Vitamin D ... An important supplement this winter

As a nutritionist, I am not a big supporter of lots of supplements in our diet and I believe that eating an unprocessed, whole foods diet with lots of variety will ensure most of us get all the nutrients we need for a healthy body and mind. However, there is one vitamin that I strongly recommend my clients to take as a supplement during the winter months where optimum levels of this vitamin cannot be achieved due to Ireland's latitude. For that reason, I want to give you a little information on this health-boosting vitamin, Vitamin D and let you decide if you feel supplementation in the months ahead would be good for you. 

It has long been recognised that people living at higher latitudes are at an increased risk of many chronic diseases including: different cancers, type 2 diabetes, cardiovascular disease, MS, rheumatoid arthritis, osteoarthritis, depression and Alzheimers’ disease among others (Holick, 2010). Evidence suggests that the rates of these diseases could be lowered significantly if we have adequate vitamin D levels (Holick, 2004). 

Studies also show that vitamin D may also help prevent respiratory infection for those who have low vitamin D levels (Martineau et al., 2017). A recent report (Laird & Kenny, 2020) which studied older adults in Ireland highlighted the high levels of vitamin D deficiency among those aged 55+ and the very high levels of deficiency from those who are obese and with pre-existing lung conditions. Both of these conditions make individuals particularly vulnerable to COVID-19 and complication from the virus. Professor of medical gerontology at Trinity College Dublin, Rose Anne Kenny, the author of this paper was also quoted in The Irish Times today, 5th October 2020 “There seems nothing to lose and potentially much to gain by recommending vitamin D supplementation for all, making it clear that this is to help ensure immune health and not solely for bone and muscle health” . Prof Kenny also said that new US research indicates that virus patients are four times less likely to require admission to ICU if they have normal levels of vitamin D.

This raises the question: should we be prudent and avoid vitamin D deficiency to help us achieve optimum health and immunity?

Vitamin D plays a complex role in our bodies. It is quite unique in that it behaves more like a hormone than a vitamin. It’s hormonal actions can influence almost every tissue in the body and that is why it is so important for our health and it plays a far more intricate role in the body than just protecting our bones.

Even if you eat relatively good sources of vitamin D such as oily fish, eggs, liver, meat and fortified foods you’re still going to fall short of optimum levels as diet typically provides less that 10% of our vitamin D requirements with more than 90% needed to come from exposure to the sun (Holick, 2004).

Studies have shown that just 10-20 minutes of safe summer sun exposure on at least a quarter of the body in a young white person can produce 1000IU of Vitamin D. If you have darker skin you may need longer than that to maintain optimal vitamin D levels. I would recommend keeping your face protected, as the skin is much thinner than other areas of the body and at a higher risk of damage, but aim to get at least a quarter of the rest of your body exposed for this short period of time when the sun is high.

That’s all fine during the summer months when the sun is shining and the temperatures are warm, however if you live high in the northern hemisphere like Ireland, the correct UVB wavelength of sunlight for making vitamin D does not reach us between end of October and end of March, which makes it highly unlikely to sustain adequate vitamin D levels throughout winter without supplementation.

A study in the UK concluded that 47% of adults don’t even reach levels of 16ng/ml in the winter/spring season and 87% do not reach the desirable level of 32ng/ml. They observed that as much as 61% of people still failed to reach 32ng/ml in the summer months. (Hypponen, 2007).

If we look at recent research in Ireland 47% of adults aged >85 are deficient in winter, 27% of the over 70s who are “Cocooning” are likely to be deficient and 13% of adults over 55 are deficient all year (Laird & Kenny, 2020)

With the vitamin D status of those in Ireland lower than many countries who have systematic vitamin D food fortification, it begs the questions does Ireland need a formal vitamin D food policy? Finland which receives less sunshine that Ireland has just about eliminated vitamin D deficiency in its population (Jääskeläinen et al., 2017)  and this is due partly to a very successful food fortification and vitamin D supplementation policy and educating the population and medical worker on the importance of vitamin D

Supplementation: How much do we need?

There are different views on the exact level of supplementation of vitamin D. However, it is suggested a recommended range of 20-32ng/ml of vitamin D should be maintained all year round for adults. With careful sun exposure this can be achieved in Ireland in the summer months. However, during the winter months when UVB rays are not available (due to Ireland’s high latitude) how much vitamin D should we be taking?

An Irish study calculated to be confident that most adults (97.5%) maintain levels about 20ng/ml during winter a dose of 1,200IU per day is needed (Cashman, 2008) Other Irish studies (Laird & Kenny, 2020) recommend lower levels (600-800IU/day)are sufficient to maintain adequate levels for most at risk groups.  

It is worth noting that there are a number of factors that affect the production of vitamin D in the skin:

Age: As you get older, your body is less effective at converting the sun’s UVB radiation into vitamin D

Latitude: For those of us living in higher latitudes, the correct wavelength of UVB light to manufacture vitamin D does not reach us from mid October to the end of March

Skin Colour: The darker your skin colour, the more melanin you have which absorbs UVB so more time is needed in the sun to make vitamin D

Sunscreen: using sunblock as low as SPF 15 can reduce vitamin D production by 98%

Body fat: Vitamin D is taken up by fat cells which means less is in circulation

Skin exposure: greater skin exposure means great areas available for vitamin D synthesis.

Time of day: The higher the sun the more UVB rays reach the ground

Therefore to maximize health and reduce the risk of many chronic diseases it is not a bad idea to keep an eye on your 25(OH)D (measurement of vitamin D) blood concentration (just as most of us watch the cholesterol levels). The only way to be sure you are supplementing with the right amount for your body is to have your blood levels tested by your doctor on your annual check-up to ensure you are keeping it within an optimal, healthy range.

References

Cashman, K.D., Hill, T. R., Lucey, A. J., Taylor, N., Seamans, K. M., Muldowney, S., et al. (2008) Am J Clin Nutr., 88(6): 1535-42

Holick, M.F., (2004) Sunlight and vitamin D for bone health and prevention of autoimmune diseases, cancers, and cardiovascular disease. The American Journal of Clinical Nutrition. 80(6) 1678S-1688S

Holick, M.F., (2010) The Vitamin D Deficiency Pandemic: a Forgotten Hormone Important for Health. The Public Health Reviews. 32(1), 267-283

Hypponen, E., Power, C., (2007) Hypovitaminosis D in British adults at age 45 y: nationwide cohort study of dietary and lifestyle predictors. The American Journal of Clinical Nutrition. 85(3): 860-8.

Jääskeläinen T, Itkonen ST, Lundqvist A, Erkkola M, Koskela T, Lakkala K, et l. (2017) The positive impact of general vitamin D food fortification policy on vitamin D status in a representative adult Finnish population: evidence from an 11-y follow-up based on standardized 25-hydroxyvitamin D data. AJCN. 105(6):1512-20 

Laird, E., Kenny, RA., (2020) Vitamin D deficiency in Ireland – Implication for COVID-19. Results from the Irish Longitudianl Study on Ageing (TILDA)

Martineau, AR., Jolliffe, DA., Hooper RL., Greenberg., L., Aloia, JF., Bergman P., Et al. (2017) Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data. BMJ. 36:i6583