Whats Vitamin D Do For You
Asked by: Darrick Macejkovic DVM
Your body uses it to absorb minerals like calcium and phosphorus. That makes your teeth and bones strong. Vitamin D also supports your muscles, nerves, and immune system. You can get it from sunshine on your skin and from eating eggs, fatty fish, and fortified foods like milk and cereal.
Vitamin D Can Help Strengthen Muscles
Along with its bone-building abilities, vitamin D is also influential in strengthening muscles, according to a 2018 study in the Journal of the Academy of Orthopaedic Surgeons. “Lack of vitamin D in the body can increase the risk of having weak muscles, which in turn increases the risk of falls,” Lana Nasrallah, MPH, RD, clinical dietician at UNC Health, told Health. This is especially important for the elderly. “Vitamin D may help increase muscle strength thus preventing falls, which is a common problem that leads to substantial disability and death in older adults,” Nasrallah said.
Is It Best To Get Your Vitamin D From The Sun Definitely Not
David J. Leffell, MD, Yale Medicine dermatologist and chief of Dermatologic Surgery
One of the biggest challenges weve faced in dermatology and in the world of skin cancer prevention has been a lot of misinformation about vitamin D metabolism.
There are claims that one needs to get a certain amount of sun exposure every day in order to produce enough vitamin D to be healthy. Its just not true. The majority of people can get their vitamin D from nutritional supplements and from vitamin D-fortified foods.
There are some people who have advocated for tanning to get vitamin D. But we know that UVB light causes skin cancer and that protecting yourself against it makes sense. As a doctor who treats patients who have melanomas, I want the general public to be advised that under no circumstances can use of a tanning bed or tanning in general be justified on the basis of vitamin D. Take a supplement instead.
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Did The Iom Report Make Recommendations With Respect To Serum Vitamin D Levels
Serum concentration of 25-hydroxy-vitamin-D D) is the best indicator of vitamin D status. It reflects total vitamin D input – from food, supplements, and sun exposure.
There is considerable discussion surrounding the serum concentrations of 25D associated with optimal health, and cut points have not been developed by a scientific consensus process.
However, the IOM expert committee stated that its review of the data suggests that, relative to bone health:
- People are at risk of vitamin D deficiency at serum 25D concentrations < 30 nmol/L. Some are potentially at risk for inadequacy at levels ranging from 3050 nmol/L.
- Practically all people are sufficient at levels 50 nmol/L
- There may be reason for concern at serum concentrations > 125 nmol/L
The IOM expert committee encouraged the development of evidence-based cut points for serum vitamin D measures relative to deficiency as well as excess.
Those Who Live Farther Away From The Equator
Countries close to the equator get plenty of sunlight all year round. Conversely, countries farther away from the equator get less sunlight all year round.
This can cause low blood vitamin D levels, especially during winter months when there is even less sunlight.
For instance, a study of Norwegians discovered that they dont produce much vitamin D3 from their skin during the winter months of October to March .
If you live far from the equator, then you need to get more vitamin D from your diet and supplements. Many experts believe that people in these countries should consume at least 1,000 IU daily .
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What Vitamin D Dosage Is Best
Vitamin D is commonly known as the sunshine vitamin.
Thats because your skin makes vitamin D when it is exposed to sunlight .
Getting enough vitamin D is important for optimal health. It helps maintain strong and healthy bones, aids your immune system and may help protect against many harmful conditions .
Despite its importance, roughly 42% of people in the US have a vitamin D deficiency. This number rises to a staggering 82.1% of black people and 69.2% of Hispanic people .
There are several other groups of people that have higher vitamin D needs because of their age, where they live and certain medical conditions.
This article will help you discover how much vitamin D you need daily.
