“Russia cannot provide itself with dairy products, fish, vegetables and other types of food,” said Mikhail Anshakov, the head of the Society for the Protection of Consumer Rights, which calls for food sanctions to be rescinded. “Self-imposed sanctions under these circumstances were madness.”

The public has generally supported the sanctions, however, because the Kremlin wrapped the idea in nationalist colors, and state-run television regularly broadcasts programs showing supermarkets bursting with goods from Africa, Asia and Latin America. While the foreign news media tend to focus on the dismay of the urban elite over the sudden dearth of oysters and foie gras, Mr. Anshakov said, the real story is the potential gap in providing staples like milk.

Dairy farms have plenty of forage at the end of summer, he said, but with winter comes the main challenge to farming in Russia — virtually the entire country freezes. At that point dairy companies usually import vast amounts of powdered milk to mix with real milk, Mr. Anshakov said. “Now with the sanctions that is impossible,” he said, with powdered milk from traditional suppliers barred.

Some farmers, however, have been slightly gleeful about their prospects under sanctions.

Justus Walker, an American immigrant farmer in Siberia, became a YouTube sensation for a short news clip showing him laughing at the thought that he could finally sell the mozzarella he produces because the cheaper Italian variety would no longer be available.

Chicken is another example. Only about 10 percent of chickens sold in Russia come from abroad, mostly from the United States. Sanctions were a gold mine for local producers as imports no longer kept prices down.

But experts said that over the long run higher prices would not overcome more basic problems faced by small local farmers like those who sell through LavkaLavka. (Lavka means “little shop” in Russian.)

Andrey Ovchinnikov, 53, worked as an interior designer when a friend’s endeavor persuaded him to become a chicken farmer. Sales went well, but he could get neither the credit nor the land to expand. He raises thousands of birds on less than an acre. Since his farm sits about 50 miles from Moscow, prime country for dachas, the local government has been reluctant to give him land it can sell at a premium.