Vitamin D 101: Foods, Benefits, Supplement and Deficiency Symptoms
2. Types of Vitamin D
3. Vitamin D Dose
4. Benefits of Vitamin D
5. Vitamin D Foods
6. Vitamin D and Other Supplements
7. Vitamin D Deficiency Symptoms
8. Side Effects of Vitamin D
11. Vitamin D and Covid-19
1. What is Vitamin D
Vitamin D or known as “calciferol” is a fat-soluble vitamin that can be found naturally in certain types of food. Sunlight is also a natural source of Vitamin D. Our skin produces Vitamin D when exposed to the sun’s ultraviolet B (UVB) rays.
a. How the Body Processes Vitamin D – Vitamin D activation
First, it is converted to calcidiol, or 25(OH)D, in your liver. This is the storage form of the vitamin.
When the active form of vitamin D binds to this receptor, it turns genes on or off, leading to changes in your cells. This is similar to how most other steroid hormones work (Trusted Source, Trusted Source).
c. How Long is Vitamin D Stored in the Body?
Vitamin D undergoes two hydroxylations in the body for activation. Calcitriol (1,25-dihydroxyvitamin D3), the active form of Vitamin D, has a half-life of about 15 h, while calcidiol (25-hydroxyvitamin D3) has a half-life of about 15 days. (Source)
Vitamin D2 is known as ergocalciferol. It is found in some plants, mushrooms, and yeasts.
Vitamin D2 vs Vitamin D3
Both are effectively absorbed into the bloodstream. However, the liver metabolizes them differently.
3. Vitamin D Dosage
The RDI for Vitamin D is as follows (nih.gov):
400 IU (10 mcg): infants, 0–12 months
600 IU (15 mcg): children and adults, 1–70 years old
800 IU (20 mcg): older adults and pregnant or breastfeeding women
According to the U.S. National Academy of Medicine, the safe upper limit is 4,000 IU (100 mcg) per day (nih.gov).
However, don’t consume more than 4,000 IU of vitamin D without your doctor’s permission. It exceeds the safe upper limits of intake and is not linked to more health benefits (Trusted Source).
4. Benefits of Vitamin D
Vitamin D is important to the body in many ways. It plays a significant role in optimizing health. Scientists are still discovering the many ways in which your body uses vitamin D for regulation and modulation.
a. Vitamin D Benefits for Immune System
b. Vitamin D Benefits For Acne
According to a study, Vitamin D has an immune regulatory function in sebocytes, implying that Vitamin D may have anti-inflammatory properties in acne patients.
c. Vitamin D Benefits for Skin
Severe dryness of the skin or Ichty can be an indicator of Vitamin D deficiency. Getting enough Vitamin D can improve symptoms of skin disorders that cause dry, itchy skin.
ii. Vitamin D and Psoriasis
Oral Vitamin D supplementation is an important supplementary therapeutic choice for psoriatic patients. Vitamin D supplementation may also be crucial in preventing psoriasis-related comorbidities, hypertension and metabolic syndromes.
iii. Vitamin D and Vitiligo
According to one study, high-dose Vitamin D therapy may be both safe and beneficial in the treatment of vitiligo. Sixteen vitiligo patients with low Vitamin D status were given 35,000 IU per day for six months, along with a dairy and calcium-rich food limitation and minimum hydration of 2.5 L per day. And the outcome, fourteen of them had repigmentation ranging from 25 to 75%.
It’s still uncertain if high-dose supplementation provides any benefits for long-term patients with vitiligo.
iv. Vitamin D and Atopic Dermatitis
Vitamin D may play a role in improving the symptoms of Atopic Dermatitis. The findings of this study imply that Vitamin D supplementation may help reduce the severity of atopic dermatitis and can be considered as safe and manageable treatment option. However, this conclusion still needs larger-scale studies over a longer duration of treatment.
d. Vitamin D Benefits For Women
i. Does Vitamin D Help Balance Hormones?
Yes. This is because Vitamin D is a hormone that communicates with other hormones. Thus, having sufficient Vitamin D2 and D3 can help ease and prevent hormonal fluctuations.
ii. Does Vitamin D Raise Estrogen Levels?
Yes, the Vitamin D levels in a woman’s body has a positive correlation with a woman’s estrogen levels. Those with higher levels of Vitamin D in their bodies tend to have higher levels of estrogen.
