The Importance Of Boosting Our Vitamin D

Autumn Colors
Photo by Aaron Burden on Unsplash

Why Vitamin D Is So Important

Ah, September! New school year; nights drawing in; days cooling; advertisements for Hallowe’en, Bonfire Night and Christmas ramping up. It’s autumn! And that means we must consider the importance of boosting our vitamin D

Autumn means lots of different things, but one of the most important things that happens in September can have a profound effect on our health. In the south of the UK, from early September until mid-April the following year, we cannot make vitamin D from sunshine. And the further north you go in the UK, the earlier that cut-off point happens.

Making Vitamin D From Sunshine

This is because, to make vitamin D from sunshine, a specific wavelength of light (ultraviolet B or UVB) needs to be able to get through the atmosphere. UVB can only get through the atmosphere in enough quantities to stimulate the production of vitamin D in our skin when the sun is above a 45º angle in the sky.  

Personally, I have no idea how to measure the angle of the sun in the sky. But luckily there is an easy way to tell if the sun is high enough to make vitamin D in our skin. If your shadow is shorter than you are, then you are making vitamin D.

Always assuming you don’t have your skin covered with clothing or loads of sunscreen. If your shadow is taller than you, then the UVB getting through the atmosphere simply isn’t powerful enough to trigger the chemical process that makes vitamin D in our skin.

What Stops Us Making Vitamin D?

In the UK, most of us only need about 20 minutes of sun exposure a day during the summertime. But even on sunny summer days, we don’t spend nearly enough time out of doors. We sit in offices or our houses. All too often, at lunchtime when the summer sun is at its highest, we eat in front of our computers instead of going out.

When we do venture out, we cover our skin in sunscreen, which blocks the UVB rays and prevents vitamin D production. Or we wear long sleeves and hats, protecting ourselves from the sun because we fear skin cancer. Staying out in the sun without protection for half the amount of time it would take for skin to start going pink makes plenty of vitamin D – and does not raise the risk of skin cancer.

There are some population groups in the UK that struggle to make enough vitamin D from sunlight alone. The pale skin of Europeans evolved specifically to make enough vitamin D from less intense sunlight. People whose ancestors originated in hotter parts of the world have maintained higher levels of melanin (which makes skin dark) because it protects them from stronger sunlight. Unfortunately, this also makes it difficult for them to make enough vitamin D from the weak sunlight we get here.

Shouldn’t We Get Vitamins From Our Food?

Well, yes, but vitamin D is actually very different from any of the other nutrients that we need to keep us healthy and happy, because there aren’t high quantities in many foods. 

Salmon and Salad: Photo by Caroline Attwood on Unsplash

Vitamin D is a fat-soluble vitamin, which means that it is found in the fat content of foods. But where it does turn up, there isn’t a lot of it. The one food source that is high in vitamin D is oily fish, which only a quarter of the UK population eats. The other foods which contain good levels of vitamin D are eggs, fortified breakfast cereals, and mushrooms that have been exposed to UVB.

The best way to guarantee getting enough vitamin D is to take food supplements from early September to mid-April. And, if you don’t get much sun exposure from mid-April to the end of August, then carry on taking the supplements all year round.

Because vitamin D is a fat-soluble substance you should always take supplements with foods that contain fat, otherwise you won’t be able to absorb it. Taking supplements or eating fortified breakfast cereal with skimmed milk is actually pretty useless because it is the fat content in the milk that lets us absorb the vitamin D.

So How Much Do We Need?

We only need vitamin D in tiny quantities. It is measured in micrograms, which is written as “µg” or “mcg” on food labels, and there are one thousand micrograms to a milligram. But those micrograms are incredibly important for our health.  

Public Health England states that through autumn and winter everyone “should consider taking” a vitamin D food supplement of 10µg. However, a lot of the rest of the world thinks that 10µg is too low. The United States, and countries in the European Union, advise their citizens to take at least 15µg a day, with the elderly and women who are pregnant or breastfeeding, needing 20µg a day.

How Much Vitamin D Is There In Food?

