What Do Nitrites and Nitrates Do to Your Body? The Complete Guide

December 9, 2025 •

5 min read

Approximately 80% of dietary nitrates are sourced from vegetables, a fact that contrasts sharply with the public's perception of these compounds being primarily harmful food additives. The truth is that nitrites and nitrates have a complex, dual nature within the human body, offering both significant health benefits and potential risks depending on their source and how they are processed.

Quick Summary

Nitrites and nitrates are compounds with dual effects, playing roles in cardiovascular function and also potentially forming carcinogenic nitrosamines. Their impact depends heavily on their source, such as antioxidant-rich vegetables versus processed meats, as well as cooking methods.

Key Points

Dual Nature: Nitrites and nitrates can have both beneficial (vasodilation, exercise performance) and harmful effects (carcinogenic nitrosamines) within the body, depending on their source and context.
Vegetables Are Key: Most dietary nitrates come from vegetables like spinach and beetroot, where they are accompanied by protective antioxidants that inhibit the formation of harmful compounds.
Processed Meat Risk: Nitrites added to processed meats like bacon can react with proteins during high-heat cooking to form carcinogenic nitrosamines, a primary health concern.
Nitric Oxide's Role: The conversion of nitrites to nitric oxide provides significant health benefits, including lowered blood pressure and improved blood flow.
Infant Sensitivity: Infants under six months are at higher risk for methemoglobinemia ('blue baby syndrome') from high nitrate levels, most commonly from contaminated well water used in formula.
Risk Mitigation: Reducing processed meat consumption and ensuring a diet rich in vegetables are key strategies to minimize nitrosamine exposure while maximizing the benefits of nitrates.

What are Nitrites and Nitrates?

Nitrates (NO3) and nitrites (NO2) are simple chemical compounds composed of nitrogen and oxygen. The key difference lies in their atomic structure and stability: nitrates have three oxygen atoms, making them more stable or 'inert,' while nitrites have two, making them more reactive. In the body, bacteria, primarily in the mouth and gut, convert harmless nitrates into the more reactive nitrites. From there, nitrites can take one of two very different paths.

The Body's Conversion Pathways

The human body has an active metabolic cycle involving nitrates and nitrites. After ingestion, nitrates are absorbed into the bloodstream. A significant portion is then actively concentrated in the salivary glands and secreted back into the mouth. Here, oral bacteria reduce the nitrate to nitrite, which is then swallowed and proceeds through one of the following pathways:

Beneficial Pathway: In the acidic stomach, nitrite can be converted into nitric oxide (NO). Nitric oxide is a vital signaling molecule that provides numerous health benefits.
Harmful Pathway: If nitrites are present with high levels of protein (amines) under certain conditions, such as high heat cooking or in a less acidic stomach environment, they can form N-nitroso compounds, also known as nitrosamines. Many nitrosamines are carcinogenic and can pose a health risk.

The Dual Effects of Nitrates and Nitrites

The two conversion pathways explain why these compounds are often called the 'Jekyll and Hyde' of nutrition.

Beneficial Effects from Nitric Oxide

When nitrites are converted into nitric oxide, they can provide powerful cardiovascular benefits.

Blood Pressure Reduction: Nitric oxide signals the tiny muscle cells around arteries to relax, causing blood vessels to dilate and thus lowering blood pressure. This is why foods high in natural nitrates, like beetroot juice, are linked to reduced blood pressure.
Improved Exercise Performance: Nitric oxide enhances blood flow and improves the efficiency of mitochondria, the energy-producing powerhouses of cells. This allows for better oxygen utilization, boosting performance during high-intensity endurance exercise.
Enhanced Tissue Healing: Nitric oxide plays a role in promoting the healing process within the body.

The Harmful Potential of Nitrosamines

The formation of nitrosamines is the primary health concern associated with nitrates and nitrites, particularly from processed meats. The combination of high protein (amines) and nitrite, especially when cooked at high heat, creates the ideal conditions for these carcinogenic compounds to form. The International Agency for Research on Cancer (IARC) classifies ingested nitrate and nitrite as 'probably carcinogenic to humans' under conditions that result in endogenous nitrosation, or the formation of nitrosamines within the body. This has been linked to an increased risk of certain cancers, including stomach and colorectal cancer.

Sources of Nitrates and Nitrites: A Critical Distinction

Understanding the source of nitrates and nitrites is crucial to understanding their health impact. The perception that all nitrates and nitrites are harmful often stems from their use in processed meats, but this overlooks the fact that most dietary intake comes from vegetables.

