Vitamin D came to public attention in 2016 when the Government changed its guidelines to recommend that everyone over the age of five in the UK should take a daily supplement containing 10µg (micrograms) of vitamin D during the autumn and winter months.
The guidelines also recommended that the following groups of people should take a daily supplement containing 10µg of vitamin D throughout the year:
In addition, infants from birth to one year should be given a daily supplement containing 8.5-10µg of vitamin D, unless they are receiving at least 500ml of infant formula milk per day.
With many people experiencing reduced exposure to sunlight while staying at home or self-isolating during the national lockdown, Public Health England (PHE) updated its guidance on vitamin D in April 2020 to prevent people developing or exacerbating a low vitamin D status.
“The Government reissued its advice to recommend that everyone considers a daily vitamin D supplement [of 10µg] throughout the spring and summer months too, particularly those people who are shielding or self-isolating,” explains Sarah Coe, nutrition scientist at the British Nutrition Foundation (BNF), stressing that “this recommendation is in order to protect musculoskeletal health, rather than provide protection against Covid-19”.
Some 17 per cent of adults aged 19-64 years have a vitamin D deficiency
So why is vitamin D important enough to warrant a change in Government guidelines?
Vitamin D has several important functions in various body systems. It helps regulate the amount of calcium and phosphate in the body, which are needed to keep bones and teeth healthy and maintain strong muscles. It is also “essential for immune function – a claim which is allowed by the European Food Safety Authority”, according to Emma Derbyshire, nutritionist at the Health and Food Supplements Information Service.
Humans make most of their vitamin D under the skin in reaction to sunlight. In an ideal world, this should supply all the vitamin D people need, but in the UK the winter sun is not strong enough for this to be the case.
The vitamin is also found in some foods such as oily fish, eggs, fortified yoghurts and fat spreads, fortified breakfast cereals and bread, and some powdered milks. However, it is hard for most people to get sufficient vitamin D from food alone, hence Government advice to use supplementation during the colder, darker months and while people are spending more time indoors than usual, such as during the Covid-19 pandemic.
Vitamin D deficiency has a role in many conditions affecting various population groups. Most commonly these include children and babies, pregnant women, the elderly, people with kidney disease, those taking anticonvulsant medications, as well as people with darker skin – such as those of African, African-Caribbean and south Asian origin – and those who cover their skin or are confined indoors and so don’t get enough sun exposure.
Worryingly, the most recent National Diet and Nutrition Survey (NDNS) data shows that 17 per cent of adults aged 19-64 years have a vitamin D deficiency, which puts them at risk of developing a number of illnesses and conditions.
At the extreme end of the scale, this includes rickets in children and adolescents and osteomalacia in adults – painful conditions where bones become soft and deformed. In adults over the age of 50, vitamin D deficiency puts them at increased risk of falls and fractures.
In addition, Emma says low vitamin D levels are associated with increased risk of respiratory tract infection. “A systematic review of epidemiological studies found increased risk of upper and lower respiratory tract infections with low serum vitamin D levels,” she explains.
Some people may be confused by current messaging around vitamin D, putting community pharmacy teams in a vital position when it comes to explaining the updated guidance, as well as advising on how customers can protect their vitamin D levels.
As the vitamin is best obtained from sunlight. Getting 15 minutes sun exposure on the arms and face on sunny days through the summer is thought to be enough for fair-skinned people to produce vitamin D, with double that amount necessary for those with darker skin.
If this isn’t possible, or in addition to this, people may want to turn to food sources. The BNF suggests that one way people looking to increase their vitamin D intake from food could be to start the day with a breakfast cereal fortified with vitamin D, have some poached eggs or an omelette at lunchtime, and then have a dinner including canned or fresh oily fish like salmon.
Food fortification has been identified by the World Health Organization (WHO) and the Food and Agricultural Organization of the United Nations (FAO) as a way of addressing low intake of vitamins and minerals – including vitamin D.
However, the regulatory landscape for food manufacturers in Europe is complex, with fortification allowed in some countries including the UK, Austria, Finland, Sweden and prohibited in others like Norway and Denmark.
Currently, in the UK, infant formula milks and spreadable fats are fortified with vitamin D, along with some other foods including breakfast cereals. Recent studies at the University of Birmingham claim that adding vitamin D to wheat flour would prevent 10 million new cases of vitamin D deficiency in England and Wales over the next 90 years.
