A margarine factory owner in Iran, who asked not to be identified, said there was a shortage in supply of the oils needed to make margarine that could halt production soon.
"The way things are going, I predict that over next three to four months our edible oil will run out because of sanctions. It is no longer being imported and Iran itself cannot produce that much."
A Tehran market wholesaler said: "There is a big shortage of margarine in the market, due to drop in imports. What is being sold now is our previous stockpiles."
A default by Iranian buyers on purchases of 200,000 tonnes of Indian rice is potentially more crippling. The average Iranian eats 40 kilos of rice a year, 45 percent of which is imported, according to the U.S. Department of Agriculture. India is the main supplier.
The president of the All India Rice Exporters' Association said it was advising exporters to stop selling rice to Iran with the customary 90 days credit for payment.
"As part of our efforts to minimise losses, we are asking our colleagues to avoid sending rice on credit," Vijay Setia said.
Exporters have also had difficulty in Pakistan, another of Iran's major sources of rice.
Javed Agha, head of the Rice Exporters Association of Pakistan said: "We use lines of credit opened through agents in Dubai, but that too has become difficult because of sanctions and the resulting currency fluctuations."
Iranian buyers normally pay for Indian rice through middlemen in the UAE, but falls in Iran's rial means buyers have trouble covering the cost in hard currency.
While it is too early to talk of hunger from the rising prices of food in Iran, international organisations are keeping an eye out for a sign of hardship.
Gaelle Stevenier, spokeswoman for the U.N.'s World Food Programme, said the agency was "monitoring" the situation but had no further comment.