Is Dietary Nitrate Good or Bad for the Health?

In the world of science, there is a lot of controversy surrounding the impact of dietary nitrate on human health [1, 2, 3].  Nitrate (NO₃^-) is a compound composed of nitrogen and oxygen atoms that occurs naturally in plant-based foods, including beets, spinach, rocket and kale.  After consumption, nitrate is broken down into a molecule known as nitrite (NO₂^-) and nitric oxide (NO) through a series of processes inside the body [2].

 

Several studies have shown that nitric oxide is beneficial for oral and heart health [1, 4]. It can also be added to processed meats for preservation purposes [5]. Unfortunately, scientists have discovered that a high consumption of processed foods can increase an individual’s risk of cancer.  So, should we include nitrate-rich foods in our diet or err on the side of cation? This answer ultimately depends on the food source.

 

What are the Health Benefits of Good Nitrates?

 

Green veggies, such as spinach, celery and lettuce, and root vegetables such as beetroot, are loaded with nitrates [6]. When we eat these vegetables, nitrite and nitric oxide are produced [7].  Nitric oxide is an important signalling molecule that causes blood vessels to dilate, improves blood circulation and reduces blood pressure levels. 

 

These factors can lower an individual’s cardiovascular disease risk. In fact, one study showed beetroot juice can reduce blood pressure levels within a couple of hours of consumption. Additionally, nitric oxide can also improve exercise performance by enhancing the flow of oxygen and nutrients to working muscles and increasing energy production inside human cells [6]. 

 

Another benefit of plant-based nitrates relates to brain function.  As nitric oxide improves cerebral blood flow, this can reduce an individual’s risk of cognitive disorders, such as dementia and Alzheimer’s disease [1, 4].   

 

What are the Risks of Bad Nitrates?

 

Processed meats like hot dogs, ham, sausages and bacon contain high levels of nitrates/nitrites [5, 6]. For example, sodium nitrate and sodium nitrite are typically added to meats to enhance their taste, limit the growth of harmful bacteria and for colouration purposes. Unfortunately, unlike green vegetables, nitrates/nitrites in processed-meat products can lead to the production of carcinogenic (cancer-causing) compounds known as nitrosamines [3]. 

 

Most notably, nitrosamines have been associated with the development of colorectal cancer.  The World Health Organisation (WHO) recently reported that a daily portion of 50 grams of processed meat (on average, 5 slices of bacon) can increase an individual’s risk of colorectal cancer by 18% [7].

 

 

The Health Benefits of Dietary Nitrate

 

The health effects of dietary nitrate depend on the food source. Nitrate can either be converted to nitric oxide which is positive for health or nitrosamines which can have a detrimental impact on the body. Processed meats are high in protein and when nitrates/nitrites are added to meats for preservation purposes, they can combine with amino acids in proteins to form cancer-causing compounds known as nitrosamines [5, 6, 7]. 

 

High cooking temperatures also promotes the formation of nitrosamines.  In contrast, vitamins and antioxidations present in vegetables inhibits the production of these cancer-causing compounds [1, 7]. 

 

Overall, although there is no “one size fits all” approach, a daily serving of nitrate-rich vegetables is a positive way to improve heart health whilst the consumption of processed meats should be limited to lower the risk of cancer.

 

 

By: Siobhan Moran BSc (Hons) MSc