Study title and author:
Vegetable-borne nitrate and nitrite and the risk of methaemoglobinaemia.
Chan TY.
Division of Clinical Pharmacology, Department of Medicine and Therapeutics, Faculty of Medicine, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, New Territories, Hong Kong. tykchan@cuhk.edu.hk
This paper can be accessed at: http://www.ncbi.nlm.nih.gov/pubmed/21075182
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Chan notes that high levels of nitrate in vegetables are frequently reported. Nitrates themselves are relatively
nontoxic. However, when swallowed, they are converted to nitrites that can react with hemoglobin in the blood, creating methemoglobin. This methemoglobin cannot bind oxygen, which decreases the capacity of the blood to transport oxygen so less oxygen is transported from the lungs to the body tissues, thus causing a condition known as methemoglobinemia which is an abnormally low amount of oxygen in the blood, which can cause respiratory failure.
nontoxic. However, when swallowed, they are converted to nitrites that can react with hemoglobin in the blood, creating methemoglobin. This methemoglobin cannot bind oxygen, which decreases the capacity of the blood to transport oxygen so less oxygen is transported from the lungs to the body tissues, thus causing a condition known as methemoglobinemia which is an abnormally low amount of oxygen in the blood, which can cause respiratory failure.Chan found that:
(a) Infants under 3 months old are particularly susceptible to methaemoglobinaemia.
(b) Older infants and children are also at risk.
(c) Adults are not thought to be at risk of vegetable-borne nitrate or nitrite induced methaemoglobinaemia. This view should now change if the high nitrate levels in some vegetables and the effects of storage and food processing on its conversion to nitrite are taken into consideration.
(d) Measures should be taken to reduce the nitrate and nitrite in vegetables.
(i) Excessive use of nitrogen fertilizers should be avoided so as to reduce nitrate build up in soil or vegetables.
(ii) Removal of stem and midrib results in a decrease of nitrate content in lettuce and spinach.
(iii) Peeling of potatoes and beetroot decreases the nitrate content.
(iv) Nitrate levels in some vegetables can decrease after cooking in water or blanching.
(e) Home prepared infant food containing vegetables should be avoided until the infant is 3 months or older.
To conclude: Children, especially infants under 3 months old should avoid vegetables (and processed meats) because of the risk of methaemoglobinaemia. Adults should not be at risk of methaemoglobinaemia, however this view should now change if the high nitrate levels in some vegetables and the effects of storage and food processing on its conversion to nitrite are taken into consideration.
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Recipe of the day
Quick Steak
serves 3-4
Ingredients:
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1 1/2-2 lbs ribeye or T-bone steak
1-2 tablespoons cracked pepper 1 tablespoon butter
1 tablespoon extra virgin olive oil
Instructions:
Sprinkle steaks with pepper and press in.
Melt butter and olive oil in a skillet.
Saute steaks a few minutes a side until desired doneness.
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