Good day everyone
I hope we are all keeping fit and healthy. I am going to leave you in the capable hands of Dr Simon (MBBCh MRCGP Dip SEM) to explain a little about the intricacies of supplementation (using Vitamin D as a focus). With a trans-Atlantic house move out of the way, Dr Simon will now be blogging on a more frequent basis, so please feel free to leave your comments below today’s post for any future queries you’d like Dr Simon to answer in future. I hope you enjoy and have a great week 🙂

In an ever increasingly commercialized world of health and sports promotion, there appears to be an endless pool of potions, lotions, foods and fads laying claim to a wide variety of benefits for our bodies; fat loss, increased stamina, boosts in strength and immune system function to name but a few.  A need for the cutting edge or a short cut to success can be a very attractive proposition for both elite sports people and recreational fitness enthusiasts alike.  Sifting the wheat from the chaff can be a difficult undertaking.
The more commonly thought of supplements, such as protein and creatine in sport will spring to mind but I will be focusing today mainly on one specific vitamin – D3 – and talking through issues with supplementation in general.  Like many other vitamins and minerals that may be neglected, supplementation of  vitamin D3 has been the subject of much recent research, outlining vast implications for our health.

What is Vitamin D3?

Vitamins are essential requirements for the human body to function.  Vitamin D is a fat-soluble vitamin which has a structure similar to steroid hormones (3).  There are two forms, D2 and D3, the latter being considered preferable for supplementation(3).  Some vitamins are acquired through dietary intake alone, some the body is able to produce for itself with the right conditions.  In the case of vitamin D3, the condition required for production is UV (B) light exposure to the skin, although small amounts of vitamin D can be found in foods such as:

  • Oily fish (a great source of Omega-3s too)
  • Egg yolks (another positive for eggs, in a world that is unnecessarily anti-egg)
  • Milk (although high in lactose)
  • Orange juice (although high in fructose)
  • Cereals
  • Margarine

But, dietary intake alone is insufficient to provide enough vitamin D (3). So, we rely on UV light to top ourselves up.  However, in temperate latitudes North and South of the equator (35), with modern lifestyles involving working indoors, training indoors and being fully clothed, the requisite amounts of UV light hitting our skin are often not enough to generate sufficient vitamin D3 levels.  As Vitamin D plays a key role in bone metabolism and it appears to have anti-inflammatory and immune system regulating properties, it is key that we have enough of this (1).

D-ficiency versus Optimal Levels?

Some of you will rightly question whether as an individual, you are deficient in vitamin D.  This can only be quantified through a blood test in which case see your physician and to be on the safe side, it is best to get these checked every 3-6 months. However, deficiency is a loaded word. Even vitamin D levels in the normal range can be improved on through supplementing and this is why some sporting and government health bodies have completely different reference ranges. Although you may not be deficient in a certain micronutrient, you can always optimize your levels through supplementation. The small difference between optimal and sub-optimal may well make a big difference in terms of optimal immune function, optimal sports performance, optimal fat loss, optimal energy levels, to name a few. I stress here the word OPTIMAL. From country to country, from body to body, these levels vary, the suggested level changes. In France the suggested level for intake is 7.5µg (300IU) (6). This is definitely not enough for optimal health and performance (6). See the below table to see how much variance there is:

Levels of 25(OH)D producing health benefit

A spike in the numbers of cases of Ricketts recently in the UK has seen the production of public health guidelines, developed by the National Institute for Clinical Excellence (NICE), recommend a dietary intake through supplements of 10 micrograms of Vitamin D3 a day through pregnancy and whilst breast feeding (2) to increase stores of this vitamin and prevent Ricketts (bone softening and malformation in childhood). Osetoporosis, especially in later life is associated with a lack of vitamin D3. It is not only bone problems that are linked with vitamin D deficiency states.  Other disease states include:

  1. Cardiovascular disease
  2. Autoimmune diseases such as multiple sclerosis
  3. Certain types of cancer
  4. Type 2 diabetes (1)
  5. Male reproductive health.

