Written by Iona Hudson
Over the past year or so, many of us have experienced changes in our dietary patterns. Market research has shown that since the beginning of the COVID-19 pandemic there has been a sharp rise in the use of dietary supplements in the UK and around the world, with consumers aiming to support their immune system (1,2,3). In the UK, 71.2% of adults are now taking dietary supplements, with vitamin D and vitamin C being the most popular (4).
It’s unclear whether dietary supplements play a role in reducing the risk of COVID-19.
Current studies have found no evidence that vitamin C, garlic or zinc have any benefits in terms of preventing or treating COVID-19, although there have been modest associations between intakes of probiotics, multivitamins, vitamin D and omega-3 and a lower risk of testing positive for the virus (5,6). However, these associations were only found in women, not men, and are based on self-reported observational data; further controlled trials are needed to clarify these associations. There has been much discussion about the benefits of vitamin D for COVID-19, although this has not yet been confirmed by scientific evidence, with mixed findings from observational studies (6,7,8). Consequently, there have been no government recommendations on dietary supplements for the prevention or treatment of COVID-19.
Nevertheless, a benefit of increased supplement intakes is that more people have been taking vitamin D than before the pandemic (4). This is especially important due to the increased time spent indoors, reducing our exposure to the sunlight needed for vitamin D production. Vitamin D plays an important role in many metabolic pathways and inessential for bone health. To meet vitamin D requirements, UK guidelines recommend a daily 10 μg vitamin D supplement over the winter months or when spending increased time indoors, yet mean intakes are below the recommendations for all age groups except women aged 65-74 years (9,10). Therefore, despite the benefits for COVID-19 being unclear, the fact that more people are taking vitamin D is extremely useful for enabling people to meet requirements.
Furthermore, whether it’s due to boredom, comfort eating or fewer trips to the supermarket, being stuck at home for months on end during the pandemic has, for many of us, led to a shift towards less varied balanced diets, including consuming more processed foods and snacks, and fewer fresh fruits and vegetables (11,12,13,14). Therefore, increased intakes of dietary supplements may have benefits for supporting people to meet vitamin and mineral requirements in a time when eating habits have changed. However, as their name suggests, supplements are intended to complement rather than compensate for a balanced diet; consuming supplements instead of eating a diet that includes fruit, vegetables, and wholegrains can have negative consequences in terms of intakes of fibre and other important nutrients. So, it’s important to note that we should not rely on supplements for vitamin and mineral intakes and instead aim to get these from a balanced diet.
Overall, based on the available evidence so far, it’s unlikely that dietary supplements play a major role in terms of preventing or treating COVID-19. Despite this, increases in supplement intakes are likely to have had other COVID-19related benefits, including raising vitamin D levels in people who have spent more time indoors, and helping people who have altered their dietary patterns during lockdown to meet their micronutrient requirements.