Are Nitrites and Nitrates Bad for Us?

What are nitrates and nitrites?

Nitrates and nitrites are chemicals with an increasing reputation. They’re naturally found in plants, animals and the environment, but it’s their use as an artificial additive that’s got some scientists concerned.

In this article, we’ll explore how nitrites and nitrates are used in food and some of the benefits and risks.  

Nitrites vs nitrates

Both molecules are made up of nitrogen and oxygen, the difference lies in the numbers. Nitrates (NO₃) consist of one nitrogen atom and three oxygen atoms, while nitrites (NO₂) consist of one nitrogen atom and two oxygen atoms.

Where can nitrites naturally be found?

We get most of our nitrite and nitrates (between 50% and 75%) from eating fruit and vegetables. It’s the nitrites and nitrates in meat that are a source of controversy, because most of these are added artificially. The most common additive is sodium nitrite.

We add nitrite to foods such as bacon as a way of preserving the meat, because nitrite controls water activity and bacterial growth, meaning it’s very important for food safety. Too much nitrite in our bowel cells, however, can increase the risk of cancer.

Are nitrates and nitrites bad for us?

We know that processed meat containing nitrites are a risk – they’re a known carcinogen. The risk is also linked with some pickled vegetables, particularly green vegetables, which are high in nitrates when you ferment them. Kimchi, for instance, could be a possible carcinogen in that sense.

How? Well, nitrites change the way some of the proteins are structured as we digest them; the acids and the enzymes and bacteria break them down, which produces nitrogenous-based compounds. These compounds can interfere with how the cells lining our colon work. If there is a lot of contact, they may trigger changes in DNA. Genetic alterations can disrupt normal cell function, resulting in the initial stages of cancer.

Nitrates can also affect our blood pressure, triggering blood vessels to relax, because we have a pathway that allows us to break down nitrates into nitrites, which are further converted into nitric oxide. This, basically, involves ripping off two oxygens and leaving the molecule with one oxygen. It generates a free radical, and that’s something we know can be quite damaging to cells and has been linked to cancer risk.

Yet, we know that a controlled amount of nitric oxide can actually help relax blood vessels; it makes them bouncier and reduces our risk of heart disease. So that’s why beetroot shots have become popular, although you can also get nitric oxide from dark green vegetables. Watercress is another good example, as well as kale and cabbages. But the salad ones tend to be a better source, like rocket (arugula).

There actually used to be a warning in Europe for rocket because it’s such a high source of nitrate that it was linked to potential risk.

In summary, we add nitrites to bacon and wine to stop them from spoiling. We also need to remember that some of the nitrite is produced in our bodies from nitrates that we ingest from vegetables. What we don’t know is, what is it that makes the nitrites from vegetables safer? Are there other factors, for example, fiber, which stop those nitrites from being harmful? Are those things missing from bacon and wine?

Ultimately, then, should these then be banned?

It’s a nuanced issue. Remember, it’s the fermentation process that preserves the food and stops microbes like bacteria from growing and becoming harmful. If we’re looking at bacon, we can produce bacon without nitrites; there are all sorts of ways to do it. You can use salt to control the water and bacterial growth, but it’s not as effective. So, is the safety of that product without the preserving process riskier than the nitrite? And then we’ve got to think how often do we, on average, consume nitrites? Intake matters. Having bacon once per week, for instance, is probably not a risk if it is preserved with nitrites. However, if you have bacon more regularly, then it probably is more of a risk.

It’s possibly a case of trying to limit consumption while recognizing alternatives, unless they’re fully developed and packaged and so forth to keep the food safe. In my opinion, reducing intake is the first thing we need to look at, rather than necessarily looking at banning them altogether.

About the author

Dr. Duane Mellor is an award-winning registered dietitian and science communicator. They are the Aston Medical School lead for Nutrition and Evidence Based Medicine. Having a background in clinical dietetics supporting people living with diabetes, they moved into medical education when joining Aston University as well as being the Associate Dean for Public Engagement in the College of Health and Life Sciences. In this role, they work to support high-quality science and health communication alongside the wider engagement of communities in designing and developing healthcare programs.