Vitamin D and Immune System: Fullest Guide To Protect and Improve Your Health

Vitamin D suddenly became the most ‘popular’ component of our health, since recent research confirmed that there is a direct correlation between Vitamin D deficiency and Coronavirus death rates.

If you have some general health and medical knowledge, you have most likely associated the sunlight vitamin with bone health. However, Vitamin D plays a significant role in a number of bodily functions, including immune system health and protection. Low levels of vitamin D have been associated with frequent infections and in 2009, the National Institute of Health warned that low vitamin D levels are associated with frequent colds and influenza. So it appears that vitamin D helps keep the immune system balanced much like a gymnast walking on a balance beam.  In 2017, a large analyses of prospective clinical trials showed that taking vitamin D reduces the odds of developing a respiratory infection by approximately 42% in people with low baseline levels of 25-hydroxyvitamin D; below 25 ng/mL.3

Vitamin D and Immune System Support Against Viruses

vitamin d and immunity

The flu virus wreaks the most havoc in the winter, abating in the summer months. This seasonality led a British doctor to hypothesize that a sunlight-related “seasonal stimulus” triggered influenza outbreaks.  More than 20 years after this initial hypothesis, several scientists published a paper suggesting that vitamin D may be the seasonal stimulus.  Among the evidence they cite:

  • Vitamin D levels are lowest in the winter months.
  • The active form of vitamin D tempers the damaging inflammatory response of some white blood cells, while it also boosts immune cells’ production of microbe-fighting proteins.
  • Children who have vitamin D-deficiency rickets are more likely to get respiratory infections, while children exposed to sunlight seem to have fewer respiratory infections.
  • Adults who have low vitamin D levels are more likely to report having had a recent cough, cold, or upper respiratory tract infection.

A randomized controlled trial in Japanese school children tested whether taking daily vitamin D supplements would prevent seasonal flu.  The trial followed nearly 340 children for four months during the height of the winter flu season. Half of the study participants received pills that contained 1,200 IU of vitamin D; the other half received placebo pills. Researchers found that type A influenza rates in the vitamin D group were about 40% lower than in the placebo group; there was no significant difference in type B influenza rates.

Although randomized controlled trials exploring the potential of vitamin D to prevent other acute respiratory infections have yielded mixed results,

A large meta-analysis of individual participant data indicated that daily or weekly vitamin D supplementation lowers risk of acute respiratory infections. 

vitamin d and immunity

Check out The 6 Vitamins, Hardest To Get Enough Of 

This effect was particularly prominent for very deficient individuals.

The findings from this large meta-analysis have raised the possibility that low vitamin D levels may also increase risk of or severity of novel coronavirus 2019 (COVID-19) infection. Although there is no direct evidence on this issue because this such a new disease, avoiding low levels of vitamin D makes sense for this and other reasons. And when it comes to limiting risk of COVID-19, it is important to practice careful social distancing and hand washing.

Does Vitamin D give you energy?

does vitamin d give you energy

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Vitamin D is vital for making our muscles work efficiently and boosting energy levels, research from Newcastle University has shown.

A study led by Dr Akash Sinha has shown that muscle function improves with Vitamin D supplements which are thought to enhance the activity of the mitochondria, the batteries of the cell. The researchers used non-invasive magnetic resonance scans to measure the response to exercise in 12 patients with severe deficiency before and after treatment with vitamin D.

Lead author Dr Akash Sinha who also works within the Newcastle upon Tyne Hospitals NHS Foundation Trust said:

“The scans provided a unique window into what is really going on in the muscle as it works.

“Examining this small group of patients with vitamin D deficiency who experienced symptoms of muscle fatigue, we found that those with very low vitamin D levels improved their muscle efficiency significantly when their vitamin D levels were improved.”

Alongside poor bone health, muscle fatigue is a common symptom in vitamin D deficient patients. This fatigue could be due to reduced efficiency of the mitochondria: the ‘power stations’ within each cell of the body.

Mitochondria use glucose and oxygen to make energy in a form that can be used to run the cell – an energy-rich molecule called ATP. Muscle cells need large amounts of ATP for movement and they use phosphocreatine as a ready and available energy source to make ATP. The mitochondria also replenish this phosphocreatine store after muscle contraction and measuring the time taken to replenish these stores is a measure of mitochondrial efficiency: better mitochondrial function is associated with shorter phosphocreatine recovery times.

The team found that these recovery rates significantly improved after the patients took a fixed dose of oral vitamin D for 10-12 weeks.

The average phosphocreatine recovery half time decreased from 34.4 sec to 27.8 sec. All patients reported an improvement in symptoms of fatigue after having taken the supplements. In a parallel study, the group demonstrated that low Vitamin D levels were associated with reduced mitochondrial function.

Dr Sinha added:

“We have proved for the first time a link between vitamin D and mitochondria function.

“Of the patients I see, around 60% are vitamin D deficient and most people living north of Manchester will struggle to process enough vitamin D from sunlight alone, particularly during winter and spring. So a simple vitamin D tablet could help boost your energy levels – from within the cells.”

Where does Vitamin D come from? What are the Best Sources of Vitamin D?

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Vitamin D comes from two places – we take it into our bodies in foods and supplements, and our bodies produce it after sunlight exposure. Vitamin D is found naturally in only a few foods like fatty fish (for example, cod liver oil) and egg yolks. Because there are so few natural dietary sources, vitamin D is added to foods such as fortified soymilk, fortified juice, fortified breakfast cereals, cow’s milk, and margarine. (Vegan spreads like Earth Balance do not have vitamin D added.) Typically, soymilk is fortified with vitamin D2, the vegan form of vitamin D, while cereals, juice, and margarine are fortified with vitamin D3 derived from sheep’s wool. If the label on a fortified food doesn’t say what form of vitamin D is used to fortify the food, you can contact the company.

Recently, United States Department of Agriculture (USDA) scientists reported that mushrooms that had been exposed to ultraviolet B light for 5 minutes had very high levels of vitamin D, close to 3,500 International Units (IU) in a 1-cup serving.4 These vitamin D-containing mushrooms are expected to be commercially available in the next few years and will be a plantbased source of vitamin D.

Besides vitamin D from food and supplements, our bodies are able to make vitamin D when our skin is exposed to ultraviolet B rays from sunlight under certain conditions.

How long in the Sun for Vitamin D?

how long in the sun for vitamin d

Check out 5 Signs of Nutrient Deficiencies That Are Written All Over Your Face

Vitamin D is associated with the sun for a reason — your body can produce its own vitamin D when you expose your skin to the sun for a period of time. About 15 minutes of sun exposure per day is what many experts say is sufficient to make vitamin D. This means you want to have a good amount of skin uncovered by clothing or sunscreen (like your arms and legs) since those things inhibit Vitamin D production, according to Tolentino.

How much sun you should get is also a bit complicated.

“UVB radiation from the sun triggers vitamin D synthesis in our bodies, but there are a lot of factors to consider here,” says Tolentino

She continues, “Where you live (your geographic location), sunscreen usage and coverage and the amount of melanin in your skin can all impact vitamin D absorption. That makes it really difficult to provide generalized guidelines for the appropriate amount of sun exposure. What may be a sufficient or healthy amount of time in the sun with no sun protection for one person might not be advisable for another person.”

Can you get Vitamin D Through a Window? 

can you get vitamin d through a window

Catching the sun’s rays in a sunny office or driving in a car unfortunately won’t help to obtain vitamin D as window glass completely blocks UVB ultraviolet light.

How Many IU of Vitamin D per day?

If there is reason to believe that levels might be low, such as having darker skin or limited sun exposure, taking a supplement of 1000 or 2000 IU per day is reasonable. This amount is now part of many standard multiple vitamin supplements and inexpensive.

Vitamin D toxicity is extremely rare, but does occur with extreme doses. It usually develops over time, since extra vitamin D can build up in the body. Nearly all vitamin D overdoses result from taking high amounts of vitamin D supplements. It is almost impossible to get too much vitamin D from sunlight or food.

What is the Difference Between Vitamin D2 and Vitamin D3 Supplements?

What is the Difference Between Vitamin D2 and Vitamin D3 Supplements?

If you purchase vitamin D supplements, you may see two different forms: vitamin D2 and vitamin D3. Vitamin D2 is made from plants and is found in fortified foods and some supplements. Vitamin D3 is naturally produced in the human body and is found in animal foods. There is ongoing debate whether vitamin D3 “cholecalciferol” is better than vitamin D2 “ergocalciferol” at increasing blood levels of the vitamin. A meta-analysis of randomized controlled trials that compared the effects of vitamin D2 and D3 supplements on blood levels found that D3 supplements tended to raise blood concentrations of the vitamin more and sustained those levels longer than D2. Some experts cite vitamin D3 as the preferred form as it is naturally produced in the body and found in most foods that naturally contain the vitamin.

Can We Get Too Much Vitamin D from Food or from Supplements? 

It is possible to get too much vitamin D, especially by overdoing supplements. Excess vitamin D can cause the body to absorb too much calcium and can lead to kidney damage. The highest safe level of vitamin D for people to take is controversial, with some researchers using up to 10,000 IU per day without seeing problems.2 A conservative recommendation is to stay below 2,000 IU per day. If you have had kidney stones, check with your health care provider before going above 1,000 IU per day.

Will Our Bodies Make Too Much Vitamin D?

Don’t worry about producing too much vitamin D following sun exposure because your skin stops producing it once you’ve had enough. It’s still a good idea to limit sun exposure, however, because of the link between sun exposure and skin cancer.

Guidelines for blood levels of vitamin D are as follows:

  • Sufficient: 20–30 ng/ml, or 50–75 nmol/L.
  • Safe upper limit: 60 ng/ml, or 150 nmol/L.
  • Toxic: Above 150 ng/mL, or 375 nmol/L.

How can I tell if I need vitamin D?

