What is Vitamin D and who is at risk of deficiency?
Vitamin D is a fat-soluble vitamin (alongside vitamins A, E & K) and is important in the regulation of minerals like calcium and phosphate in our body.
In the UK, deficiency is thought to be relatively common (especially over winter). According to a 2016 report from the Scientific Advisory Committee on Nutrition report on Vitamin D, roughly a quarter of adult men and 22% of adult women had blood levels of vitamin D below the cut off for deficiency (defined as <25nmol/L on a blood test) (SACN, 2016). This level increased to almost 40% of adults in the winter months, although was only 8% in the summer (SACN, 2016).
Those at increased risk of deficiency may include pregnant and breastfeeding women, babies and young children under 5, older people over 65, people who are not exposed to much sun (especially if house-bound, or cover most of their skin when outside) and people who have darker skin tones (Department of Health, 2012).
Where does Vitamin D come from?
The main source of vitamin D is sunlight.
In the UK, however, the UV light required to cause vitamin D to be produced in our skin is only strong enough in the spring and summer months (roughly April to early October). The light is not strong enough over the winter to create vitamin D in our bodies. Therefore, safe sun exposure over the summer months is an important factor in keeping our vitamin D levels sufficient across the whole year.
See my article on Summer Health for advice on safe sun exposure. We make plenty of vitamin D in our skin long before burning or tanning and additional sun exposure beyond this may increase the risk of sun damage and ultimately, skin cancer. There’s a sensible balance to be found.
Dietary sources of vitamin D may include (NHS, 2017)
- Oily fish (such as salmon, sardines, mackerel)
- Egg yolks
- Some fortified foods (such as breakfast cereals and infant formula). Note that vitamin D is not routinely fortified in dairy products in the UK, as it is elsewhere in the world.
- UV-treated or sunlight-exposed mushrooms
- Red meat / liver
However, only small quantities of vitamin D are found in food, so it is not recommended that we rely on food-forms alone. Sunlight and supplementation are also important.
Current UK Guidelines for vitamin D supplementation
The full NHS guidelines for vitamin D supplementation can be found here. This is a summary of those guidelines, taken directly from the NHS website.
10 micrograms = 400 International Units [IU] (the doses on supplement labels will usually state both, but it is helpful to know this conversion).
Please note: Some people have medical conditions that mean they cannot safely take this much vitamin D. If in doubt, you should consult your doctor. Likewise, some people may have been prescribed a different amount of vitamin D to the doses mentioned below by their doctor or other healthcare provider. You should, of course, follow any professional advice you’ve been given.
Be aware that some over-the-counter supplements contain other vitamins or ingredients. Having too much of some vitamins can be harmful. Keep to the dose recommended on the label, and be careful not to give your baby or child two supplements at the same time, unless otherwise recommended. Talk to your pharmacist about which supplement would be most suitable for you, your baby or your child to take.
- Breastfed babies from birth to 1 year should be given a daily supplement containing 8.5 – 10 micrograms of vitamin D. Tip: If you’re breastfeeding, you can put the appropriate dose (according to the label) onto your nipple before starting a feed.
- Formula-fed babies having more than 500ml of infant formula per day do NOT need supplementing (as it is already in their milk).
- Do speak to your midwife, health visitor or GP for more information and support.
- Children aged 1-4 should be given a daily supplement containing 10 micrograms of vitamin D.
- Children aged 5+ should consider taking a daily supplement of 10 micrograms vitamin D during autumn and winter.
- Everyone (including pregnant & breastfeeding women) should consider taking a daily supplement of 10 micrograms vitamin D during autumn and winter. Please note that many fertility and pregnancy supplements already contain vitamin D – so check the labels.
- As it is possible to get enough vitamin D from sunlight and diet between April and early October, you may choose not to take a supplement during these months, especially if you spend time outdoors on a regular basis.
- However, if you get very little sunshine (for example, are not often outdoors, or wear clothes that cover most of your skin when outdoors), or have a darker skin tone, you may wish to consider taking a daily supplement containing 10 micrograms of vitamin D throughout the year.
- Coronavirus Update: The NHS website now suggests that we consider taking 10 micrograms of vitamin D a day during lockdown, including over the summer months, particularly if we are indoors most of the day.
Choosing a supplement:
Taking too much vitamin D over a long period of time can cause excessive calcium build-up in the body, which may weaken bones and potentially damage the kidneys and heart. It is therefore important to be conscientious about the dose of vitamin D in your supplement, as it is possible to buy very large doses over-the-counter. More is not necessarily better.
- If you are taking a multi-nutrient already, check the label as it may well already contain the full dose of vitamin D recommended. You do not need to take a separate vitamin D on top of this, unless advised otherwise.
- Most vitamin D supplements are derived from lanolin, so if you are vegan, you will need to look out for a vegan-friendly option. This is often made from lichen, interestingly.
- Look for vitamin D3 (cholecalciferol) in your supplements.
- You can find vitamin D in spray, drop, or tablet form. I tend to use a spray, as I am not very good at remembering to take tablets, and the spray is an easy habit to get into (especially if you keep it next to your toothpaste – many are already mint flavoured, too).
What I use:
As I often get asked about the products I use or recommend, I have included a couple of them here. Please note that they might not necessarily be the best option for you personally.
These are the vitamin D drops I use for Willow (suitable from newborn).
This is the Vitamin D spray that I use (it says ‘junior’ on the label, but is also an adult-appropriate, peppermint-flavoured 400IU daily dose).
These vegan vitamin D3 drops provide 100 IU per drop, so 4 drops would give the full 400IU daily dose.
References & Bibliography
Department of Health, 2012. Manual Of Nutrition. 12th ed. The Stational Office.
NHS, 2017. Vitamins And Minerals – Vitamin D. [online] nhs.uk. Available at:
Scientific Advisory Committee on Nutrition, 2016. Vitamin D And Health. [online] Available at:
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