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.
There is a spectrum of health effects evident with nitrates that seemingly depend on their dietary source. For example, vegetable-sourced nitrate is converted to nitric oxide (NO) in the body, and NO has a demonstrably positive health effect through reducing blood pressure, improving vascular function and even enhancing physical performance in clinical trials.
With processed meats, nitrates and nitrites are considered a significant contributor to their classification as “carcinogenic to humans”, according to the International Agency for Research on Cancer. This is because, under certain conditions,the added nitrates and nitrites may form carcinogenic N-nitroso compounds. Nitrites are more toxic that nitrates.
A Danish study published earlier this year in the European Journal of Epidemiology further supported the variable effect of nitrates according to their food source. Using dietary and health data from 52,247 participants of the Danish Diet, Cancer and Health Study, researchers found that dietary intake of nitrates from plant sources was associated with a reduced risk of cardiovascular disease and cancer mortality, whereas nitrates from tap water and animal sources were linked to higher mortality risks.
“In simplistic terms, nitrates can go down two different pathways when introduced into the body,” said lead author Nicola Bondonno. “One is to form a compound called nitric oxide, which has been shown to improve blood flow, lower blood pressure and support overall cardiovascular health.
“But nitrate may also go down a second pathway, forming a group of compounds called nitrosamines, which are considered to be carcinogenic and are linked to cancer. It is thought that the antioxidant compounds in vegetables push nitrate towards the first pathway.”
Although nitrates aren’t the only health-promoting compounds in vegetables and fruits, the research highlights that eating more nitrate-rich vegetables can significantly lower the risk of death from heart disease, cancer and other causes. Certainly, there is no cause for concern about eating nitrate-rich vegetables such as beetroot in sensible quantities.
In New Zealand, most of our dietary exposure to nitrates is through fruit and vegetables, followed by animal-derived foods and drinking water. The eating advice remains the same, irrespective of nitrate content: eat more plant-derived foods and fewer animal products, while specifically limiting the amount of processed meats.
As for raw beetroot, it contains a plethora of essential nutrients and antioxidants alongside the nitrates. When you eat it, all of those important bioactive compounds are consumed simultaneously.
