Members of a group that advocates the use of Vitamin D as an additional measure to protect against Covid-19 are appearing before the Oireachtas Health Committee.
The committee is discussing studies that suggest a correlation between Vitamin D deficiency and severe symptoms of Covid-19.
Last November, the Department of Health advised those aged over 65 to take supplements of 15 micrograms per day of Vitamin D, to support their bone and muscle health.
However, the department has cautioned that there is insufficient evidence to prove that Vitamin D offers protection against Covid-19. This is also the view of the National Public Health Emergency Team (NPHET) and the British Medical Journal.
Among the members of the Covit-D Consortium is Professor Rose Anne Kenny, Head of the academic department of Medical Gerontology at Trinity College Dublin and lead investigator of TILDA (The Irish Longitudinal Study on Ageing).
Prof Kenny told Fine Gael's Bernard Durkan that the TILDA study showed that "60% of adults and older persons in Ireland have insufficient Vitamin D in winter".
Sinn Féin Health Spokesperson David Cullinane was told that many of the studies completed on the effect of Vitamin D on Covid-19 are largely academic medical studies.
Mr Cullinane said that many people are feeling particularly vulnerable at this time and cautioned against making claims that didn't stack up to robust analysis.
He asked if the group advocated the use of Vitamin D as an additional protective measure against the virus, such as hand hygiene and social distancing, as opposed to suggesting it could replace public health advice.
Dr Daniel McCartney, Director of Human Nutrition and Dietetics, TU Dublin agreed with Mr Cullinane, telling the committee: "We want to be absolutely clear here that we are recommending Vitamin D supplementation in addition to these other health messages."
The Covit-D consortium believes that vaccination is the ultimate way out of restrictions.
Dr McCartney told Mr Cullinane that the Covit-D consortium is calling on Government to recommend daily supplements of vitamin D, ranging from 20-25 micrograms.
He said that people who are severely deficient in Vitamin D may require more, but this should be done under medical supervision.
Róisín Shortall, Co-leader of the Social Democrats, said that she believed this issue needs to be pursued "actively" by the Health Committee.
She was told by the Covit-D consortium that they have not had any formal engagement with NPHET, but that they would like to.
Prof Kenny told Ms Shortall that it can be "very difficult" to get sufficient levels of Vitamin D from food. She said that the problem in Ireland is that it is also very hard to get Vitamin D from the sun during winter and for much of spring.
Gino Kenny, of People Before Profit, was told that there appears to be a link between geographic location and Vitamin D levels, with countries far away from the equator showing lower levels of Vitamin D in their population.
Dr MacCartney told Mr Kenny that there are some anomalies with this, such as in countries like Italy and Spain, where he said people might go inside during the middle of the day.
He said that in some Scandinavian countries there was "well communicated messages around Vitamin D supplementation".
When asked about the use of Vitamin D at a NPHET press briefing last week, Deputy Chief Medical Officer Dr Ronan Glynn said: "We have to be very careful about what we recommend to people to put into their bodies or the reasons that people put something into their bodies."
Dr Glynn told the conference that he was not against Vitamin D and repeated the department's guidance that anyone over 65 should be taking Vitamin D supplements.
He said: "It's clear that significant levels of the population are Vitamin-D-deficient, so we're telling everybody that their levels of Vitamin D should be optimised."
He recommended the use of Vitamin D as a "general positive thing that people can do" but cautioned that it was not the same as saying that "it's going to prevent someone from ending up in hospital with Covid".