Vitamin D deficiency is highly prevalent in Hong Kong. So much so that it’s more of a surprise when my patient’s blood tests return showing sufficiency.
There are a few reasons for this high level of deficiency that we are going to cover in the article.
One of the main reasons Vitamin D is so important is the variety of functions it performs in the body. A key controversy that illustrates how much it does in the body is its classification.
Some researchers have called VItamin D a hormone because our skin and liver transform sunlight into a form of vitamin D that acts much like a hormone.[1]
Others suggest that it is still a fat-soluble vitamin that, regardless of its variety of actions in the body, is still a vitamin, mainly because insufficient amounts can cause deficiency symptoms.[2]
Regardless of which camp you sit in, in Hong Kong, mainly due to the climate, estimates are between sixty to seventy per cent of residents are deficient in Vitamin D.[3] This differs between age groups.
Still, the message is that this deficiency of a vitamin that moonlights as a hormone is an uncomfortably familiar issue.
Vitamin D deficiency links to higher levels of diabetes, hypertension, cardiovascular diseases, certain cancers, and autoimmune and inflammatory diseases,[4] making this prevalence important.
Vitamin D is essential in maintaining bone health and preventing osteoporosis.
Whilst the connection between vitamin D and calcium is well-known, studies on its effects in China are small-scale. One study looking to shed light on this, published in 2020, found that patients with hip fractures and osteoporosis had significantly lower vitamin D levels than those without osteoporosis. Insufficiency levels were once again as high as sixty-five per cent.[5]
It’s common knowledge that vitamin D is vital for both health, but what about its other functions?
Let’s start with one of our focused gut-brain conditions here on the site, irritable bowel syndrome (IBS). Admittedly, the connection between vitamin D and IBS is not the first thought. However, it is essential. Let’s look at why.
Vitamin D is a vital part of the immune component of the digestive system.
Whilst we’ll cover other significant contributions of vitamin D to the immune system, what you’ll soon see is a consistent function.
Vitamin D can be anti-inflammatory when inflammation is present and can suppress inflammation when it is not.
An excellent example of this is the role of managing the immune response in the digestive system. It does this in a few ways, but one of the more interesting is the interaction between vitamin D and your microbiome.
For example, one study published in 2016 found that vitamin D supplementation changed the balance of bacteria in the stomach and small intestine. A feature of this study was finding lower levels of Pseudomonasspp. and Escherichia/Shigella spp. of bacteria, both of which are considered pro-inflammatory.[6]
Vitamin D also works in the lining of the GI tract. It does so by triggering anti-microbial immune cells when undesirable gram-negative bacteria release their toxic by-products, lipopolysaccharides.[7]
This anti-microbial action makes Vitamin D one of the critical nutrients to protect the bacterial environment in your gut.
Why is this important?
Small intestinal bacterial overgrowth is seen between thirty to seventy per cent of IBS cases, depending on the age group.[8] [9]
Another vital function of vitamin D in the immune component of the digestive system is its contribution to the integrity of the gut lining. This gut lining is the same lining that can become the leaky part of “leaky gut.”
One study in the British Medical Journal concluded that vitamin D deficiency status is important to monitor in all people with chronic disease.
This new focus is not only because of the broader symptoms of vitamin deficiency but also the increased prevalence of leaky gut in patients admitted to hospitals with insufficient vitamin D levels.[10]
If you have read other articles on leaky gut, you will know that whilst a lot of conditions are associated with it, i.e. higher amounts of people with these conditions have leaky gut. You will also know that there is yet to be enough research confirming that correcting a leaky gut goes on to help the conditions with which it’s associated.
This deficit in research doesn’t, of course, mean that it won’t be the case.
What we see in the clinic is undoubtedly positive in the case of most outcomes. Still, science helps us to validate our ideas.
What vitamin D’s contribution does show, though, is that there is an easy-to-test nutrient deficiency in many that could have a positive effect on not only IBS but also other conditions associated with an immune response in the digestive system.
For example, pre-clinical research, which investigates how relevant something could work before human tests, suggests that vitamin D could be essential to treatment for ulcerative colitis and Crohn’s disease.
This suggestion is for two reasons. The first is to protect from the deterioration of bone health when using commonly prescribed corticosteroid drugs, and the second is using an abundant vitamin D status to manage the immune response that causes so much chaos in these conditions.[11]
In IBS, the research into how vitamin D may help is a little more advanced but still mixed.
A systematic review pooled four placebo-controlled, randomised controlled trials found that vitamin D was superior to a placebo in treating IBS. This review saw improvements in both symptom severity scores and quality of life scores, which would be an excellent outcome for someone living with IBS over a long period.[12]
A European journal tested vitamin D in the same conditions and found no effect.[13] This study is done over twelve weeks with 3000iu of vitamin D, suggesting two things. First, the dose was too low to correct the sixty per cent of participants who were found insufficient (just personal opinion) and be therapeutic as well. Second, we need further research to see what’s going on.
