Vitamin D
It’s not a VitamiN
What you need to know...
As many know we get the vast majority of Vitamin D from exposure to the sun. It’s the sun’s UV B light at a specific wavelength of 280–320 (Bikle, 2011) that we actually need. This means that we are only able to produce vitamin D in the northern hemispheres between March and September. In the winter months we make no vitamin D!
We’re able to get a small amount of vitamin D from a limited number of foods, including oily fish, red meat and eggs however it is a very small amount. (NHS, 2017)
What does this so-called vitamin do?
Vitamin D has a big impact in our complex bodies and the biological processes that occur within us every day. In fact, it has been found to regulate more than 200 genes (Holick, 2008).
It plays a huge role in our musculoskeletal development.
It helps us absorb calcium and phosphate which are both essential in maintaining healthy bones and muscles.
A Vitamin D deficiency can lead to bone conditions such as rickets in children and Osteomalacia and osteoporosis in adults (Pludowski, et al., 2013).
Osteomalacia can cause painful bones and tenderness particularly in limbs and Osteoporosis gradually weakens bones and makes them more fragile (Pludowski, et al., 2013).
Vitamin D is vital in driving the insulin producing cells in the pancreas.
There is a growing body of evidence that suggests it has a role in reducing inflammatory events in the pulmonary system (lungs).
There is also thought to be a link between vitamin D and immune health. We find vitamin D receptors and metabolic enzymes in many immune cells, which has led scientists to believe that there is a biological reason to suggest the link. Therefore Vitamin D may be influential in the homeostasis of our immune system, it may help towards preventing autoimmune diseases and contribute to lowering risk of infections (Pludowski, et al., 2013) .
How is it made?
So, this is where we see that Vitamin D isn’t actually a vitamin (vital amine). It is actually a hormone.
UV light hits the skin and interacts with a steroid just under the skin’s surface called 7-dehydrocholesterol.
It is then converted into Previtamin D3 then Vitamin D3.
The liver then synthesis it to 25-hydroxylase which is the form that is transported around our body in our blood (Bikle, 2014).
This is then further metabolised to 1,25(OH)2D mainly in the kidneys (Bikle, 2014).
This 1,25(OH)2D is what the body uses to do wondrous things and it is a steroid hormone!
How much do we need?
This is where it gets really interesting and we see how simply incredible our bodies are.
So, to avoid vitamin D deficiency the level that is tested in the blood should be >29 ng/mL (Holick, et al., 2011).
How do we get that amount?
The sun offers a free way of getting plenty of vitamin D. What’s great is that the body also knows how much to produce and then stops.
20 - 30mins of sunlight exposure is all it takes. In fact, after this point the body will stop making vitamin D! So that means no need to think staying in the sun for any longer than 30 mins will produce any more vitamin D. We also need 10% of our bare skin exposed to get this benefit. That’s just your face, back of neck and back of hands.
Job done then?
Unfortunately, not quite...
In the winter months, October to February it’s recommended that we take a vitamin supplement of approximately 10 micrograms(μg) a day (NHS, 2017).
In fact, current guidelines (at time of writing) state this supplement is recommended for people living in the northern hemisphere throughout the year.
As vitamin D is synthesised and stored in the liver, we do need to be a little careful about how much we take in the form of supplements but the good news we really don’t need lots and lots. Current advice is to take no more than 100μg a day as an adult and no more than 50μg a day for children aged between 1 - 10 yrs. Babies under 12 months shouldn't have more than 25μg a day (NHS, 2017)
Note: If your doctor has recommended you take a different amount of vitamin D, you should follow their advice.
Take homes:
References
Bikle, D., 2011. Vitamin D Metabolism and Function in the Skin, Molecular Cell Endocrinology, 347(1-2). P. 80 – 89.
Bikle, D., 2014. Vitamin D metabolism, mechanism of action, and clinical applications, Chemistry & biology, 21(3), p. 319 – 329.
Holick, M. F., 2008. The Vitamin D Deficiency Pandemic and Consequences for Nonskeletal Health: Mechanisms of Action, Molecular Aspects of Medicine, 29(6), p. 361 – 368
Holick, M. F. et al., 2011. Evaluation, Treatment, and Prevention of Vitamin D Deficiency: an Endocrine Society Clinical Practice Guideline, The Journal of Clinical Endocrinology & Metabolism, 96 (7). p 1911–1930
Mostafa, W. Z. & Hegazy, R. A., 2015. Vitamin D and the skin: Focus on a complex relationship: A review, Journal of Advanced Research, 6(6), p. 793 – 804
NHS, 2017. Vitamin D - Vitamins and minerals. [Online]
Available at: https://www.nhs.uk/conditions/vitamins-and-minerals/vitamin-d/
[Accessed 28 05 2020].
Pludowski, P. et al., 2013. Vitamin D effects on musculoskeletal health, immunity, autoimmunity, cardiovascular disease, cancer, fertility, pregnancy, dementia and mortality—A review of recent evidence, Autoimmunity Reviews, 12(10. P 976 - 989
We’re able to get a small amount of vitamin D from a limited number of foods, including oily fish, red meat and eggs however it is a very small amount. (NHS, 2017)
What does this so-called vitamin do?
