The Benefits of Vitamin D
Vitamin D is sometimes called the “sunshine vitamin” because it’s produced in your skin in response to sunlight. It’s a fat-soluble vitamin in a family of compounds that includes vitamins D-1, D-2, and D-3.
Your body produces vitamin D naturally when it’s directly exposed to sunlight. You can also get it through certain foods and supplements to ensure adequate levels of the vitamin in your blood.
Vitamin D has several important functions. Perhaps the most vital are regulating the absorption of calcium and phosphorus, and facilitating normal immune system function. Getting a sufficient amount of vitamin D is important for normal growth and development of bones and teeth, as well as improved resistance against certain diseases.
If your body doesn’t get enough vitamin D, you’re at risk of developing bone abnormalities such as soft bones (osteomalacia) or fragile bones (osteoporosis).
Here are three more surprising benefits of vitamin D.
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In addition to its primary benefits, research suggests that vitamin D may also play a role in:
- reducing your risk of multiple sclerosis, according to a 2006 study published in the Journal of the American Medical Association
- decreasing your chance of developing heart disease, according to 2008 findings published in CirculationTrusted Source
- helping to reduce your likelihood of developing the flu, according to 2010 research published in the American Journal of Clinical NutritionTrusted Source
Research has shown that vitamin D might play an important role in regulating mood and warding off depression. In one study, scientists found that people with depression who received vitamin D supplements noticed an improvement in their symptoms.
Consider adding vitamin D supplements to your diet if you’re trying to lose weight or prevent heart disease.
In one study, people taking a daily calcium and vitamin D supplement were able to lose more weight than subjects taking a placebo supplement. The scientists said the extra calcium and vitamin D had an appetite-suppressing effect.
In another study, overweight people who took a daily vitamin D supplement improved their heart disease risk markers.
Many factors can affect your ability to get sufficient amounts of vitamin D through the sun alone. These factors include:
- Being in an area with high pollution
- Using sunscreen
- Spending more time indoors
- Living in big cities where buildings block sunlight
- Having darker skin. (The higher the levels of melanin, the less vitamin D the skin can absorb.)
These factors contribute to vitamin D deficiency in an increasing number of people. That’s why it’s important to get some of your vitamin D from sources besides sunlight.
The symptoms of a vitamin D deficiency in adults include:
- tiredness, aches and pains, and a general sense of not feeling well
- severe bone or muscle pain or weakness that may cause difficulty climbing stairs or getting up from the floor or a low chair, or cause you to walk with a waddling gait
- stress fractures, especially in your legs, pelvis, and hips
Doctors can diagnose a vitamin D deficiency by performing a simple blood test. If you have a deficiency, your doctor may order X-rays to check the strength of your bones.
If you’re diagnosed with a vitamin D deficiency, your doctor will likely recommend you take daily vitamin D supplements. If you have a severe deficiency, they may instead recommend high-dose vitamin D tablets or liquids. You should also make sure to get vitamin D through sunlight and the foods you eat.
Few foods contain vitamin D naturally. Because of this, some foods are fortified. This means that vitamin D has been added. Foods that contain vitamin D include:
- egg yolk
- milk (fortified)
- cereal (fortified)
- yogurt (fortified)
- orange juice (fortified)
It can be hard to get enough vitamin D each day through sun exposure and food alone, so taking vitamin D supplements can help.
There has been some controversy over the amount of vitamin D needed for healthy functioning. Recent research indicates that you need more vitamin D than was once thought. Normal blood serum levels range from 50 to 100 micrograms per deciliter. Depending on your blood level, you may need more vitamin D.
The Institute of Food and Agricultural Sciences reports new recommendations based on international units (IUs) per day. IUs are a standard type of measurement for drugs and vitamins. IUs help experts determine recommended dose, toxicity, and deficiency levels for each person.
One IU is not the same for each type of vitamin. An IU is determined by how much of a substance produces an effect in your body. The recommended IUs for vitamin D are:
- children and teens: 600 IU
- adults up to age 70: 600 IU
- adults over age 70: 800 IU
- pregnant or breastfeeding women: 600 IU
6 Side Effects of Too Much Vitamin D
Vitamin D is extremely important for good health.
