Why Vitamin D is so important for your health- Part 1

Dr Harry explains all things Vitamin D

- Written by Dr. Harrison Weisinger MBBS, PhD.

One in every three people in the UK is deficient in Vitamin D - this proportion fluctuates throughout the year but is highest in the winter months [1, 2].  

Unfortunately, the long-term consequences of Vitamin D deficiency include an increased risk of osteoporosis and cancer, but also decreased life expectancy [3].


Almost everyone knows that you ‘get’ Vitamin D from the sun.  And the truth is that you really don’t need much to get by. In fact, it’s estimated that as little as a few minutes outdoors each day, during the summer months, (and more like 3 or so hours a week during winter) provides enough Vitamin D to function normally.

The term ‘Vitamin D’ actually refers to a collection of naturally-occurring chemicals that are derived from cholesterol. The precursor to Vitamin D is called 7-dehydrocholesterol.  This is converted to Vitamin D3 when exposed to UV(B) light in the skin - hence, we need sun exposure to make Vitamin D (unless we consume it, directly - more on this soon!). Vitamin D3 undergoes its final processing in the kidneys to become ‘calcitriol’ - which is the active form of the vitamin.  Phew!


Vitamin D basically has one function in the body, but it’s a big one!  It enables the absorption of calcium in the gut [4]. Vitamin D deficiency equates to inadequate calcium absorption.  

The term ‘Vitamin D’ actually refers to a collection of naturally-occurring chemicals that are derived from cholesterol. The precursor to Vitamin D is called 7-dehydrocholesterol.  This is converted to Vitamin D3 when exposed to UV(B) light in the skin - hence, we need sun exposure to make Vitamin D (unless we consume it, directly - more on this soon!). Vitamin D3 undergoes its final processing in the kidneys to become ‘calcitriol’ - which is the active form of the vitamin.  Phew!

Vitamin D basically has one function in the body, but it’s a big one!  It enables the absorption of calcium in the gut [4]. Vitamin D deficiency equates to inadequate calcium absorption.  

 And since calcium is crucial for the normal function of muscles, nerves, the immune system and the brain (among other things), the body has a system to deal with inadequate absorption.  Low levels of calcium in the blood trigger the parathyroid glands in the neck to release parathyroid hormone. This, in turn, triggers the bones to ‘release’ calcium, thus somewhat restoring the balance.  The problem, of course, is that over time, the bones will have lost so much calcium as to become brittle. In other words, osteoporotic.

People with osteoporosis are prone to crush fractures of the spine, as well as non-traumatic fractures of the hips and long bones.  These fractures are very significant and are well-known to be associated with loss of independence, institutionalisation and premature death. 


Osteoporosis is such a major problem in our society that doctors actively seek to identify those susceptible to it and start medical treatment as early as possible.  Women, after menopause, are particularly prone to osteoporosis. However, people who smoke, or have gut (e.g. coeliac disease) or liver issues are just as likely to develop the condition [1].  Children that don’t get enough Vitamin D develop serious bone conditions such as Rickett’s Disease and Osteomalacia.

People with osteoporosis are prone to crush fractures of the spine, as well as non-traumatic fractures of the hips and long bones.  These fractures are very significant and are well-known to be associated with loss of independence, institutionalisation and premature death. 


Osteoporosis is such a major problem in our society that doctors actively seek to identify those susceptible to it and start medical treatment as early as possible.  Women, after menopause, are particularly prone to osteoporosis. However, people who smoke, or have gut (e.g. coeliac disease) or liver issues are just as likely to develop the condition [1].  Children that don’t get enough Vitamin D develop serious bone conditions such as Rickett’s Disease and Osteomalacia.

As a GP, I will often test people’s Vitamin D levels at the end of summer because if they’re low then, they’ll definitely be low during the colder months of the year!  We consider someone with a Vitamin D level of around 70nmol/l at the end of summer to be susceptible to deficiency (because under 50nmol/l is considered insufficient).


Maintaining higher Vitamin D levels (> 50nmol/l) has been found, in a study of over 400 people suffering from knee osteoarthritis [5], to improve both knee structure (such as increased knee cartilage volume, and a reduction in cartilage defects and bone marrow lesions) and reduce symptoms.

All of the above, and the fact that it is almost impossible to develop Vitamin D toxicity (you would need to take 5 times the recommended dose for an extended period), leads to a pretty simple conclusion: make sure you have enough Vitamin D! 


Now that you know the importance of Vitamin D...stay tuned for next week's blog on Dr Harry's tips to maintain adequate levels of it!

References


[1] https://www.guidelinesinpractice.co.uk/nutrition/top-tips-vitamin-d-deficiency/454118.article

[2] NICE. Vitamin D deficiency in adults—treatment and prevention. NICE Clinical Knowledge Summary. NICE, 2016. cks.nice.org.uk/vitamin-d-deficiency-in-adults-treatment-and-prevention (accessed 11 October 2019).

[3] https://www.health.harvard.edu/staying-healthy/vitamin-d-and-your-health-breaking-old-rules-raising-new-hopes

[4] Zmijewski M. A. (2019). Vitamin D and Human Health. International journal of molecular sciences, 20(1), 145.

[5] Zheng S, Jin X, Cicuttini F, Wang X, Zhu Z, Wluka A, Han W, Winzenberg T, Antony B, Aitken D, Blizzard L, Jones G, Ding C. Maintaining Vitamin D Sufficiency Is Associated with Improved Structural and Symptomatic Outcomes in Knee Osteoarthritis. Am J Med. 2017 Oct;130(10):1211-1218. Epub 2017 May 24. PubMed PMID: 28549923.

[6] Kimmie Ng, Jeffrey A. Meyerhardt, Kana Wu, Diane Feskanich, Bruce W. Hollis, Edward L. Giovannucci, and Charles S. Fuchs Circulating 25-Hydroxyvitamin D Levels and Survival in Patients With Colorectal Cancer. Journal of Clinical Oncology 2008 26:18, 2984-2991 

[7] Going, C. C., Alexandrova, L., Lau, K., Yeh, C. Y., Feldman, D., & Pitteri, S. J. (2018). Vitamin D supplementation decreases serum 27-hydroxycholesterol in a pilot breast cancer trial. Breast cancer research and treatment, 167(3), 797–802. doi:10.1007/s10549-017-4562-4

Dr. Harrison Weisinger (MBBS, Ph.D.)

Dr. Harry is the Medical Director for Truth Origins, and a practicing medical doctor in Australia. Throughout his working career as medical doctor, university professor, and scientist, Dr. Harry has committed his life to improving human health. Each month he reads the various journals and studies being conducted across the world’s leading universities and research hospitals to bring you the latest research surrounding the truth about plant-based medicine.

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