What has come out of the research into functional digestive disorders and vitamin D is its role in positively managing the immune system. No more do we see this than in literally preventing and treating upper respiratory infections like colds and flu.
Vitamin D may be one of the best cold and flu remedies available.
Whilst the research we’ve looked at into IBS and digestive conditions is positive. It’s still mixed. However, the research into vitamin D’s role in acute respiratory tract infections used to be positive across the board but is now under question.
I wouldn’t be doing my job if I didn’t give you a balanced view and say there isn’t conjecture here. A meta-analysis looking at vitamin D found no overall protection besides some positive benefits in those who supplemented daily.[14]
Now more than ever, with the looming risk of new and old variants of viruses, it seems that vitamin D can be an essential tool in protecting and treating upper respiratory infections like colds and flu, regardless of the mixed views.
A meta-analysis published in the British Medical Journal found that people who were very deficient at the time of the study benefitted the most, as well as those who supplemented daily or weekly.[15]
These mixed results are an excellent example of how research reviews confuse practitioners and patients.
I say confusing for practitioners because up until compiling the research for this article, I had read a large quantity of positive research for vitamin D, colds and flu.
It’s frustrating, right?!
Does this mean it’s a waste of time?
The answer is a definite no. It’s not a waste of time.
Another study released this year looked at another age group where vitamin D is often overlooked but imperative, infancy. This study confirmed that for every 100 IU per day increment in vitamin D supplementation, infants experienced a twenty-one per cent lower risk of lower respiratory tract infections.[16]
This study has the recommended dose for infants at roughly 400 IU a day. If you, as an adult, live in a climate like Hong Kong, where being outside isn’t as common due to the heat and humidity most of the year, there is a good chance you are missing out on an easy way to protect your baby with just one drop a day.
A note about vitamin D, the brain and its role in mental health.
We often see in nutrient-based studies that deficiency is the key driver of most of the issues.
For example, zinc, a typically deficient mineral in many regions of the world, plays a significant role in many biochemical transactions in the body and the brain. When the body doesn’t receive enough zinc from the diet, it then has to choose which transactions it doesn’t pay.
When the body can pay all its bills, it leads to problems down the road, as you can imagine.
Vitamin D and depression is a good example of this.
Low vitamin D levels are associated with depression.
One meta-analysis released in 2020, pooling twenty-five trials totalling seven thousand five hundred participants, found that supplementation of vitamin D at a dose of around 4000 IU for either eight weeks or beyond reduced negative emotions. This result was primarily for those with insufficient levels at the beginning of the trials, suggesting that deficiency states are involved in some way.[17]
There are two reasons this might be the case. The first is that receptors for vitamin D (think of receptors as a lock and vitamin D as the key for that specific lock) in two brain areas play a critical role in mood regulation.[18]
The second is vitamin D’s role in managing inflammation. It seems the same anti-inflammatory action that vitamin D has in the digestive system also radiates to the brain.[19]
Vitamin D could also assist with anxiety symptoms.
An important note is that these studies are either small or not strong enough to make a clinical call. However, over six months, there seems to be promise in using vitamin D for anxiety.[20]
Another study looking into generalised anxiety disorder (GAD) found vitamin D supplementation has positive effects on reducing the symptoms of GAD over three months. An important note is that these participants were under supervision and using extremely high doses of vitamin D over three months. Something I would only recommend if you are under supervision.[21]
That’s not all. Vitamin D may also help with sleep!
For example, vitamin D is heavily involved in the transactions that build melatonin in our brains to help us sleep. Some studies also theorise that vitamin D may directly contribute to sleep issues.[22]
It’s crazy to me that I feel like I’m just getting started putting this article together, and we’ve already covered so much. Vitamin D is undoubtedly one of the most effortless nutrients to be tested and treated by any healthcare practitioner, no matter where you live.
Not only if you are looking to protect your bone health but also, as we have seen in this article if you are looking to help your digestion, brain and immune system too!