Last year, a forum of nutrition scientists discussed the potential of food fortification as a strategy for increasing vitamin D intake across the UK. They found that the lack of consistency between the reference intake (RI) for vitamin D that must currently be used for labelling purposes in Europe (5μg/day) and the UK Government’s reference nutrient intake (RNI) for the vitamin (10μg/day) is a potential barrier to voluntary fortification by food manufacturers, and risks compromising clear communication.
With PHE advice on vitamin D supplementation extended across the whole year now that people are tending to spend more time indoors, Emma says pharmacy teams should be prepared to “highlight the Public Health England recommendation to all customers to take vitamin D 10µg daily”.
Two major forms of the vitamin – D3 (colecalciferol) and D2 (ergocalciferol) – are licensed for the prevention and treatment of vitamin D deficiency. The National Institute for Health and Care Excellence (NICE) guidance is that 10µg is enough for most people, with an upper limit of no more than 100µg a day. The Royal Osteoporosis Society (ROS) advises that the upper limit is 50µg a day for children from one to 10 years and 25µg for babies under a year.
If customers are already taking a number of different supplements, pharmacy teams should remind them to check how much vitamin D it adds up to in total to ensure it stays under the upper limit. Taking too much vitamin D over a long period of time can cause more calcium to be absorbed than can be excreted. The excess can be deposited in and damage the kidneys, and can also encourage calcium to be removed from bones, which can soften and weaken them.
NICE recommends that people who are taking higher therapeutic doses of vitamin D for medical reasons should be monitored by a GP or specialist. Similarly, the ROS says those who have a medical condition such as Crohn’s disease that could affect how they absorb medicines, or people who have bone pain that continues despite taking supplements, should see a GP for repeat blood tests “as the results may affect treatment decisions”.
The ROS also adds a warning that anyone taking an osteoporosis drug treatment, such as alendronic acid or risedronate (bisphosphonates), must “separate them out from any supplements” because “bisphosphonate drugs can’t be absorbed by the body and therefore won’t work unless you take them on a completely empty stomach (drinking water is not a problem)”.
It is hard for most people to get sufficient vitamin D from food alone
Because there are many different brands and formulations of vitamin D supplements, some of which are often combined with other nutrients such as calcium, customers may need advice about which to choose.
For example, most supplements contain vitamin D3 and vitamin D2, but as D3 is derived from lamb’s wool, it may not be an option for customers following a vegan or vegetarian diet. Some customers may also want to know about the halal options available. The ROS advises that for people taking vitamin D because they have a bone condition such as osteoporosis, “it might be preferable to take a prescribed supplement from your doctor as these products will have been carefully tested to make absolutely sure that they work well”.
Pointing out the risks of vitamin D deficiency to customers can open up opportunities for continuing care but, as ever, it’s a good idea to suggest they talk to a GP if they have a history of chronic health conditions and are considering taking any supplements.
Covid-19 is an infectious disease caused by a coronavirus known as the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).
In June 2020, the National Institute for Health and Care Excellence (NICE) conducted a rapid evidence summary in response to claims that vitamin D may have a role in the body’s immune response to respiratory viruses and therefore may have a role in preventing or treating Covid-19.
The evidence summary concluded that: “There is no evidence to support taking vitamin D supplements to specifically prevent or treat Covid-19. However, all people should continue to follow UK Government advice on daily vitamin D supplementation to maintain bone and muscle health during the Covid-19 pandemic.”
The British Association of Dietitians has also made its position clear, saying: “Simply put, you cannot ‘boost’ your immune system through diet, and no specific food or supplement will prevent you catching Covid-19/Coronavirus. There are many nutrients that are involved with the normal functioning of the immune system, so we would encourage maintaining a healthy balanced diet in order to support immune function (include copper, folate, iron, selenium, zinc and vitamins A, B6, B12, C and D).”
However, some scientists believe the potential role of low vitamin D levels as a risk factor for Covid-19 needs further investigation, and studies continue as new evidence emerges about the disease.
Martin Hewison, professor of molecular endocrinology at University of Birmingham, is part of a research group investigating the link between vitamin D and the immune system. Speaking at a webinar organised by pharmaceutical company Thornton & Ross in July, which interrogated whether vitamin D has a role against Covid-19, he said: “Vitamin D is a potent anti-inflammatory agent that can protect against cytokine storms that follows viral infections such as Covid-19. We don’t know the optimum level needed, when is the best time to use supplementation – before or after infection – and does it affect the actions of other drugs such as dexamethasone. What we do know is that there is a strong case for including vitamin D in the future management of pandemics such as Covid-19.”