Are nitrates good or bad for health? Why?

Studies also suggest that certain sources of nitrate may inhibit the production of N-nitrosamines

ISLAMABAD, (Online) - Nitrates are compounds made from nitrogen and oxygen atoms. They are commonly found in vegetables, meat, and drinking water.

In 1976, two studies showed that nitrates can form N-nitrosamines, which are highly carcinogenic in lab animals and linked to cancer in humans, too. These studies and others have formed the basis of guidelines monitoring nitrate intake.

However, other research suggests that vegetables high in nitrates may protect against cardiovascular disease.

Studies also suggest that certain sources of nitrate may inhibit the production of N-nitrosamines. One study found that nitrates from vegetables that contain vitamin C or polyphenols may prevent its production, meaning consumers can enjoy the nutrient’s benefits while avoiding its negative consequences.

Further study on the health impact of nitrates could lead to the development of healthier diets and prevention strategies for various conditions.

Nitrates: Good or bad?

Recently, a team led by researchers from Edith Cowan University, Australia, reviewed studies investigating the health benefits and disadvantages of dietary nitrates.

They concluded that evidence is insufficient to say that nitrates in food and water are carcinogenic and that more studies are needed to understand the scale of their effects.

“Nearly 80% of our dietary nitrate intake comes from vegetable consumption,” Dr. Kelly Johnson-Arbor, medical toxicologist, co-medical director, and interim executive director at the National Capital Poison Center, who was not involved in the study, told Medical News Today.

“When food sources of nitrate are consumed, the nitrate is absorbed by salivary glands, where it is converted into nitrite. From there, the nitrite is absorbed into the bloodstream and transformed into nitric oxide. Nitric oxide plays a key role in many functions within the human body, including blood pressure regulation and heart health,” she added.

The study was published in Trends in Food Science and Technology.

Which foods are a source of nitrates?

Current guidelines suggest nitrate intakes of 0–3.7 milligrams per kilogram (mg/kg) of body weight — or around 260 milligrams (mg) for an adult weighing 70 kilograms (kg).

Plants are major sources of nitrates. Leafy vegetables such as arugula, Chinese spinach, and butterhead lettuce contain the highest levels of nitrates at over 2,500 mg/kg. Fruits such as nectarines and peaches have the lowest quantities of nitrates at less than 25 mg/kg.

Nitrates are found in lower quantities in animal-based food products. Most animal-based products, such as red meat, poultry, and fish contain less than 50 mg/kg. Dairy products also contain lower levels, with skimmed milk containing less than 0.5 mg/kg.

Processed meat products contain higher levels of nitrates as sodium and potassium nitrate are often used as additives. Chorizo, for example, contained a median of 101 mg/ kg, and fresh sausage had a median of 77 mg/kg.

Dr. Johnson-Arbor told MNT: “Nitrates and nitrites are added to processed meats to reduce bacterial contamination and prevent foodborne diseases like botulism. This process is called ‘curing.’ Since cured meats contain nitrates, many people choose to avoid consumption of ham, bologna, bacon, or other processed meats in an effort to avoid nitrate consumption and reduce cancer risk.”

“Some people choose to eat ‘uncured’ or ‘naturally cured’ meat products instead. These meat products are cured with celery or other vegetable juices, instead of nitrates and salt. However, since vegetables are a good source of nitrates, ‘naturally cured’ or ‘uncured’ meats will still often still contain significant amounts of nitrates, and there are likely little health benefits to consuming those products.” – Dr. Kelly Johnson-Arbor

Nitrates are also found in both surface and groundwater. The World Health Organization’s (WHO) guideline value for nitrate in drinking water is of 50 milligrams per literTrusted Source (mg/L).

A report by the European Commission in 2021 found that 14% of groundwater monitoring sites had above 50 mg/L although the majority contained less than 25 mg/L or nitrates.

Health benefits of nitrates

Several comprehensive reviews have found that dietary nitrates improve cardiovascular function and health and lower long-term risk for cardiovascular disease. Most of these studies investigated the effects of nitrate intake from plant sources.

In addition, dietary nitrate intake can increase nitric oxide levels, a molecule involved in the regulation of the central nervous and cardiovascular systems, both of which affect cognition and brain function.

The researchers note that nitric oxide inhibits the phosphorylation of the protein tau, which may be relevant given that Alzheimer’s disease is associated with a hyperphosphorylation of tau.

They added that seven out of 12 clinical trials observed that dietary nitrate from beetroot juice is linked to improved cognitive function and cerebral blood flow. Four of the studies, however, found that nitrate had no effect on cognitive function.

Studies also show that nitrates taken either as supplements or from dietary sources:

• increase muscle function and strength

• increase exercise time to exhaustion, power output, and distance traveled

• benefit eye health and lower risk of age-related macular degeneration

• have anti-inflammatory effects

• may lower diabetes risk.

Few trials have explored the direct effects of nitrates on type 2 diabetes. However, one trial of beetroot powder as a source of dietary nitrate found no significant impact on glucose or insulin parameters.

“Dietary nitrates found in fruits/vegetables have healthful cardiovascular effects by opening up blood vessels, as well as acting as antioxidants and anti-inflammatory compounds as well that may inhibit the formation of harmful N-nitrosamines which are associated with cancer,” Dr. Dana Ellis Hunnes, a senior clinical dietitian at the UCLA Medical Center and an adjunct assistant professor at the UCLA Fielding School of Public Health in Los Angeles, not involved in the study, told MNT.