London, Amid the Covid-19 pandemic, researchers, including one of Indian-origin, have found that high intake of vitamins A, E, and D may be linked to fewer respiratory complaints in adults.

Nutrition has a key role in cutting the risk of several infections, although exactly how it boosts immunity is complex and not fully understood, the study, published in the journal the BMJ Nutrition, Prevention & Health, reported.

"Micronutrient deficiencies are often overlooked as a key contributor to the burden of malnutrition and poor health, presenting an additional layer of challenge during the Covid-19 pandemic," said study author Sumantra Ray from Imperial College London in the UK.

The researchers wanted to explore whether the intake of these vitamins from both diet and supplements might be linked to the prevalence of respiratory complaints in a nationally representative sample of UK adults.

They 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.

Respiratory complaints were reported by the participants and had not been diagnosed by a clinician.

They were broadly defined, and included both infectious and non-infectious conditions, such as colds, chronic obstructive pulmonary disease, and asthma.

The researchers looked at dietary intake only and that from diet and supplements, accounting for potentially influential factors, such as age, sex, weight (BMI), smoking, household income and total energy intake.

In all, there were 33 cases of respiratory complaints. These respondents were generally older and less likely to say they regularly took vitamins A, E, C or D supplements.

There was no obvious association between BMI and vitamin intake, or between BMI and respiratory complaints.

But vitamin A and E intake from both diet and supplements was associated with a lower prevalence of respiratory complaints in UK adults.

And vitamin D intake from supplements, but not from diet, was associated with fewer respiratory complaints, prompting 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 and potentially indicate that intake of vitamin D from diet alone cannot help maintain adequate vitamin D status," the authors wrote.