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Why Vitamin D is Better Than the Flu Vaccine Add to cart
A 2009 study published in the Archives of Internal Medicine, the largest study of its kind at the time, revealed the link between common respiratory infections and vitamin D.
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Does Vitamin D Prevent the Flu?


Many who oppose the flu vaccine are strong proponents of Vitamin D’s preventative powers. Medical research around the world shows that in some individuals the ‘sunshine vitamin’ is as effective in flu prevention as the flu vaccine.

One of Vitamin D‘s main roles is modulating immune function. Michael Zasloff, a professor of surgery and pediatrics at Georgetown University Medical Center says,

Vitamin D boosts immunity by stimulating the production of cathelicidin, an antimicrobial protein that serves as a "natural antibiotic" in the body.

Seasonal Support

A BBC article says vitamin D is, “...used by the immune system to help puncture holes in bacteria and viruses.”

Additionally, some studies have demonstrated a specific link between vitamin D in the body and a person’s risk of getting the flu. As the Vitamin D Council says, “People who have low vitamin D levels may have an increased risk of developing influenza.”


Vitamin D and Flu: What the Research Says


According to Dr. Joseph M. Mercola, alternative medicine proponent and osteopathic physician, “your vitamin D level is one of the absolute best flu-prevention and optimal health strategies available.” He also adds that your diet lays the foundation for good immune function and plays a big role in preventing the flu.

To support these claims, below is a review of research which investigates vitamin D’s effectiveness in fighting the flu.

Higher vitamin D levels = Less likely to get colds and flu

A 2009 study published in the Archives of Internal Medicine, the largest study of its kind at the time, revealed the link between common respiratory infections and vitamin D. The study concludes that people with low vitamin D levels are more likely to get colds and the flu than those with higher levels of vitamin D.

The study examined data the Third National Health and Nutrition Examination Survey (NHANES III). Information on nearly 19,000 adults and adolescents who participated in the survey showed that:

...those with the lowest vitamin D levels (less than 10 nanograms per milliliter of blood) were 36% more likely to report having a recent upper respiratory tract infection than those with higher levels (30 ng/mL or higher).

Adit Ginde, MD, MPH of the University of Colorado School of Medicine states that people with respiratory diseases and infections, like asthma or emphysema, are more susceptible to respiratory infections if they have a vitamin D deficiency. Ginde said, "The findings of our study support an important role for vitamin D in prevention of common respiratory infections, such as colds and the flu.”

Vitamin D is better for the flu (and helps with asthma)

In a study done by Japanese researchers which was published in 2010, vitamin D was shown to decrease incidences of the flu in children by 8%. Although this may not sound like much, the flu vaccine only reduces the flu by an average of 1%.

This means that in this study, vitamin D was eight times more effective for combating the flu. In addition, the study also revealed that vitamin D, “strongly suppressed symptoms of asthma”, further showing its effectiveness at regulating respiratory issues.

A summary of 25 controlled trials

In the UK, acute respiratory infections like the flu hospitalize 300,000 people and cause 35,000 deaths annually. Professor Adrian Martineau, a clinical professor of respiratory infection and immunity at Queen Mary University of London led a study which reviewed data from 25 other studies done in 14 countries on vitamin D’s effectiveness for cutting down on respiratory infections. Almost 11,000 participants took part in these various studies.

Dr. Martineau cites a “modest protective effect" of vitamin D and says that overall, vitamin D supplements reduced the risk of respiratory infection by about 10%. Martineau says:

Assuming a UK population of 65 million, and that 70% have at least one acute respiratory infection each year, then daily or weekly vitamin D supplements will mean 3.25 million fewer people would get at least one acute respiratory infection a year.

Martineau concludes by saying, “This research has yielded the first definitive evidence that vitamin D really does protect against respiratory infections.” Here were the key findings:

  • Participants with a vitamin D deficiency saw the most benefits. 
  • Individuals with the biggest vitamin D deficiencies who took it daily reduced their risk of respiratory infection by half.
  • “After adjusting for other potentially influential factors, the researchers found that vitamin D supplementation cut the proportion of participants experiencing at least one acute respiratory tract infection by 12%.”



Getting Enough Vitamin D


Many sources agree that vitamin D supplements won’t reduce the risk of flu in people who aren’t deficient. Yet 40% of Americans are vitamin D deficient because they don’t spend enough time in the sun and don’t eat many vitamin D-rich foods. Also, older people, obese people and those with dark skin are more likely to be deficient. In these individuals, vitamin D supplements do great things by, “reducing the risk of the flu and respiratory infections, including pneumonia.”

Getting Vitamin D Naturally from Sunshine

There are a number of ways to get vitamin D. You can get it from the foods you eat or dietary supplements. But you can also get the ‘sunshine vitamin’ naturally from sunlight. When UV-B rays from direct sunlight strike the skin, your body produces vitamin D. Yet for Americans, who spend on average of 90% of their time indoors, how much ‘sunshine time’ is enough to synthesize vitamin D?

Those who live north of Atlanta (35° latitude in the Northern Hemisphere) can get enough UV-B rays to produce an adequate amount of vitamin D, but only from May to October. The rest of the year, the sun is not high enough for UV-B rays to penetrate the atmosphere. Also, your body only produces vitamin D when sunlight hits your skin directly. Sitting in the shade, wearing sunscreen, and sitting in sunlight filtered by windows doesn’t work.

According to the Vitamin D Council, “when the sun is high enough in the sky, so your shadow is shorter than you are, is the most conservative and sure way to get vitamin D.” A shorter shadow equals more intense sun rays and more exposure to the, “small spectrum ultraviolet radiation that allows for vitamin D production.”

Another helpful guideline suggests being in direct sunlight for about half the time it takes to start to get a sunburn. To learn more about sun exposure and vitamin D production where you live, read these more specific guidelines from the Vitamin D Council.

When the conditions are right, adequate time in the sunshine can produce about 10,000 international units (IU) of vitamin D. The amount of vitamin D your body produces depends on:

  • The time of day 
  • The length of time spent in direct sunlight
  • Your complexion
  • The amount of skin exposed

In general, the more skin you expose to the sun, the more vitamin D your body produces. For example, a fair-skinned person wearing shorts, a tank top, and no sunscreen can get enough vitamin D from about 10 minutes in the sun. Dark-skinned individuals need more time in the sun.

Although direct sunlight produces vitamin D, limiting sun exposure lowers your risk of skin cancer. If you spend more time in the sun that is needed to synthesize vitamin D, wear sunscreen with an SPF of 8 or greater along with protective clothing. If you do not spend regular time in the sun, you should get vitamin D from foods or supplements.


Recommended Daily Dose of Vitamin D


How much vitamin D do you need? Those who are vitamin D deficient need significantly more than those with normal levels. Also, overweight individuals with a higher BMI (body mass index) typically need more than people with a lower BMI. Depending on the source, daily vitamin D recommendations vary:

Vitamin D Council
Recommends that adults take 5000 IU of vitamin D3 daily. 
The Institute of Medicine

Recommends that most adults should get about 600 IU of vitamin D daily and people over 70 should get 800 IU daily. According to the IOM, 4000 IU daily is the most a person should take. Anything above this could be harmful and warns that it is risky to take more than 10,000 IU a day. 

Endocrine Society Practice Guidelines
An adult can safely take up to 10,000 IU of vitamin D3 daily.

Even though the daily vitamin D recommendations are based on the assumption that a person receives little sun exposure, there is a large gap between the recommendations of the IOM and the Vitamin D Council. Dr. Mercola says that vitamin D deficient people need much more than what the IOM suggests:

If it's very low, you may need 8,000 to 10,000 IUs of vitamin D3 per day in order to reach and maintain a clinically relevant level of 45 to 60 nanograms per milliliter (ng/mL)...If you've been supplementing for some time and your levels are still below 45 ng/mL, you then know you have to increase your dose further. If using an oral supplement, also make sure to boost your vitamin K2 and magnesium intake, as these nutrients help optimize vitamin D levels.

Instead of eating more processed foods fortified with vitamin D, Dr. Mercola believes sensible exposure to the sun is the best way to get the vitamin. He only recommends a supplement In certain cases, such as during wintertime when people aren’t spending as much time outdoors.

He also says that most people who are vitamin D deficient cannot reach optimal vitamin D levels through the recommended 600 IUs of vitamin D from fortified foods. However, the amount of vitamin D you need depends on how much is currently in your body. Dr. Mercola suggests getting your vitamin D levels tested twice annually.


Do I Need a Vitamin D Supplement


Although some people are vitamin D deficient, not everyone needs a supplement. Since the body produces it from spending time in the sunshine, you might be able to simply be outside more. Also, you could eat more of certain foods that naturally contain vitamin D. One serving of oily fish, like salmon, has a day’s recommended amount of vitamin D. Plus, many foods are fortified with vitamin D. Lastly, if you already have adequate levels, a supplement won’t bring additional health benefits.

Yet not everyone gets enough time outdoors and not everyone eats a healthy, balanced diet. If someone is not getting the recommended daily amount of vitamin D for their age group, a supplement is a good idea. Regarding supplements, Dr. Martineau says:

The bottom line is that the protective effects of vitamin D supplementation are strongest in those who have the lowest vitamin D levels and when supplementation is given daily or weekly rather than in more widely spaced doses.

Chief academic officer at Winthrop University Hospital and author John Aloia, says that if vitamin D has a positive effect on the immune system it would be necessary to begin taking supplements several months in advance of flu season to build up your levels.

As is the case with any dietary supplement, it is wise to get a professional opinion from a healthcare provider before taking vitamin D. Although it is safe to take, high doses can lead to kidney problems and heart disease. In addition, too much vitamin D can leach calcium from your bones.


Vitamin D Vs The Flu Vaccine


There is a clear, demonstrated link between vitamin D levels in the body and respiratory issues. According to the studies cited above, sufficient vitamin D combats respiratory infections, like the flu, and even helps regulate asthma. In addition, quercetin can also boost your body’s ability to fight viral infections, such as the flu.

And unlike the flu vaccine, which aims at moving targets (constantly-changing viruses) and comes with side effects, vitamin D and quercetin are immune system boosters which keep you healthier in general without side effects.




Vitamin D Supplement Facts

Serving Size 1 softgel Amount Per Serving Daily Value
Servings Per Container 240
Vitamin D3 ( as Cholecalciferol) 5000 IU 1250%

Other ingredients: Organic olive oil, softgel capsule (gelatin, glycerin, purified water).
*Daily Value Not Established




These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.

*Results may vary from person to person.


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