"Healthy through eating" series | Where are nitrites hidden? Eating this way can reduce your intake

In recent years, the media has repeatedly reported that nitrite content in food testing exceeds the standard. It is not uncommon for people to mistake nitrite for table salt and cause poisoning. So, what is the difference between nitrite and table salt? How can we effectively reduce its pollution and harm and ensure food safety? Let's talk about topics related to nitrite.

Nitrite is a commonly used industrial salt. It is used in the chemical industry to synthesize amino acids and various organic acids. It is used to dissolve pigments and promote the absorption of dyes in the printing and dyeing industry. It can also be used as a bleaching agent for silk and linen, a metal heat treatment agent, and a steel corrosion inhibitor.

Nitrite can react with myoglobin in meat to improve the color of meat, and can also prevent fat oxidation in meat products from producing bad odors and improve the taste of food. However, it is precisely because of the widespread use of nitrite and its appearance and taste that are similar to edible salt that we should pay more attention to its dangerous chemical properties and harm to the human body.

Nitrite can oxidize the normal oxygen-carrying hemoglobin in the blood into methemoglobin and cause tissue hypoxia. Mild symptoms include cyanosis of the lips, tip of the tongue or skin all over the body; moderate symptoms include dizziness, headache, fatigue, drowsiness or irritability, difficulty breathing, diarrhea, etc.; severe cases may cause coma, convulsions, incontinence, and even death from respiratory failure.

Nitrite is a highly toxic substance. If an adult ingests 0.2-0.5 grams, it can cause poisoning, and 3 grams can be fatal. Nitrosamines can also pass through the placenta into the fetus and have teratogenic effects on the fetus.

What are the common sources of nitrite in food?

1. Vegetables are prone to nitrite accumulation. Fresh vegetables absorb nitrates from the soil, and under certain conditions, nitrates are reduced to nitrites for human consumption. The nitrite content of unfresh vegetables will surge.

2. Pickled vegetables are also a common source of nitrite. The nitrite content reaches its peak on the sixth day of pickling and is completely decomposed after about 20 days.

3. Nitrite has also been detected in some grains and fish. The use of pesticides and fertilizers, the discharge of industrial wastewater, and sewage irrigation can all lead to the release and deposition of nitrite.

How can we reduce the intake of nitrite?

1. Nitrite is very similar to table salt, so it must be properly labeled to avoid misuse.

2. When purchasing processed foods, pay attention to the labeled nitrite content. The national standard for food additives clearly stipulates that the residual sodium nitrite in canned meat must not exceed 30 mg/kg. Avoid purchasing processed foods that exceed this range.

3. Do not eat unfresh vegetables and eat less leftovers.

4. Pickled vegetables are safe to eat after 20 days, and avoid eating pickled vegetables for a long time.

5. Garlic, onion and ginger have a certain clearing effect on nitrite.

6. Apples, pears, and blueberries can reduce the absorption of nitrite.

7. Apple juice, tangerine juice, pineapple juice, pear juice, etc. also have a certain cleansing effect on nitrite.

Authors: Tong Yao and Hu Mengdie, Department of Special Medical Care, Cancer Hospital, Chinese Academy of Medical Sciences

Review expert: Xin Xiaowei, nutritionist and deputy director of the Nutrition Department of Cancer Hospital, Chinese Academy of Medical Sciences