Vitamin D Can Support The Immune System And Fight Inflammation
Vitamin D can also help build immunity, Nasrallah said. “It can support the immune system by fighting off harmful bacteria and viruses.” In fact, this role in possibly preventing infections has become a critical concern during the COVID-19 pandemic, as researchers are interested in its potential role in infection outcomes. “There is particular interest in its role in viral infections such as influenza and coronavirus,” Barry Boyd, MD, RDN, a Yale Medicine hematologist, oncologist, and nutritionist, told Health. He pointed to a 2017 BMJ analysis of 25 randomized control trials comparing vitamin D supplements to placebos, which found that vitamin D reduced the risk of acute respiratory infection with either daily or weekly vitamin D supplementation, particularly in individuals who were deficient in it.
A study in a 2017 Journal of Osteopathic Medicine found that high latitudes and winter season are risk factors for low vitamin D, as well as influenza, and other respiratory illness and adverse outcomes. “We now are seeing a similar pattern with higher mortality rates in COVID-19 infections,” though more research still needs to be done to determine whether the link is causal or merely a correlation,” said Dr. Boyd.
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What Is A Low Vitamin D Level
There is a bit of controversy regarding what is considered a low vitamin D level between different expert organizations. A vitamin D level measures levels of 25D in the blood .
Most experts recommend:
- Levels of 20-50 nanograms/milliliter of 25D: Sufficient
- Levels of 12-19 ng/ml: Borderline
- Levels of less than 12 ng/ml: Deficient
However, not everybody agrees, and some organizations suggest different cut-off values.
The Institute of Medicine states:
- Levels above 20 ng/ml: Sufficient
- Levels below 20 ng/ml: Deficient
Note that several members of the IOM committee publicly stated that over screening for vitamin D deficiency was a problem which typically resulted in unnecessary treatment. They were not in agreement with a cut-off level of 20 ng/ml for deficiency and recommended a lower level of 12.5 ng/ml.
The Endocrine Society states:
- Levels above 30 ng/ml: Sufficient however, some assays are inaccurate and levels of 40-60 ng/ml better guarantee sufficiency
- Levels of 21-29 ng/ml: Insufficient
- Levels below 20 ng/ml: Deficient
Talk to your doctor about what he/she considers to be a low vitamin D level.
Food Sources Of Vitamin D
- Smaller Portions
Vitamin D: Nutrient-densea Food and Beverage Sources, Amounts of Vitamin D and Energy per Smaller Portion
FOODbc Dairy and Fortified Soy Alternatives Soy beverage , unsweetened 1/2 cup Cheese, American, low fat or fat free, fortified 1/2 ounce Almond beverage , unsweetened 1/2 cup Rice beverage , unsweetened 1/2 cup
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It May Help Protect Against Heart Disease And Stroke
Is vitamin D heart-healthy? A review of 19 studies linked adequate vitamin D to a reduced risk of heart disease, stroke, and heart failure, although it did not establish whether vitamin D alone was responsible for that outcome. Yet a study published in May 2022 in the American Journal of Clinical Nutrition found that taking a much higher dose of vitamin D than recommended for five years did not affect total mortality or the incidence of cardiovascular disease in older men and women, most of whom had adequate intakes of the vitamin at the studys onset.
To corroborate those findings, a review and statement released in June 2022 by the U.S. Preventive Services Task Force noted that vitamin D supplements have not been shown to prevent cardiovascular disease-related deaths, the outcome of a cardiovascular event, or stroke.
Additionally, the VITAL study, a randomized clinical trial involving more than 25,000 participants, published in January 2019 TheNew England Journal of Medicine, found no risk reduction for strokes, heart attacks, or cardiovascular deaths in people who took 2,000 IU supplements daily.
Some Perspective On What Is And Isnt Vitamin D Deficiency
I spoke with osteoporosis expert Dr. Joel Finkelstein, associate director of the Bone Density Center at Massachusetts General Hospital, whose research in this field spans over three decades. He agreed with the authors of the NEJM article that we are currently over-screening for vitamin D deficiency, and overtreating people who are getting enough vitamin D through diet and sun exposure. “Vitamin D has been hyped massively,” he states. “We do not need to be checking the vitamin D levels of most healthy individuals.”
