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Vitamin D and Your Immunity

Updated: Nov 1, 2023

Since the pandemic, and especially during the winter months we should be aware of our vitamin D status. A very recent retrospective cohort study published in the JAMA Network (2020), concluded that vitamin D deficiency was associated with an almost doubled increased risk of contracting the COVID-19 infection (1).

We can easily get deficient in Vitamin D, especially during the winter months, so, besides protecting us against the virus, it’s important to know some of the other reasons why getting enough of this fat soluble vitamin is so vitally essential to our health and wellbeing.

So why do we need it? Here are 6 more reasons to ensure you get an adequate supply:

  1. Vitamin D protects bone density, so therefore we need it to prevent osteoporosis.

  2. Reduces depression and enhances the mood.

  3. Alleviates musculoskeletal pain.

  4. Vitamin D is implicated in the prevention of Cardiovascular disease, Rickets, Depression, Type 1 Diabetes, Cancer, Epilepsy, Polycystic Ovary Syndrome, and Multiple Sclerosis.

  5. Improves our overall sense of wellbeing (2).

  6. Balances Th-1 and Th-2 immune system responses, therefore plays a role in the prevention of autoimmune diseases such as Hashimoto’s thyroiditis, Graves disease, and rheumatoid arthritis (3).

Vitamin D is not actually a vitamin at all, it is a hormone (or a pro-hormone) and it plays a role in influencing hormone receptor gene interactions, which can then influence disease expression (2).

Interestingly, recent research is also showing evidence to support the hypothesis that vitamin D positively influences the composition of the gastrointestinal microbiota , although further studies are needed to fully understand the extent that vitamin D can modulate the gut microbiome (4).

There are 3 ways to get Vitamin D:

  • From the sun

  • From supplements

  • Limited amounts from food

By far the best and most natural way to get our vitamin D (or Vitamin D3 – cholecalciferol) is from the sun. For this to occur, we need to expose as much of our skin as possible to the sun to get Ultraviolet B (or UVB). And it doesn’t take long. In fact, you can get adequate daily vitamin D3 from the sun in half the time then it takes to get a tan, or to burn. Fifteen minutes of full body exposure (or as much as possible) should be plenty for most people. Your skin will produce more Vitamin D when it is exposed to the sun during the middle of the day.

However, people with dark skin require more exposure, as pale skin makes vitamin D more quickly than dark skin. This is because the pigments in dark or black skin, acts as a natural sunscreen.

Obviously, in the UK we don’t always get the opportunity to get enough sun exposure, therefore we need to look at other ways of ensuring we get a good supply of vitamin D.

There are only a few foods that contain vitamin D, oily fish, egg yolks, beef liver, vitamin D-enriched mushrooms, and fortified foods. Unfortunately, these foods only have small amounts, which are not enough for our body’s needs. Therefore, supplementing with vitamin D is a recommended strategy especially for those living in colder climates.

Unless you are getting 15 minutes of full skin exposure to the sun on a daily basis, then supplementation is the way to go. Very black skin may require up to 2 hours in the sun to get adequate amounts.

Various government organisations recommend daily dosages of 600IU (International Units) per day for adults and children, and 400IU for infants. The Vitamin D Council recommends 5000IU per day adults, however dosages between 2000IU and 4000IU are often used safely, depending on your current levels, and your genetic predisposition.

Bear in mind that vitamin D is a fat-soluble vitamin, and it can be difficult for the body to get rid of large amounts, however, for toxicity to occur, you would need to be taking around 40,000IU/day for at least 2 months. Research has shown that some disease states, like multiple sclerosis and prostate cancer, may benefit from high doses (5).

Always ensure that your supplement is Vitamin D3, which is the same type that we get from the sun, and not vitamin D2. Please be aware that most D3 supplements are not vegetarian, but vegetarian and vegan supplements are also available.

** If you are taking certain heart medications like digoxin, thiazide diuretics, or medication for high blood pressure, then please don’t take high doses of vitamin D. Other conditions that require caution include Hodgkin’s and non-Hodgkin’s lymphoma; hyperparathyroidism; kidney, liver or hormonal diseases. Always check with your GP to ensure you are taking a safe amount.

When exposed to the sun, it is important not to allow your skin to burn. As there is contradictory research on the use of sunscreens for preventing various skin cancers, it is always a safer option to protect your skin (after your 15 minutes of exposure) by wearing suitable clothing or getting into the shade, to avoid getting too much sun exposure. Infants have very delicate skin and extra care should be taken to avoid sunburn.

Choose a natural sunscreen product if necessary. There are many on the market now without the harmful chemicals, which can be toxic to us, and the marine environment (6).

Always look for a natural and organic product that uses titanium oxide or zinc oxide, as opposed to oxybenzone or octinoxate as the main sunscreen agent. Reputable companies in the UK include Green People, JÂSÖN, UVBIO, EQ, Neils Yard, Lavera, and Yaoh.

This article was written by Helen Ross, a degree qualified registered nutritionist, mBANT CNHC, and owner of The Well Life Lab. She specialises in IBS and natural solutions for a healthy gut.

My clinic is currently operating in a virtual setting, via Zoom or Skype, so distance is not an issue. Book in for a FREE 15 minute call so we can determine how best I may be able to help you find relief from your symptoms.

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  1. Meltzer, D. O. et al. (2020) ‘Association of Vitamin D Status and Other Clinical Characteristics With COVID-19 Test Results’, JAMA network open. doi: 10.1001/jamanetworkopen.2020.19722.

  2. Institute for Functional Medicine, 2005. The Textbook of Functional Medicine,

  3. Wentz PhD., I., 2013. Hashimoto’s Thyroiditis: Lifestyle Interventions for finding and treating the Root Cause,

  4. Waterhouse, M. et al. (2019) ‘Vitamin D and the gut microbiome: a systematic review of in vivo studies’, European Journal of Nutrition. doi: 10.1007/s00394-018-1842-7.


  6. Downs, C.A. et al., 2016. Toxicopathological Effects of the Sunscreen UV Filter, Oxybenzone (Benzophenone-3), on Coral Planulae and Cultured Primary Cells and Its Environmental Contamination in Hawaii and the U.S. Virgin Islands. Archives of Environmental Contamination and Toxicology, 70(2), pp.265–288.

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