Grocery sales rose 1.7% in the 12 weeks to January 27, the latest Kantar Worldpanel data shows.
Fresh produce performed well as customers embraced the Veganuary trend.
Tesco delivered the best overall performance among the big four, recording a sales advance of 1% – its fastest rate of growth since September 2018.
Tesco’s market share stood at 27.7% versus 27.9% in the comparable period the previous year.
Aldi achieved the highest sales growth in the market, with a 9.1% advance, giving it a market share of 7.5% versus 7% the previous year.
Sainsbury’s was the only multiple grocer to record a sales decline in the period – down 0.3%. Its market share fell from 16.3% to 15.9%.
Lidl’s sales were up 7.3%, taking its market share from 5% to 5.3% year on year.
Other than the discounters, only the Co-op increased market share over the period. Its share increased 0.1 points to 5.9%.
Kantar Worldpanel head of retail and consumer insight Fraser McKevitt said: “Looking back on 2018 as a whole, one of the most notable consumer trends is the shift to a more plant-based diet.
“Today, 1% of all households include a vegan, 5% have a vegetarian and 10% have flexitarians in their ranks. This has contributed to consumers eating a total of 4.4 billion meat-free dinners in 2018, an increase of 150 million meals on the year before.
“Following an indulgent Christmas period, health-conscious shoppers and Veganuary participants helped sales of fruit, vegetables and salad surge by £46m compared with January last year.”
He said 18.3 million households shopped in at least one of the discounters over the period, spending an average of £204 – up £8 year on year.