The Australian Institute of Sport (AIS) has recommendations for the use of different supplements in the sports setting.  There are different levels of evidence available behind the use of individual supplements, in part due to the problems involved in study design to achieve what is known as Level 1 evidence, that is individual studies that are randomized (double-blind where appropriate) control studies or systematic reviews of these studies.  Vitamin D is Grade A, categorised for use in deficiency states in sports, meaning studies performed on it consistently show this highly regarded evidence.  Vitamin D levels are associated with skeletal muscle function (6) and there is emerging evidence that Vitamin D levels have a beneficial effect on athletic performance including strength and power, coordination and reaction times (3). However, as with many studies on supplementation and their effects on the human body, there is a dearth of impeccably-designed Level 1 evidence. So when you read about ‘so-and-so’ supplement that is great for ‘this-or-that’, it is usually advice based on poor quality designed studies or second-hand information. If it is not Level 1 evidence you read or hear, ensure you seek sound advice from your thoroughly-read, highly-educated and experienced practitioner or health professional.

Why Don’t I Just Go and Catch Some Rays?

A nice idea, but practically this can be difficult to achieve.  Even the majority of readers based in the South of France will have difficulties getting enough UV(B) light exposure through the winter months.  Even if you have the time and are fortunate to experience such a climate, the potential for skin damage such as premature skin aging and the risk of developing skin cancers is omnipresent through sun bathing, hence the advice to cover up in the midday sun and use high sun protection factor sun screen. What is good for our skin though is bad for our vitamin D levels.  It therefore seems intuitive that if we can’t ingest enough Vitamin D in our diets, if we can’t make enough in our skin then we should consider supplementing. It is important to understand the difference between taking high doses of D vitamin and the real absorption of it. It’s not how much you take, it’s how much you absorb and what the plasma level is on a consistent basis. Ensure absorption by using a quality product, as with most supplements, quality over quantity always holds true.

Take Home Messages

The smaller the differences become between winning and losing in elite level sports, the more research and understanding will be gleaned about current supplements and those which have yet to be explored.  This will filter down to recreational sports and fitness enthusiasts alike.  With so many products and different research methods and conclusions reached, I would like to convey these take home messages:

  1. The best supplement in the world will be ineffective without the foundation of a healthy and balanced diet.
  2. Vitamin D3 is just one of a multitude of vitamins and minerals that can be considered for supplementation.  Multivitamins and minerals can be a good way of addressing your individual needs and ‘ticking all the boxes’.
  3. The best nutrition and appropriate supplementation will be ineffective without the hard work put in through training to achieve your fitness goals.
  4. The quality of products on the market is wide-ranging.  As with food, you generally get what you pay for, so shop smartly, make sure you know what you are getting and if in doubt consult your physician or a suitably qualified sports trainer.

Until next time, stay healthy,
Dr Simon.

  1. Kulie, T.MD, Groff, A.DO, Redmer, J.MD,MPH, Hounshell, J.MD, Shrager, S.MD,MS. Vitamin D: An Evidence-Based Review. Journal of American Board Family Medicine. 2009. 22(6). 698-706.
  2.  Maternal and Child Nutrition. NICE Public Health Guidance.  Issued March 2008.
  4. Cannell, J., Hollis, B., Sorenson, M., Taft, T., Anderson, J.J.B. Athletic performance and vitamin D. Medicine and Science of Sports Exercise. 2009. 41(5), 1102-1110.
  5. Williams, M. Dietary Supplements and Sports Performance: Introduction and Vitamins.  Journal of International Sports Nutrition. 2004. 1(2)  1–6.
  6. Holick, M.F. Vitamin D deficiency. New England Journal of Medicine. 2007. 357(3), 266-281.
  7. Boland, R. The role of vitamin D in skeletal muscle function. Endocrine Reviews. 1986. 7(4), 434-448.
  8. Jensen, M., Bjerrum, P., Jessen, T., Nielsen, J., Joensen, U., Olesen, I., Petersen, J. Vitamin D is positively associated with sperm motility and increases intracellular calcium in human spermatozoa. European Journal of Human Reproduction and Embryology. 2011. 26(6), 1307-131.



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