As daylight hours grow colder and shorter, incidences of the common cold, flu, and respiratory infections spike upwards. Scientists have identified reduced vitamin D levels in winter months as a prime suspect for this increase in infectious disease cases.
Vitamin D in all forms (sunlight, sun lamps, or supplements) reduces the incidence of respiratory infections.[24,26] Dutch children with the least sun exposure are twice as likely to develop a cough and three times more likely to develop a runny nose compared with children with the most sun exposure. When Russian athletes were given access to a sun lamp to stimulate vitamin D synthesis in the body, there were 50% fewer respiratory infections and 300% fewer days of absence.
Children with the lowest vitamin D serum levels are 11 times more likely to develop respiratory infection. When 60,000 IU per week of vitamin D was administered (for six weeks) to children with frequent respiratory infections, the result was a complete disappearance of such infections in the following six months.
In a controlled trial of African women, a low dose (800 IU a day) of vitamin D resulted in a 3-fold reduction in cold and flu symptoms compared to those given placebo. Influenza kills thousands of Americans each year. Ensuring optimal vitamin D status could slash influenza incidence and morality.
How Vitamin D Boosts Immune Function and Suppresses Inflammation
When Vitamin D is lacking, we become a prime target for the flu, including the H1N1 Swine Flu. By contrast, individuals with sufficient levels of Vitamin D are able to fight off or throw off these attacking pathogens. Vitamin D boosts the innate immune response in many ways, but in particular by turning on an antimicrobial protein.
Vitamin D also balances the immune response, preventing inflammation that can lead to flu-related complications such as bacterial pneumonia or lung infection. Inflammation was the leading cause of deaths in the 1918 influenza pandemic and it appears to be the leading cause of death in deaths from SARS-CoV-2.
Flu viruses (including swine flu) and SARS Coronaviruses induce a massive inflammatory response that can kill the victim. In other words, it is not the virus that often kills, but the body’s hyper-reaction to the virus—in the form of uncontrolled over-production of pro-inflammatory cytokines. Vitamin D down-regulates the expression of pro-inflammatory cytokines such as tumor necrosis factor-alpha. 
As people age, they often over-express these same destructive pro-inflammatory cytokines. The result is chronic low-level inflammation that damages aging arteries, joints, and neurons[40-44]. By down-regulating excess pro-inflammatory cytokine production, vitamin D could save the lives of those stricken with acute influenza, Coronaviruses, or the dozens of other inflammatory diseases that afflict millions of aging Americans each year.
Antimicrobial peptides found in Vitamin D, known as Cathelecidins, are components of the immune system that protect against bacterial, fungal and viral infections. Secreted by immune cells throughout the body, Cathelecidins damage the outer lipid membrane of infectious agents (including influenza and coronaviruses), rending them vulnerable to eradication. A daily oral dose of 4000 iu of Vitamin D3 dramatically induces the production of Catehlecidin.
Recent studies confirm that vitamin D dramatically up-regulates the expression of these antimicrobial peptides in immune cells. We now have a definitive biological mechanism to explain why vitamin D confers such dramatic protection against common winter illnesses.
Testing Your Vitamin D Blood Levels
When blood is tested to assess Vitamin D status, what is actually measured is the metabolically active 25-hydroxyvitamin D form of the vitamin in the serum. This form is known as Vitamin D3.
When data emerged about vitamin D’s role in preventing disease, experts initially recommended a minimum target blood level of 30 ng/mL of 25-hydroxyvitamin D. In recognition of findings showing reduced incidences of disease in those with higher vitamin D levels, the standard laboratory reference range for 25-hydroxyvitamin D was raised to 32-100 ng/mL.
Based on recent and conclusive published studies, the new minimum target level for optimal disease prevention is over 50 ng/mL of Vitamin D3.[46-51]
A startling 36% [52-55,56] of the general population has 25-hydroxyvitamin D levels below 20 ng/dL, which may represent the world’s leading cause of unnecessary disease and death.
What Can Be Done this Flu Season?
As Bill Faloon of the Life Extension Foundation has pointed out, many doctors are not trained to recognize a Vitamin D deficiency until rickets develop in children or osteomalacia (softening of the bones) develops in adults . Even so, many doctors are now urging their patients to supplement with Vitamin D-3.
Whether your doctor is up to date or not, you should take the initiative. Have your Vitamin D level checked. If you are below an optimum Vitamin D level, take a Vitamin D-3 supplement. Changing your diet alone cannot create optimal Vitamin D levels. Only supplementation or sufficient exposure to the sun (without sun block and when the sun’s rays are sufficiently strong) can do that.
The blood work that checks Vitamin D status is called the 25, hydroxy vitamin D test. Some experts are satisfied with a minimum reading of 30 ng/ml, but it is doubtful that this is high enough to make your immune system work at optimal levels. While a level of 30 ng/ml defines the bottom of the normal range, Integrative doctors often like to see levels of 70 or 80 (but no higher than 100) ng/ml. Use of the blood test is the best way to prevent over-dosing.
Seniors are especially apt to be vitamin D deficient and have been found to be less likely to succumb to all causes of mortality when they have optimal levels of vitamin D. Young people are also often deficient even though Vitamin D is essential as the body grows and matures.
The most recent Harvard Heart Letter confirms that at least one-third of Americans of all ages are Vitamin D deficient. “Deficient” in this instance was defined as less than 20 ng/ml of 25-hydroxy vitamin D. The Harvard letter stated that supplements are the simplest and safest way to get Vitamin D and recommended 800 to 1,000 IU from supplements as a daily goal. The Vitamin D Council recommends 5,000 IU daily, but in conjunction with blood testing. The U.S. government claims to be highly concerned about Swine flu and the general health of the American public, but does not even recommend 800 IU. For the most part, it says nothing.
For more research on Vitamin D see the following:
- NaturalNews.com provides links to more than 200 featured Vitamin D articles.
- Natural Health Science News, includes studies that explain how Vitamin D works to prevent flus and respiratory disease as well as to minimize flu symptoms
- Vitamin D Council also features numerous studies on influenza and Vitamin D
- Life Extension Magazine also provides additional important articles (shown below), covering the critical role of Vitamin D and an assessment of just how Vitamin D deficient we all probably are.
- Take Action and help us end the Government’s Silence on Vitamin D’s use in Preventing the flu
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Source: Alliance for Natural Health