Monday, 11 October 2010 13:12
Ten of the 20 processed meat most eaten by Filipinos are treated with nitrate and nitrite, two vital chemicals which when ingested in high concentrations expose a person to the risk of acquiring serious illnesses like methemoglobinemia, colon cancer and diabetes.
Results of the 6th National Nutrition Survey (NNS) recently conducted by the Food and Nutrition Research Institute (FNRI) indicated that 10 nitrate-and nitrite-treated meat products rank among the top 20 processed meats consumed by Filipinos.
Nitrate and nitrites when ingested in high concentrations have been implicated in foreign literature as factors in the etiology of methemoglobinemia, colon cancer and type 1 diabetes.
The NNS was aimed at determining the contents of nitrites in the commonly consumed processed meats and the potential nitrite exposure risks from processed meats available in local markets.
Nitrite contents of samples of canned and plastic-packaged processed meats like hotdog, corned beef, luncheon meats, tocino, longganisa, chorizo, Vienna sausage and beef loaf purchased from groceries, malls and department stores were determined and compared against the Bureau of Foods and Drugs (BFAD) Guidelines on Food Additives (2006).
Expectedly, results indicate that nitrite contents of all the test samples were within the BFAD maximum levels.
The 6th NNS processed meat daily intakes compared against the acceptable daily intake of the World Health Organization and Food and Agriculture Organization (FAO) however indicated potential exposure risks from processed nitrites.
Acceptable daily intake (ADI) for WHO and FAO is 0.07 milligram (mg) nitrite per kilogram (kg) body weight which when attributed to a 59 kg Filipino male is 4.13 mg.
In recommendation based on the 6th NNS, FNRI director Mario Capanzana in a statement reaching here over the weekend said a review of nitrite maximum levels in processed meat should be undertaken.
At the same time, he said, the conduct of special study on actual nitrite contents and intakes of processed meat by or specific age groups is necessary so that the consuming public is forewarned of the risk.
Nitrate as defined by the dictionary is a compound containing the nitrate ion as in salts. It serves as natural constituents of plants and found in drinking water as a result of excessive use of fertilizers.
Maximum levels have been established for nitrate in drinking water in an upper limit of 45-50 mg nitrate per liter has been recommended for infants.
Sodium nitrite is used as a food preservative and in reddening meats. Many nutritionists recommend the avoidance of foods that contain sodium nitrite because it can undergo chemical reactions that produce nitrosamines, which are known carcinogens.
Sodium nitrite is also used in dyeing textiles, bleaching fibers, photography, metal coatings, and the manufacture of rubber chemicals. In medicine, it has been used as a vasodilator, bronchodilator and intestinal relaxant or laxative. Both sodium nitrite and amyl nitrite may be used to treat heart disease and cyanide poisoning.
Nitrates, if a factor in a specific case, would most often be ingested by infants in high nitrate drinking water. However, nitrate exposure may also occur if eating, for instance, vegetables containing high levels of nitrate.
Lettuce may contain elevated nitrate under growth conditions such as reduced sunlight, undersupply of the essential micronutrients molybdenum and iron or high concentrations of nitrate due to reduced assimilation of nitrate in the plant.
High levels of nitrate fertilization also contribute to elevated levels of nitrate in the harvested plant.
The Kentucky, USA-based Leaf for Life said in its website information that nitrates are fairly stable nitrogen compounds that can be degraded into nitrites which when combine with other compounds in the digestive tract forms carcinogenic nitrosamines.
It said the amount of nitrate in plants is determined mainly from its genetically based metabolism, the age of the plant, and the amount of available nitrate in the soil. Leafy green vegetables and some root crops contain the highest concentrations of nitrates, it said.
Among commonly eaten vegetables, beetroot, celery, lettuce, spinach, and radishes have the most nitrate. There is often a tenfold variation in nitrate levels of the same variety of vegetables sampled from supermarkets.
This is largely a function of the age of the vegetable when picked and the amount of nitrate fertilizer used to grow the crop. Nitrate levels of vegetables have gone up significantly in recent years because of increased use of nitrate fertilizers.
There are two basic strategies to reduce the risks of nitrosamine exposure while greatly increasing your consumption of vegetables, especially leafy vegetables. The first is to reduce the amount of nitrate in your diet; and the second is to prevent the nitrate from being converted to nitrites in the body.
Some plants such as lettuce and spinach are very high in nitrates relative to the nutritional contribution they make, and it may be reasonable to use other vegetables in their place when possible.
Vegetable plants grown without excessive nitrogen fertilizer have far less nitrate. Nitrate fertilizer applied shortly before harvest causes the greatest increase in nitrate levels and should be avoided.
Slower releasing nitrogen sources such as animal and green manures can produce vegetables with significantly lower nitrates, and this is an area where the organic foods movement has led the way.
If non-organic fertilizers are being used, ammonium nitrogen and nitropyrin will grow lower nitrate vegetables than those fertilized with nitrate nitrogen.
Some adults can be more susceptible to the effects of nitrate than others. The methemoglobin reductase enzyme may be under-produced or absent in certain people that have an inherited mutation.
Infants in particular are especially vulnerable to methemoglobinemia due to nitrate metabolizing triglycerides present at higher concentrations than at other stages of development.
Methemoglobinemia is a disorder characterized by the presence of a higher than normal level of methemoglobin in the blood. Methemoglobin is an oxidized form of hemoglobin that has almost no affinity for oxygen, resulting in almost no oxygen delivery to the tissues. When its concentration is elevated in red blood cells, tissue hypoxia can occur.
In infants, it is known as blue baby syndrome which is now thought to be the product of a number of factors including those that causes gastric upset, such as diarrhoeal infection, protein intolerance, heavy metal toxicity, among others, with nitrates playing a minor role.
Those with insufficient stomach acid including some vegetarians and vegans may also be at risk. It is the increased consumption of green, leafy vegetables that typically accompany these types of diets may lead to increased nitrate intake.
A wide variety of medical conditions, including food allergies, asthmahepatitis and gallstones may be linked with low stomach acid; these individuals may also be highly sensitive to the effects of nitrate. (PNA)
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