The use vitamin D supplements in the battle against the coronavirus could be approved as a useful health boost by the end of this week.
A report on the advisability of promoting the use of the vitamin to aid the immune system has been sought from the National Public Health Emergency Team (Nphet).
Irish people have a vitamin D deficiency, which is most often derived from sunshine, Leo Varadkar told the Dáil last Thursday.
Independent TD Marian Harkin is urging the promotion of vitamin D and Mr Varadkar acknowledged: "A lot of Irish people are vitamin D deficient, not least because we don't have much exposure to the sun."
He added: "There is evidence of benefits (of vitamin D) in terms of Covid-19 outcomes. And there's very little evidence of any harm being done should somebody take vitamin D supplements."
Research from Spain, from the long-range Tilda project at Trinity College and from articles published in the British Medical Journal and The Lancet all suggest that it is "uncontroversial" to promote vitamin D for general use.
"There is a chance that it may be beneficial in terms of Covid-19 outcomes and the Government has asked Nphet to examine this and to provide us formal advice, which we can then stand over and give to the general public," Mr Varadkar said.
The HSE advice is that most people don't need extra vitamin D as they get sufficient in a balanced diet every day.
But the body cannot store vitamin D efficiently, and the Food Safety Authority and the HSE both recommend extra for all babies in their first year.
"Most people should be able to get enough vitamin D from a varied and balanced diet. But if you take supplements be careful not to take too much," the Tánaiste warned.
The literature indicates taking 25 micrograms or less per day is unlikely to cause any harm, he said, "and may cause some benefit".