Vitamin D is fat soluble vitamin/hormone whose primary role is the absorption, metabolism and storage of both calcium and phosphorus in the bone, to maintain bone strength, density and resilience.
In recent years extensive scientific research has unearthed a veritable treasure trove of secondary health benefits that occur, only when the body has optimal levels of Vitamin D.
The human body requires both fat and water soluble vitamins on a daily basis, but the fat soluble ones (vitamin A, D, E, K) have the ability to be stored in the body’s fat tissues for later use; whereas water soluble vitamins are normally excreted within a day if they are not utilised.
Five forms of Vitamin D have been discovered - Vitamin D1, D2, D3, D4, D5. The two most commonly used forms in humans are Vitamins D2 (ergocalciferol) and D3 (cholecalciferol). Of the two, D3 is the most biologically active and is the preferred form for dietary supplementation. Vitamin D3 is what the body naturally produces via sunlight, while Vitamin D2 is a plant-derived form of Vitamin D first produced in the early 1920s through ultraviolet exposure of foods.
Where do humans get Vitamin D from?
Vitamin D is normally produced in the body in great quantities during summer when the suns UVB rays are close enough to stimulate mass production in exposed skin. The greater the skin exposure the greater the amount of Vitamin D produced. However the ability to produce Vitamin D in the skin reduces with advancing age and with increased skin pigmentation. Dark skin requires more sun exposure as melanin the substance responsible for skin pigmentation acts as a natural sunscreen to block Vitamin D production.
Once the UVB rays hit the skin, it converts cholesterol stored in the skin into cholecalciferol or pre-vitamin D. This is transported to the liver where it is converted to 25-hydroxycholecalciferol (also known as 25-hydroxyvitamin D or calcidiol) and is then transported to the kidneys or stored in the body for later use. In the kidneys and other tissues 25-hydroxycholecalciferol is converted to its active form 1,25-dihydroxycholecalciferol (also known as 1,25-hydroxyvitamin D or calcitriol), and it is this active form of Vitamin D that is now known to be responsible Vitamin D’s multiple health benefits.
During the winter months sun exposure is greatly reduced and hence the ability to produce Vitamin D is also greatly reduced. Depending on where you live in the world it may be nonexistent for several months over winter. As a result Vitamin D levels dip during winter and as few foods are fortified with Vitamin D, supplementation may be necessary to maintain healthy levels.
Dietary sources include certain foods such as salmon, sardines, herring, egg yolks and organ meats; though it is doubtful that we can ingest enough to maintain optimum blood levels of Vitamin D especially during the winter months.
Can too much sun produce too much vitamin D?
Up to 30 minutes of sun on your legs, arms and back can produce up to 50,000 IU of Vitamin D. This level is not toxic as your body has built in mechanisms that will store it rather than turning it all into active Vitamin D.
What functions does Vitamin D perform in the body?
- Optimal bone health
- Muscle strength and Joint mobility
For years it was thought that Vitamin D only helped calcium absorption and metabolism, with most the research being done in the 1920’s on Rickets. In recent years the focus has been on the wider cellular actions of Vitamin D in the body and its ability to “unlock our cells genetic library” and regulate gene expression to “turn on” genes that enhance many biological processes and “turn off” genes that have a negative impact on health.
Immune system function, muscle strength, joint mobility, auto-immune conditions, cancer, heart disease, low mood, diabetes, anxiety, dementia, depression, skin disorders, autism, asthma, respiratory infections, and women’s hormonal imbalances can all be regulated when Vitamin D is at optimum blood levels.
Without going into the above conditions in detail, low blood levels of Vitamin D produce sufficient calcitriol to maintain Vitamin D’s primary role in calcium, bone and muscle strength and health. Higher levels of Vitamin D are need to “unlock our cells genetic library” for the body to benefit from Vitamin D’s secondary role in this treasure trove of other health benefits.
When Vitamin D levels are sufficient calcidiol from the liver can be converted into the active form calcitriol inside our body’s cells and it is this which starts the many cascading benefits of Vitamin D. For example, cells are able to produce antimicrobial substances such as cathelicidin and defensins, natural antibacterial and antiviral compounds that assist with reducing the incidence of infections in the body. Hence Vitamin D supplementation can help boost immunity during winter. Other secondary actions of Vitamin D include the production of natural anti-inflammatory substances, supporting healthy brain function (brain cells are dotted with Vitamin D receptors), lowering blood pressure, increase insulin sensitivity, strengthen heart and skeletal muscle, and many more benefits that time and space prevent me from mentioning.
