Food for Thought: Vitamin D

Whilst the media may suggest otherwise, in general, there is a clinical need for only a few supplements. These include vitamin D, calcium, iron and vitamin B12. Vitamin D, sometimes referred to as the sunshine vitamin, in particular is a cause for concern among the Irish population. This is because vitamin is mainly synthesised by the action of sunlight on the skin. However, this action can only take place when the sun is strong enough from April to September. This means that for half of the year, we cannot manufacture vitamin D and must rely on our stores and/or our alternative sources.

Vitamin D is required to help the body absorb calcium, important for the maintenance of normal bones and teeth. Low levels of vitamin D can result in Rickets, a condition whereby absorption of calcium is poor. This leads to the bones becoming soft and weak, resulting in characteristic “bow legs”.

While vitamin D is mainly synthesised from the action of the sun on the skin, it can be obtained through dietary sources too. Eggs and oily fish (salmon, mackerel and trout) are two of the limited natural food sources of vitamin D. Mainly fortified milks, margarines, breads and breakfast cereal now contain vitamin D too. All of these foods provide a myriad of micronutrients and macronutrients and should be considered in the context of an overall balanced diet.

Interestingly, mushrooms can be a source of vitamin D if they are allowed spend time in the sun as opposed to being in mushroom houses. In the summer, if you buy mushrooms, let them sit outside in the sun for a little while. They manufacture vitamin D in a similar way to the skin of the human body.

In terms of supplementation, it is recommended in Ireland that we take a 10µg Vitamin D supplement from Hallowe’en to St. Patrick’s Day (October to March inclusive). When buying a supplement, be sure to look on the back of the pack to see what type of Vitamin D you are choosing. There are two types typically found in supplement form – vitamin D2 and vitamin D3. You want to choose vitamin D3 as it is more readily absorbed than vitamin D2. During COVID times there was a school of thought that we should be upping our dose of vitamin D to 20-25µg per day. This was because we were spending less time outdoors due to lockdown and also because some research suggested that optimum vitamin D status could lead to better outcomes if we were to catch COVID-19. For breast-fed infants, the FSAI now recommends a 5µg supplement from birth.

Working exclusively indoors, exercising exclusively indoors, the use of sun-screen (due to legitimate concerns about the increased risk of skin cancer associated with extended sun exposure) and/or dressing for specific cultures and religions all result in less exposure to sunlight. People in these cohorts should strongly consider a daily vitamin D supplement.

There is some evidence and many news headlines to suggest that there is an association between vitamin D status and mental health. Whilst those with low vitamin D status maybe be more likely have poor mental health, that doesn’t necessarily mean that the lack of vitamin D is causing the mental health outcome. Think about it, low vitamin D would suggest that a person isn’t spending a lot or any time outdoors in the sun. We knows ourselves that our moods perk up on the sunnier days of the year. Maybe it’s the lack of sun that is causing people to feel down. Or maybe they are indoors due to illness or physical limitations, that would cause a person to feel down too. What I am trying to say here is don’t believe everything you read. Put on your scientist hat and always think about other factors.

If you are concerned about your vitamin D status or have questions about supplementation, speak to your healthcare professional for advise.

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