With the clocks going back this weekend, I hate to say it, but winter is well and truly on its way. With that in mind, let's look at one of the easiest, yet beneficial, changes you can make to your health over the coming months. It's all about Vitamin D today on the blog. So sit back, have a read and hopefully some of this info will be worthwhile for you.
First of all, what is Vitamin D? Well, Vitamin D is a fat-soluble vitamin, it's only found in foods in small amounts, but is available as a dietary supplement.
Despite the name vitamin D, it is actually a hormone. Vitamin D receptors are found in a lot of tissues in the body, therefore it has a significant effect on the body, such as supporting bone health through aiding the absorption of calcium and supporting immune function. http://onlinelibrary.wiley.com/doi/10.1359/jbmr.07s211/pdf.
Recent research suggests it may play a role in muscle protein synthesis and muscle function. Further research has shown that low levels of vitamin D may be linked to depression – which may scientifically explain seasonal affective disorder (SAD); which occurs when the days get shorter in the winter, as well as the wide-held notion that a lack of sunlight due to being indoors is linked to low mood. Although it must be noted that depression may lead to a lack of desire to be outdoors, and thus a low level of vitamin D.
The major source of vitamin D is sun exposure – which, let's face it, in Ireland, is difficult to come by at the best of times, let alone coming into the winter months. Therefore, it can be postulated that many people in Ireland may become vitamin D deficient during these months.
Vitamin D supplements come in two forms; Vitamin D2 or Vitamin D3. It is important to note the scientific names for each of these forms of vitamin D, as some supplement labels may only show the scientific name: Vitamin D2 is also known as ergocalciferol, and Vitamin D3 is known as cholecalciferol.
Vitamin D3 is the type that most experts believe should be utilized in clinical practice. This is for numerous reasons:
- Vitamin D3 is the more potent form of vitamin D.
- UVB light from the sun strikes the skin, and humans synthesize vitamin D3, so it is the most "natural" form. We cannot synthesize vitamin D2 naturally.
- Vitamin D3 is more likely to remain active for a longer period of time when in storage compared with vitamin D2 when exposed to different conditions (temperature etc.).
- Vitamin D3 has been the most utilized form of vitamin D in clinical trials.
- Vitamin D3 is more effective at raising and maintaining the vitamin D blood test. https://www.ncbi.nlm.nih.gov/pubmed/22552031. https://www.ncbi.nlm.nih.gov/pubmed/16443061.
Toxicity from vitamin D3 supplementation is rare. However, the current tolerable upper intake level (UL) for vitamin D as set by the Institute of Medicine is 4000 IU/day. https://www.nap.edu/catalog/13050/dietary-reference-intakes-for-calcium-and-vitamin-d.
Data from the HSE, National Osteoporosis Foundation USA and The American Academy of Paediatrics has suggested the following intakes for Vitamin D3
Babies 0-12 months breast fed or formula fed = 5µ/200 IU
Children 1-18 years= 10µ/400 IU per day
Adult women 19-49 years = 10-20µ/400-800 IU per day
Adult women 50+ years = 20-30µ/800-1000 IU per day
19+ years pregnant and/or breastfeeding = 20-30µ/800-1000 IU per day
Adult men 19-49 years =10-20µ/400-800 IU per day
Adult men 50+ years =20-30µ/800-1000 IU per day
Some of the best food sources of vitamin D3 include: Cod liver oil, wild cooked salmon, mackerel, fortified orange juice, beef liver, eggs and fortified milk. It would be recommended however, to supplement with vitamin D3 during the winter months as the best source of Vitamin D is taken away from us during the winter..although some may argue this s a year round problem in Ireland.
As always, if you have any questions or need more info on a topic please let me know.
PFP S & C Coach