Two years ago, I published an article titled: ‘Can vitamin D supplements protect you from COVID-19?’

In the article, I made the following points:

• There was insufficient evidence (in February 2021) to show that vitamin D supplementation reduced the risk of COVID-19, but there was some suggestion that it might
• Given the importance of vitamin D to overall health, and the fact that many people in the UK are deficient (especially in autumn and winter), and the good safety profile of vitamin D supplementation, and the indications that vitamin D supplementation may protect against COVID-19, most people in the UK should be supplementing with vitamin D
• The Recommended Nutrient Intake (RNI) of 400 IU per day (in the autumn and winter months only) is likely to be far too low for most people, and significantly higher doses (2000-4000 IU per day for adults and 1000-2000 IU per day for children) should be considered

Well, now we have definitive evidence that supplementing with vitamin D does reduce the risk of COVID-19.

In a meta-analysis (a review and synthesis of the evidence) published in January 2023, a research group in Italy concluded that giving vitamin D to hospitalised COVID-19 patients:

• Reduced the risk of admission to the ICU by 72%
• Reduced the risk of death by 51%

Five randomised controlled trials were included in the meta-analysis. The lowest dose of vitamin D was equivalent to more than 2000 IU per day, and doses in the four other trials were significantly higher.

The scientists also performed a relatively new statistical test called a Trial Sequential Analysis (TSA), which assesses the conclusiveness of a meta-analysis . The TSA showed that:

• The positive results in ICU admission risk reduction are definitive
• More data is required before we can say the positive results in mortality risk reduction are definitive

This study did not investigate the effects of vitamin D supplementation on the risk of SARS-CoV-2 infection, but an earlier meta-analysis – published in February 2022 by a group in India – did. The rates of getting a positive PCR test was 54% lower in the vitamin D intervention groups compared to the control groups (given no vitamin D). This study also showed the protective effect of vitamin D on ICU admission and mortality. (No TSAs were performed so can’t say whether these positive results are definitive or not.)

So, there you have it. Back in 2021, there wasn’t enough data for us to conclude that supplementing with vitamin D protected against COVID-19. But now there is.

Why, then, is the UK government still not recommending vitamin D supplementation as an effective, safe, and very cheap treatment (or prophylactic) for COVID-19?