He points out that from an evolutionary standpoint, it doesnt make sense that higher vitamin D levels would be beneficial to humans. “Vitamin D is actually quite hard to find in naturally occurring food sources,” he points out. “Yes, we can get vitamin D from the sun, but our bodies evolved to create darker skin in the parts of the world that get the most sun. If vitamin D is so critical to humans, why would we evolve in this way, to require something that is hard to come by, and then evolve in such a way as to make it harder to absorb?”
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It Provides Relief For Symptoms Of Autoimmune Conditions
Researchers have long been fascinated with the potential effect that vitamin D may have on autoimmune disorders because of the nutrients role in regulating the immune system, according to the Harvard T.H. Chan School of Public Health. To confirm its role, more research is needed, but a study published in 2022 in The BMJ made some significant headway. Among nearly 26,000 participants, the study found that people who took vitamin D, or vitamin D and omega-3 fatty acids, had a significantly lower rate of autoimmune diseases like rheumatoid arthritis, polymyalgia rheumatica, autoimmune thyroid disease, and psoriasis than people who took a placebo.
Babies Need A Vitamin D Boost
Because a typical mothers breast milk does not give her baby enough vitamin D, breastfed babies need vitamin D supplementation. Either the baby can be given drops of 400 IU a day directly or the mother can take 5,000 IU a day , which will fortify her milk with enough vitamin D for the baby. We call this super milk!
Although all standard infant formulas are fortified with vitamin D, vitamin D supplementation is also recommended for formula-fed babies. A baby would need to drink a quart of formula each day to get the recommended amount of vitamin D, Dr. Levine says, and young infants may not take in that much. Consult with your babys pediatrician or healthcare provider to make sure they are getting all the vitamin D they need.
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How Do I Get Vitamin D
Our skin makes vitamin D when it is exposed to the sun. It can also be obtained from foods containing vitamin D, and D2/D3 supplements.
- Vitamin D2 supplements
- Fortified foods containing D2
- Exposing our skin to sunlight
- Oily fish and fish oil
- Vitamin D3 supplements made using lanolin from sheeps wool
- Vitamin D3 supplements made using lichen
- Fortified foods containing D3
Since D2 is cheaper to produce, its the most common form in fortified foods.
Why Are Cancer Researchers Studying A Possible Connection Between Vitamin D And Cancer Risk
Early epidemiologic research showed that incidence and death rates for certain cancers were lower among individuals living in southern latitudes, where levels of sunlight exposure are relatively high, than among those living at northern latitudes. Because exposure to ultraviolet light from sunlight leads to the production of vitamin D, researchers hypothesized that variation in vitamin D levels might account for this association. However, additional research based on stronger study designs is required to determine whether higher vitamin D levels are related to lower cancer incidence or death rates.
Experimental evidence has also suggested a possible association between vitamin D and cancer risk. In studies of cancer cells and of tumors in mice, vitamin D has been found to have several activities that might slow or prevent the development of cancer, including promoting cellular differentiation, decreasing cancer cell growth, stimulating cell death , and reducing tumor blood vessel formation .
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Can You Take Too Much Vitamin D
While it is possible to take too much vitamin D, toxicity is very rare.
In fact, you would need to take extremely high doses of 50,000 IU or more for a long period of time .
Its also worth noting that it is impossible to overdose on vitamin D from sunlight .
Although 4,000 IU is set as the maximum amount of vitamin D you can take safely, several studies have shown that taking up to 10,000 IU daily wont cause side effects (
How Much Vitamin D Does My Child Need
Vitamin D is measured in international units .
- Babies younger than 1 year old need 400 IU of vitamin D a day. Baby formula has 400 IU per liter, so babies who drink at least 32 ounces of formula each day get enough. If your baby drinks only breast milk or gets less than 32 ounces of formula each day, ask your health care provider about giving your baby a vitamin D supplement.
