Risk assessment of nitrate, nitrite and nitrosamines

"Excessive intake of carcinogenic nitrosamines from food is the most serious finding," says Trine Husøy, who has led the work in VKM.

Background

Nitrate and nitrite occur naturally in food, particularly in vegetables, and are used as food additives in certain products because they inhibit bacterial growth and thereby increase shelf life. Nitrate is permitted for use, for example, in certain types of cheese, meat and fish, while nitrite is permitted in certain types of processed meat.

Nitrate can be converted to nitrite both in food and in the body. High levels of nitrite in the blood can lead to methemoglobinemia, a condition in which the body’s ability to transport oxygen is reduced. This condition is rare, but serious. Nitrite can react with naturally occurring amines to form nitrosamines, several of which are carcinogenic.

This assessment was commissioned by the Norwegian Food Safety Authority, which requested an evaluation of whether exposure to these substances may pose a health risk for different population groups. They also requested more knowledge about how changes in diet may affect the exposure to nitrate and nitrite.

Methods

VKM has estimated how much nitrate, nitrite and nitrosamines we are exposed to from food and drink, and how much nitrite and nitrosamines are formed in the body. Furthermore, we have assessed whether the estimated levels may constitute a health risk.

Findings

• Exposure to nitrite and nitrosamines in the Norwegian population is at a level comparable to other European countries.

• Vegetables were the main source of dietary exposure to nitrate for most age groups.

• The endogenous synthesis of nitrite from nitrate was up to five-fold higher than the estimated nitrite exposure from food .

• Meat and meat products were the main sources of dietary nitrite.

• Meat and meat products were the main sources of dietary nitrosamines.

VKM concludes that

• The risk associated with nitrite from food is low for most people at typical intake levels, but at high intake levels, and when the body’s own production from nitrate is included, total exposure may pose a risk of adverse health effects in several age groups.

• The amount of nitrosamines we are exposed to gives reason for concern for an increased cancer incidence in the population.

VKM emphasises that the risk assessment is associated with uncertainty, particularly due to limited data on the occurrence of nitrate, nitrite and nitrosamines in food. This uncertainty means that the levels of nitrite and nitrosamines are likely underestimated.