Food prices rose last month as salads became more expensive with winter approaching, but bananas and chicken became cheaper.
Food prices were up 0.6 per cent last month after a similar gain in April, though prices fell earlier in the year.
For the year to May, food prices were up 1.8 per cent, Statistics New Zealand said.
"Higher food prices in May were influenced by seasonally higher prices for fresh vegetables, particularly lettuce, tomatoes and cucumbers," Statistics New Zealand prices manager Chris Pike said.
"However, prices were lower for bananas and chicken."
Vegetable prices rose 16 per cent, while fruit prices fell 3.9 per cent.
Banana prices fell 14 per cent to an average price of $2.33 a kilogram, their lowest level since August 2011.
Prices for meat, poultry and fish fell 1.5 per cent, reflecting cheaper prices for most meats, including chicken, beef and pork.
Grocery food prices barely changed, falling 0.1 per cent.
Lower prices for confectionery, nuts and snacks (down 1.4 per cent) were offset by price rises for milk, cheese and eggs (up 1.7 per cent), including fresh milk (up 1.3 per cent), which reached its highest level last month.