The Role of Protective Antioxidants

Vegetables, particularly leafy greens and root vegetables, are the primary source of dietary nitrates, accounting for 70-80% of intake. However, the nitrates in vegetables are not typically a cause for concern. The reason is that these plants are also rich in antioxidants like Vitamin C and polyphenols. These compounds actively inhibit the formation of harmful nitrosamines, effectively neutralizing the risk. Processed meats, by contrast, lack these protective antioxidants, making the added nitrites more problematic.

What About Methemoglobinemia?

Methemoglobinemia, or 'blue baby syndrome,' is a rare condition linked to excessive nitrate exposure, primarily in infants under six months of age. In infants, certain intestinal bacteria can convert nitrate to nitrite at a higher rate. The nitrite then oxidizes the iron in hemoglobin, preventing red blood cells from carrying oxygen. This is most often caused by mixing infant formula with well water highly contaminated with nitrates. Healthy adults and older children have more developed enzymes to reverse this process, making them less susceptible.

Reducing Your Risk

Given the dual nature of nitrates and nitrites, a balanced approach is best for health:

Prioritize Vegetables: Continue to eat a diet rich in vegetables like spinach, celery, and beetroot to reap the cardiovascular benefits of nitric oxide without the nitrosamine risk.
Minimize Processed Meats: Limit your intake of cured and processed meats such as hot dogs, bacon, and cold cuts, as these are the main sources of dietary nitrosamine exposure.
Cook Processed Meats Carefully: Avoid cooking processed meats at very high temperatures, such as frying bacon until crispy, as this promotes nitrosamine formation.
Test Your Well Water: If you use well water, especially when preparing formula for an infant, have it tested for nitrate levels to avoid contamination risks.

Nitrates vs. Nitrites Comparison Table


Characteristic	Nitrates ($$NO_3$$)	Nitrites ($$NO_2$$)
Chemical Structure	One nitrogen, three oxygen atoms	One nitrogen, two oxygen atoms
Primary Source	Naturally in vegetables, water, soil; minor amounts added to processed meats	Produced in the body from nitrates; added to processed meats
Relative Stability	Generally inert and stable	Reactive intermediate in the body
Body Conversion	Reduced to nitrite by oral and gut bacteria	Converted to nitric oxide (beneficial) or nitrosamines (harmful)
Primary Health Concern	None from natural sources; risk of methemoglobinemia in infants from excessive intake	Formation of carcinogenic nitrosamines, especially from processed meats cooked at high heat

Conclusion

Understanding what nitrites and nitrates do to your body reveals a more nuanced picture than commonly presented. While the risk of forming carcinogenic nitrosamines from processed meats is a valid concern, it's a mistake to categorize all nitrates and nitrites as harmful. The overwhelming majority of our intake comes from vegetables, where nitrates are converted into beneficial nitric oxide, promoting heart health and exercise performance. By focusing on a balanced diet rich in vegetables and limiting processed meat consumption, individuals can maximize the health benefits while minimizing the potential risks associated with these compounds. It is the context—the source, the accompanying nutrients, and the cooking method—that ultimately determines their impact on health.

Learn more about the dual nature of these compounds from the Centers for Disease Control and Prevention (CDC)(https://wwwn.cdc.gov/TSP/ToxFAQs/ToxFAQsDetails.aspx?faqid=1186&toxid=258).

Frequently Asked Questions

The main difference is their chemical structure and reactivity. Nitrates ($$NO_3$$) have three oxygen atoms and are relatively stable, while nitrites ($$NO_2$$) have two oxygen atoms and are more reactive. Nitrates are converted into nitrites in the body by bacteria.

Nitrates in vegetables are accompanied by high levels of protective antioxidants like Vitamin C. These antioxidants prevent the formation of harmful nitrosamines, a risk that is higher with nitrites found in processed meats due to their protein content and cooking methods.

When converted to nitric oxide in the body, nitrites can cause blood vessels to dilate and relax. This wider vessel opening leads to lower blood pressure and improved overall cardiovascular health.

Nitrosamines are N-nitroso compounds formed when nitrites react with amines (from protein). Many are carcinogenic and have been linked to an increased risk of certain cancers, especially when associated with cooked processed meats.

'Blue baby syndrome,' or methemoglobinemia, is a rare condition where excessive nitrite exposure prevents red blood cells from carrying oxygen. Infants under six months are most at risk, typically from consuming formula made with high-nitrate contaminated well water.

Yes. High-heat cooking, like frying bacon, increases the likelihood of nitrosamine formation when nitrites are present with meat proteins. Cooking vegetables, even at high heat, is less likely to produce these harmful compounds.

You can reduce your risk by minimizing the consumption of processed and cured meats. Checking product labels for added sodium or potassium nitrites and testing well water for contamination are also effective measures.