Shoppers made two million fewer trips to the supermarket than expected in the week after face mask rules came into force, according to latest industry figures.
Data company Kantar, which compiled the report, said it suggested the introduction of mandatory face coverings in stores "has taken some getting used to".
The report said that "the public may need time to adjust to the new regulations, and they now have to plan ahead for every shopping trip".
But it also suggested that local lockdowns to combat outbreaks of the coronavirus may have played a part in reducing the overall number of trips to stores.
The figures were part of a regular monthly update on the sector, which also showed the share of online grocery sales had hit a new record, at 13.5%.
Face coverings were made mandatory in shops in England from Friday 24 July.
In the first full week of data recorded by Kantar after that, ending 2 August, there were just over 100 million shopping trips.
More from Covid-19
That was 20 million fewer than in the same week a year before. The following week also saw shopping trips 20 million down year-on-year.
In each of the two prior weeks, supermarket shopping trips had been down by about 18 million compared with the year before.
That suggested that, even allowing for the lower numbers of people going to stores now compared to the pre-pandemic norm, visits were fewer than expected after masks became compulsory.
But other possible reasons given for lower numbers of shopping visits in recent weeks included local lockdowns and a decline in stockpiling.
Charlotte Scott, consumer insight director at Kantar, said: "Although the current average of 14 shopping trips per month per household is lower than it was last month, it is higher than in April and May, when lockdown rRead More – Source