It plays several roles in keeping your body’s cells healthy and functioning the way they should.
Most people don’t get enough vitamin D, so supplements are common.
However, it’s also possible — although rare — for this vitamin to build up and reach toxic levels in your body.
This article discusses 6 potential side effects of getting excessive amounts of this important vitamin.
Vitamin D is involved in calcium absorption, immune function, and protecting bone, muscle, and heart health. It occurs naturally in food and can also be produced by your body when your skin is exposed to sunlight.
Yet, aside from fatty fish, there are few foods rich in vitamin D. What’s more, most people don’t get enough sun exposure to produce adequate vitamin D.
Supplements are very common, and both vitamin D2 and vitamin D3 can be taken in supplement form. Vitamin D3 is produced in response to sun exposure and is found in animal products, whereas vitamin D2 occurs in plants.
Vitamin D3 has been found to increase blood levels significantly more than D2. Studies have shown that each additional 100 IU of vitamin D3 you consume per day will raise your blood vitamin D levels by 1 ng/ml (2.5 nmol/l), on average (2Trusted Source, 3Trusted Source).
However, taking extremely high doses of vitamin D3 for long periods may lead to excessive buildup in your body.
Vitamin D intoxication occurs when blood levels rise above 150 ng/ml (375 nmol/l). Because the vitamin is stored in body fat and released into the bloodstream slowly, the effects of toxicity may last for several months after you stop taking supplements (4Trusted Source).
Importantly, toxicity isn’t common and occurs almost exclusively in people who take long-term, high-dose supplements without monitoring their blood levels.
It’s also possible to inadvertently consume too much vitamin D by taking supplements that contain much higher amounts than are listed on the label.
In contrast, you cannot reach dangerously high blood levels through diet and sun exposure alone.
Below are the 6 main side effects of too much vitamin D.
However, there isn’t agreement on an optimal range for adequate levels.
Although a vitamin D level of 30 ng/ml (75 nmol/l) is typically considered adequate, the Vitamin D Council recommends maintaining levels of 40–80 ng/ml (100–200 nmol/l) and states that anything over 100 ng/ml (250 nmol/l) may be harmful (6Trusted Source, 7).
While an increasing number of people are supplementing with vitamin D, it’s rare to find someone with very high blood levels of this vitamin.
One recent study looked at data from more than 20,000 people over a 10-year period. It found that only 37 people had levels above 100 ng/ml (250 nmol/l). Only one person had true toxicity, at 364 ng/ml (899 nmol/l) (8Trusted Source).
In one case study, a woman had a level of 476 ng/ml (1,171 nmol/l) after taking a supplement that gave her 186,900 IU of vitamin D3 per day for two months (9).
This was a whopping 47 times the generally recommended safe upper limit of 4,000 IU per day.
The woman was admitted to the hospital after she experienced fatigue, forgetfulness, nausea, vomiting, slurred speech, and other symptoms (9).
Although only extremely large doses can cause toxicity so rapidly, even strong supporters of these supplements recommend an upper limit of 10,000 IU per day (3Trusted Source).
Summary Vitamin D levels greater than 100
ng/ml (250 nmol/l) are considered potentially harmful. Toxicity symptoms have
been reported at extremely high blood levels resulting from megadoses.
Vitamin D helps your body absorb calcium from the food you eat. In fact, this is one of its most important roles.
However, if vitamin D intake is excessive, blood calcium may reach levels that can cause unpleasant and potentially dangerous symptoms.
Symptoms of hypercalcemia, or high blood calcium levels, include:
- digestive distress, such as vomiting, nausea, and
- fatigue, dizziness, and confusion
- excessive thirst
- frequent urination
The normal range of blood calcium is 8.5–10.2 mg/dl (2.1–2.5 mmol/l).
In one case study, an older man with dementia who received 50,000 IU of vitamin D daily for 6 months was repeatedly hospitalized with symptoms related to high calcium levels (10Trusted Source).