In fact, a deficiency in Vitamin D can lead to lower estrogen levels. This may lead to depression, hot flashes and mood swings.
e. Vitamin D Benefits for Men
i. Is Vitamin D Good For Testosterone?
Yes, Vitamin D may boost testosterone levels and also improve sperm quality.
f. Vitamin D Benefits for Brain Health
i. Is Vitamin D Good For Depression?
It’s believed that vitamin D regulates more than 200 different genes by binding to vitamin D receptors that are responsible for driving a number of biological processes.
ii. How Much Vitamin D Should I Take For Depression ?
To know if you need high or low dosage, you’ll need to get a blood test. A result of 30 nmol/L (nanomoles per liter) or under is too low, and anything over 125 nmol/L is too high. Aim for 50 nmol/L or slightly above, according to the National Institutes of Health Office of Dietary Supplements (ODS).
iii. Benefits of Vitamin D for Anxiety
A study found that taking Vitamin D supplements improved both depression and anxiety in women with type 2 diabetes.
The link between anxiety and Vitamin D still inconsistent, therefore further research is needed to fully understand the connection.
g. Vitamin D Benefits for Weight Loss
Vitamin D is involved in the regulation of metabolic processes and development. This includes nerve conduction, normal mineralization of bone, muscle contraction, and general cellular function throughout the body. Vitamin D supplementation can increase physical strength in both upper and lower limbs (Trusted Source).
ii. Does Vitamin D Help Lose Belly Fat?
Yes, Vitamin D can help trigger weight loss primarily in the belly. This is because Vitamin D and Calcium may work synergistically to reduce the production of cortisol, which is a stress hormone that causes you to store belly fat.
Scientists found that people with the highest blood levels of vitamin D (over 33 ng/ml or 82.4 nmol/l) had a 50% lower risk of colorectal cancer than people with the lowest levels of vitamin D (less than 12 ng/ml or 30 nmol/l).
j. Vitamin D Benefits for Sleep
5. Vitamin D Foods
Vitamin D is a fat-soluble vitamin, which means it does not dissolve in water and is best absorbed in the bloodstream when consumed with high-fat meals. That’s why the best way to take vitamin D supplement is with food to maximize absorption.
|Cod liver oil, 1 tablespoon (15 ml)||1,360 IU / 34 mcg||227%|
|Salmon, cooked, 3 ounces (85 grams)||447 IU / 11 mcg||75%|
|Tuna, canned in water, 3 ounces (85 grams)||154 IU / 4 mcg||26%|
|Beef liver, cooked, 3 ounces (85 grams)||42 IU / 1 mcg||7%|
|1 large whole egg (D is found in yolk)||41 IU / 1 mcg||7%|
|1 sardine, canned in oil, drained||23 IU / 0.6 mcg||4%|
The only excellent dietary source of vitamin D is fish liver oil — such as cod liver oil — which contains upwards of two times the Reference Daily Intake (RDI) in a single tablespoon (15 ml).
Keep in mind that dairy products and cereals are often fortified with vitamin D (NIH).
Orange juice - A cup (237 ml) of fortified orange juice contains up to 100 IU of Vitamin D.
d. Vitamin D Vegetables
Mushrooms - Mushrooms are a good source of Vitamin D2. Mushrooms produce Vitamin D2 when exposed to UV light.
This is likely because vitamin D gets the calcium into the blood, then vitamin K tells the calcium where it is most needed.
7. Vitamin D Deficiency
- Deficiency: Less than 20 ng/ml (50 nmol/L)
- Insufficiency: 21 - 29 ng/ml (52 - 72 nmol/L)
- Sufficiency: More than 30 ng/ml (75 nmol/L)
a. Symptoms of Vitamin D Deficiency
- Aching muscles
- Painful bones
- Reduced muscle performance
- Brain health
- Poor sleep
- Sweaty head
- Hair loss
- Slow-healing wounds
- Heart problems
- Excess weight
- Recurring infections
- Reduced cognitive function
Deficiency is also linked to osteoporosis, reduced mineral density, and increased risk of falls and fractures in older adults (Source).
What’s more, studies indicate that people with low Vitamin D levels have a much greater risk of heart disease, diabetes (types 1 and 2), cancer, dementia, and autoimmune diseases like multiple sclerosis (Trusted Source).
