DRY January and a growing appetite for vegan fare spurred Irish consumers to cut back on meat, dairy and particularly alcohol, according to the latest Kantar market survey.
It found that 22pc of households purchased no alcoholic beverages in the 12 weeks to January 26, up from 19pc a year ago.
Overall sales rose 1.3pc versus the previous 12-week span - the smallest gain in Kantar's index since March 2017.
Matthew Botham, strategic insight director at Kantar, said consumer spending dropped sharply after Christmas amid "falling consumer confidence".
He said shoppers increased their purchase of vegan-friendly products as part of supermarkets' "Veganuary" promotions.
He said these "brought plant-based foods to the fore".
Sales of alternative milks grew by 20pc, while sales of meat, fish and poultry dropped by 3pc.
"This points to an increase in flexitarian lifestyles as people look to cut back rather than go cold turkey," Mr Botham said.
Only Lidl and SuperValu increased their market share over the 12-week period. Lidl gained 0.4 percentage points to 11pc - still in fifth place behind Aldi on 11.4pc - while SuperValu rose a tenth of a point to 21.7pc to close the gap on Tesco's 21.8pc.
Dunnes retained top spot, on 23.6pc - a position it has held since October 2018.
Taking a longer view, Kantar said all major supermarkets besides Tesco grew the value of their sales over the past 12 months.
The German discounters posted the strongest gains - Lidl was up 5.6pc and Aldi 5.4pc versus January 2019 -while Dunnes managed 3.3pc growth and SuperValu 2pc.
Tesco was unchanged over the year. But Mr Botham said initiatives recently announced by Tesco to boost its use of "sustainable packaging" -including the removal of plastic wrap from multipack tinned items - "is bound to be popular with eco-conscious consumers."
A bundle of other niche or specialist grocery outlets -including M&S, Boots, Spar, Centra as well as butcher and greengrocer shops - saw their combined consumer spending slump by 9.4pc over the year as trade increasingly shifted to the top five chains.
Kantar said the average cost of groceries has risen by 0.9pc over the past year.
Its 12-week survey reflects the grocery purchasing habits of 5,000 households across the State.