13 Excessive intake of vitamin A can cause adverse effects and may also interfere with vitamin D mediated effects on the immune system. Finally, cod liver oil also contains a substantial amount of vitamin A, which is a potent immunomodulator. Most participants were women (65%), most had normal body mass index (mean 26.1), and the mean age was 44.9 years. 11 Jolliffe and colleagues randomised 3100 participants to a vitamin D test and either 3200 IU/day or 800 IU/day of vitamin D 3 for six months if their blood 25-hydroxyvitamin D concentrations were 50 nmol/L) at baseline.

The first study (doi: 10.1136/bmj-2022-071230) was conducted in the United Kingdom between May and October 2021. Two linked new randomised studies add much needed evidence to this important question. 8 However, this association could be due to reverse causality or confounding 9 10: both covid-19 and vitamin D deficiency are independently associated with obesity, old age (>65 years), and male sex, for example.

6 7 Data from observational studies suggest that low levels of 25-hydroxyvitamin D (25(OH)D) may be a risk factor for severe covid-19. 4 5 Could vitamin D help protect against covid-19?Īt a mechanistic level, vitamin D boosts antiviral defences against other respiratory viruses, such as influenza A virus and rhinovirus. 3 Results from randomised controlled trials were mixed, but two large meta-analyses found some evidence of a protective effect of vitamin D supplementation against respiratory tract infections, particularly in vitamin D deficient individuals. 1 2 Observational studies from the pre-pandemic era found an association between low levels of vitamin D and an increased risk of respiratory tract infections. In addition, it has important effects on the immune system, directly inducing antimicrobial peptides at mucosal surfaces and modulating the function of T cells. Vitamin D is an important regulator of calcium balance. Two new trials find no effect, but aren’t the final word

Vitamin r 2 product review