Dr. Daniel McCartney:

That is an excellent question and one that is very pertinent to the discussion today. This is really why we need explicit guidance for the population on vitamin D. There is lots of justified discussion on the role of vitamin D in immunological health as it relates to SARS-CoV 2 and what we need from the Department of Health are explicit guidelines on the appropriate level of supplementation so that people do not over-supplement and put themselves at risk. We heard today that a number of agencies including the European Food Safety Authority, the Institute of Medicine in the US and the Scientific Advisory Committee on Nutrition in the UK, are all unanimous that oral intake of vitamin D up to 100 mcg per day is safe. We have very large population studies of people who have been supplemented at 50 to 100 mcg over extended periods of two to five years which have shown no instances of toxicity. Professor Walsh's work is also relevant. Of the 36,000 people whose blood levels were evaluated in the Dublin region over the past five years, only 21 had levels over 250 nanomillilitres per litre and none had high calcium levels in their blood, which is the tell-tale sign that one has too much. Vitamin D toxicity is extremely rare. One can encounter it in some clinical conditions like sarcoidosis, tuberculosis, lymphoma and other granulomatous diseases but those hazards, or potential hazards, with vitamin D will be telegraphed to such patients by their primary physician. I will hand over to Professor Kenny who may want to comment on this further but overall, vitamin D supplementation is a very, very safe and effective intervention.