Professor Rose Anne Kenny:

I thank the Deputy for the opportunity to respond. In respect of his first question, there are no symptoms of deficiency as such, unless the vitamin D deficiency is very low, so the Deputy will not know whether or not he is deficient as I speak to him now and I certainly do not know by looking at him. However, in the TILDA study, it was found that 60% of middle-aged adults and older persons in Ireland have insufficient vitamin D in winter.

There is no downside to taking vitamin D up to levels of 4,000 international units. Our request and recommendation is for 800 to 1,000 international units so that is the next thing. It has not been reported that Guillain-Barré syndrome is a side effect of taking vitamin D. Whether or not Guillain-Barré syndrome is associated with severe deficiencies has not been reported to my knowledge. Immunity is certainly much lower generally speaking if someone has insufficiency or deficiency of vitamin D. There are immune underlying causes of Guillain-Barré syndrome likely.