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Vitamin D and Immunity -a nutrigenomic view

Nutrigenomics is the scientific discipline that studies the interaction between genes, diet and our health.

Our personal and collective health is at the forefront of most people's minds right now, and the importance of our immune system and the relationship to vitamin D is a huge subject.

Globally, people are experiencing varying symptoms from COVID-19 and research has shown a variety of host factors such as, vitamins C & A, selenium, zinc,manganese and omega -3 status, that may impact an individual's response to a respiratory infection.

It is clear that vitamin D plays a vital role in human health far beyond the commonly accepted areas of mineral metabolism and bone health.

As we age, there is a decline in immune function as well as bacterial diversity in the gut and dysfunction in the gut barrier. Age-related decline in T cell function and increased low-grade chronic inflammation contribute to a compromised immune defence system.

Nutritional and environmental interventions can be enhanced in order to improve and support the immune function.

Vitamin D3 promotes the intestinal absorption of phosphate and calcium and is essential for cellular function and immunity due to its control over calcium homeostasis as well as modulating the response between the innate and adaptive immune system. It is worth noting that vitamin D deficiency extends way beyond rickets and osteoporosis.

Vitamin D deficiency, or insufficiency is associated with cardiovascular disease and increased autoimmunity such as type 1 diabetes, rheumatoid arthritis, inflammatory bowel disease and susceptibility to infection.

The immune system defends the body from foreign, invading organisms while promoting a protective immunity and tolerance to self. When there is an imbalance in this sensitive and complex network, autoimmunity can result. Metabolism, inflammation and immunity are closely linked and impacted by a variation in gene expression and environment.

This is a peek into the nutrigenomic aspect of the Vitamin D Receptor gene (VDR) and the altered genomic response to vitamin D.

The most effective form of vitamin D is via UV-B exposure from sunlight. Humans can synthesize (manufacture) vitamin D3 in their skin, but an individual's molecular response to absorption and transportation of vitamin D varies greatly in their genetic makeup.

There are 4 well-known VDR SNP's (Apa1, Bsm1, Taq1 and Fok1) that have been studied for their potential role in autoimmunity. There is much on-going research into this field along with the current developments in COVID-19 symptoms and genetic response to inflammation and immune system triggers.

Variations in HLA genes (human leucocyte antigens) particularly in the skin, gut and lungs also present some interesting insights into human immune response.

Vitamin D metabolism plays a role in maintaining a balance between pro-inflammatory and anti-inflammatory reactions.

SNP's on Cytochrome P450 genes such as CYP2R1 & CYP27B1 may also impact the activation of vitamin D as it passes from the liver to the kidneys. Obesity, as always plays a negative role as well.

Our lifestyles can impact our exposure to sunlight and the application of sunblock and protective clothing, as well as working indoors can reduce this effect as well. Variations in skin colour and ethnicity can also impact the effect of a genetic variation in the VDR gene expression. Diet alone may not be enough and vitamin D supplementation may be required for many people. A study published in 2007, (Holick, M.F. N Engl. J. Med) estimated that more than a billion people worldwide, were deficient in vitamin D.

Fatty fish such as tuna, herring, salmon, sardines and mackerel are good sources of dietary vitamin D. Liver, cheese, egg yolks and shitake mushrooms are great too. Some countries fortify foods such as milk, orange juice and cereals with vitamin D, however the dosage may not be high enough to induce gene expression.

Some Functional Medicine practitioners are prescribing very high-dose vitamin D in conjunction with closely monitored PTH (parathyroid hormone) and urinary calcium measurements to determine optimal and personalised treatments for many autoimmune disorders.

If you have a SNP in your VDR gene, or think you may be at risk for vitamin D deficiency, consult your medical practitioner and get your 25(OH)D (plasma vitamin D) checked.

To make the most of your ability to synthesize vitamin D, try and get into the sunshine without sunblock for the first 15-20 minutes, and then apply sunblock to protect your skin from overexposure to sun damage.

As with most things in life, finding balance is the key to health and the pursuit of wellness.


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