Chances are you do need more vitamin D. Most children and adults in North America and Europe need extra vitamin D. If you want to know for certain, ask your physician to request a blood test for serum 25(OH)D. Most clinical investigators today would recommend the result be at least 40 ng/mL. A recent, informal survey of the principal clinical scientists working in the vitamin D field revealed that each of them, to a
person, considered himself or herself to be vitamin D deficient.

Do vitamin D supplements expire?

Yes. An expiration date will be printed on the label; look for it and use it while it is fresh. “Expire” means the supplement has lost some of its potency. If you use expired vitamin D, you won’t be harmed, but you may no longer be getting as much as the label says.

Is Vitamin D a Special Concern for Vegans?

A vegan diet can be planned to provide adequate amounts of vitamin D through use of fortified foods like fortified soymilk. Any person, whether vegan or not, who does not include good sources of vitamin D in his or her diet or take vitamin D supplements can be at risk for not getting adequate vitamin D, especially if sunlight exposure is limited.

Check out Vitamin D for Vegans: The Full Lowdown on the Sunlight Vitamin

Does milk have vitamin D?

These days, milk is almost always fortified with vitamin D and the reason dates back to the 1900s. At the turn of the century, rickets ―a childhood bone disorder that can lead to weak and soft bones, stunted growth and sometimes skeletal deformities ―was rampant. Roughly 80 percent of children in Boston suffered from it. The cause of rickets is a deficiency in vitamin D or calcium.

Cow milk, however, can have many harmful effects to the body, which you can read about here. Cow milk certainly isn’t a mandatory requirement in your diet in order to source enough of the sunlight vitamin.

Check out 7 Proven Ways Milk And Dairy Products Are Making You Sick 

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Vitamin D Sources for Vegans

Fortified Plant Milks Vitamin D
(IU per 8-oz. Serving)
Living Harvest Hemp Milk 160
Silk Soymilk 120
Pacific UltraSoy 100
Soy Dream Enriched 100
West Plus Soymilk 100
Almond Breeze 100
Pacific Almond Milk 100
Pacific Hazelnut Milk 100
Pacific Oat Milk 100
Rice Dream Enriched 100
Pacific Rice Milk 100
VitaSoy Enriched Soymilk 80
Eden Soy Extra Soymilk 40

These products are examples of foods and supplements that contain vitamin D. Because product formulations change, check labels to get the most recent information. Vitamin D on a label is expressed as a percent of the Daily Value for vitamin D. The Daily Value is 400 IU, so a product that contains 25 percent of the Daily Value for vitamin D would contain 100 IU of vitamin D.

Vegan Supplements Vitamin D
(IU per Tablet/Chew/Capsule/Spray)
Veg Life Supreme Vegan D 2,000
Deva Vegan Vitamin D2 800
Freeda Vitamin D2 400
Now Liquid Multivitamin 400 (per Tbsp.)
Pure Vegan Vitamin D2 Spray 400
Freeda Joint Boost Formula 200
Deva Vegan Cal-Mag-Plus 133
Vegan Life Multivitamin 133
Nutrition Now Vegan Calcium Soft Chews* 100
Prescription 2000 Bone Support Formula 100
Rhino Soft Calcium Chews for Kids 100
Veg Life Vegan Cal-Mag Citrate &#43 D 67
*Assorted Fruit flavor Calcium Soft Chews appear to be free of all animal products; Chocolate flavor contains dairy products.


*There has never been a more critical time to focus on healthy living and eating. You can easily do this with The Complete Vegan Recipe Solution – a complete wellness package with 145 delicious plant-based recipes, scientifically designed to boost your health, strengthen your immune system and help you prevent nutrient deficiencies.*


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  2. Cannell JJ, Vieth R, Umhau JC, Holick MF, Grant WB, Madronich S, Garland CF, Giovannucci E. Epidemic influenza and vitamin D. Epidemiology & Infection. 2006 Dec;134(6):1129-40.
  3. Ginde AA, Mansbach JM, Camargo CA. Association between serum 25-hydroxyvitamin D level and upper respiratory tract infection in the Third National Health and Nutrition Examination Survey. Archives of internal medicine. 2009 Feb 23;169(4):384-90.
  4. Tripkovic L, Lambert H, Hart K, Smith CP, Bucca G, Penson S, Chope G, Hyppönen E, Berry J, Vieth R, Lanham-New S. Comparison of vitamin D2 and vitamin D3 supplementation in raising serum 25-hydroxyvitamin D status: a systematic review and meta-analysis. The American journal of clinical nutrition. 2012 Jun 1;95(6):1357-64.
  5. Wilson LR, Tripkovic L, Hart KH, Lanham-New SA. Vitamin D deficiency as a public health issue: using vitamin D 2 or vitamin D 3 in future fortification strategies. Proceedings of the Nutrition Society. 2017 Aug;76(3):392-9.
  6. Liebman B. Are you Deficient? Nutrition Action Healthletter Nov.
    2006; 23:1, 3-7.
  7. Holick MF. 2007. Vitamin D deficiency. N Engl J Med 357:266-81.

The information contained in this article is for educational and informational purposes only and is not intended as health or medical advice. Always consult a physician or other qualified health provider regarding any questions you may have about a medical condition or health objectives.