Chemical reaction

Nitrates in processed meats are well known to cause harm, but consumed from plant sources, their effect is quite different.

- JENNIFER BOWDEN

QUESTION: I want to eat more raw beetroot but was reading about compounds called nitrates and nitrites and wondered if it was safe to eat beets raw. Can you advise?

ANSWER: Raw beetroot and leafy greens are a rich source of beneficial nutrients, but their high nitrate content has led to debates about whether they are friend or foe when it comes to health.

Diets rich in nitrates have been linked to a reduced risk of cardiovascular disease, dementia and diabetes. But concerns have been raised about possible links between dietary nitrates and cancer risk.

Many home gardeners will know that nitrate is a naturally occurring compound that plays an important role in the nutrition and function of plants. Plant fertilisers contain nitrates, which the plants take up through their roots and transport to their above-ground organs.

So many plant-derived foods naturally contain nitrates, which tend to accumulate in leaves more than in seeds or tubers. Therefore, leaf crops such as lettuce and spinach tend to have higher nitrate concentrations than carrots and potatoes.

The amount of nitrate that accumulates differs by species: those known to be nitrate accumulators include radish, beetroot, Swiss chard, spinach, lettuce, celery and parsley.

Nitrates and nitrites (which are slightly different chemically) in their salt form are also used to cure processed meats, giving them the distinctive pink colour. However, the nitrates and nitrites in processed meat are viewed entirely differently from those found naturally in vegetables and fruit.