In another, two men took improperly labeled vitamin D supplements, leading to blood calcium levels of 13.2–15 mg/dl (3.3–3.7 mmol/l). What’s more, it took a year for their levels to normalize after they stopped taking the supplements (11Trusted Source).
Summary Taking too much vitamin D may result
in excessive absorption of calcium, which can cause several potentially
Many side effects of too much vitamin D are related to excessive calcium in the blood.
These include nausea, vomiting, and poor appetite.
However, these symptoms don’t occur in everyone with elevated calcium levels.
One study followed 10 people who had developed excessive calcium levels after they had taken high-dose vitamin D to correct deficiency.
Four of them experienced nausea and vomiting, and three of them had a loss of appetite (12Trusted Source).
Similar responses to vitamin D megadoses have been reported in other studies. One woman experienced nausea and weight loss after taking a supplement that was found to contain 78 times more vitamin D than stated on the label (13Trusted Source, 14Trusted Source).
Importantly, these symptoms occurred in response to extremely high doses of vitamin D3, which led to calcium levels greater than 12 mg/dl (3.0 mmol/l).
Summary In some people, high-dose vitamin D
therapy has been found to cause nausea, vomiting, and lack of appetite due to
high blood calcium levels.
Stomach pain, constipation, and diarrhea are common digestive complaints that are often related to food intolerances or irritable bowel syndrome.
However, they can also be a sign of elevated calcium levels caused by vitamin D intoxication (15Trusted Source).
These symptoms may occur in those receiving high doses of vitamin D to correct deficiency. As with other symptoms, response appears to be individualized even when vitamin D blood levels are similarly elevated.
In one case study, a boy developed stomach pain and constipation after taking improperly labeled vitamin D supplements, whereas his brother experienced elevated blood levels without any other symptoms (16Trusted Source).
In another case study, an 18-month-old child who was given 50,000 IU of vitamin D3 for 3 months experienced diarrhea, stomach pain, and other symptoms. These symptoms resolved after the child stopped taking the supplements (17Trusted Source).
Summary Stomach pain, constipation, or
diarrhea may result from large vitamin D doses that lead to elevated calcium
levels in the blood.
Because vitamin D plays an important role in calcium absorption and bone metabolism, getting enough is crucial for maintaining strong bones.
However, too much vitamin D can be detrimental to bone health.
Although many symptoms of excessive vitamin D are attributed to high blood calcium levels, some researchers suggest that megadoses may lead to low levels of vitamin K2 in the blood (18Trusted Source).
One of vitamin K2’s most important functions is to keep calcium in the bones and out of the blood. It’s believed that very high vitamin D levels may reduce vitamin K2 activity (18Trusted Source, 19Trusted Source).
To protect against bone loss, avoid taking excessive vitamin D supplements and take a vitamin K2 supplement. You can also eat foods rich in vitamin K2, such as grass-fed dairy and meat.
Summary Although vitamin D is required for
calcium absorption, high levels may cause bone loss by interfering with vitamin
Excessive vitamin D intake frequently results in kidney injury.
In one case study, a man was hospitalized for kidney failure, elevated blood calcium levels, and other symptoms that occurred after he received vitamin D injections prescribed by his doctor (20Trusted Source).
Indeed, most studies have reported moderate-to-severe kidney injury in people who develop vitamin D toxicity (9, 12Trusted Source, 13Trusted Source, 14Trusted Source, 16Trusted Source, 17Trusted Source, 21Trusted Source).
In one study in 62 people who received excessively high-dose vitamin D injections, each person experienced kidney failure — whether they had healthy kidneys or existing kidney disease (21Trusted Source).
Kidney failure is treated with oral or intravenous hydration and medication.
Summary Too much vitamin D may lead to kidney
injury in people with healthy kidneys, as well as those with established kidney
Vitamin D is extremely important for your overall health. Even if you follow a healthy diet, you may require supplements to achieve optimal blood levels.
However, it’s also possible to have too much of a good thing.
Make sure to avoid excessive doses of vitamin D. Generally, 4,000 IU or less per day is considered safe, as long as your blood values are being monitored.
