How to win against winter bugs with Vitamin D

Winter sun Vitamin D

As we head towards the cold and flu season, I’m sure like me, you do everything you can to stay away from catching a nasty bout of sniffles which can leave you feeling rotten for weeks.

Vitamin D is where I turn to at this time of year. It is an essential vitamin that supports our body’s immune response by improving our ability to fight infections and viruses. Read on and learn more about vitamin D, why it’s so important for immune health, and how best to top up your stores so you stay fit and healthy through the winter months.

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What is vitamin D?

Vitamin D (also called 25-hydroxyvitamin D) is a fat-soluble vitamin and there are three key sources to keep us topped up. We make vitamin D internally when our skin is exposed to the sun; it is present in some foods, but only in small amounts, and lastly in vitamin D food supplements. Our bodies can’t make vitamin D without the aid of sunlight and food; it is therefore considered ‘essential’.

In food and dietary supplements there are two main types of vitamin D: vitamin D2 (ergocalciferol) which is found in plants, and vitamin D3 (cholecalciferol) mostly found in animal products. Our body naturally makes vitamin D3 and prefers this version as it is more bioavailable to us, meaning our body finds it easier to use. When buying vitamin D food supplements, it’s important to purchase ones which contain vitamin D3 and be mindful that fortified foods are usually fortified with vitamin D2 which is harder to assimilate.

Why is vitamin D important for our immunity?

Your immune system requires vitamin D to function properly because all immune cells have vitamin D receptors on them, and vitamin D itself is considered an ‘immune modulator’. Research shows that it could be involved in protecting against the development of infections, viruses, autoimmune conditions as well as colds and flu.

Vitamin D supports our immune system by suppressing the ability of some viruses to replicate and grow. Importantly 70-80% of immune cells are located in the gut and vitamin D is thought to provide gut support by protecting the mucosal lining, whilst supporting the integrity of the gut lining. As well as infections and immunity, a 2019 review also suggests that vitamin D may provide some protection against cancer, diabetes, heart disease and depression.

When we don’t obtain enough vitamin D through sunlight, foods, or supplements, we become deficient and that leaves us at a greater risk of picking up illnesses, such as the common cold. In the UK, the National Institute for Health and Care Excellence (NICE) suggest that vitamin D deficiency affects one in six children and one in five adults. This equates to a whopping 10 million people. That’s a huge number of people with a deficiency that impacts their immune health, which can easily be remedied and overcome.

How do I boost my vitamin D levels?

It is really easy to keep vitamin D levels topped up when you know how and you may need to mix and match depending on the time of year. The three main sources to obtain vitamin D are sunlight, food, and supplements.

Sunlight: Ultraviolet B rays (UVB) from the sun are absorbed by cholesterol through our skin and then synthesised into vitamin D3. Magnesium also plays a role in the synthesis of Vitamin D from the sun. In the UK, as we are at quite a high latitude, these rays are only useful from April to September, so this is why vitamin D supplementation is recommended from October to March. However, if you are someone who tends to cover up or always uses sun cream during the summer months (which further prevents UVB rays from penetrating our skin), then a year-round supplement may be appropriate.

Foods that contain vitamin D: Oily fish (such as mackerel, salmon, trout and tuna), shellfish, beef liver, eggs, organic dairy products, grass-fed meat, mushrooms and some fortified foods such as plant-based milks all contain vitamin D but only in very small amounts. So, in order to obtain the minimum recommended daily intake of 400 IU, you would need to eat 2 cans of tuna, 3kg of cheese and 8 eggs every day which is not advisable!

Vitamin D supplements: Due to the limited availability of vitamin D through foods and to some extent from our lack of sunshine, it’s important to find a good quality supplement. Vitamin D is available in drops, sprays, and capsules so it’s easy to find one that suits all members of the family. Please be mindful that vitamin D may interact with some medications such as statins and steroids, so please check with your GP before using them.

How much vitamin D do I need?

It is recommended by Public Health England and the NHS that anyone above the age of 12 months old should take a minimum of 10mcg (400 IU) of vitamin D per day, with babies requiring 8.5-10 mcg as a precaution to ensure they obtain adequate amounts. If your little one is having more than 500ml of infant formula a day, you wouldn’t need to top up with a supplement.

However, even though all of the US (except Alaska!) is at a lower latitude than the UK, the US-based National Institutes of Health (NIH) suggests higher recommended daily amounts of 15 mcg (600 IU) per day for anyone aged between 9 and 70, with upper tolerable limits set at 100 mcg (4000 IU) for teens and above. This means children over the age of 12 and adults can safely take up to 4,000 IU of vitamin D daily from October through to March. Most people find that a 3,000 IU daily food supplement top-up serves them very well.

I hope this has been helpful for you and your family. Although vitamin D is recommended by the NHS and Public Health England, many of us still do not take a vitamin D supplement from October to March, so this is a little reminder. If you want to support your family’s immune health and be proactive at keeping those nasty coughs, colds, and infections at bay this year, make sure you stock up on this essential vitamin.

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  1. Is there a best time of day to take a supplement? With or without food?

    Also I’d be interested in knowing more about the links between vit D and steroids.

    1. Vitamin D being fat soluble means it is better to be taken with a meal or a snack, but it does not matter what time of the day otherwise.

      From our research there does not seem to be any significant interactions between prescribed steroids such as prednisolone and Vitamin D3. However, it is always important to check with your consultant or GP.