Vitamin D Explained
October 13, 2008 by Tom
Vitamin D is a fat soluble vitamin and is often known as the sunshine vitamin because sunlight can prompt the body to produce it. Early signs of the benefits of vitamin D were discovered in the early nineteenth century when researchers suggested that sunbathing and cod liver oil could cure rickets (softening of the bones in children and young animals which is now known to be caused by vitamin D deficiency). Vitamin D was officially discovered in 1919 when Edward Mellanby raised a group of dogs on nothing but porridge and also kept them inside (unintentionally) meaning they had no exposure to ultraviolet rays from the sun. The dogs developed rickets but Mellanby discovered this could be cured by feeding the dogs cod liver oil. He concluded that rickets was caused by a deficiency of a trace factor that was not found in oats. Elmer McCollum followed up on this work and in 1922 dubbed this trace factor vitamin D.
The most notable function of vitamin D is that it helps the body absorb calcium and phosphorous which help bones and teeth grow properly. It also helps regulate the use of these minerals in the body, signaling to the kidneys when they should be deposited into the bone and when they should be extracted for use elsewhere. On top of this vitamin D also has a number of important roles in the body which include:
- Possible colon cancer prevention (according to How Stuff Works).
- Protection from conditions that weaken the bones such as osteoporosis (reduced bone density) and rickets.
Vitamin D can be sourced from food but unlike the majority of vitamins it can also be produced by your body when exposed to sunlight. The recommended daily allowance (RDA) for vitamin D is 0.01mg for both men and women and experts suggest that a short periods of exposure to the sun each day will allow the body to produce adequate levels of vitamin D. However, if you are not getting enough exposure to sunlight you can also top up your vitamin D levels through your diet. Dairy products such as eggs, milk and butter are all rich sources of vitamin D. On top of this fatty fish and fish oils also contain vitamin D whilst some cereals are fortified with it.
As already discussed, vitamin D deficiency can cause rickets in children which leads to the bones swelling, bending and fracturing more easily. Rickets also causes teething to be delayed. In adults, vitamin D deficiency leads to osteomalacia (the loss of calcium and protein from the bones) which is similar to rickets and makes your bones more fragile.
Overdosing on vitamin D can also be harmful to your body. The most serious side effect of overdosing is increased blood calcium levels which causes calcium to be deposited in various organs and leads to permanent damage. Other unpleasant side effects of too much vitamin D include diarrhea and nausea.
It is rare that you will need vitamin D supplements unless you get very little exposure to the sun. If you do use a vitamin D supplement to compensate for a lack of sunlight make sure that you check its concentration. Excess vitamin D is stored in the liver and fatty tissues of the body, so overdosing on supplements can cause these stores to become toxic and lead to the side effects discussed above.
I hope this article has showed you just how crucial vitamin D is for the healthy development of your bones. It is essential that you get enough because a deficiency can leave you with long term health problems and bones that are easily damaged. However, with vitamin D being available from both food and the sunlight it is rare that you will require vitamin D supplementation. If you do decide to use vitamin D supplements make sure that you do not exceed the RDA. Otherwise you could be doing long term damage to your bones and your overall health.
Sources:
Toxicity of Vitamins Information (Medical News Today)
Unravelling the enigma of Vitamin D (Beyond Discovery)
Vitamin D Information (Food Standards Agency)
Vitamin D Information (How Stuff Works)
Vitamin D Information (Life Clinic)
Vitamin D Information (Wikipedia)
My goal for this winter is to bundle up (I hate the cold) and go outside for 10 -15 minutes on sunny days. I’m hoping that will help boost my vitamin D levels over the course of the dreary months!
For many people in the high latitudes getting enough sunlight during winter can be tricky. Office workers can suffer especially, as some do not see daylight for weeks. Really important to take a stroll at lunch time if you can, to catch some rays.
Angie – I do agree it is often difficult to get outside, especially in the winter months when the conditions are often drab and miserable. Your plan is a good one though – actually scheduling time in the day to get some sunlight.
Jon – I didn’t consider the effect that high latitudes would have. Definitely agree with you on the importance of taking a lunch time stroll. It’s just hard to get away from the desk every day. Nice blog by the way.
Glad you like it. Is it good enough to make it on to your list of Favourite Fitness Websites?
Hey Jon. It certainly is. Drop me an email and we can get some kind of link exchange set up.