from sunlight

Sunlight can be a potent natural driver of vitamin D synthesis. A 20 minute total-body exposure (e.g., only wearing a bathing suit) to sunlight produces approximately 10,000–20,000 IU of vitamin D.2,3 This exposure is considered 1 minimal erythemal dose (MED), which is the minimum dose needed to produce pink skin coloration 24 hours after total-body sun exposure.3 Anything that reduces or interferes with UVB radiation from sunlight penetrating the skin affects the skin’s ability to make vitamin D. Many factors influence vitamin D production by the body, from geographical location to environmental conditions.

  • Geographical location, time of year, time of day: Differences in sun exposure greatly depend on the angle at which sunlight reaches the earth, which changes based on where one lives, the time of year, and the time of day. Those living at higher latitudes, above 30oN or 30oS, receive less UVB radiation than those closer to the equator, and this limits how much vitamin D can be made by the skin.31 Vitamin D synthesis is lower during the winter season, and in early morning and late afternoon, when skin exposure to sunlight is minimal.5
  • Skin pigmentation:32 Melanin is a pigment in the skin, hair, and eyes that acts as a natural sunscreen by absorbing UVB radiation. Because melanin is so efficient at doing its job, the more melanin that’s in the skin, (i.e. the darker the skin pigmentation) the more vitamin D production is diminished. Very dark skin is estimated to have a natural SPF of 15, effectively reducing vitamin D synthesis by the skin up to 99%.33 The total amount of vitamin D made by the skin is not limited in people with darker skin, but it can take 3-6 times longer to make the same amount of vitamin D, compared to people with lighter skin tones.2 Because of darker skin pigmentation, vitamin D deficiency is highest in African Americans, followed by Hispanics, and White Americans.1
  • Aging: The body’s ability to make vitamin D diminishes with age. For the body to make vitamin D, the presence of a compound called 7-dehydrocholesterol is needed when UVB rays from sunlight penetrate the skin. However, with increasing age, smaller amounts of this compound are produced. Consequently, even with the same amount of sun exposure, less vitamin D is produced. It’s estimated that the elderly can have up to a 75% reduction in their ability to make vitamin D due to lower levels of 7-dehydrocholesterol.5,34
  • Sunscreen:32 Acting in similar fashion as melanin, sunscreen blocks the absorption of UVB radiation. As a result, when sunscreen is properly applied it can reduce how much vitamin D is made by the skin by up to 99%.
  • Other factors:31 Time indoors, cloudiness, fog, smog, and clothing all decrease the amount of UVB rays that reach the skin, and as a result, the amount of vitamin D that can be made.

Dietary sources of vitamin D

Considering all the factors that influence the amount of vitamin D naturally produced by the skin, it’s no wonder that most people need help getting reliable amounts through their diets. Natural food sources of vitamin D3 (or cholecalciferol, a primarily animal-based form of vitamin D) include fatty fish, egg yolks, and cod liver oils. For vitamin D2 (or ergocalciferol, the plant-based source of vitamin D), shiitake mushrooms are an excellent source. Although there are natural variations, the table below provides estimates for the amounts of vitamin D3 (naturally-occurring and fortified) and D2 that may be found in certain food sources.

Supplements: Which form of vitamin D is best?

Because many people don’t get enough vitamin D through sun exposure and diet, it may become necessary to supplement. Two forms of vitamin D are available for supplementation: vitamin D2 and vitamin D3. These two forms primarily differ in structure and sources. However, both are converted, by the liver, into calcitriol , the same form of vitamin D that is measured in the blood to determine a person’s vitamin D status. Strong evidence indicates that vitamin D3 is more effective at sustaining vitamin D blood levels over time than vitamin D2.35–38

Vegans and others who prefer a plant-based source of vitamin D typically choose to supplement with vitamin D2, compared to animal-based vitamin D3 sources. Fortunately, there is a plant-based vitamin D3 available in the form of lichen, a fungi and algae plant-like organism.

Multivitamins typically include either 400, 500, or 1000 IU vitamin D in the form of D2 or D3 or a combination of both. Vitamin D stand-alone supplements can be found in vitamin D3 form with values of 400–50,000 IU.3

Vitamin D: How much is enough?

