Vitamin D & Immunity

Every cold and flu season we encourage people to invest in healthy vitamin D levels. Once thought to be only involved in bone health, a wealth of evidence has been found over the past two decades that demonstrate Vitamin D3 is perhaps the most important nutrient for supporting the function of the immune system. There is statistically significant evidence that low levels of Vitamin D are associated with auto-immune diseases and a greater risk of viral and bacterial infection (1).

Since the global COVID-19 pandemic is viral in nature, it begs the question on whether this novel coronavirus responds to Vitamin D the way that so many other infectious viruses do. So far, the evidence is very promising. There are now three major studies that have shown correlation between low Vitamin D levels with poor or fatal outcomes of COVID-19 infections (2).


The most recent one was just published in September, and it demonstrated a 50% higher risk of contraction in people with low Vitamin D levels (3). Now, that is a very strong statistic, but unfortunately, like all things related to the SARS-CoV-2 virus, we still don’t know the best way to use this information. Part of the problem is that there is no magic dose of Vitamin D that will guarantee you protection. Our needs are all different, because we all have unique biochemistry. So recommending a “one size fits all” model could be dangerous if someone were to regard Vitamin D, or really any other tool in the battle against the pandemic, as if it were some kind of holy grail.  

The scientific way to approach this is to have your blood levels tested. Classic deficiency was defined as 20 ng/mL (which was defined back in the days when we thought that D was only for bone health), but the optimal range is likely much higher since toxicity symptoms generally do not occur under 150ng/mL. Unfortunately, most of the hard clinical research on this subject focused on levels required to preserve bone integrity and did not correlate serum levels with boosted immune system responses, leading to a lack of objective consensus on whether 30, 60, or 80 ng/mL is optimal. Those are the three most common numbers batted around by nutritionists.

For home use, it is not rare for people to use 5,000 or 10,000 IU long term with no adverse effects, while doses of 400IU for children and 2,000IU for adults are likely adequate to maintain healthy levels for those who test in the normal range. When a patient tests with clinically low serum D3 levels, it is not unreasonable for a physician to temporarily apply dosages of 50,000IU to boost those levels, which is clinically considered to be safe, at least while treating a measurable deficiency. Without the test, though, you are just guessing on your needs.

We are supposed to be able to make Vitamin D from being exposed to the sun, but during the fall and winter months, the UV spectrum is not in the right range, so it is very common for our blood levels to drop, which brings us back to the very reason why we look into this every cold and flu season. Yet, this year, it has become far more important than ever before.

If you have questions about vitamin D use, feel free to ask at your next chiropractic appointment.

 (1). Aranow C. Vitamin D and the Immune System. J Investig Med. Aug 2011; 59(6): 881-6.
(2) Meltzer, DO; Best, TJ; Zhang, H; et al. Association of Vitamin D Status and Other Clinical Characteristics With COVID-19 Test Results. JAMA Netw Open, 2020; 3(9) e2019722.doi:10.1001/jamanetworkopen. 2020.19722
 Ilie, PC;  Stefanescu, S; Smith, L. The Role of Vitamin D in the Prevention of Coronavirus Disease 2019 Infection and Mortality. Aging Clin Exp Res. 2020 Jul;22(7): 1195-1198.
(3) Kaufman, HW; Niles, JK; Kroll, MH; Bi, C; Holick, MF. SARS-CoV-2 Positivity Rates Associated With Circulating 25-HydroxyVitamin D Levels. PLOS ONE, September 17, 2020


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