In addition, make sure you purchase supplements from reputable manufacturers to reduce the risk of accidental overdose due to improper labeling.
If you’ve been taking vitamin D supplements and are experiencing any of the symptoms listed in this article, consult a healthcare professional as soon as possible.
How Much Vitamin D Should You Take For Optimal Health?
Vitamin D is absolutely essential for good health.
Also known as the sunshine vitamin, it is made in your skin when exposed to sunlight.
In spite of that, vitamin D deficiency is one of the most common nutrient deficiencies in the world.
Vitamin D is particularly important for bone health and immune system function.
This article discusses how much vitamin D you need.
Vitamin D is a fat-soluble vitamin that functions like a steroid hormone in the body.
There are two forms of vitamin D in the diet:
- Vitamin D2 (ergocalciferol): found in some mushrooms.
- Vitamin D3 (cholecalciferol): found in oily fish, fish liver oil and egg yolks.
Large amounts of vitamin D can also be made in your skin when it is exposed to UV-rays from sunlight. Any excess vitamin D is stored in your body fat for later use.
Every cell in your body has a receptor for vitamin D. This vitamin is involved in many processes, including bone health, immune system function and protection against cancer (8Trusted Source, 9Trusted Source, 10Trusted Source, 11Trusted Source).
Vitamin D functions like a steroid hormone in your body. There are two forms in the diet, D2 and D3. It can also be produced in your skin when exposed to sunlight.
Vitamin D deficiency is a problem all over the world.
About 42% of the US population is vitamin D deficient. However, this rate rises to 82% in black people and 70% in Hispanics (5Trusted Source).
If you have access to strong sun all year, then occasional sun exposure may be enough to fulfill your vitamin D requirements.
However, if you live far north or south of the equator then your vitamin D levels may fluctuate depending on the season. The levels may go down during the winter months, due to a lack of sufficient sunlight (14Trusted Source, 15Trusted Source, 16Trusted Source).
In that case, you need to rely on your diet (or supplements) for vitamin D, as well as on vitamin D that is stored in body fat during the summer (15Trusted Source).
- Cause muscle weakness.
- Intensify bone loss.
- Increase the risk of fractures.
In children, a severe vitamin D deficiency can cause delays in growth as well as rickets, a disease where the bones become soft.
Vitamin D deficiency is very common worldwide, but occurs at higher rates in specific populations. A deficiency in vitamin D is linked to various health problems.
How much vitamin D you need depends on many factors. These include age, race, latitude, season, sun exposure, clothing and more.
However, some studies have shown that the daily intake needs to be higher than that if you aren’t being exposed to sun.
Depending on who you ask, blood levels above 20 ng/ml or 30 ng/ml are considered as “sufficient.” One study of healthy adults showed that a daily intake of 1120–1680 IU was needed to maintain sufficient blood levels (23Trusted Source).
In the same study, individuals who were vitamin D deficient needed 5000 IU to reach blood levels above 30 ng/ml.
Studies in postmenopausal women with vitamin D levels below 20 ng/ml found that ingesting 800–2000 IU raised blood levels above 20 ng/ml. However, higher doses were needed to reach 30 ng/ml (24Trusted Source, 25Trusted Source).
All things considered, a daily vitamin D intake of 1000–4000 IU, or 25–100 micrograms, should be enough to ensure optimal blood levels in most people.
4000 IU is the safe upper limit according to the Institute of Medicine (IOM). Make sure not to take more than that without consulting with a health professional.
Vitamin D intake is recommended at 400–800 IU/day, or 10–20 micrograms. However, some studies suggest that a higher daily intake of 1000–4000 IU (25–100 micrograms) is needed to maintain optimal blood levels.
Blood levels of vitamin D are assessed by measuring 25(OH)D in the blood, which is the storage form of vitamin D in the body (28Trusted Source).
However, there has been some debate over the definition of optimal blood levels.
- Sufficient: 25(OH)D greater than 20 ng/ml (50 nmol/l).
- Insufficient: 25(OH)D less than 20 ng/ml (50 nmol/l).
- Deficient: 25(OH)D less than 12 ng/ml (25 nmol/l).
