In 1845 the Potato Famine hit Ireland. Potatoes were an essential crop for the Irish. This is around the time Irish soda bread grew popular, possibly due to a lack of potatoes.
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In 1850, The Dublin Quarterly Journal of Medical Science explained how people began to depend on Irish soda bread instead of potatoes. "During the failure of the potato crop, a large quantity of bicarbonate of soda was employed by the poorer classes in the preparation of bread; the article consequently became scarce, owing to the increased demand, and the price rose accordingly."