17 Jan 2022

Does vitamin D help fight the coronavirus? All you need to know with Laurann O'Reilly...

This week's column in The Nationalist

Six top nutrition tips for boosting your immune health with Laurann O'Reilly

Laurann O'Reilly

There are many nutrients, vitamins and minerals required for maintaining our health but the most recent one which has come into the limelight is vitamin D due to our most recent Oireachtas report. An all-rounder, vitamin D is both required for many body processes and holds many benefits in both the prevention and treatment of illness.

Here nutritionist Laurann O’Reilly and owner of Nutrition by Laurann, explains everything you need to know about vitamin D.

What is Vitamin D?

Vitamin D is an essential nutrient and critical for the development and normal functioning of many organs in the body and for maintaining optimal health throughout our whole lives.

Where Can We Get It?

Sun exposure via our skin, specifically ultraviolet B (UVB) rays, which is why it’s also known as ‘the sunshine vitamin’. The World Health Organisation advice is to get 5 to 15 minutes of casual sun exposure to hands, face and arms two to three times a week during the summer months.
It can also be found in small amounts of food products with Vitamin D2 (ergocalciferol) found in some plant based products and Vitamin D3 (cholecalciferol) found in some animal based products. However, the richest dietary sources are found in fortified foods. Vitamin D is also fat soluble meaning when taken through the diet, it needs to be consumed with an oil in order to be absorbed in the body.

What Are The Benefits?

Whilst Vitamin D has numerous benefits here are some of the few:

- Healthy Bones & Teeth- Vitamin D is essential for strong bones as it is required for the absorption calcium and phosphorus from food. These are both essential minerals for maintaining healthy teeth and bones whilst also helping to prevent osteoporosis.

- Supporting The Immune System - Evidence suggests that vitamin D may have an important and supportive role for the immune system, particularly in regulating immune response and reduction of proteins known to trigger inflammation.
- Improving Gut Health – A study carried out last year found that Vitamin D supplementation can significantly increase the variety of our gut bacteria, which play an important role in digestion, immunity and hormone balance.

- Mood - As our bodies produce vitamin D from sunlight, our levels of this vitamin can seriously decrease during the dark winter months. It has also been suggested that this drop in vitamin D may be linked to ‘Seasonal Affective Disorder’ or SAD, a mood disorder which is also common in individuals during this time.
This is because vitamin D is involved in regulating the production of serotonin. The Irish TILDA study also found that individuals over the age of 50 years are 75% more likely to experience depression if their Vitamin D levels are low.

- Respiratory Health - Vitamin D is known to assist in fighting bacteria and viruses and reduce acute respiratory infections. An international study (the Jolliffe papers) showed “a 25% reduction of the risk of respiratory infections in those taking a daily vitamin D supplement”.

Potential Use with Covid-19 – Most of us have now heard of the newly published Oireachtas report which aims to improve public health measures which can prevent the spread of the disease in the community. The report discusses the potential role of Vitamin D in “preventing ill health and respiratory illness” and how “Vitamin D is known to assist the immune system in fighting harmful bacteria and viruses” along with “reducing the risk of acute respiratory (lung) infection”. The report discusses how evidence from the Jolliffe papers above as well as additional studies “strongly support a causal relationship between low Vitamin D status and increased risk and severity of Covid-19 infection”.
As a result, they have recommended that the entire Irish population takes a vitamin D supplement.

What Affects Our Vitamin D Levels?

Skin Pigmentation - People with darker skin are at higher risk of low vitamin D due to a higher level melanin in their skin. Unfortunately, melanin reduces the ability of UVB rays to pass through the skin, lowering the body’s ability to make vitamin D.

Age – As we age, our body’s ability to produce vitamin D from the sun becomes less efficient due to the effect that the ageing process has on the skin. A study comparing the amount of Vitamin D3 produced in the skin from the 8 and 18 year old subjects with the amount produced in the skin from the 77 and 82 year old subjects revealed that the younger group had greater than twice the capacity to produce Vitamin D.

The season - In Ireland we have reduced daylight hours from autumn to mid spring which limits our opportunity for creating vitamin D. Other factors which can limit our exposure to the sun are long hours working or studying indoors as well as a lack of opportunity to access the outdoors such as residents of nursing homes and as well as those who don’t have a safe outdoor recreation area.

Clothing – As we require our skin to be exposed to the sun in order to create Vitamin D and in Ireland it’s rarely warm enough to go without a jumper, jacket or scarf, this again impairs the chance for creating the vitamin.

Sun protection - It’s highly important to take care when exposing the skin to the sun to prevent skin cancer. It has been shown that correct application of a product containing an SPF of 15 almost completely prevents skin production of vitamin D which is why adequate food sources and supplementation is important.


In addition to not getting enough sunshine in Ireland, the quality of sun generally doesn’t provide enough in UVB to generate adequate Vitamin D, particularly during the winter months to support our immune system. The recent Oireachtas report discussed how deficiency is can be found across all age groups, with deficiency found in almost half of 18-39 year olds, over a third of 50-59 year olds, 64% of the over 80s, 67% of nursing home residents and 93% of BAME communities (black, Asian and minority ethnic).

Recommendation: The report recommends that the entire Irish Adult population should take a supplement of 20-25 μg/day or 800-1000 IU/day, whilst children should take 10μg or 400IU/day as a public health measure as an aim to reduce the risk of respiratory conditions and other illnesses such as osteoporosis. If you have any pre-existing medical conditions or are taking medications please consult with your GP or pharmacist first.

Food Sources: Vitamin D can be found in oily fish such as mackerel, sardines, tinned salmon, herring and kippers and a small amount in sources such as red meat, liver and eggs
Fortified milk such as super milk and cereals are also great sources. The Oireachtas report suggests that the above supplement recommendation is taken alongside dietary sources in order to adequately meet requirements.

Supplements: The report also discusses the importance of Vitamin D supplementation not only for the Irish adult population but also for vulnerable groups such as those in nursing homes and health care workers. Vitamin D supplements commonly come in the form of a spray or a capsule, when choosing a Vitamin D supplement, it’s best to choose Vitamin D3, which is the most efficient form of the vitamin and is also the most effective at improving the blood’s vitamin D levels. Recommendations: my preferred Vitamin D supplement is the PharmaNord BioActive Vitamin D pearls (available in a 38μg/1520 and a stronger 75μg/3000 IU)

Vitamin D Boosting Recipe: Lemon Pepper Salmon

1 Salmon Darne = 292 IU

4 Darnes of salmon
4 Teaspoons of thyme
1 Large lemon, sliced
1 Large lemon, zested and juiced
2 Tablespoons extra virgin olive oil
2 Cloves of garlic, crushed
1 Teaspoon salt
1 Teaspoon freshly ground black pepper
A handful of finely chopped fresh parsley and basil

Preheat your oven to 180°Celcius and line a baking tray with tin foil
Lightly coat the foil with half tablespoon of olive oil, sprinkle half the thyme, evenly spread the chopped lemon and place the salmon on top; Top the salmon with the remaining olive oil, lemon zest, lemon juice, crushed garlic salt and pepper and the remaining thyme
Cover the salmon with another sheet of tin foil and bake for 15-20 minutes; Remove the salmon from the oven, and carefully remove the foil (as steam may have built up; Serve on a bed of wholegrain rice and vegetables

Laurann O’Reilly is qualified and experienced nutritionist with a BSc. Degree in Human Nutrition from University of Nottingham and a Master’s in Public Health Nutrition from University College Dublin. For further information see or contact Laurann at 

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