- Kids older than 1 year need 600 IU or more of vitamin D a day. Health care providers often want healthy kids to take 600 to 1,000 IU daily.
Some kids might need more vitamin D, such as those who:
- have certain medical problems
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What Is Vitamin D
Vitamin D has to be one of sciences most misunderstood vitamins.
For a start, it is not actually a vitamin, but a prohormone, which means that it is converted into a hormone by our body. It is also not just one substance, but five different substances, of which two have been identified as being the most important to humans. These are:
In addition, research has discovered that vitamin D is not only vital for calcium absorption and bone growth and remodeling, but several other important processes as well, such as modulating cell growth and immune system function.
Vitamin D acts on our bones, intestines, kidneys and parathyroid glands to keep calcium in balance throughout our body. Vitamin D receptors are also located within our cardiovascular system, lungs, pancreas, skeletal muscle, skin, and reproductive organs. In summary, vitamin D is a prohormone that is essential for good health.
Only 10% of the vitamin D our body needs is obtained from food. The rest is made by our bodies when our skin is exposed to sunlight.
How Do I Know If I Have Vitamin D Deficiency
Vitamin D deficiency is measured with a blood test that measures 25D. This is the form of D3 that has undergone conversion by the liver although it is still inactive and requires further conversion by the kidneys to active vitamin D3, 1,25D.
The reason 25D is measured is because it is the most stable form of D3. It is also the most abundant form and lasts several weeks in the body. It is a good representation of how much vitamin D has been obtained from both diet and sun exposure.
Conversely, 1,25D only lasts for a few hours in the body and levels are a thousand-fold less than those of 25D. Our body also has a way of increasing the production of active D3 by the kidneys during times of deficiency and insufficiency, so a blood test for 1,25D may appear normal or elevated even when your actual levels of vitamin D are low. However, in some disorders of calcium metabolism, the 1,25D test may be used.
25D levels will tell your doctor if you are deficient in vitamin D, borderline, sufficient, or vitamin D toxic.
See the flow chart above for an overview of the different forms of vitamin d.
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Special Precautions And Warnings
When taken by mouthPregnancy and breast-feedingChildrenHardening of the arteries A type of fungal infection called histoplasmosisHigh levels of calcium in the bloodOver-active parathyroid gland LymphomaKidney diseaseA disease that causes swelling in body organs, usually the lungs or lymph nodes Tuberculosis
What Are The Signs And Symptoms Of Vitamin D Deficiency
Severe lack of vitamin D in children causes rickets. Symptoms of rickets include:
- Incorrect growth patterns due to bowed or bent bones.
- Muscle weakness.
- Deformities in joints.
This is very rare. Children with a mild vitamin deficiency may just have weak, sore and/or painful muscles.
Lack of vitamin D isnt quite as obvious in adults. Signs and symptoms might include:
However, you may have no signs or symptoms of vitamin D deficiency.
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It May Help Prevent Cognitive Decline And Dementia
Foroutan points out that there are vitamin D receptors in brain tissue, which suggests that the vitamin may play a role in cognitive function and, potentially, the risk of dementia. Research increasingly supports this notion a study published in April 2022 in The American Journal of Clinical Nutrition linked vitamin D deficiency with an increased risk of dementia and justified its causal effect on the condition. Another research article suggests that vitamin D may help clear up amyloid plaque, the hallmark of Alzheimers disease . The authors note that more research is needed to confirm a cause-and-effect relationship between an adequate level of vitamin D and Alzheimers specifically.
Meanwhile, a large review published in July 2018 in Nutritional Neuroscience found insufficient evidence that vitamin D supplements protect against neurodegenerative diseases such as Alzheimers and Parkinsons disease. Researchers wrote that they also couldnt confirm that vitamin D synthesized from sun exposure helps protect against neurodegenerative diseases.