• Published on: Apr 17, 2020
  • 4 minute read
  • By: Dr Rajan Choudhary

Vitamin D In Reducing The Risk Of COVID 19

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Why Vitamin D is the only supplement we will recommend for you.

Most of our blogs have looked at theories posted on social media, and shown how they are usually not true, or have no factual basis behind them. But here we will show some evidence that supports something truly interesting, especially during the time of this pandemic.

For a number of years research has shown a possible link between vitamin D and illnesses, specifically respiratory infections. In our previous blogs we have shown that vitamin supplementation is unnecessary, except for vitamin D. Here we will show why supplementation may be in your best interest for reducing the risk of COVID.

Now I’ll be honest. Vitamin D and immunity was not something we were taught at medical school, or in medical practice. The fact that such a large amount of research exists on this topic is certainly interesting, and whilst researching this topic I have certainly learnt a lot myself, enough to change my own medical practice. And it is because of the high quality of evidence present that I feel confident in supporting the claims below.

SUMMARY

  • Many people are low in Vitamin D due to various risk factors (see our blog on vitamin D)
  • Vitamin D appears to have a role in modulating immune function
  • Low Vitamin D levels appear to increase the severity of autoimmune disorders
  • Low Vitamin D levels appear to increase the risk of getting respiratory infections
  • Vitamin D supplementation appears to reduce the risk of getting respiratory infections
  • Those who are at risk of having low vitamin D should take low dose supplementations.

If you want the good stuff, skip to the section on SUPPLEMENTATION

IMMUNE FUNCTIONS

As we’ve discussed, vitamin D is key in maintaining the right balance of calcium, ensuring the right amount is taken up from the food we eat, integrated into our bones, and removed in our urine if not required. We know that there are some people who are at risk of vitamin D deficiency, and this is more common in countries closer to the poles and with cloudy weather.

But there also appears to be a role for vitamin D in modulating the immune system. We have found many more cells in our body other than bone, intestine and kidney that possess the vitamin D receptor. These include immune cells, and one role may be to promote proliferation of these cells as well as promote their protective immunity.

AUTOIMMUNE

Due to its role in immune function, studies have been performed to see whether there is a link between autoimmune diseases and vitamin D. Common autoimmune disorders (and the organs the affect) include multiple sclerosis (nerves), rheumatoid arthritis (joints), diabetes mellitus (pancreas), inflammatory bowel disease (bowels) and systemic lupus erythematous (the entire body). All of these diseases lead to loss in function of an organ or system as the immune system recognises the organ as an “invader” and begins to destroy it.

One study looked at 161 patients with early forms of autoimmune diseases over 2 years. Out of them, 35 went on to develop full blown autoimmune disorders (like rheumatoid and lupus). Whilst the two groups of patients were mostly similar, vitamin D was noticeably lower in the group that progressed to disease. But this is one study, with a small number of patients.

Other studies have looked at vitamin D levels in patients across the globe, and the majority of them have shown there to be a correlation between low vitamin D or severe deficiency, and the severity of autoimmune disorder they have. We will not go into them in detail because this is beyond the scope of this blog, but it certainly is interesting and supports this new role for vitamin D.

RESPIRATORY INFECTIONS

We have unknowingly tried to use Vitamin D to treat infections prior to the advent of antibiotics. A common treatment for tuberculosis was to send patients to sanatoriums, where treatments included exposure to sunlight, and provision of cod liver oil, a rich source of vitamin D.

Large population studies done in the 1980s and 1990s involving 19,000 people showed that those with low vitamin D levels were more likely to self report recent upper respiratory tract infections than those with normal levels. This was true even if age, gender, season and race were accounted for. Similar studies have shown similar results when looking at rates of influenza, bacterial vaginosis and HIV.

Normally we are very skeptical with such studies, and look for weaknesses in their methodology and conclusions. After all, we could just cherry pick the studies that show a benefit. Furthermore, just because there is a trend with vitamin D levels and infection, this does not imply a direct link. More evidence is required. However, the fact 19,000 people were surveyed provides this study with good statistical power, and lends it validity. But lets look for more.

SUPPLEMENTATION

Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data – Martineau 2017, British Medical Journal

A systematic review and meta analysis is the highest level of evidence in the realm of medical research. It is the absolute pinnacle of thorough research, looking and comparing other studies with very close scrutiny to see whether we have conducted enough research worldwide to support a theory. In this case this systematic review was published in the British Medical Journal, a highly reputable source that again scrutinises any study submitted thoroughly before accepting it for publication. In my eyes, this is some of the best evidence we will have on this topic. And it is a far sight better than any WhatsApp forwards.

So what does this say?

Vitamin D supplementation was safe and it protected against acute respiratory tract infection overall. Patients who were very vitamin D deficient and those not receiving bolus doses experienced the most benefit.

I don’t think I could have summarised it better myself. If you wish to read the study yourself you can use this link: https://www.bmj.com/content/356/bmj.i6583 Vitamin D supplementation to prevent acute respiratory tract infections

WHAT DOES THIS MEAN FOR ME?

