Nitrates (NO2–) and nitrates NO3–) are commonly found in foods (nitrate is the oxidised form of nitrate). Increased intakes of nitrates and nitrites are associated with an increased risk of gastrointestinal cancers. In humans and other animals, dietary nitrates and nitrites are converted to nitrosamines in the gastrointestinal tract. Nitrosamines are damaging because they act as free radicals and can cause oxidative stress to the cells within the gut. Oxidative damage to the genetic material in these cells may initiate cancer and this explains the association between dietary nitrates and nitrites with gastrointestinal cancer. Although processed meats can contain high amounts of nitrites in the form of the preservative sodium nitrite, vegetables and fruits also deliver dietary nitrites through the use of fertilisers. Vegetables can contribute 80 % of the nitrates in the diet. In fact the World Health Organisation’s recommendation for nitrate is exceeded by diets recommended to lower blood pressure through increased vegetable intake.
For example, the DASh (dietary approaches to stop hypertension) diet exceeded the WHO recommended nitrate intake by 550 %1. However many studies show that the DASH diet is beneficial to the health and may have blood pressure lowering effects that in turn decrease the risk of cardiovascular death. Therefore there exists a contradiction in that some healthy diets are at the same time high in nitrates. One solution to this would be to eat only organic foods, that are devoid of added nitrate, and in this way benefit from both a low nitrate intake and a high vegetable intake. However, for some the exclusive use of organic foods is not cost effective and therefore non-organic alternatives are the only vegetables available. Based on this, it is likely that the benefits of high vegetable diets far outweigh any negative effects of the nitrate present, and the recommendation therefore must be to consume vegetables along with the added nitrates, as this will likely still have a beneficial effect on health.
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