If you open any health blog you are almost guaranteed to come across an article about Vitamin D. For years this vitamin has been a source of debate with people either advocating for increased intakes or arguing against vitamin D supplementation. But why is this vitamin so important and why has it been
the source of so much misinformation and debate over the years?
Types of Vitamin D
Vitamin D is sometimes nicknamed the sunshine Vitamin! It comes in 2 major forms: Vitamin D2 and Vitamin D3.
Vitamin D2 is sometimes referred to as 'Ergocalciferol' and it comes mostly from plant sources, especially fungi (like mushrooms).
Vitamin D3 is probably the type of Vitamin D we are most familiar with. It is also known as 'Cholecalciferol' and is formed when our skin is exposed to sunlight. Some foods like eggs and oily fish are also rich in Vitamin D3.
Many of our foods are fortified with vitamin D - this means that during the process of making foods, such as cereal, small portions of Vitamin D are added in. Because we tend to eat fortified foods, plants and spend time outdoors, we have both types of Vitamin D in our bodies. The way our body processes these two types of Vitamin D does not differ drastically and they both work to increase the concentration of Vitamin D in our bodies. This concentration is referred to as 25(OH)D, which simply indicates how much vitamin D is in our body stores and can help identify people who could be deficient in the vitamin.
These two forms of Vitamin D have been greatly explored to see if one is better absorbed by the body or superior at raising our Vitamin D concentrations. Meta-analysis have been used to study this question. In a meta-analysis, data and results from a variety of high quality studies are pooled together to get a clear picture of a topic. In this case, studies looking at the two types of Vitamin D were gathered to identify if one was 'better' than the other. One meta-analysis concluded Vitamin D3 to be more efficient at raising our Vitamin D concentrations. However, it should be noted that both types of Vitamin D are still important for our bodies and having both sources is a good way to make sure we meet daily requirement.
Having discussed the types of Vitamin D let's now talk about why they are so important for our health. Vitamin D is important for preventing rickets and works alongside calcium to maintain our bone health. Vitamin D is responsible for controlling the levels of calcium in our bodies (knows as calcium homeostasis). When an individual lacks vitamin D, this deficiency (especially in the elderly) has been shown to lead to fatigue, increased fractures, pain and muscle weakness. These effects of low Vitamin D intake are partly due to the body not absorbing enough calcium. Calcium is the building block of bones and teeth and if Vitamin D is reduced, our bodies cannot absorb enough calcium leading to the effects mentioned above, as well as increasing risks of osteomalacia and rickets. Because Vitamin D and calcium are dependent on each other for health, it is often important to think of them together, especially when trying to improve bone and muscular health.
In the UK, the recommendations for Vitamin D are 10µg (micrograms) per day for men and women. In addition, it is recommended to take supplementation during the winter months when people may spend less time outdoors and therefore be exposed to less sunlight. These recommendations have been established based on research conducted by many health boards including Public Health England and SACN. However, despite these recommendations existing, many people do not meet their daily Vitamin D needs or are not aware of how much they should have. The National Diet and Nutrition Survey (conducted across the UK) 2016-2019 showed a high percentage of adults, particularly those aged 65+, to have very low Vitamin D concentrations indicating deficient vitamin D status. In 2021, a report by SACN showed that in all age and sex groups, mean intakes of vitamin D were below the daily recommended level. Therefore, it seems that the push for an increase in vitamin D intake and vitamin D supplementation may be warranted. However, it is important to remember these recommendations are based on population averages. Individual intakes and requirements may vary. Before you begin purchasing supplements think about your own diet, sunlight exposure and when in doubt talk to a professional.
Vitamin D has been greatly researched for its importance to our general health. Environmental associations such as increased colds and flus during the winter times (when there is less sunshine) have lead researchers to investigate whether or not vitamin D may be an important part of our immune system. Results from two high quality reviews (1, 2) have found that vitamin D reduced the risks and recovery outcomes of acute respiratory infections. The reduction in risks was very small in both studies but it does provide some evidence of the benefits vitamin D has on our health and immune system. However, as mentioned above, these effects may not be seen within every individual. Our individual requirements of nutrients and supplements will differ from one person to the next due to factors such as our genes, gut microbiota, lifestyle and diet. Furthermore, another study showed that after a certain point, excess vitamin D may in fact increase risks of non-communicable diseases. Toxicity can also occur if too much vitamin D is consumed. Toxicity can lead to hypercalcemia (too much calcium in the blood), gut issues, vomiting and dehydration. Therefore, we need to be aware that our Vitamin D intake, as with many things in life, is about a balance rather than excess. Finally, in this time of Covid19, many studies have tried to identify if Vitamin D is successful in preventing/treating Covid19 outcomes. Rigorous, scientific-based studies assessing this have found no clear result.
While vitamin D is certainly an essential vitamin for our normal functioning and health we must
always be cautious of individuals trying to sell us supplementation. Question when people and companies that are not professional health boards are trying to sell you supplementation. Think about their motives - are they truly interested in improving health or are they solely interested in financial rewards. Your health is important. Always make sure you assess your own diet and speak to a professional if you are concerned that you may be lacking in essential nutrients and minerals.
Finally, sunshine is a great source of vitamin D, but still remember to protect your skin when you go
outdoors!
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