In the UK an average egg contains 3.2µg, and 100g of farmed salmon (the most commonly eaten oily fish in the UK) contains around 6.8µg. Fortified breakfast cereals contain around 2.5µg per serving. Mushrooms that have been exposed to UVB light can contain as much as 10µg per 100 grams.

Unfortunately, people in the UK eat neither eggs nor oily fish in great quantities, and the majority of mushrooms sold in the UK have not been exposed to UVB.

The Safety Of Vitamin D

There has never been a case of vitamin D overdose from sunlight – the body makes what it needs and stops when it has enough.

For vitamin D from food (including supplements), we know that vitamin D is safe up to an intake of 100µg a day over a long period of time. Not that anyone would be likely to overdose from food alone – who fancies 31 eggs or a kilo of mushrooms every day? The highest food intake we can get is from food supplements. Most single nutrient vitamin D food supplements are sold in either 10µg or 25µg daily doses, although there are some on the market that contain a higher dose.  

Sometimes vitamin D food supplement labels show “IU”. These are “international units”. 400IU is equivalent to 10µg, 1,000IU is equivalent to 25µg and 4,000IU is equivalent to 100µg. You should never take more than 4,000IU (equivalent to 100µg) unless a medical practitioner has advised you to do so.

What Vitamin D Does

Most people know that vitamin D makes your bones strong.  Some people know that it does the same for your teeth. But the more science looks into vitamin D, the more things we are finding out that it does, and it goes way beyond keeping our bones and teeth healthy.


Almost every single cell in our immune system has special receptors that only respond to vitamin D. Although science is still working out what exactly vitamin D does for those cells, it is clear that vitamin D supports the working of the immune system. Low levels of vitamin D have been linked with an increased risk of all kinds of infection, as well as autoimmune diseases, some cancers, and even flu and Covid.

Mental health

Vitamin D impacts our mental health, and low levels of vitamin D can lead to depression, anxiety and even suicidal behaviour. And low vitamin D levels may also be a cause of seasonal affective disorder (SAD), sometimes called the winter blues.


Inflammation is not as simple as something being swollen and sore. It also happens at a very deep level, affecting our cells in ways that we may not be aware of. Cellular inflammation is one of the things that triggers auto-immune diseases like Type 1 Diabetes, multiple sclerosis, arthritis, inflammatory bowel diseases like Crohn’s disease and IBS, and skin conditions like psoriasis.

Vitamin D actually helps to stop inflammation happening or, when inflammation does happen, it helps to reduce it. Which is why low levels of vitamin D are linked with a higher risk of developing a lot of these autoimmune diseases.  

Vitamin D Levels In the UK

UK Government data shows that around 50% of the population have vitamin D blood levels below the recommended level, which means that a huge proportion of the UK population are vitamin D deficient. And some population groups in the UK are more severely impacted than others.

Up to 60% of Afro-Caribbean and South Asian populations in the UK are severely deficient in vitamin D. Severe deficiency brings a whole host of health issues including rickets, osteomalacia (the adult form of rickets which causes bone pain and bone and muscle weakness), weakened immunity, a greater risk of autoimmune diseases and some cancers.

Vitamin Supplement: Photo by Nicolas Solerieu on Unsplash

So, What Should I Do?

Everyone should take a vitamin D supplement from the beginning of September to the beginning of April. There is little evidence for safe levels in children under the age of 12 so, taking a precautionary approach, children under the age of 12 should take a 10µg supplement.

Adults should take a 25µg supplement. If you are already taking a multivitamin which contains vitamin D, check the nutrition label on the back of the pack. It probably contains between 5 and 10µg. Still take the extra supplement – vitamin D is safe up to 100µg over long periods of time.

If you have dark skin, cover up for religious or cultural reasons, or stay out of the summer sun, you need to take vitamin D supplements all year round.

Take your supplement with food that contains fat so that you can absorb it.

There are loads of vitamin D products on the market. The big chemist chains sell them. The supermarkets sell them. Health food stores sell them. Most of them are not expensive and some work out at a couple of pence per tablet. Taking vitamin D means you are practising self care and actively protecting your own health and wellbeing.