Hope this helps xx
References
[1] Fleet JC. Vitamin D and Gut Health. Adv Exp Med Biol. 2022;1390:155-167. doi:10.1007/978-3-031-11836-4_9
[2] Vieth R. Why “Vitamin D” is not a hormone, and not a synonym for 1,25-dihydroxy-vitamin D, its analogs or deltanoids. J Steroid Biochem Mol Biol. 2004;89-90(1-5):571-573. doi:10.1016/j.jsbmb.2004.03.037
[3] Cheung TF, Cheuk KY, Yu FW, et al. Prevalence of vitamin D insufficiency among adolescents and its correlation with bone parameters using high-resolution peripheral quantitative computed tomography. Osteoporos Int. 2016;27(8):2477-2488. doi:10.1007/s00198-016-3552-4
[4] Wang H, Chen W, Li D, et al. Vitamin D and Chronic Diseases. Aging Dis. 2017;8(3):346-353. Published 2017 May 2. doi:10.14336/AD.2016.1021
[5] Wang Q, Yu D, Wang J, Lin S. Association between vitamin D deficiency and fragility fractures in Chinese elderly patients: a cross-sectional study. Ann Palliat Med. 2020;9(4):1660-1665. doi:10.21037/apm-19-610
[6] Bashir M, Prietl B, Tauschmann M, et al. Effects of high doses of vitamin D3 on mucosa-associated gut microbiome vary between regions of the human gastrointestinal tract. Eur J Nutr. 2016;55(4):1479-1489. doi:10.1007/s00394-015-0966-2
[7] Kempker JA, Han JE, Tangpricha V, Ziegler TR, Martin GS. Vitamin D and sepsis: An emerging relationship. Dermatoendocrinol. 2012;4(2):101-108. doi:10.4161/derm.19859
[8] Scarpellini E, Giorgio V, Gabrielli M, et al. Prevalence of small intestinal bacterial overgrowth in children with irritable bowel syndrome: a case-control study. J Pediatr. 2009;155(3):416-420. doi:10.1016/j.jpeds.2009.03.033
[9] Poon, D., Law, G.R., Major, G. et al. A systematic review and meta-analysis on the prevalence of non-malignant, organic gastrointestinal disorders misdiagnosed as irritable bowel syndrome. Sci Rep 12, 1949 (2022). https://doi.org/10.1038/s41598-022-05933-1
[10] Eslamian G, Ardehali SH, Hajimohammadebrahim-Ketabforoush M, Vahdat Shariatpanahi Z. Association of intestinal permeability with admission vitamin D deficiency in patients who are critically ill. J Investig Med. 2020;68(2):397-402. doi:10.1136/jim-2019-001132
More references!
[11] Hlavaty T, Krajcovicova A, Payer J. Vitamin D therapy in inflammatory bowel diseases: who, in what form, and how much?. J Crohns Colitis. 2015;9(2):198-209. doi:10.1093/ecco-jcc/jju004
[12] Huang H, Lu L, Chen Y, Zeng Y, Xu C. The efficacy of vitamin D supplementation for irritable bowel syndrome: a systematic review with meta-analysis. Nutr J. 2022;21(1):24. Published 2022 May 5. doi:10.1186/s12937-022-00777-x
[13] Williams CE, Williams EA, Corfe BM. Vitamin D supplementation in people with IBS has no effect on symptom severity and quality of life: results of a randomised controlled trial. Eur J Nutr. 2022;61(1):299-308. doi:10.1007/s00394-021-02633-w
[14] Cho HE, Myung SK, Cho H. Efficacy of Vitamin D Supplements in Prevention of Acute Respiratory Infection: A Meta-Analysis for Randomized Controlled Trials. Nutrients. 2022;14(4):818. Published 2022 Feb 15. doi:10.3390/nu14040818
[15] Martineau AR, Jolliffe DA, Hooper RL, et al. Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data. BMJ. 2017;356:i6583. Published 2017 Feb 15. doi:10.1136/bmj.i6583
Wait, more references?!
[16] Hong M, Xiong T, Huang J, et al. Vitamin D supplementation and lower respiratory tract infection in infants: a nested case-control study [published online ahead of print, 2022 May 24]. Infection. 2022;1-10. doi:10.1007/s15010-022-01845-4
[17] Cheng YC, Huang YC, Huang WL. The effect of vitamin D supplement on negative emotions: A systematic review and meta-analysis. Depress Anxiety. 2020;37(6):549-564. doi:10.1002/da.23025
[18] Prüfer K, Veenstra TD, Jirikowski GF, Kumar R. Distribution of 1,25-dihydroxyvitamin D3 receptor immunoreactivity in the rat brain and spinal cord. J Chem Neuroanat. 1999;16(2):135-145. doi:10.1016/s0891-0618(99)00002-2
[19] Menon V, Kar SK, Suthar N, Nebhinani N. Vitamin D and Depression: A Critical Appraisal of the Evidence and Future Directions. Indian J Psychol Med. 2020;42(1):11-21. Published 2020 Jan 6. doi:10.4103/IJPSYM.IJPSYM_160_19
[20] Zhu C, Zhang Y, Wang T, et al. Vitamin D supplementation improves anxiety but not depression symptoms in patients with vitamin D deficiency. Brain Behav. 2020;10(11):e01760. doi:10.1002/brb3.1760
[21] Eid A, Khoja S, AlGhamdi S, et al. Vitamin D supplementation ameliorates severity of generalized anxiety disorder (GAD). Metab Brain Dis. 2019;34(6):1781-1786. doi:10.1007/s11011-019-00486-1
[22] Romano F, Muscogiuri G, Di Benedetto E, et al. Vitamin D and Sleep Regulation: Is there a Role for Vitamin D?. Curr Pharm Des. 2020;26(21):2492-2496. doi:10.2174/1381612826666200310145935
