Vitamin D and Our Health by Coach Jesse

Winter is approaching.  It’s getting colder, damper and gets dark far too early.  Those of us that reside in the Northern Hemisphere are seeing very little sunshine, particularly those who work indoors or are housebound, thus our exposure to the so-called sunshine vitamin (D) is somewhat limited.

But what is the impact of this on our overall health status?

Vitamin D is probably one of the most important vitamins that our body requires in order to function optimally.  But what exactly are its benefits are and how we can practically address our intake for the sake of our health?

Here I examine these whys and hows in a bit more detail.


Vitamin d is a fat soluble vitamin, the main source is that from which is synthesised from sunlight.  Simply put, upon exposure to sunlight, ultraviolet B (UVB) photons are synthesised via the skin to vitamin d in the body.

During the winter months especially, our exposure to the sun is limited.  Even in the summer many of us use high factor sunscreen and cover our skin up, so arguably are limited then too.

Dietary sources, although in low amounts, include oily fish (salmon, mackerel, sardines), eggs, red meat, liver and fortified foods such as spreads and cereals and yoghurt.

When our body’s receive vitamin d, it is turned by the kidneys into ‘active vitamin d’ or calcitriol, which is actually a steroid hormone, having the ability to affect the way in which proteins are made in the body.  Because proteins are the building blocks of life, this therefore has profound effects within the body.


You’ve probably heard that it is good for “healthy bones”,  acting as a promoter to enhance the absorption and storage of bone minerals such as calcium, phosphorus and magnesium.  It essentially allows them to work their magic to improve bone density and maintain bone homeostasis.

Beyond healthy bones, there are a plethora of other benefits including:

  • It has an important role in immune function (1) and the prevention of acute respiratory tract infections. (2)
  • It is hypothesised that there is a link between vitamin d deficiency and depression as well as the supplementation benefits in protecting seasonal affective disorder (SAD). (3)
  • There is growing research into the role of vitamin d in the prevention of certain cancers (4), heart function (5), autoimmune disease (6) and testosterone production in men (7).


 It is estimated that 50 per cent of the world’s population are deficient (8).   This is a worrying statistic, with deficiency being cited as being responsible for delayed growth and rickets in children, the acceleration and severity of osteopenia and osteoporosis in adults, particularly post menopausal women, and thus increased risk of falls and subsequent fractures.   Vitamin D deficiency has also been associated with the increased risk of cancers, autoimmune diseases, infectious  and cardiovascular diseases and potential subsequent increased mortality rates.

With this is mind, it would seem prudent to supplement.

The UK’s Scientific Advisory Committee on Nutrition (SACN) recommends the following vitamin D3 supplementation (9):

  • Adults and children over the age of five (including pregnant women) should consider supplementing from October to March with 400iu (international units) or 10 micrograms of vitamin d per day.
  • Children aged one to four should be given a daily supplement of 400iu/ 10 micrograms per day
  • All breastfed infants aged 0 to one year should be given a supplement of 8.5-10 micrograms per day.
  • Formula fed infants do not need to supplement as formula milk is fortified already.
  • Special populations such as those who are housebound or cover their skin and thus have little or no exposure to the sun should supplement with 10 micrograms per day throughout the year.
  • Those from minority ethnic groups, with darker skin, should consider a daily supplement of 10 micrograms per day.

Despite the above recommendation, there is strong evidence to suggest that this is supplemental dosage above 400iu may be more optimal (10).

If you suspect you may be at risk of deficiency, you should request a test with your GP, and women of peri and post menopausal status should consider supplementing all year round due to an increased risk of poor bone mineral density.


Adequate vitamin D is important for bone health and keeping those winter colds, flu’s and blues at bay.

When we consider the high percentage of those that are deficient and the consequences,  there is a strong argument that suggests that vitamin D supplementation is one of the most important you can take.

There is also strong evidence to suggest that supplementation beyond the SACN recommendation could provide additional protective benefits to the body.

Always make time to get outside, regardless of supplementation.  The winter sun still counts, if there is any, and being outdoors is a powerful mood booster.

Why not get involved one of the Her Spirit challenges?  The Winter Swim Challenge is just one way of staying accountable over the winter and if you choose to take it to a lake or the sea, at some point you’ll see daylight and if you’re lucky the low, winter sun.

For the latest, easy to digest information, refer to – a great resource for all the latest evidence on all supplementation.

Thanks for reading.

Jesse – Her Spirit Fuel coach 🤩


(1) Aranow, C. (2011). Vitamin D and the Immune System. Journal of Investigative Medicine, 59(6), pp.881-886.

(2) Martineau, A. et al: Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data. BMJ, p.i6583.

(3) Anglin, R. et al (2013). Vitamin D deficiency and depression in adults: systematic review and meta-analysis. The British Journal of Psychiatry, 202(2), pp.100-107.

(4) Garland, C. et al (2006). The Role of Vitamin D in Cancer Prevention. American Journal of Public Health, 96(2), pp.252-261.

(5) University of Leeds. “Vitamin D improves heart function, study finds.” ScienceDaily. ScienceDaily, 4 April 2016.

(6) Yang, C., Leung, P., Adamopoulos, I. and Gershwin, M. (2013). The Implication of Vitamin D and Autoimmunity: a Comprehensive Review. Clinical Reviews in Allergy & Immunology, 45(2), pp.217-226.

(7) Pilz, S., Frisch, S., Koertke, H., Kuhn, J., Dreier, J., Obermayer-Pietsch, B., Wehr, E. and Zittermann, A. (2010). Effect of Vitamin D Supplementation on Testosterone Levels in Men. Hormone and Metabolic Research, 43(03), pp.223-225.

(8) Holick, M. (n.d.). Sunlight, UV-Radiation, Vitamin D and Skin Cancer: How Much Sunlight Do We Need?. Sunlight, Vitamin D and Skin Cancer, pp.1-15.

(9) (2017). SACN vitamin D and health report – GOV.UK. [online] Available at: