NITRATE AND NITRITE SENSITIVITY
Nitrates and nitrites are used in foods as preservatives, particularly as protection against the deadly bacterium Clostridium botulinum, the cause of botulism, a frequently fatal neuromuscular disease with paralysis caused by the toxin produced by the bacterium, which multiplies within the food. They are also used to give flavor and color to manufactured foods, especially processed meats.
Nitrites and nitrates represent one of the oldest and most effective ways of preserving meats. Without nitrites and nitrates there would be many deaths from the growth of toxic microorganisms. However, the mechanisms that allow these chemicals to kill bacteria may also cause adverse effects in the human body when the food containing the nitrate or nitrite is consumed in excessive quantities. People who are sensitive to the chemicals react at a lower dosage (level) than others, but anyone can develop symptoms if they consume very high doses.
This chapter will provide you with information on when and how nitrates and nitrites enter our foods and how to avoid excessive intake of both chemicals.
Symptoms of Sensitivity
Nitrites preserve the red color of meat by changing the nature of the hemoglobin of the red blood cells. The function of hemoglobin is to carry oxygen throughout the body. When nitrites enter the bloodstream of persons who have eaten the nitrite-treated meat, their hemoglobin is likewise changed if the nitrite level is excessive. This may lead to a condition known as methemoglobinemia with symptoms such as anemia, breathing difficulty, palor, dizziness, and headaches. Because of their small size, infants and young children are more susceptible to nitrite poisoning than adults, and nitrites are not permitted in foods intended for babies under the age of six months.
Nitrites can react with substances called amines in the digestive tract to form nitrosamines, which may be carcinogenic when exposure to the chemicals is excessive and prolonged. There is evidence that consumption of vitamins A, C, and E (antioxidants) in the form of fresh yellow and green vegetables, fish, and plant oils, protects against stomach and intestinal cancer in this situation. Potassium nitrite has been linked to atrophy of the site in the adrenal gland that is responsible for secreting aldosterone, the hormone that maintains the balance of sodium, potassium, and chloride in the blood.
Prolonged exposure to nitrates may cause anemia and inflammation of the kidneys, and ingestion of a large quantity may result in gastrointestinal inflammation with severe abdominal pain, vomiting, vertigo (a sensation as if the world is revolving around the person, similar, but different from, dizziness), muscular weakness, and irregular pulse (nitrate toxicity). A high intake of sodium nitrate has been associated with inhibition of the functioning of the thyroid gland. Nitrates may be converted to nitrites during food spoilage or by intestinal bacteria after consumption. They then have the same effect as nitrites discussed above.
Other reported symptoms include recurrent hives and migraine and nonmigraine headaches.
Nitrates and Nitrites in Foods
The presence of nitrates or nitrites in manufactured foods will be indicated on the label as sodium nitrate, potassium nitrate, sodium nitrite, or potassium nitrite. High levels are found in processed meats such as pepperoni, frankfurters, weiners, sausages, salami, bologna, other luncheon meats, bacon, and ham, as well as in smoked fish and some imported cheeses.
Plants can contain naturally occurring nitrates derived mainly from nitrate-containing fertilizers.
The following plant species tend to have higher levels of nitrates than others do:
| ♦ Beetroot and beet greens | ♦ Lettuce |
| ♦ Cabbage | ♦ Parsley |
| ♦ Carrot | ♦ Potato |
| ♦ Celery | ♦ Radishes |
| ♦ Collards | ♦ Spinach |
| ♦ Eggplant | ♦ Strawberry |
| ♦ Fennel | ♦ String beans (green beans;
french beans) |
| ♦ Leeks | |
| ♦ Turnip greens |
Table Summary of the use and effects of nitrates and nitrites in foods provides information about the use of nitrates and nitrites in foods and where you are likely to encounter nitrates and nitrites in your diet. In the United States and Canada, the terms “nitrate” and “nitrite” will appear on product labels; in European countries, the E-numbers will indicate which chemical is present in the food.
People vary in their tolerance of nitrates and nitrites. It is therefore very difficult to give guidelines on how much of a food a sensitive person can eat without having symptoms. The best advice is this: A person who is intolerant to nitrites and nitrates should avoid those foods that have been shown to have the highest levels of the chemicals, as indicated in Table Level of nitrates and nitrites in some meats and vegetables.
Table Level of nitrates and nitrites in some meats and vegetables gives you some idea of the actual levels of nitrates and nitrites in certain foods, demonstrating how these vary among different food types and products. Because the levels of nitrates and nitrites vary according to how much is added to a processed meat, or how much is in the soil in which a plant is grown, it is not possible to provide an accurate measure in each food.
Table Summary of the use and effects of nitrates and nitrites in foods
| Compound | E Number | Effect and Function | Used in | |
| Potassium nitrite
• Potassium salt of nitrous acid • Occurs naturally • May be manufactured by reacting nitrous oxide and nitric oxide with potassium hydroxide |
E249 | • Converts the iron-containing
pigments in the flesh to stable bright pink compounds • Preservative in meat, particularly in preventing the development of spores of Clostridium botulinum, the bacterium that causes botulism |
• Cooked meats
• Canned meats • Corned meat • Liver sausage • Meat pate • Pickled meats • Sausages • Smoked fish |
|
| Sodium nitrite
• Does not occur naturally • Derived from sodium nitrate by bacterial or chemical action |
E250 | • Preservative, especially by
inhibition of Clostridium botulinum • Used in meat curing to give a red color to the meat |
• Cured meat
• Cured meat products • Salted meat • Pork sausage • Bacon • Turkey and ham loaf • Smoked frankfurters • Weiners • Tongue • Pressed meats • Canned meats • Frozen pizza • Smoked fish |
|
| Sodium nitrate
(Chile saltpeter) • Naturally occurring mineral, especially in the Chilean desert • Formed by reaction between nitric acid and sodium carbonate |
E251 | • Preservative
• Added to salt in curing meats • Prevents loss of color in meats |
• Bacon
• Pressed meats • Ham • Tongue • Beef • Canned meats • Cheese, other than - Cheddar - Cheshire - granapadano - provolone • Frozen pizza |
|
| Potassium nitrate
(Saltpeter) • Naturally occurring mineral |
E252 | • Inhibition of Clostridium
botulinum • Added to salt in curing of meat products • Prevents loss of color |
• Cured meats
• Sausages • Smoked frankfurters • Weiners |
|
| Potassium nitrate
(Saltpeter), (continued) • Formed by reaction of potassium chloride and concentrated nitric acid • May be manufactured artificially from waste animal and vegetable material |
• Bacon
• Ham • Tongue • Pressed meats • Canned meats • Dutch cheeses • Fish products • Spirits |
|||
Table Level of nitrates and nitrites in some meats and vegetables
| FOOD | Mean Level
(mg/100 g) |
| NITRITES | |
| Meats | |
| Bacon | 1.3 |
| Bacon, smoked | 3.1 |
| Luncheon meat | 0.3 |
| Ham, smoked | 3.0 |
| Salami | 0.3 |
| Salami, kosher | 38.0 |
| Vegetables | |
| Cucumber, raw | 2.4 |
| Green beans, raw | 25.3 |
| Eggplant, raw | 30.2 |
| Lettuce, raw | 85.0 |
| Lima beans, raw | 5.4 |
| Melon, raw | 43.3 |
| Onion, raw | 13.4 |
| Peas, raw | 2.8 |
| Pepper, sweet, raw | 12.5 |
| Pickles | 5.9 |
| Potato, raw | 11.9 |
| Pumpkin, raw | 41.3 |
| Sauerkraut | 19.1 |
| Spinach, raw | 186.0 |
| Sweet potato, raw | 5.3 |
| Tomato, raw | 6.2 |
| NITRATES | |
| Vegetables | |
| Asparagus, raw | 2.1 |
| Beet, raw | 276.0 |
| Beans, dry | 1.3 |
| Broccoli, raw | 78.3 |
| Cabbage, raw | 63.5 |
| Carrot, raw | 11.9 |
| Cauliflower, raw | 84.7 |
| Corn, raw | 4.5 |
Note: Nitrates may be converted to nitrites in the mouth and intestine. Thus, the level of the chemical in food does not always reflect the level in the body after digestion.
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