Ari Kulmanen, an organic farmer from the town of Ikaalinen in western Finland, studied nitrate levels in lettuce because no official studies on lettuce nitrate content exist. His research showed sharp differences in the nitrate levels of organic and conventional lettuce.

”The nitrate levels for organic lettuce were 150 mg/kg. Conventional lettuce carried levels of over 3,500 mg/kg," says Kulmanen.

In Finland conventionally grown produce is often presented as “near organic,” according to Jouni Kujala, a research director at Helsinki University’s Ruralia Institute.

“It seems as if Finnish authorities have not wanted to make conventional and organic segments compete for consumer choice,” says Kujala.

Only one percent of produce sold in Finnish shops is organic, which is in stark contrast to growing organic market shares in other countries.

Fertilisers Boost Nitrate Levels

Nitrate occurs naturally in most plants and vegetables. The amount of nitrate in plants is affected by fertiliser, growing conditions and the amount of light. The use of extra fertilisers in past decades has led to increased nitrate levels in produce.

The Finnish Food Safety Authortity, Evira, points out that some lettuce types, such as rucola, may have nitrate levels as high as 8,000 mg/kg. Evira, however, underscores that the health benefits of lettuce and other produce outweigh any possible health risks.

An EU regulation has set limits of 4,500 mg/kg for nitrates in lettuce. Excessive amounts of dietary nitrates have been linked to some forms of cancer and can reduce the ability of the blood to carry oxygen.