Are Nitrates and Nitrites in Foods Harmful?
There is a lot of confusion about Nitrates and Nitrites in the diet.
These are compounds found naturally in some foods (like vegetables) but also added to processed foods (like bacon) as a preservative.
Some people believe that they are harmful and can cause cancer.
However, the science isn't as clear and some studies suggest that they may even be healthy.
So... what is the truth about nitrates/nitrites in the diet? Let's have a look...
In order to understand what nitrates and nitrites are, we need to delve into a bit of chemistry.
These are two types of compounds, consisting of a single Nitrogen atom bonded to a number of Oxygen atoms.
- Nitrate: 1 Nitrogen, 3 Oxygens - Chemical Formula: NO3-
- Nitrite: 1 Nitrogen, 2 Oxygens - Chemical Formula: NO2-
So... Nitr-a-tes have 3 oxygen atoms, while Nitr-i-tes have 2 oxygen atoms.
It seems that the nitrates themselves are relatively inert, until they are turned into nitrites by bacteria in the mouth or enzymes in the body.
Nitrites are the key players here... they can either turn into Nitric Oxide (good) or nitrosamines (bad) - which we will cover in detail shortly (1).
Nitrites are the reason cured meat is pink or red. Nitrites turn into Nitric Oxide, which reacts with the oxygen-binding proteins in the meat, changing its color (2).
Without additives like nitrites, the meat would turn brown very quickly.
Bottom Line: Nitrates and Nitrites are compounds consisting of Nitrogen and Oxygen atoms. Nitrates can turn into Nitrites, which can then form either Nitric Oxide (good) or Nitrosamines (bad).
Nitrates and nitrites are frequently added to processed meats like bacon, ham, sausages and hot dogs.
They function as preservatives, helping to prevent the growth of harmful bacteria.
They also add a salty flavour and improve the appearance of the meat products by giving them a red or pink color.
Vegetables are actually the biggest dietary source of nitrates... by far. The amount you get from processed meat is small compared to vegetables (7).
Nitrates and nitrites actually circulate from the digestive system, into the blood, then into saliva and then back into the digestive system. This is known as the entero-salivary circulation (10).
They seem to function as antimicrobials in the digestive system, helping to kill pathogenic bacteria like Salmonella (11, 12). They can also turn into Nitric Oxide (NO), an important signalling molecule (13).
Nitrates can even be found in drinking water in some areas. This can be a problem for infants under 6 months of age, which are unable to process a lot of nitrate.
This can lead to a dangerous condition called methemoglobinemia, which is why nitrate amounts in drinking water are regulated.
However, this is not a problem in adults or older children, who can process nitrates just fine.
Bottom Line: Nitrates are found in small amounts in processed meats, and in much larger amounts in healthy foods like vegetables. They are also found in drinking water and produced by our own bodies.
If nitrite loses an oxygen atom, it turns into Nitric Oxide, an important molecule.
Nitric Oxide (NO) is a short-lived gas, which has various functions in the body (14).
Most importantly, it is a signalling molecule. It travels through the artery wall and sends signals to the tiny muscle cells around the arteries, telling them to relax (15).
When these cells relax, our blood vessels dilate and blood pressure goes down.
This is actually how the well known drug nitroglycerin works. It is a source of nitrate, which quickly turns into nitric oxide and dilates the blood vessels (16).
This can prevent or reverse angina, chest pain that occurs when the heart muscle doesn't get enough oxygen due to reduced blood flow.
Dietary nitrates and nitrites can also turn into Nitric Oxide, dilate the blood vessels and lower blood pressure (17).
Studies have shown that nitrate supplements, such as beet roots or beet root juice, can reduce blood pressure by up to 4-10 mm/Hg over a period of a few hours. The effect may be weaker in women (18, 19, 20).
Elevated blood pressure is one of the strongest risk factors for heart disease and stroke (the world's biggest killers), so the importance of this can not be overstated.
Bottom Line: Nitrites can be turned into Nitric Oxide (NO) in the body, a signalling molecule that makes blood vessels dilate and reduces blood pressure.
Numerous studies suggest that nitrates can enhance physical performance, especially during high intensity endurance exercise.
Beet roots (or beet root juice) are often used for this purpose, because they are very high in nitrates.
This appears to be due to nitrates increasing the efficiency of mitochondria, the parts of cells that produce energy (21).
A few studies have shown that beet roots (high in nitrates) can reduce the oxygen cost of exercise by 5.4%, increase time to exhaustion when running by 15% and improve sprinting performance by 4% (22, 23, 24).
Bottom Line: Numerous studies show that dietary nitrates/nitrites can enhance physical performance, especially during high intensity endurance exercise.
Unfortunately, there is a dark side to all of this.
When nitrites are exposed to high heat, in the presence of amino acids, they can turn into compounds called nitrosamines (25).
They are among the main carcinogens in tobacco smoke, for example.
Because most bacon, hot dogs and processed meat tend to be high in sodium nitrite and they're high protein foods (a source of amino acids), exposing them to high heat creates the perfect conditions for nitrosamine formation (27).
It's important to keep in mind that nitrosamines mostly form during very high heat. Even though vegetables also contain nitrates/nitrites, they are rarely exposed to such high heat.
Nitrosamines can also form during the acidic conditions in the stomach.
Bottom Line: When nitrites and amino acids are present, carcinogenic compounds called nitrosamines can form during high heat cooking.
Nitrosamines are a well known problem in processed meats, and manufacturers are required to limit the amount of nitrites they use.
They are also required to add Vitamin C, which inhibits nitrosamine formation (28).
The processed meat eaten today contains about 80% less nitrites than it did a few decades ago (29).
For these reasons, today's processed meat may not be nearly as carcinogenic as it used to be.
But just to be on the safe side, then there are some steps you can take to minimize your nitrosamine exposure even further... without having to give up bacon.
You can choose quality bacon that is truly nitrate-free, not laden with celery salt or something similar that also contains nitrates. A lot of "nitrate free" bacon can even contain more nitrates than conventional bacon (30).
The one I get is basically just salted pork belly. I buy it frozen because it doesn't keep well without the nitrates/nitrites.
It tastes just as good, if not better, than regular bacon.
Try to buy local if you can, or from a farmer's market. If you can get your hands on it, bacon from pasture-raised pigs should be much healthier than bacon from "conventionally" raised pigs.
Another thing you can change is the way you cook your bacon. Frying it at a lower heat for longer will produce less nitrosamines than a higher heat for a shorter amount of time. Burnt bacon is the worst.
According to one study, cooking bacon in a microwave is the best way to minimize nitrosamine formation (31).
Here is a video with instructions on how to do it. I've personally tried it and it worked surprisingly well.