Nitrates are compounds of nitrogen and oxygen, found naturally in some foods and added to others, particularly processed meats like bacon, ham, and hot dogs. In the food industry, synthetic forms like sodium nitrate and potassium nitrate are used as additives. These compounds also occur naturally in the human body and are a normal part of our environment.
The Role of Nitrates in Meat Processing
The use of nitrates and their related compounds, nitrites, in meat curing is a long-standing practice developed to preserve meat before refrigeration was available. The primary function of these additives is food safety. They are effective at preventing the growth of harmful bacteria, most notably Clostridium botulinum, which produces a life-threatening toxin that causes botulism.
Beyond preservation, these compounds are responsible for the defining characteristics of cured meats. During the curing process, nitrates convert to nitrites, which then change into nitric oxide. This nitric oxide interacts with proteins in the meat, which, upon heating, creates the stable pink or red pigment characteristic of products like ham and bacon. Without these additives, the meat would quickly turn brown.
This chemical reaction also contributes to the distinct salty and savory flavor associated with cured products. Nitrates and nitrites also help to prevent off-flavors that can result from the oxidation of fats during storage, maintaining the quality of the meat for longer.
Health Implications of Consuming Nitrates
The health discussion surrounding nitrates in meat centers on their potential to form N-nitroso compounds (NOCs), such as nitrosamines. This transformation can happen when nitrates, which convert to nitrites in the body, are exposed to high heat during cooking in the presence of amino acids in meat. Most nitrosamines are recognized as carcinogenic, meaning they are substances capable of causing cancer.
This link is a reason the International Agency for Research on Cancer (IARC), a part of the World Health Organization, classified processed meat as a Group 1 carcinogen, indicating sufficient evidence that it causes cancer in humans. The consumption of processed meat is associated with an increased risk of colorectal cancer. The IARC’s analysis suggests that daily consumption of a 50-gram portion of processed meat increases the risk of colorectal cancer by 18%.
This classification is not solely due to nitrates but also considers other factors like heme iron, which is found in red meat. The combination of heme iron and added nitrites is thought to promote the conversion of nitrites into carcinogenic nitrosamines within the digestive tract. While the risk increases with the amount of processed meat consumed, regulatory agencies have established acceptable daily intake levels for nitrates and nitrites to minimize potential health concerns.
Natural vs. Artificial Nitrates
In response to consumer interest in “cleaner” labels, many meat products are now marketed as “uncured” or having “no nitrates or nitrites added.” These products rely on natural sources of nitrates, such as celery powder or beet juice, to achieve the same curing effects. Celery, in particular, is naturally high in nitrates, and its powder serves as a source for the same chemical reactions that occur with synthetic nitrates.
From a chemical standpoint, the nitrate molecule from a plant source is identical to the one produced synthetically. This means that once in the body, they behave in the same way, and the potential for forming nitrosamines still exists. Consequently, labeling a product as “uncured” can be confusing, as it has still undergone a curing process, just with a plant-based source of nitrates.
A point of difference lies in the other compounds present in these natural sources. Vegetable powders contain antioxidants like vitamin C, which can inhibit the conversion of nitrites into nitrosamines. Some manufacturers add antioxidants such as sodium ascorbate to conventionally cured meats for this purpose. However, whether the levels of antioxidants in natural sources are sufficient to offer a significant health advantage is still a matter of scientific discussion.
Nitrates in Other Foods
While processed meats are a focal point of the nitrate debate, they are not the primary source in the average diet. The vast majority of dietary nitrates, around 80%, come from vegetables. Leafy greens like spinach, arugula, and lettuce, as well as root vegetables like beets and carrots, are naturally rich in these compounds.
The health implications of nitrates from vegetables are viewed very differently. In this context, nitrates are not associated with an increased cancer risk and may offer cardiovascular benefits. When we eat vegetables, the nitrates can be converted into nitric oxide in the body, a molecule that helps relax blood vessels, improve blood flow, and lower blood pressure.
This difference is attributed to the food “matrix.” Vegetables are low in the proteins and high heat cooking methods that facilitate nitrosamine formation in meat. Vegetables are also rich in antioxidants, such as vitamin C and polyphenols, which actively prevent the formation of harmful nitrosamines. The health effect of a compound like nitrate depends heavily on its food source and what is consumed with it.