Vitamin D has a big impact in our complex bodies and the biological processes that occur within us every day. In fact, it has been found to regulate more than 200 genes (Holick, 2008).
It plays a huge role in our musculoskeletal development.
It helps us absorb calcium and phosphate which are both essential in maintaining healthy bones and muscles.
A Vitamin D deficiency can lead to bone conditions such as rickets in children and Osteomalacia and osteoporosis in adults (Pludowski, et al., 2013).
Osteomalacia can cause painful bones and tenderness particularly in limbs and Osteoporosis gradually weakens bones and makes them more fragile (Pludowski, et al., 2013).
Vitamin D is vital in driving the insulin producing cells in the pancreas.
There is a growing body of evidence that suggests it has a role in reducing inflammatory events in the pulmonary system (lungs).
There is also thought to be a link between vitamin D and immune health. We find vitamin D receptors and metabolic enzymes in many immune cells, which has led scientists to believe that there is a biological reason to suggest the link. Therefore Vitamin D may be influential in the homeostasis of our immune system, it may help towards preventing autoimmune diseases and contribute to lowering risk of infections (Pludowski, et al., 2013) .
How is it made?
So, this is where we see that Vitamin D isn’t actually a vitamin (vital amine). It is actually a hormone.
UV light hits the skin and interacts with a steroid just under the skin’s surface called 7-dehydrocholesterol.
It is then converted into Previtamin D3 then Vitamin D3.
The liver then synthesis it to 25-hydroxylase which is the form that is transported around our body in our blood (Bikle, 2014).
This is then further metabolised to 1,25(OH)2D mainly in the kidneys (Bikle, 2014).
This 1,25(OH)2D is what the body uses to do wondrous things and it is a steroid hormone!
How much do we need?
This is where it gets really interesting and we see how simply incredible our bodies are.
So, to avoid vitamin D deficiency the level that is tested in the blood should be >29 ng/mL (Holick, et al., 2011).
How do we get that amount?
The sun offers a free way of getting plenty of vitamin D. What’s great is that the body also knows how much to produce and then stops.
20 - 30mins of sunlight exposure is all it takes. In fact, after this point the body will stop making vitamin D! So that means no need to think staying in the sun for any longer than 30 mins will produce any more vitamin D. We also need 10% of our bare skin exposed to get this benefit. That’s just your face, back of neck and back of hands.
Job done then?
Unfortunately, not quite...
In the winter months, October to February it’s recommended that we take a vitamin supplement of approximately 10 micrograms(μg) a day (NHS, 2017).
In fact, current guidelines (at time of writing) state this supplement is recommended for people living in the northern hemisphere throughout the year.
As vitamin D is synthesised and stored in the liver, we do need to be a little careful about how much we take in the form of supplements but the good news we really don’t need lots and lots. Current advice is to take no more than 100μg a day as an adult and no more than 50μg a day for children aged between 1 - 10 yrs. Babies under 12 months shouldn't have more than 25μg a day (NHS, 2017)
Note: If your doctor has recommended you take a different amount of vitamin D, you should follow their advice.
Take homes:
- Vitamin D is actually a hormone and an essential one at that!
- It plays a vital part in musculoskeletal growth and development plus the production of insulin in the pancreas. It may also help reduce inflammatory events in the respiratory system.
- From March to September we need only expose 10% of our skin to sunlight for 25 - 30mins a day.
- In winter months we are unable to use sunlight to synthesis vitamin D.
- A supplement of vitamin D is recommended all year round if living in the northern hemisphere but certainly between October and February.
References
Bikle, D., 2011. Vitamin D Metabolism and Function in the Skin, Molecular Cell Endocrinology, 347(1-2). P. 80 – 89.
Bikle, D., 2014. Vitamin D metabolism, mechanism of action, and clinical applications, Chemistry & biology, 21(3), p. 319 – 329.
Holick, M. F., 2008. The Vitamin D Deficiency Pandemic and Consequences for Nonskeletal Health: Mechanisms of Action, Molecular Aspects of Medicine, 29(6), p. 361 – 368
Holick, M. F. et al., 2011. Evaluation, Treatment, and Prevention of Vitamin D Deficiency: an Endocrine Society Clinical Practice Guideline, The Journal of Clinical Endocrinology & Metabolism, 96 (7). p 1911–1930
Mostafa, W. Z. & Hegazy, R. A., 2015. Vitamin D and the skin: Focus on a complex relationship: A review, Journal of Advanced Research, 6(6), p. 793 – 804
NHS, 2017. Vitamin D - Vitamins and minerals. [Online]
Available at: https://www.nhs.uk/conditions/vitamins-and-minerals/vitamin-d/
[Accessed 28 05 2020].
Pludowski, P. et al., 2013. Vitamin D effects on musculoskeletal health, immunity, autoimmunity, cardiovascular disease, cancer, fertility, pregnancy, dementia and mortality—A review of recent evidence, Autoimmunity Reviews, 12(10. P 976 - 989
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