Finally, Vitamin D deficiency is linked to a reduced life expectancy (Trusted Source, Trusted Source, Trusted Source).
That said, it’s unclear whether deficiency contributes to these diseases or whether people with low levels are just more likely to get them.
Mark Alipio with GrassrootsHealth conducted a retrospective multicenter study involving 212 patients in Southeast Asia who had COVID-19. He too found a strong correlation between Vitamin D levels and disease severity. Those with the mildest disease had the highest Vitamin D levels, and vice versa.
Another study, published in the Irish Medical Journal (May 2020) showed that the calculated COVID-19 mortality rate from 12 European countries shows a significant (P = .046) inverse correlation with the mean 25(OH)D plasma concentration.
8. Side Effects of Vitamin D
The main symptoms of toxicity include confusion, lack of concentration, drowsiness, depression, vomiting, abdominal pain, constipation, and high blood pressure (Trusted Source). Other side effects of Vitamin D include..
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 (Trusted Source).
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) (Trusted 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.
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.
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 (Trusted Source).
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
- stomach pain
- fatigue, dizziness, and confusion
- excessive thirst
- frequent urination
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 (Trusted 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 (Trusted Source).
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 (Trusted 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 (Trusted Source, Trusted 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).
d. Stomach pain, constipation, or diarrhea
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 (Trusted 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 (Trusted 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 (Trusted Source).
e. Bone loss
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 (Trusted 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 (Trusted Source, Trusted 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.
f. Kidney failure
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 (Trusted Source).
Indeed, most studies have reported moderate-to-severe kidney injury in people who develop vitamin D toxicity (Trusted Source, Trusted Source, Trusted Source, Trusted Source, Trusted Source, Trusted 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 (Trusted Source). Kidney failure is treated with oral or intravenous hydration and medication.
i. What is 25-hydroxy Vitamin D?Vitamin D must go through several processes in your body before your body can use it. The first transformation occurs in the liver.
Calcifediol is the main circulating form of vitamin D, and its blood levels reflect your body’s stores of this nutrient.
For this reason, your health care provider can estimate your vitamin D status by measuring your levels of calcifediol (Trusted Source).
However, vitamin D2 seems to yield less calcifediol than an equal amount of vitamin D3.
Most studies show that vitamin D3 is more effective than vitamin D2 at raising blood levels of calcifediol (Trusted Source, Trusted Source).
ii. What is the 25-hydroxy Vitamin D test?The 25-hydroxy vitamin D test is the best way to monitor vitamin D levels. The amount of 25-hydroxyvitamin D in your blood is a good indication of how much vitamin D your body has. The test can determine if your vitamin D levels are too high or too low.
The test is also known as the 25-OH vitamin D test and the calcidiol 25-hydroxycholecalciferol test. It can be an important indicator of osteoporosis (bone weakness) and rickets (bone malformation).
iii. What is the 25 Dihydroxy Vitamin D1 test?
The Vitamin D, 1,25 Dihydroxy level does not have a major change until normal Vitamin D levels drop to levels that are considered a VERY severe Vitamin D deficiency. Calcidiol is converted to calcitriol, or 1,25(OH)2D, mostly in your kidneys. This is the active, steroid-hormone form of vitamin D.
Calcitriol interacts with the vitamin D receptor (VDR), which is found in almost every single cell in your body (Trusted Source, Trusted Source). When the active form of vitamin D binds to this receptor, it turns genes on or off, leading to changes in your cells. This is similar to how most other steroid hormones work (Trusted Source, Trusted Source).
Normal Vitamin D Lab Values for 1,25 Dihydroxy Vitamin D
- Adults in good health (age 20-50) : 17 - 53 pg/ml
- Children up to 12: ca. 40% higher values
- Pregnant women (8-42 week): ca. 60% higher values
- Persons older than 70: ca. 40% lower values
- The normal range is independent of the season.
Most considered the most potent form of vitamin D. It stimulates calcium absorption from our small intestines and bones (along with PTH) and increases reabsorption of calcium by the kidneys.
The level of serum 1,25-dihydroxy-vitamin D is not typically used to know vitamin D status. It has a short half-life of only 15 hours. It is regulated by parathyroid hormone, calcium, and phosphate. So a decrease will not be noted until vitamin D deficiency is severe.
iv. Why is a 25-hydroxy Vitamin D test done?Your doctor may request a 25-hydroxy vitamin D test for several different reasons. It can help them figure out whether too much or too little vitamin D is causing bone weakness or other abnormalities. It can also monitor people who are at risk for having a vitamin D deficiency.
