How safe are nitrate-containing foods like dried fruit?

A survey funded by Food Standards Australia New Zealand estimated the major sources of nitrate in the average Australian diet were vegetables (42-78%) and fruit, including juices, (11-30%).

The nitrates in processed meats, however, are considered a significant factor in the International Agency for Research on Cancer’s classification of the likes of salami, bacon, ham and sausages as “carcinogenic to humans”. The nitrate itself is relatively non-toxic, but the metabolites formed during processing and/or digestion of nitrate in the body – namely, nitrite, nitric oxide and N-nitroso compounds – are linked to certain cancers.

Understanding why nitrates in fruits and vegetables are okay, whereas those in processed meats aren’t, calls for looking at the bigger picture.

Fruit and vegetables are widely recommended thanks to the range of valuable nutrients and components they contain and a pile of evidence about their beneficial health effects. Confusingly, nitrate metabolites and by-products are also useful for our health. For example, the antimicrobial activity of nitrite that is harnessed for curing processed meat also contributes to our immune response. Nitric oxide, meanwhile, plays a role in the regulation of our vascular system.

But most significantly, when nitrate is consumed in the form of vegetables and fruit, other important bioactive compounds, such as antioxidant vitamin C, which suppresses the formation of nasties like nitrosamines, are being consumed at the same time. Processed meat, however, doesn’t contain these beneficial substances, but instead has other cancer-causing compounds such as polycyclic aromatic hydrocarbons.

So zeroing in on one compound or contaminant can lead us to unwittingly make harmful changes to our diet. A recent example was the publication by the US Environmental Working Group (EWG) of its Dirty Dozen report – a list of fruits and vegetables it claims to have the highest pesticide residue levels.

Certainly, the fewer pesticides we ingest the better. However, a study by the World Health Organisation and United Nations found the EWG’s report put people off fruit and vegetables. What’s more, a survey of low-income shoppers found those who’d heard messages about pesticide residues on produce were less likely to buy any fruit and vegetables, not realising the health effects of eating none are much worse than the residue dangers.

So what does this mean for the safety of nitrates in dried fruit and processed meats? The former is fine, the latter not so.

This article was first published in the May 27, 2017 issue of the New Zealand Listener.