To fortify or supplement? COVID-19 and vitamin D links reignite debate on addressing deficiency

02 Nov 2020 --- Experts are once again debating the best ways to avoid vitamin D deficiency following the discovery that over 80 percent of COVID-19 patients in a Spanish hospital were suffering from it.

The author of the recent analysis, Dr. José Hernández of the University of Cantabria in Santander, Spain, urges that vitamin D treatment should be recommended in COVID-19 patients with low vitamin D levels circulating in the blood. 

“We think that vitamin D treatment should be recommended in COVID-19 patients with serum 25OHD deficiency since this approach might have beneficial effects in both the musculoskeletal and the immune system,” Hernández tells NutritionInsight. 

He posits that the best approach could be to identify and treat vitamin D deficiency, especially in high-risk individuals such as the elderly and patients with comorbidities. 

Fortification a “bridge too far”
The investigation of 200 COVID-19 patients, published in The Journal of Clinical Endocrinology & Metabolism, also found that men had lower vitamin D levels than women. 

Hernández explains that this may be due to different lifestyle and dietary habits. For example, he notes that women may be more likely to consume dairy products that have been fortified with vitamin D than men.

While this may raise the question of whether fortification should be embraced as a tactic to address COVID-19, Dr. Adrian Martineau warns that this may be overly simplistic. While he was uninvolved with the Spanish investigation, he is heading the UK’s CoronaVit trial.

The half-year clinical trial aims to determine whether a “test-and-treat” approach to correct people’s vitamin D deficiency during the winter months will reduce the risk and/or severity of COVID-19 and other acute respiratory infections.

“It’s a stretch to make the claim that fortification could help address COVID-19. The potential benefits of vitamin D to prevent COVID-19 are currently unproven. Therefore it is a bridge too far to claim that fortification would impact the risk of the disease,” he says. 

Moreover, Martineau points out that the timelines of fortification and addressing the pandemic do not align. “Fortification would take months or years to get off the ground, but COVID-19 requires urgent action.”Fortification would take months or years to get off the ground, but COVID-19 requires urgent action, argues Martineau.

Benefits from supplements but not diet
A separate UK analysis assessing data gathered before the pandemic has found that vitamin D intake from supplements, but not from diet, was associated with fewer respiratory complaints. 

This has prompted the researchers to suggest that the findings add to the current scientific debate on the value of vitamin D supplementation.

“Our findings are consistent with the hypothesis that supplementation is critical to ensuring adequate vitamin D status is maintained. [The findings] potentially indicate that intake of vitamin D from diet alone cannot help maintain adequate vitamin D status,” they write. 

Vitamins A, E and C for respiratory complaints 
Published in BMJ Nutrition Prevention & Health, the analysis drew on information provided by 6,115 adult participants in the 2008–2016 National Diet and Nutrition Survey Rolling Programme (NDNS RP) who had completed three or more days of diet diaries.

Notably, the researchers also found that respondents who reported respiratory complaints were generally older and less likely to say they regularly took vitamins A, C, D or E supplements. 

In contrast to investigations of COVID-19 specifically, there was no obvious association between BMI and respiratory complaints – or between BMI and vitamin intake.Vitamin D intake from supplements, but not from diet, was associated with fewer respiratory complaints.

Vitamin D supplementation on the table
Commenting on the UK analysis, Shane McAuliffe, science communications lead for the NNEdPro Nutrition & COVID-19 Taskforce says: “While acknowledging the limitations of this data, it does add further to a growing body of interest and evidence for the role of vitamin D in respiratory health.”

He continues that given the knowledge of the extent of vitamin D deficiency in the population, balanced with the low cost and low risk of adverse events, it seems “sensible” to provide supplementation of this key vitamin, particularly to those most likely to be deficient. 

Hernández adds that we must wait for the results of the ongoing large and properly designed studies to determine whether vitamin D administration can prevent SARS-COV-2 infection or reduce its severity.

“However, given the large safety margin of vitamin D treatment and its low cost, it seems reasonable to treat those populations at high risk for vitamin D deficiency. In general, this group coincides with the patients most affected by COVID-19,” he concludes. 

In recent weeks, the UK’s health minister, Matt Hancock, has been weighing up vitamin D in light of COVID-19. Most recently, he announced that the government will be increasing the public messaging around vitamin D.

This marks a U-turn from previous government conclusions that there was no evidence to support taking vitamin D supplements to prevent or treat COVID‑19 specifically. 

By Katherine Durrell