Processed Meat, Nitrates and Nitrites

Author: Nicole Recine RN MSN AGPCNP-BC

The International Agency for Research on Cancer (IARC), a division of the World Health Organization (WHO), classifies processed meat as a Group 1 carcinogen (World Health Organization, 2015a).  This places processed meat in the same category as tobacco.  Although unproven, the IARC (and the general public) speculates that the nitrates and nitrites in processed meat are the cancer-causing agents.  Is there reason to be concerned?

What are Nitrates and Nitrites?

Nitrates and nitrites are compound that are fundamental in the process of curing meat. But they are also present naturally in many other foods such as fruits and vegetables. In fact, an estimated 80% of dietary nitrites come from vegetables.  Nitrites are even produced in our own bodies by bacteria that occur naturally in the digestive tract.  These bacteria use nitrates to produce nitrite and nitric oxide, which have many functions in the body including lowering blood pressure (Hord, Tang, & Bryan, 2009).   It is commonly argued that excess nitrates are found in processed meats, and that these excessive levels can cause cancer.  While it is true that nitrites are toxic in extremely excessive levels, the FDA and USDA have strictly limited the amount of nitrate that can be used as a food additive (Honikel, 2008).  As stated earlier, it is probable that you are getting more nitrite exposure from fruits, vegetables, and drinking water than from processed meats.

Nitrates have been used to preserve foods since ancient times, dating before the birth of Christ.  We now know that nitrates work as curing agents by preventing the growth of harmful bacteria.  Salt is used in the meat curing process to remove water, which inhibits bacteria growth. Salt alone cannot act as a curing agent.  Nitrate and nitrites function as antioxidants to prevent rancidity, and to give the finished product its characteristic red color.  Sodium nitrite specifically prevents the growth of C. botulism, a bacteria that causes severe food poisoning.  Sodium nitrate and potassium nitrate are the most common compounds used as curing agents. Food products that claim to be “nitrate-free” simply use other sources of nitrates, such as celery powder. As mentioned above, vegetables contain large amounts of nitrate.  When used as a curing agent, the nitrates in celery powder break down into nitrites, providing the same curing properties as synthesized nitrites. Because the USDA does not recognize celery powder as a nitrate, products that use celery powder as the curing agent can be labeled “nitrate-free.”   As such, the FDA does not regulate the amounts of nitrites from natural sources that are added to food products.

Nitrosamines

A larger concern seems to be when nitrites are exposed to high temperatures.  When heated, nitrites can turn into nitrosamines, which are potentially carcinogenic. This isn’t a problem when traditional curing methods are used. Dry curing is the oldest method of curing meat. Dry curing requires no heat, and the meat is cured over weeks to months. Wet curing is a bit faster.  This involves curing the meat in pickling brine and allowing it to cure at low temperatures (around 45° F) for several days to up to two weeks.  Injecting the brine directly into the meat (injection curing) can shorten the curing period to less than 48 hours. Nitrosamines are more likely to form when meats cured in nitrites are processed at high temperatures (above 140°F).  This process is used for cooked meat products like ham, bacon, hot dogs, and bologna.

Is Eating Processed Meat the Same as Smoking?

Does this mean that eating processed meat is as carcinogenic as smoking?  Not necessarily. For one, the IARC does not differentiate between the varying methods of meat processing. Hot dogs are lumped together with dry-aged prosciutto. Second, the IARC does not classify potential carcinogens based on how dangerous an agent is. The classification is based on strength of the evidence available to determine whether or not an agent causes cancer.  For processed meat, twenty-two “experts” evaluated the available evidence.  Notably, they looked at 400 epidemiological studies, which look at correlations between reported food consumption and disease rates in different populations.  These types of studies, especially those of larger scale, are notoriously flawed (Satija, Yu, Willett, & Hu, 2015). There is simply no way to control the extensive number of variables that influence health (lifestyle, socioeconomic status, etc.) or accurately measure what people eat. More importantly, they are unable to show a causal relationship.  In other words, the IARC cannot tell you how processed meat causes cancer from the evidence they assessed. The IARC, as well as many consumers, speculates that the nitrates and nitrites in processed meat cause cancer.  But, as the IARC state in their report, they do not understand how cancer risk is increased by processed meat consumption (World Health Organization, 2015).  This point should not be taken lightly.  Many of the concerned public believe that placing an agent in a category as a carcinogen means that the WHO has a clear understanding how something cancer, and that it definitely causes disease. But, they simply cannot say this from the available evidence.

My recommendation would be to educate yourself about how your food is made.  As always, find products that are minimally processed and prepared using traditional curing methods.  Lastly, it isn’t necessary to give up bacon completely, but it is probably best to avoid burning it when possible.

About The Author: 

Nicole Recine is a nurse practitioner that specializes in diabetes. Nicole was a featured speaker at the 2017 KetoCon. Watch her KetoCon presentation.