Recommended amounts of vitamin D

General vitamin D supplementation guidelines have been proposed by various federal and research-based institutions. The table below provides recommendations from three agencies and institutions, including the Endocrine Society whose guidelines most reflect recent research. Keep in mind, the FDA recently changed its regulations for reporting vitamin D values in nutrition supplement facts. Beginning in January 2020, all supplement companies will be required to report amounts of vitamin D in micrograms (mcg) instead of the current International Units (IU) (1 mcg = 40 IU).

Below are some general guidelines:

Vitamin D Recommendations IOM FDA Endocrine Society
(RDA) (RDI) (Daily Allowance)
0-6 months 400 IU 400-1000 IU
6-12 months 400 IU 400-1000 IU
1-3 years 600 IU 600 IU 600-1000 IU
4-8 years 600 IU 800 IU 600-1000 IU
9-18 years 600 IU 800 IU 600-1000 IU
19-70 years 600 IU 800 IU 1500-2000 IU
>70 years 800 IU 800 IU 1500-2000 IU
14-18 years 600 IU 600 IU 600-1000 IU
19-50 years 600 IU 600 IU 1500-2000 IU
14-18 years 600 IU 600 IU 600-1000 IU
19-50 years 600 IU 600 IU 1500-2000 IU

*4000–6000 IU/day is mother’s required intake if infant is not receiving 400 IU/day.

IOM = Institute of Medicine; RDA = Recommended Dietary Allowance; RDI = Recommended Dietary Intake; IU = International Units.

Most vitamin D researchers agree that vitamin D levels are sufficient at levels >30 ng/mL (or 75 nmol/L). Levels of 20 ng/mL or below (< 50 nmol/L) are considered indicative of vitamin D deficiency, while blood levels 21–29 ng/mL (or 51-74 nmol/L) may indicate insufficiency.39

Why testing for vitamin D is important

Measuring blood levels of vitamin D is the most significant factor in determining if someone is getting enough because the same dose of vitamin D in one person can result in different blood levels in another. Numerous factors determine how vitamin D supplementation will affect an individual’s vitamin D blood levels, including baseline vitamin D levels (vitamin D blood levels prior to vitamin D supplementation), age, body weight, digestive health, diet, current medications, and many more. Blood levels of vitamin D, measured as calcitriol , can be easily and accurately detected with a blood test requested by your doctor.

  • The lower a person’s vitamin D blood levels prior to supplementation, the more vitamin D is required to achieve sufficient levels. Researchers reported that a 50% higher dose of vitamin D was needed to reach sufficient levels (>75 nmol/L or 30 ng/mL) in patients with lower baseline vitamin D levels, compared to patients with higher baseline levels.40
  • With a higher body mass index (BMI), more vitamin D is needed to reach target blood levels. According to one study, after supplementing with 2000 IU of vitamin D per day, those with a higher BMI had significantly lower vitamin D levels than those with a lower BMI.41
  • Other studies show that age also has an important influence on vitamin D levels after supplementation.42–44 Research suggests that as age increases, it may take more amounts of vitamin D to increase blood levels.42

How much vitamin D is too much?

While the proper care and precautions should be exercised when taking dietary supplements, research suggests that the risk of taking too much vitamin D3 is extremely rare. In fact, a growing body of research informs us that most people need to increase their daily vitamin D intake. Clinical Practice Guidelines indicate the following:3

These levels are based on studies demonstrating that the use of these amounts within their respective age groups was safe, and no signs of vitamin D toxicity were reported.39 It’s also important to note that research shows the same safety profile for supplemental vitamin D3 doses beyond 40,000 IU/day!2 Which reiterates that the most reliable way to determine one’s specific vitamin D needs is through testing.

Vitamin D is important for overall health

Vitamin D is extremely important for overall health and a growing body of research is continually unveiling its significance. This hormone-like molecule supports the health of the entire body throughout life, from a healthy pregnancy, to bone and muscles integrity, immune and respiratory health, cardiovascular functions, immune activity, and more. Although some people may think their sun exposure and diets are sufficient to obtain enough vitamin D, scientific evidence suggestions that most people need more. Testing, supplementation, appropriate sun exposure and consuming food sources of vitamin D provide a balanced approach to achieving optimal amounts of this vital nutrient.

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