If you are someone who may be at risk of vitamin D deficiency, then low dose supplements (NOT treatment dose) may be beneficial in reducing the risk of getting a respiratory infection. Since COVID is caused by a respiratory virus, we can extrapolate that Vitamin D supplementations may reduce your risk of getting COVID. This is not a cure, and it is not a guaranteed protection. If you already have a balanced diet and are not low in Vit D, it may be less beneficial.

Dr Rajan Choudhary, UK, Chief Product Officer, Second Medic Inc

www.secondmedic.com

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Frequent

Early Signs of a Weakened Immune System: Symptoms You Should Not Ignore

The immune system is the body’s natural defense mechanism against infections, bacteria and viruses. It works continuously to identify and eliminate harmful pathogens that may threaten health. However, when the immune system becomes weakened, the body becomes more vulnerable to illness and infections.

Recognizing the early signs of a weakened immune system is essential for maintaining overall health and preventing serious complications. Early awareness allows individuals to make lifestyle changes and seek medical advice if necessary.

 

Understanding the Immune System

The immune system is composed of:

  • White blood cells
     

  • Antibodies
     

  • Lymph nodes
     

  • Bone marrow
     

  • The spleen and thymus
     

These components work together to detect and destroy harmful organisms. When immunity is compromised, this protective mechanism becomes less effective.

 

1. Frequent Infections

One of the most common signs of weakened immunity is experiencing frequent infections.

These may include:

  • Recurrent colds
     

  • Sinus infections
     

  • Ear infections
     

  • Respiratory illnesses
     

If infections occur repeatedly or take longer than usual to recover, it may indicate reduced immune strength.

 

2. Persistent Fatigue

Constant tiredness despite adequate sleep may signal an underlying immune imbalance.

When the immune system is weakened, the body uses more energy to fight potential threats, leading to prolonged fatigue.

3. Slow Wound Healing

A healthy immune system supports tissue repair and healing.

Cuts, bruises or minor injuries that take longer than usual to heal may indicate weakened immune function.

Delayed healing may also increase infection risk.

 

4. Digestive Problems

A significant portion of the immune system is located in the gastrointestinal tract.

Digestive symptoms such as:

  • Frequent diarrhea
     

  • Bloating
     

  • Constipation
     

may reflect imbalance in gut health and immunity.

 

5. Frequent Allergies or Sensitivities

A weakened immune system may overreact to harmless substances, causing allergic reactions.

Symptoms may include:

  • Sneezing
     

  • Skin irritation
     

  • Food sensitivities
     

Maintaining immune balance helps regulate these responses.

 

6. Recurring Fever

Frequent low-grade fever may occur when the body is constantly attempting to fight infections.

This may indicate ongoing immune stress.

 

7. Increased Susceptibility to Stress

Chronic stress significantly affects immune function.

Stress hormones such as cortisol may suppress immune responses, making the body more vulnerable to illness.

 

Common Causes of Weak Immunity

Several lifestyle and health factors can weaken the immune system:

  • Poor nutrition
     

  • Lack of sleep
     

  • Chronic stress
     

  • Sedentary lifestyle
     

  • Smoking or excessive alcohol consumption
     

  • Chronic illnesses
     

Identifying these factors is important for improving immune health.

 

Strengthening the Immune System Naturally

Maintain a Balanced Diet

Consume foods rich in:

  • Vitamin C
     

  • Vitamin D
     

  • Zinc
     

  • Antioxidants
     

Fruits, vegetables, nuts and whole grains support immune function.

 

Prioritize Sleep

Adequate sleep allows the immune system to repair and regenerate.

Adults should aim for 7–8 hours of sleep daily.

 

Stay Physically Active

Moderate physical activity improves circulation and supports immune response.

Regular exercise also reduces stress levels.

 

Manage Stress

Practices such as meditation, breathing exercises and relaxation techniques help regulate stress hormones.

 

Maintain Hygiene

Simple habits like handwashing reduce exposure to harmful pathogens.

 

Weak Immunity in the Indian Context

In India, factors such as nutritional deficiencies, pollution exposure and high stress levels contribute to weakened immunity among many individuals.

Public health initiatives increasingly emphasize balanced nutrition, vaccination and healthy lifestyle habits to improve immune resilience.

 

When to Consult a Doctor

Seek medical advice if you experience:

  • Frequent infections
     

  • Persistent fatigue
     

  • Unexplained weight loss
     

  • Recurrent fever
     

  • Slow healing wounds
     

Medical evaluation may identify underlying health conditions affecting immunity.

 

Conclusion

Recognizing the early signs of a weakened immune system is essential for protecting long-term health. Symptoms such as frequent infections, fatigue and slow wound healing may indicate that the body’s defense mechanisms need support.

By adopting healthy lifestyle habits, maintaining balanced nutrition and managing stress effectively, individuals can strengthen immune function and reduce the risk of illness.

Listening to the body’s warning signals and seeking timely medical guidance ensures better health outcomes and improved wellbeing.

A strong immune system is the foundation of a healthy life.

 

References

  • Indian Council of Medical Research – Immunity and Nutrition Reports

  • World Health Organization – Immune Health Guidelines

  • National Institute of Nutrition India – Dietary Recommendations

  • Journal of Clinical Immunology – Immune System Research

  • Lancet Global Health – Public Health and Immunity Studies

See all

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