These organizations claim that blood levels of over 20 ng/ml meet the vitamin D requirements of more than 97.5% of the population.
A committee at the IOM did not find higher blood levels to be associated with any additional health benefits (21Trusted Source).
However, other experts, including the Endocrine Society, recommend aiming for higher blood levels that are closer to 30 ng/ml (75 nmol/l) (17Trusted Source, 29Trusted Source, 30Trusted Source, 31Trusted Source).
Vitamin D levels are generally considered sufficient when above 20 ng/ml (50 nmol/l). However, some experts claim that blood levels above 30 ng/ml (75 nmol/l) are optimal.
You can get vitamin D from:
- Sun exposure.
- Foods that contain vitamin D.
Vitamin D intake is generally quite low, since very few foods contain significant amounts (32Trusted Source).
Foods that do contain vitamin D include fatty fish like salmon, as well as fish liver oils.
However, supplements are also widely available, and are both safe and effective.
The main sources of vitamin D are sunshine, fatty fish, egg yolks, fish liver oils, fortified foods and supplements.
Summer sun exposure is the best way to get enough vitamin D.
However, the amount of sunlight needed varies.
Older individuals and dark-skinned people produce less vitamin D in the skin.
Geographic location and season are very important, because vitamin D can’t be produced year round in countries that are far from the equator.
Even though the sun may be shining, it is not necessarily strong enough to produce vitamin D.
Here are a few facts about vitamin D production in the sun:
- In the more than 70 countries that are positioned north of 35°N, no vitamin D is produced during the winter months (34Trusted Source, 35Trusted Source).
- Further north, in countries like Norway (69°N), no vitamin D is produced from October until March (36Trusted Source).
- Factors such as clothing, weather, pollution, sunscreen use, weight and genetics may also affect the body’s ability to produce vitamin D.
In strong sun, exposing arms and legs for 5–30 minutes between 10 AM and 3 PM is usually enough to meet the daily requirements of most light-skinned people. People with darker skin may need a little more time (22Trusted Source).
One study showed that extended sun exposure during summer was enough to ensure excellent vitamin D levels during winter, regardless of vitamin D intake (37Trusted Source).
However, if you live far from the equator, you probably need to consume supplements or foods that contain vitamin D.
Vitamin D requirements can be met by sunshine alone during the summer. During the winter, and for those living far from the equator, supplements may be needed.
Information about vitamin D overdose is outdated, and toxicity is extremely rare.
It is associated with dangerously high amounts of calcium and phosphates in the blood, along with low levels of parathyroid hormone.
This is typically only seen in individuals who have accidentally or intentionally taken extremely high doses of vitamin D for long periods of time, such as 50,000–1 million IU/day for months (38Trusted Source, 39Trusted Source).
The upper level of harmless intake is set at 4000 IU, or 100 micrograms, per day.
However, up to 10,000 IU per day has not been shown to cause harm to healthy individuals (21Trusted Source).
That being said, very few people actually need more than 4000 IU a day (40Trusted Source).
A study of 17 thousand people taking varying doses of vitamin D, up to 20,000 IU/day, did not demonstrate any signs of toxicity. Their blood levels were still lower than the upper range of normal, which is 100 ng/ml, or 250 nmol/l (26Trusted Source).
Also, it is not possible to overdose on vitamin D from sunlight.
Keep in mind that although large doses are unlikely to cause harm or toxicity, they may be completely unnecessary.
Vitamin D is essential for bone health and many other aspects of health.
A deficiency is incredibly common, and may have severe health consequences for many people.
If you’re thinking about adding more vitamin D to your diet, consider the following factors:
- If you live somewhere where there is sun year-round, then you may not need extra vitamin D as long as you make sure to get enough sun.
- If you do not have access to the sun, then vitamin D3 supplements of 1000–4000 IU (25–100 micrograms) should be enough for most people.
- The only way to know if you actually need to take a vitamin D supplement is to have your blood levels measured.
At the end of the day, vitamin D is highly important. Correcting a deficiency is simple, cheap and can have immense health benefits.