Vitamin D is a commonly discussed vitamin and there is an array of Vitamin D supplements for us to chose from to ‘top up our levels’. But do we really understand what it does for us and why it is so important? With 1 in 6 people in the UK thought to have low levels of Vitamin D, this article looks at why we need Vitamin D, how we get it, and how do we know if have enough.
Why we need Vitamin D
Bone Health
- Vitamin D promotes calcium absorption in our gut, maintains adequate serum calcium and phosphates which support bone mineralisation, and prevents muscle cramps and spasms. It is vital for bone growth and bone remodelling and without it our bones will become brittle and break.
Inflammation
- The presence of Vitamin D has been discovered in almost all our immune cells. It helps regulate our innate immune responses to microbial threats and is a key component of antiviral responses.
- Recent studies have shown that composition of our gut microbiome can be altered by our Vitamin D status. Healthy individuals with optimum levels of Vitamin D have been found to have bacterial enrichment in their guts. There is growing evidence associating inflammatory conditions such as IBD and Auto Immune conditions with individuals with low levels of Vitamin D. Whilst little is currently known about the direct effects of Vitamin D on bacteria, it is evident that our immune system and our gut microbiome are interconnected and that Vitamin D is a critical player in this dynamic.
- Adequate levels of Vitamin D during early life have been associated with reduced risks of developing allergies. This is likely to be due to Vitamin D modulating inflammatory processes.
Improved mental and emotional health
- There is evidence to suggest that circulating Vitamin D levels in our bodies plays an important role in our psycho-physiologic health. Studies have found that people with low levels of Vitamin D may experience higher levels of stress and anxiety.
Supports Insulin Resistance
- Both genomic and non genomic molecular actions of Vitamin D are involved in the maintenance of insulin sensitivity. Whilst studies are ongoing to understand further the involvement Vitamin D has in this process, research has already demonstrated that Vitamin D deficiency is a crucial factor that may contribute to the formation of insulin resistance.
Support Hormonal Health
- Studies have found correlations between menstrual disorders and low levels of Vitamin D
What is Vitamin D and How do we Get It?
Vitamin D (also known as calciferol) is commonly referred to as a fat soluble vitamin. It consists of 2 bio equivalent forms:
- D2 (ergocalciferol)
- D3 (cholecalciferol).
We obtain Vitamin D through 2 routes: Dietary Consumption and Skin Production (hence Vitamin D is often called the sunshine vitamin!).
Unfortunately very few foods are a natural source of Vitamin D. The primary foods are animal sources and include oily fish (sardines, mackerel, salmon, herring), liver and eggs. However all of these provide very small quantities. Some foods will include fortified Vitamin D but the quality and amount will vary by product.
Vitamin D is produced when our skin is exposed to the sun (UVB rays). However there are many variables that influence the amount of UVB rays that actually reach our skin and how effective they are. These include our individual skin pigmentation, what we are wearing, the sunscreen we apply, the time of day we get exposure and where we live in the world. For us in the UK, during our winters, the sun rays are at an oblique angle and thus the ozone layer absorbs a higher amount of UVB radiation. Therefore, less UVB rays will reach our skin and consequently we see a decrease in the production of Vitamin D.
Even if we have exposure to adequate UVB rays we must remember that UV radiation is a carcinogen. UV exposure is the most preventable cause of skin cancer and thus it is important to take measures to protect our skin from these rays. Sunscreens with a SPF of 8 or more appear to block Vitamin D producing UV rays.
Ultimately dietary and sun exposure of Vitamin D are generally too low to maintain the sufficient levels we need. Study reports suggest that approximately 1 billion people worldwide are affected with Vitamin-D deficiency.
How do we absorb Vitamin D?
Both forms (Vitamins D2 and D3) are biologically inert. In order for us to obtain the benefits of Vitamin D, our bodies undertake complex absorption and conversion processes. At a very high level, the process is as follows:
- We absorb Vitamins D2 and D3 in our intestine.
- Our Liver metabolises it into what we call Calcidiol.
- Our Kidneys (and other select tissues) convert Calcidiol to Calcitriol (the active form of Vitamin D).
- Before Calcitriol can start to work, it binds with our Vitamin D Receptors found in the nucleus of our body cells.
- These Vitamin D Receptors then bind with another receptor in our cells called Retinoic Acid X Receptor.
- So we now have Calcitriol, Vitamin D Receptors and Retinoic Acid X Receptors. Together these 3 finally bind small sequences of DNA known as Vitamin D Response Elements and these directly and or indirectly regulate 100’s of our genes.
It is indeed a complex process but the actions that Vitamin D provide us with are critical for us to maintain our health.
How do we know if we have sufficient Vitamin D levels?
The NHS consider an adequate level of Vitamin D to be equal to or greater than is 30mol/l. However levels between 30 and 74mmol/l may be inadequate for some people and for others an optimal range is is 125-199mmol/l. Individually we will have our own unique requirements and needs.
If you are Vitamin D deficient you may not have any definitive symptoms however, deficiency can often cause:
- Fatigue
- Bone and Joint Pain
- Irritability / low mood
Even if you don’t have any symptoms is always beneficial to get your Vitamin D levels tested. Once you know your baseline it is then possible to look at if and how your levels need to be increased to optimise your health and wellbeing.
If you suspect your levels are low you can ask your Doctor to test you. Alternatively there are a plethora of private tests that can be accessed.
Should we supplement with Vitamin D?
Public Health England advise supplementing with 10 micrograms (400IU) of Vitamin D daily during the winter months.
Whether 10 micrograms is sufficient for you will depend on a number of personal variables including what your existing levels are, your exposure to the sun, and existing medical conditions, your body weight and how well your body is at absorbing and converting to active Vitamin D.
When supplementing remember Vitamin D is a fat soluble vitamin. This means that it is best absorbed with fat, so take your Vitamin D supplement with food.
Is supplementation enough?
Vitamin D does not work in isolation. It requires ‘co-factors’ to enable it to be effective. These co factors are nutrients that many of us will obtain through eating a balanced and healthy diet. It is therefore important to ensure that our diets contain a diverse range of whole foods (i.e. fruits, vegetables, nuts, seeds, meat, fish, eggs) that provide us with the following nutrients:
- Magnesium – assists in Vitamin D activation
- Vitamin A – works with Vitamin D to ensure our genetic code functions appropriately
- Vitamin K – together with Vitamin D helps the body deposit calcium in the appropriate locations such as bones and teeth
- Vitamin C, Vitamin E, Zinc, Selenium and Omega 3 Fatty Acids – supports Vitamin D with immune boosting properties
- Iron and Vitamin B12 – together with Vitamin D enhance skeletal muscle growth
Summary
Vitamin D is a key vitamin that enables critical body process to function. The challenges we have in obtaining it through diet and sun exposure as well as the complex bodily process it undergoes to become an active form, creates insufficiency risk for all us.
Identifying your Vitamin D levels is the best way to know if and how much supplementation you need. Vitamin D is a vital nutrient we all need but it important to remember it is part of a spectrum of nutrients that we need in order maintain optimum health.
References
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