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Rucola may contain very high levels of nitrate

05/2005, 02.02.2005

BfR advises moderate consumption

According to new study results of the regulatory authorities of the federal states, rucola, like spinach and green salad, ranks amongst the types of vegetables in which high levels of nitrate are regularly detectable. Nitrate levels of more than 5,000 mg/kg were measured in around half of the 350 rucola samples. Depending on individual eating habits, this may mean an intake of substantial amounts of nitrate and a clear exceeding of the Acceptable Daily Intake (ADI) recommended by WHO. BfR, therefore, advises moderate consumption of rucola and other nitrate-rich vegetables.

The Acceptable Daily Intake (ADI) for nitrate recommended by WHO is 3.7 milligrams per kilogram body weight (mg/kg BW). According to BfR, the occasional exceeding of the ADI will not lead to a significant risk to health. „Until the health relevance of a higher nitrate intake has been clarified scientifically, consumers should, for precautionary reasons, ensure that their meals do not contain too many foods which have been identified as possible sources of very high nitrate levels“, recommends Dr. Eberhard Schmidt, an expert for food contaminants in BfR.

Nitrates are nitrogen compounds which occur naturally in the ground but are also applied as fertilisers to fields. Plants need nitrate to make protein. Furthermore, nitrate may be used as an additive in specific foods like meat, cheese and fish products.

Plants have different nitrate storage capacities: green salad, spinach, kale and white cabbage, large radish, red radish and beetroot may contain substantial amounts of nitrate. Genetic, geographical and seasonal factors also influence nitrate levels in plants. For instance, the mean values of nitrate concentrations in various types of vegetable may differ naturally by factors of between 2 and 60. The individual values within one type of vegetable may also fluctuate markedly and differ by factors of between 5 and 70. Aside from the nitrate levels in the soil, the time of harvesting also plays in important role. High light intensity promotes the breakdown of nitrate in plants and high temperatures reduce the nitrate levels, too. Dryness, by contrast, encourages accumulation in the plant. In addition, the use of fertilisers and the type of cultivation also have an impact on nitrate levels. The nitrate levels in vegetables grown under glass are normally higher than those for outdoor plants. Rucola seems to accumulate nitrate to a particularly high degree.

Nitrate itself is not very toxic. However, nitrite can develop from nitrate in the body from which, in turn, N-nitroso compounds, so-called nitrosamines, can be formed. Many of them have proved to be carcinogenic in animal experiments. That’s why nitrate intake should be kept to a minimum. At the present time, the average daily intake of nitrate in Germany is estimated to be between 80 and 100 mg. Of this amount, around 60 percent is taken up from vegetables and another 26 percent from drinking water.

The studies in the federal states showed that around half of the rucola samples had a nitrate level of more than 5,000 mg/kg. Now, rucola is a type of green salad that is normally consumed in small amounts. Individual eating habits, combined with regional specificities like high nitrate contents in drinking water, may however lead to high long-term nitrate intake in individual cases. That’s why, in its assessment of the risk of increased nitrate intake through the consumption of rucola, BfR looked at various consumption scenarios and also took additional nitrate sources into account. The result: people who eat several foods with high nitrate levels take in up to 300 mg nitrate daily and thus considerably exceed the acceptable daily intake.

Give the health concerns about nitrate, in particular its role in the formation of nitrosamines and the unclarified questions about its carcinogenic properties in humans, BfR is of the opinion that nitrate intake should be reduced as much as possible.

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