What are optimum levels of Vitamin D?
According to the Vitamin D Council’s website greater than 50% of the world is low in Vitamin D, or has blood levels below the optimum level needed to gain full health benefits.
Full health benefits kick in at levels higher than 50 ng/mLwhich is 125 nmol/L in New Zealand levels. A simple blood test will tell you your Vitamin D levels. In some countries it may not be a free test, but should be cheap and easy enough to obtain.
Which is the best form of supplemental Vitamin D?
Vitamin D3 (cholecalciferol) is the best assimilated form of Vitamin D when compared with Vitamin D2 (ergocalciferol). Research has shown that Vitamin D3 is at least three times more potent than Vitamin D2 and is able to elevate blood levels of 25-hydroxyvitmain D for longer periods of time. Vitamin D3 is also the form that is predominately produced in the skin from sun exposure.
When is the best time for it to be used?
Vitamin D should be supplemented during winter or when there are health, social, religious issues or beliefs that prevent a person soaking up the sun during summer. Those in extreme northern and southern latitudes may want to consider supplementing all year round.
How much Vitamin D do you need?
Based on the body's indicated daily Vitamin D usage, the Vitamin D Council recommends the following amounts of supplemental Vitamin D3 per day in the absence of proper sun exposure. Due to the variable response discussed above, these are only estimated amounts.
- Healthy children under the age of 1 year – 1,000 IU;
- Healthy children over the age of 1 year – 1,000 IU per every 11.34 kg of body weight
- Healthy adults and adolescents – at least 5,000 IU
- Pregnant and lactating mothers – at least 6,000 IU
Additionally, children and adults with chronic health conditions such as autism, multiple sclerosis, cancer, heart disease, or obesity may need as much as double these amounts.
Can I use sun beds to get my dose of vitamin D during winter?
Experts on this subject seem divided on this; though the health risks associated with overuse of sun beds do seem to outweigh any conceived benefits. They can never replace the full effect of the sun. The sun stimulates over 200 photo-chemicals in the skin, and it is doubtful any sun bed can mimic that.
Is too much Vitamin D toxic?
Can too much vitamin D be harmful? Yes, it certainly can - though anything can be toxic in excess, even water. As one of the safest substances known to man, vitamin D toxicity is very rare. Toxicity is usually due to very high levels of Vitamin D supplementation over a prolonged period of time, this should only be done under health professional supervision with regular blood testing to monitor Vitamin D levels. In fact, people are at far greater risk of vitamin D deficiency than they are of Vitamin D toxicity. (Vitamin D Council website)
Are there any cofactors that help with Vitamin D’s health benefits?
Research has shown that vitamin K2 (menaquinone) has both a synergistic and complimentary role with Vitamin D3 it also assists with calcium transport to the bone where it is needed most. Vitamin K2 is naturally found in the pancreas, testes and arterial vessels of the human body. Vitamin K2 is naturally present in eggs, meat, cheese, yoghurt8 and natto (a Japanese fermented soybean food). Other Vitamin D cofactors include magnesium, boron, zinc and vitamin A.
It seems then that Vitamin D is a powerful underestimated vitamin that has many wide reaching health benefits and is used by every cell in the body. Deficiency or insufficiency is common even in sunny countries like New Zealand and Australia. Some researchers are even calling it the most powerful modern day health discovery and hail it as a cheap option for countries to use on their populace to improve overall health statistics. For further information “D place to go” is the Vitamin D Council website (www.vitamindcouncil.org) a non profit organisation dedicated to spreading reliable information on Vitamin D deficiency, sun exposure and the Vitamin D deficiency pandemic to the public and health professionals.
In choosing a Vitamin D supplement the minimum amount needed each day is a 1000 IU and should contain Vitamin K2 as a much needed co-factor. Make sure it comes from a reputable company that manufactures to the highest standard possible. Sam and the Team at the Pharmacy can help recommend the product right for you.