No evidence that vitamin D prevents coronavirus, say experts

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Posted 30 June 2020

Nice says topic is under review, but still advises taking supplements for bone health

Haroon Siddique Published on Mon 29 Jun 2020 18.12 BST

The Guardian

No evidence exists to support taking vitamin D supplements to prevent Covid-19, UK public health experts have found.

A rapid review of evidence for claims that the so-called sunshine vitamin could reduce the risk of coronavirus was launched amid concerns about the disproportionate number of black, Asian and minority ethnic people contracting and dying from the disease. Higher levels of melanin in the skin lead to less absorption of vitamin D from sunlight.

However, on Monday, the National Institute for Health and Care Excellence (Nice) said that, having examined five studies, it had not found evidence to support any benefit from vitamin D with respect to Covid-19.

“While there are health benefits associated with vitamin D, our rapid evidence summary did not identify sufficient evidence to support the use of vitamin D supplements for the treatment or prevention of Covid-19,” said Paul Chrisp, the director of the centre for guidelines at Nice. “We know that the research on this subject is ongoing, and Nice is continuing to monitor new published evidence.”

At the same time, the Scientific Advisory Committee on Nutrition (SACN) reached similar conclusions, stating that the evidence did not support recommending vitamin D supplementation to prevent acute respiratory tract infections.

However, both Nice and the SACN advised that people should continue to follow official guidance, which was updated in April, advising people to consider taking 10 micrograms of vitamin D a day to maintain bone and muscle health, amid concerns people were not getting enough sunlight during lockdown.

Prior to April, the advice was for people with little exposure to sunlight and/or with dark skin to take 10 micrograms all year round and for others to consider doing so in autumn and winter.

Nice said the five studies it had examined all had very low quality of evidence, noting that none had adjusted for confounding factors, such as body mass index, higher socioeconomic deprivation and poorer self-reported health.

The SACN said that one of the most widely supported studies to support the hypothesis that vitamin D reduces the risk of acute respiratory tract infections was one led by Prof Adrian Martineau in 2017. But Martineau, a professor of respiratory infection and immunity at Queen Mary University of London, has himself described the evidence on vitamin D as “mixed” and the SACN said randomised controlled trials published since 2017 had not supported its conclusions.

The committee said it would keep the topic “under urgent review” and consider updating its assessment if new evidence emerged from randomised controlled trials.

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COVID-19 rapid evidence summary: vitamin D for COVID-19 Evidence summary [ES28]

Published date: 29 June 2020

https://www.nice.org.uk/advice/es28/chapter/Factors-for-decision-making

Effectiveness and safety

Evidence was from 5 published studies in peer-reviewed journals. One observational cohort study (D’Avolio et al. 2020), 3 observational prognostic studies involving published data sets using correlation or regression (Hastie et al. 2020, Ilie et al. 2020 and Laird et al. 2020) and 1 case-control survey (Fasano et al. 2020) looked retrospectively at the association between vitamin D status and development of COVID‑19. None of the studies were intervention trials of vitamin D supplementation for the prevention or treatment of COVID‑19.

Four of the studies found an association or correlation between a lower vitamin D status and subsequent development of COVID‑19. However, confounders such as body mass index (BMI) or underlying health conditions, which may have independent correlations with vitamin D status or COVID‑19, were not adjusted for (D’Avolio et al. 2020, Fasano et al. 2020, Ilie et al. 2020 and Laird et al. 2020). Vitamin D status was based on serum 25‑hydroxyvitamin D (25(OH)D) levels in 3 studies and the proportion of participants taking a vitamin D supplement in 1 study. The largest UK study (Hastie et al. 2020) found an association between vitamin D status and COVID‑19 only in a univariable analysis (with this single potential causative factor). Importantly, no causal relationship between vitamin D status and COVID‑19 was found after adjustment for confounders such as comorbidity, socio-demographics, ethnicity, BMI and other baseline factors.

Limitations of the evidence

All 5 studies were assessed as being at high risk of bias (very low quality of evidence). None of the studies were intervention studies of vitamin D supplementation (for example randomised controlled trials), so no data on appropriate doses or adverse events was given.

Apart from Hastie et al. 2020, none of the studies adjusted for confounding factors, such as BMI, higher socioeconomic deprivation and poorer self-reported health, which may have independent correlations with vitamin D status or COVID‑19. Three studies (Hastie et al. 2020, Ilie et al. 2020 and Laird et al. 2020) used historic data up to 20 years old on serum 25(OH)D levels for their included populations. The use or reporting of COVID‑19 case and mortality data is also limited in all 3 studies, with differences in national and international reporting and screening meaning some countries data may not include milder or asymptomatic cases. All 3 of these studies had poorly reported methods for model selection, model fit and checking (either correlation or regression). Two studies (D’Avolio et al. 2020 and Fasano et al. 2020) are limited by the representativeness of their samples and issues with diagnostic criteria for either COVID‑19 or its sequelae.

Person-centred factors

A person’s individual risk of vitamin D deficiency may have changed during the COVID-19 pandemic, particularly if they are spending more time indoors. Sunlight is the major source of vitamin D for most people, therefore vitamin D status will be influenced by sunlight exposure. People from ethnic minority groups with dark skin are also at particular risk of having a low vitamin D status.

For most people, 10 micrograms of vitamin D a day will be enough and people should not take more than 100 micrograms a day because it could be harmful. If people take higher therapeutic doses of vitamin D, monitoring is recommended.

There are many different brands and formulations of vitamin D supplements, often combined with other supplements (such as calcium), with different dosing regimens. This can make deciding which supplement to take, if any, difficult without health professional advice.

See the full evidence review for more information – https://www.nice.org.uk/advice/es28/evidence.

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