TAIPEI - A Taiwanese doctor warned Monday that a food source most consumers consider healthy - leafy green vegetables - could actually cause a potentially serious blood disorder.
Chiang Shou-shan, a nephrologist at Shin-Kong Wu Ho-Su Memorial Hospital, cited the example of a women who was recently sent to the hospital after passing out and was diagnosed with acute methemoglobinemia, a blood disorder in which the body cannot produce functional oxygen-carrying molecules in red blood cells.
The hospital determined that it was vegetables that caused her disease because of their high content of nitrites, most likely from excessive use of a certain kind of fertilizer.
The most common cause of methemoglobinemia is the ingestion of oxidizing agents such as nitrates, which are often used as additives to prevent foods such as hot dogs, bacon or ham from spoiling, Chiang said.
But excessive nitrates, which degrade into nitrites, can also be found in vegetables grown with large amounts of nitrogen fertilizer, a chemical compound commonly used in Taiwan to stimulate plant growth, he said.
Chiang said the patient, a long-time vegetarian, developed acute methemoglobinemia, which resulted in dizziness, fatigue, blue coloured lips, shortness of breath, and a rapid heart rate and left her unconscious.
After receiving oxygen therapy, the woman's oxygen-carrying molecules became functional again, he said.
The blood disorder, in some cases, can also result in esophageal cancer, gastric cancer, or bladder cancer, he said.
The Homemakers Union Consumer Cooperative, a Taipei-based green life advocacy group, said in a 2010 report on a survey of seven vegetables commonly found in the domestic market, leafy vegetables were found to carry higher levels of nitrates than root vegetables.
Some carried as much as 20,000 ppm of nitrates.
In comparison, countries with strict standards for the additive allow a maximum of 2,000 ppm of nitrates in foods, according to the report.
Chiang urged farmers to refrain from using nitrogen fertilizer to speed up the ripening process of the vegetables and to avoid rushing to harvest the plants.
The Food and Drug Administration (FDA) under the Department of Health said babies younger than six months old are prone to developingthe blood disorder, and parents should avoid feeding them vegetables with high-nitrate levels, such as spinach and beets.
Complicating the problem for consumers is that these oxidizing agents cannot be washed off of vegetables, meaning they have to pay more attention to the source of the produce and how it was cultivated, Chiang said.