Everyone’s talking about… Vitamin D


Vitamin D is in the news again! Last week, Public Health England (part of the Department of Health in the UK) advised that we all need to get at least 10 micrograms of vitamin D per day, year-round. During the Winter, we don’t make any vitamin D from sunlight on our skin (which should be our main source), and the average intake from diet is currently only 3 to 5 micrograms. This means that many people should consider taking a supplement over Winter.

Let’s have a closer look at why vitamin D is so important, how we get it, why many of us may be low in vitamin D, and how much we should be supplementing.

Vitamin D for bones and teeth

Vitamin D is vital for bone health. It helps us to absorb enough calcium and phosphorus from our food to keep our bones strong. This means that it helps to prevent conditions such as rickets in children and osteomalacia in adults, as well as fractures.

Vitamin D for muscles

Vitamin D supports healthy muscle function and muscle strength. This doesn’t mean that it will give you big muscles! Normal muscle function and ability to maintain muscle strength are vital to allow us to move our body in a healthy way, and to carry out normal daily activities. Loss of muscle in the elderly, for example, is a primary cause of health deterioration.

Vitamin D for immunity

Did you know that vitamin D is also one of the most important nutrients for your immune system? As well as helping to keep our immune system strong to fight off bugs such as colds and flus, vitamin D may help to regulate immunity – helping to prevent over-activation of the immune system that can result in allergic conditions or autoimmune conditions. In other words, your risk of these conditions may be higher if you have a long-term deficiency in vitamin D.

Vitamin D for growth, repair and reproduction

Vitamin D is also vital for normal cell division. This is particularly important when it comes to growth and repair of the body’s tissues, as well as making a baby!

Vitamin D for heart health

Studies have suggested that having healthy vitamin D levels is associated with lower risk of heart disease and high blood pressure.

Vitamin D and mood

There is a potential link between vitamin D levels and mood, too. It’s thought that one of the reasons for feeling low in Winter could be declining vitamin D levels over the darker months.

Where do we get vitamin D… and are we getting enough?

Known as the ‘sunshine vitamin’, vitamin D is made in our skin in response to UVB rays from the sun. We can also get some from food – the richest sources are egg yolks and oily fish such as salmon, mackerel, herring and sardines. But food sources are rarely enough to meet our requirements: as mentioned in the introduction above, the average intake from foods is only 3–5 micrograms per day. So our main source should be sunlight!

In the UK, sunlight is only strong enough between late March and September to stimulate vitamin D production. From October until early March, you won’t make any even if you go out on a sunny day with bare arms and legs. And even in the Summer, your production of vitamin D can be reduced by various factors, such as use of sun protection, not exposing enough of the skin to the sun, lack of sunny days – or just not getting outside! Of course, getting enough vitamin D also needs to be balanced with safe sun exposure, which can make it difficult to know how much sun is both enough and safe.

All this means that many of us don’t have adequate vitamin D stores: according to the government’s Vitamin D and Health Report [1], 30–40% of the population are deficient over winter. This is why a supplement may be helpful.

Vitamin D supplements: is 10 micrograms enough?

The official recommendation is that children and adults should be getting at least 10 micrograms per day (equal to 400 international units, or IU). We agree that it’s worthwhile for most adults and children to take at least this amount in supplement form over the Winter (unless they’re regularly spending time abroad in a warm and sunny location).

However, this recommendation is based on the amount needed to get most of the population to a minimum level of just 25 nmol/L of vitamin D in the blood. But is this really enough? Many researchers actually believe that optimal levels of vitamin D in our blood are closer to 100–125 nmol/L. This means that a much larger percentage of the population are likely to have sub-optimal levels of vitamin D, even if they’re not classed as deficient; and that more than 10 micrograms in supplement form is likely to be needed to achieve good levels – at least in adults.

However, we also need to be careful not to overdo vitamin D. As it’s stored in the body, taking large amounts in supplement form over a long period of time could cause health problems too.

So what do we recommend?

To maintain good levels throughout Winter, we suggest that adults take a supplement providing around 25 micrograms (1000 IU) of vitamin D per day.

If you’ve had a vitamin D test done and know that you’re deficient, then taking a supplement providing a higher level of 50–100 micrograms per day (2000–4000 IU) for one to two months may be helpful to increase your level more quickly. It’s then suggested to drop back to 25 micrograms a day to maintain a healthy level.  If you have a higher-dose supplement to use up, you can also achieve this by taking the higher dose supplement every two to four days to average out at around 25 micrograms a day.


  1. Scientific Advisory Committee on Nutrition. Vitamin D And Health. 2016. Print. Available at: https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/537616/SACN_Vitamin_D_and_Health_report.pdf
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