But how can we ensure we get enough vitamin D on a daily basis? And if we're hoping to source our vitamin D through diet, is it even possible to reach the recommended intake this way? If so, how much do we need to consume? People that live in UK can't get vitamin D from the sun due to the UVB rays not being strong enough or variable throughout the year, so is diet a reliable method of ensuring we don't become deficient in this essential vitamin? We've teamed up with Dr Sarah Brewer to answer these questions.
How much vitamin D do we need daily?
The optimal level of vitamin D for one person is much higher than we once thought. When vitamin D was all about calcium absorption, the recommended intake was just 5mcg per day. From 2016 Public Health England had suggested an intake of 10mcg per day during Autumn and Winter. What's more, in April 2020 this advice was updated to recommend that anyone spending a lot of time indoors should take a vitamin D supplement during the spring and summer, too.
Research now suggests that many people need higher amounts to maintain good vitamin D status – especially in later life.3 Many experts are calling for everyone to supplement at a higher level all year round. The majority of adults need between 25 mcg (1,000 IU) to 50mcg (2,000 IU) of vitamin D per day for optimum health, especially if they're already deficient or have a higher risk of deficiency.4
One thing we do know is Brits - on average - are lacking in vitamin D. The latest National Diet and Nutrition Survey (NDNS) results show that 17% of adults have low levels of vitamin D all year round.
Unfortunately, the absorption of vitamin D varies significantly per person based on factors such as skin colour and weight. For example, those with darker skin absorb less vitamin D from the sun, and those who have a larger fat percentage tend to have a higher risk of vitamin D deficiency, due to them absorbing nutrient supplements less effectively.5 Using sunscreen with a high SPF (always a sensible idea) also reduces vitamin D production in the skin by screening out UV rays.
Why can we not get vitamin D from sunlight?
During autumn and winter in the UK your skin cannot react with sunlight to produce vitamin D. Put simply, the UVB rays emitted by the sun at this time – October through to early April – are not strong enough, meaning diet is the only source of this nutrient. A good rule of thumb is that if your shadow is longer than you are, you're not producing vitamin D.
Even during the summer months, the amount of vitamin D we make from the sunshine on our bare skin is highly variable. Some factors that affect how much vitamin D we make in our skin include:
The time of day
- Our latitude
- How dark our skin is – the darker our skin, the less vitamin D we make
- The use of sun cream – sunscreen blocks our natural production of vitamin D
- How much of our body is exposed to the sun
- How old we are
- Our body size and whether we are overweight
- Even altitude, air pollution, and how overcast it is can affect how we make vitamin D from sunshine
What's more, many of us simply don't get enough sun exposure. We spend too much time indoors, or we cover up with sunscreen (something we must do to protect our skin) when we're outside, which inhibits vitamin D synthesis.
Can we get what we need from our diet?
Sadly, there are few reliable dietary sources of vitamin D. This is especially the case for vegetarians and vegans, as vitamin D is split into two different types – vitamin D2 and vitamin D3. The latter is twice as effective at raising vitamin D levels in the body compared to its plant-based vitamin D2 counterpart.6
Many vegan milks, cereals, and juices are fortified with vitamin D2 which is less easily absorbed by the body. Most products contain very low amounts of the nutrient, too – typically 0.75 mcg (30 IU) per 100ml.
Which foods contain vitamin D3?
The food group highest in vitamin D3 is oily fish, which includes salmon, sardines, and mackerel. To give some context, a small fillet of salmon (about 80g) provides around 10 mcg (400 IU) of vitamin D3, although factors such as the species of salmon, whether it's wild or farmed and the season during which the fish was caught may affect this estimation. Sardines and mackerel are also good sources of vitamin D3, with 80g of mackerel providing roughly 10 mcg (400 IU) of vitamin D and a small tin of sardines (120g) roughly 6 mcg (240 IU).7
While oily fish is a good source of vitamin D3, most of us are unlikely to eat it every day. Additionally, the most you're likely to get from one portion is 10 mcg (400 IU) – perhaps less. Given that the average Brit needs at least 25 mcg (1000 IU) of vitamin D per day, you'd have to eat several fillets of wild salmon, or five whole tins of sardines daily to reach this target.
Another good source of vitamin D3 is beef liver, with 80g providing up to 1 mcg (40 IU). While this allows you to top up your intake, it would be unrealistic and unhealthy to eat the equivalent to 25 mcg (1000 IU). Likewise, with egg yolks, which provide about1 mcg (40 IU) per egg. If you wanted to achieve a daily intake of 25 mcg (1000 IU) from eggs alone, you'd need to eat a whopping 25 eggs per day.7
It's easy to see why diet provides such a low proportion of our daily vitamin D requirements. There simply aren't enough vitamin D-rich foods that can feasibly be incorporated into our diet. Diet should always come first, so while it cannot provide enough vitamin D to stop deficiency and support optimal levels, it's important not to discount food sources of vitamin D entirely. Every little helps, after all.
So, what's the solution?
The reality is that vitamin D supplementation is the most effective and least invasive solution to maintaining healthy levels of vitamin D. Taking just one vitamin D supplement daily, all year round, helps to ensure that you're getting enough every single day. No need for unfeasible diets or continuous sun exposure.
This doesn't mean we should discount the sunshine or our diet as helpful ways to keep our vitamin D levels topped up. Rather, we should be looking to use supplements alongside the right food and sensible sun exposure to ensure we're not deficient in what's proven to be an absolutely essential nutrient.
It's easy to find a way of supplementing with vitamin D that suits you, too. If you don't like swallowing tablets, fast-acting sprays are available, and there are great-tasting gummies, too.
If you'd like a little more insight into the further benefits of vitamin D, or you'd like some extra info on how to choose the right supplement, head on over to our advice centre.