(2) Vitamin D is unique - unlike ALL other vitamins very little comes from our food.
Almost all of our Vitamin D is produced by the top layer of our skin when it is exposed to the UV radiation in strong sunlight.
However when the sun is too low in the sky you will NOT produce any Vitamin D from sunlight.
A quick way to check if the sun is too low is to look at your shadow while standing.
If your shadow is longer than you are then you will not produce any Vitamin D.
In the UK and most of the USA the sun is too low in the sky from November until March to produce ANY Vitamin D from sunlight exposure. We are supposed to build up a store during the summer to carry us through the winter, but because of lifestyle changes and the increasing use of UV sun-block this is no longer happening.
Current research shows that many people in non-equatorial regions have very low Vitamin D levels - especially during the winter. People of African decent, now living in less sunny regions, are at highest risk as the darker your skin tone the slower your Vitamin D production. If you rarely get any strong mid-day sun on unprotected skin you WILL be at high risk of deficiency - and the older you are the worse the problem, as your skin becomes less efficient at generating Vitamin D.
Vitamin D controls calcium metabolism which is vital for bone, muscle and nerve function - but recent research shows it is also critical to your immune response against viruses, bacteria and cancer.
Ever wondered why people in colder climates are more prone to colds and flu in the winter and early spring?
Researchers have discovered that as you run low on Vitamin D your immune response weakens. Trials have proved that people taking "high dose" Vitamin D3 supplements (>2000 IU/day) are extremely resistant to colds and flu. Research results published over the last 10 years show mounting evidence for major resistance to several common cancers, plus a range of neurological and auto-immune conditions.
(3) Think about this explanation for our current situation:
The human race evolved in equatorial East Africa where the sun's UVB was strong enough to manufacture all of the Vitamin D3 we required - from a natural cholesterol in our skin. When we migrated away from the equator, natural selection quickly eliminated most of the melanin pigmentation from our skin in an attempt to compensate for the much weaker levels of UV radiation in these cooler regions of the world.
This system worked well for most of human history - as the vast majority of the human population were outside in the sun for at least part of the day. But then came the industrial revolution and the majority of the workforce now remained indoors all day. This change of lifestyle caused severe Vitamin D deficiency in industrialised regions leading to mass outbreaks of the bone disease Rickets in children. Treatment with natural and artificial UV light and more recently with Vitamin D supplements had virtually eliminated this disease.
For the last 30 years sunshine has been demonised for causing skin cancer and we are advised to cover up, or apply UV sun-block, before we even go out in the sun. The unfortunate side effect of this advice, if followed rigorously, has been to remove most of the Vitamin D production from our lives. Many studies are now finding widespread Vitamin D deficiency even in sunny regions such as California and Australia - causing rising levels of osteo-malacia and osteo-porosis in adults - and in some, less sunny, northern regions cases of childhood Rickets.
Rickets in Leicester UK
The more worrying issue is that recent research has now discovered that calcium regulation is only one small part of the Vitamin D story - and in fact most tissues of the body require Vitamin D to regulate a wide range of cell processes - especially immune responses and anti-cancer mechanisms. Researchers are beginning to worry that this could explain the sudden mysterious increase in many "western" diseases over the last 25 years - diabetes, high blood pressure, various cancers including breast, prostate and colon cancer, fibromyalgia, multiple sclerosis, rheumatoid arthritis, seasonal depression, and even autism. Vitamin D Wiki - Health Conditions // Vitamin D Wiki - Autism // Vitamin D3 World - Summary of health research.More details on these websites:
(4) How much Vitamin D is required to avoid deficiency:
The current "recommended" supplement level of 400 IU/day was created when we discovered it prevented Rickets in children - the result of a SEVERE Vitamin D deficiency. Vitamin D3 supplements are added to most commercial baby formulas, and margarines to prevent severe deficiency in children. Many countries also add Vitamin D to milk, but NOT the UK at present. However this level supplementation was never shown to represent an adequate intake for an adult.
The American National Institutes for Health (NIH) recently stated that a supplement level of 1000 IU/day for infants (birth to 12 months) and 2000 IU/day for adults and older children is now certified as totally safe. Most Vitamin D researchers would prefer a system based on body weight - as it has now been shown that an adult will process 4000-7000 IU/day if available - while a young baby only requires 400 IU/day.
These levels equate to a dose of 90 IU/kg per day (or 40 IU/pound) - which can be used to calculate an individual daily dosage based on body weight. In the summer with moderate sun exposure you might only require half this dose.
One important point is that individual daily dosage levels are not critical as any excess is stored in the bodies fat reserves and released as required - so you can safely take two or three days worth of Vitamin D in one larger dose, instead of taking smaller daily doses.
To put all this in perspective, a young person working outside in the summer sun can make up to 25,000 IU/day of Vitamin D - while an elderly person may produce less than 5,000 IU/day under the same conditions. Vitamin D production from UV exposure is self limiting and stops once all the available 7DHC (7‑dehydrocholesterol) in the skin has been converted - the body produces more 7DHC but this takes a day or two to build up again. Any Vitamin D not used immediately is stored for use on days with no sun, and to carry you through the winter - but this only happens if you get enough sun or take "high dose" supplements.
Some Vitamin D researchers suggest that responsible use of a UVB certified (low-pressure tube) sunbed in the winter and moderate sunbathing in the summer is a better alternative to oral supplements. Dr. Holick recommends the safe limit is 25% of the exposure required to get a slight skin reaction - longer exposures do not create any extra Vitamin D3 and could raise your risk of skin cancer. Dr Michael F. Holick's Vitamin D Website
A small number of people experience muscle cramps after they start taking Vitamin D, or even after sun-bathing. This can occur if you are deficient in Magnesium and only becomes evident as your muscle function improves due to the higher Vitamin D levels. Magnesium & Muscle Cramps
For the USA - I recommend the following:
Amazon.com - Doctor's Best Vitamin D3: 5000 IU - 720 Softgels // 5000 IU - 360 Softgels // 2000 IU - 180 Softgels
iHerb - Vitamin D3 - Various brands:
Vitamin D3 - 5000 IU - Suitable for Adults
Vitamin D3 - 2000 IU - Suitable for Children
Vitamin D3 - Drops    - Suitable for Babies
Live Long and Prosper
DougCuk - Webmaster of Stargateuk.info