Those who are at high risk of having low levels of vitamin D include:
- people who don’t get much exposure to the sun
- older adults
- people with obesity
- babies who are breastfed only (formula is usually fortified with vitamin D)
- people who have had gastric bypass surgery
- people who have a disease that affects the intestines and makes it difficult for the body to absorb nutrients, such as Crohn’s disease
The 25-hydroxy vitamin D test requires a common blood test. Your healthcare provider will draw blood from a vein in your arm using a needle. A quick finger prick will more than likely provide enough for a blood sample in children and infants.
Your doctor will tell you not to eat anything for four to eight hours before the test.
vi. Evaluating the results of a 25-hydroxy Vitamin D test
According to the Office of Dietary Supplements (ODS), levels of vitamin D are measured by the 25-hydroxy level in nanomoles/liter (nmol/L) or nanograms/milliliter (ng/mL). The results can indicate the following:
- deficiency: less than 30 nmol/L (12 ng/mL)
- potential deficiency: between 30 nmol/L (12 ng/mL) and 50 nmol/L (20 ng/mL)
- normal levels: between 50 nmol/L (20 ng/mL) and 125 nmol/L (50 ng/mL)
- high levels: higher than 125 nmol/L (50 ng/mL)
Low blood levels of 25-hydroxy vitamin D usually mean one (or more) of the following:
- you aren’t eating a balanced, complete diet
- your intestines aren’t absorbing the vitamin properly
- you’re not spending enough time outside to absorb adequate vitamin D levels through sun exposure
vii. Risks of a 25-hydroxy Vitamin D test
10. Vitamin D and COVID-19
Of those with a vitamin D level below 20 ng/ml (deficiency), 12.5% tested positive for SARS-CoV-2, compared to 8.1% of those who had a vitamin D level between 30 and 34 ng/ml (adequacy) and 5.9% of those who had an optimal vitamin D level of 55 ng/ml or higher.
According to an editorial review (Aliment Pharmacol Ther. 2020) published in June 2020 by Irish researchers, people with Vitamin D deficiency appear to be far more prone to severe COVID-19 infections.
The epidemiology of COVID-19 provides evidence that Vitamin D might be helpful in reducing risk associated with COVID-19 deaths. A May 6, 2020, report published in Aging Clinical and Experimental Research (its prepublication featured in the Daily Mail) found that countries with lower Vitamin D levels also have higher mortality rates from COVID-19.
Another May 6, 2020 report (Nutrients. 2020) in the journal Nutrients pointed out that Vitamin D concentrations are lower in patients with positive PCR (polymerase chain reaction) tests for SARS-CoV-2. As noted in this report, which retrospectively investigated the Vitamin D levels obtained from a cohort of patients in Switzerland.
The Irish Longitudinal Study on Ageing (TILDA) published in April 2020, suggested that Vitamin D deficiency could have serious implications for COVID-19. Results from the Irish Longitudinal Study on Ageing (TILDA), showed that Vitamin D plays a critical role in preventing respiratory infections, reducing antibiotic use, and boosting the immune system response to infections.
Another study, published in the journal Nutrients (April 2, 2020), carries the telling title, “Evidence That Vitamin D Supplementation Could Reduce Risk of Influenza and COVID-19 Infections and Death.”
A preprinted study published in May 2020, looked at Vitamin D levels and inflammatory markers in hospitalized COVID-19 patients in Germany, South Korea (S. Korea), China (Hubei), Switzerland, Iran, UK, US, France, Spain, Italy (Daneshkhah, MedRxiv 2020). Patients with the lowest Vitamin D levels were about 15% more likely to get severe COVID-19 and cytokine storm. Vitamin D3 plays a role in inhibiting the cytokine storm that causes viral infections to become lethal.
In a May 18, 2020, letter to the Federal Chancellor of Germany, Angela Merkel; Bernd Glauner and Lorenz Borsche highlight these and other studies and ask whether a nationwide supply of Vitamin D has been considered in Germany. They highlighted studies showing a clear correlation between COVID-19 mortality and vitamin D levels. This graph was included in their letter.
b. High Dosage Vitamin D Covid Studies