Supplement Series: Vitamin D (Part 5 of 5)
Welcome back to our 5-part expert series on Vitamin D.
In our previous post, we talked about the importance of vitamin D in promoting a healthy metabolism and keeping your cholesterol in check.
In the final part of our vitamin D supplement series, we are exploring something that’s been on everyone’s minds lately – the string of winter infections. From influenza and the common cold to coronavirus and respiratory syncytial virus, keeping your immune system strong is one of the best ways to combat these viruses.
Vitamin D plays an important role in your immune system by helping to regulate inflammation, strengthen your body’s natural defence against viruses and bacteria, and fight off infections.[1] Research has shown that people with lower levels of vitamin D are more likely to suffer from frequent colds and flu-like illnesses than those with adequate levels of vitamin D.[2]
What are the links?
The first line of defence against infection is a healthy immune system which is supported by adequate levels of vitamin D. Receptors that respond to this important nutrient are found in almost every single immune cell in the body, highlighting its immunomodulatory and anti-infectious properties.[3]
A study published in 2017 found that people who took regular doses of high-quality vitamin D supplements had half the risk of developing respiratory infections compared to those who did not take any supplements.[4] This suggests that supplementing with vitamin D can improve your body’s ability to fight off infections like viruses and bacteria. This makes sense then that those with a blood level above 75 nmol/L (30 ng/mL) are at a 7x less risk of catching influenza.[5] The nutrient also boosts proteins that protect against bacterial [6,7] and viral infections.[8, 9]
Vitamin D also reduces inflammatory biomarkers like C-reactive protein in the body.[10] This is why scientists are interested in the fact that inflammatory disorders like rheumatoid arthritis are more prevalent in northern climates and winter months.[11] While inflammation can be protective in the short term against all manner of pathogens, chronic inflammation weakens our defence systems and allows viruses and bacteria to run rampant. A team of researchers aptly named this dichotomy, “From Jekyll to Hyde.”[12]
How does it complement other public health measures?
The first defence for many is the annual influenza vaccination, especially in vulnerable populations like the elderly or immunocompromised. It is known that vaccine efficacy is lower for the elderly compared to young adults [13,14], and this led researchers to ask the question – why? One group proposed it could be related to the lower levels of vitamin D in that age group, so they put it to the test. Their study, published in 2019, found that elderly folks who were supplemented with vitamin D had a higher TGFβ plasma level in response to the influenza vaccine.[15]
Vitamin D is an essential nutrient for keeping your immune system functioning at its best.
Research has shown that supplementing with vitamin D can help reduce your risk for respiratory infections and support a balanced inflammatory response, reducing your risk for developing chronic illnesses like allergies or asthma.
We hope this blog series has helped you learn more about why it's so important to get enough vitamin D. If you're looking to add some extra protection to your diet, talk to a licensed ND about adding a daily dose of high-quality vitamin D supplements into your routine.
It could make all the difference when it comes to keeping you healthy this winter season!
References
Reider, Carroll A., et al. "Inadequacy of immune health nutrients: Intakes in US adults, the 2005–2016 NHANES." Nutrients 12.6 (2020): 1735.
Prietl, Barbara, et al. "Vitamin D and immune function." Nutrients 5.7 (2013): 2502-2521.
Takahashi, Katsushi, et al. "Human neutrophils express messenger RNA of vitamin D receptor and respond to 1 α, 25-dihydroxyvitamin D3." Immunopharmacology and immunotoxicology 24.3 (2002): 335-347.
Martineau, Adrian R., et al. "Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data." bmj 356 (2017).
Nanri, Akiko, et al. "Association of serum 25-hydroxyvitamin D with influenza in case-control study nested in a cohort of Japanese employees." Clinical Nutrition 36.5 (2017): 1288-1293.
Liu, Philip T., et al. "Toll-like receptor triggering of a vitamin D-mediated human antimicrobial response." Science 311.5768 (2006): 1770-1773.
Hansdottir, Sif, et al. "Respiratory epithelial cells convert inactive vitamin D to its active form: potential effects on host defense." The Journal of Immunology 181.10 (2008): 7090-7099.
Barlow, Peter G., et al. "Antiviral activity and increased host defense against influenza infection elicited by the human cathelicidin LL-37." PloS one 6.10 (2011): e25333.
White, Mitchell R., et al. "Collectins, H-ficolin and LL-37 reduce influence viral replication in human monocytes and modulate virus-induced cytokine production." Innate Immunity 23.1 (2017): 77-88.
Trombetta, Amelia C., Sabrina Paolino, and Maurizio Cutolo. "Vitamin D, inflammation and immunity: review of literature and considerations on recent translational and clinical research developments." The Open Rheumatology Journal 12.1 (2018).
Cutolo, M., et al. "Circannual vitamin d serum levels and disease activity in rheumatoid arthritis: Northern versus Southern Europe." Clin Exp Rheumatol 24.6 (2006): 702-4.
Zhou, Ang, and Elina Hyppönen. "Vitamin D deficiency and C-reactive protein: a bidirectional Mendelian randomization study." International Journal of Epidemiology (2022).
Xu, Weili, and Anis Larbi. "Immunity and inflammation: from Jekyll to Hyde." Experimental Gerontology 107 (2018): 98-101.
Goodwin, Katherine, Cécile Viboud, and Lone Simonsen. "Antibody response to influenza vaccination in the elderly: a quantitative review." Vaccine 24.8 (2006): 1159-1169.
Jackson, Lisa A., et al. "Evidence of bias in estimates of influenza vaccine effectiveness in seniors." International journal of epidemiology 35.2 (2006): 337-344.
Goncalves-Mendes, Nicolas, et al. "Impact of vitamin D supplementation on influenza vaccine response and immune functions in deficient elderly persons: a randomized placebo-controlled trial." Frontiers in immunology 10 (2019): 65.