lj@ewj01.UUCP (Leonard Jacobs) (08/24/85)
Several weeks ago I posted the following as I was searching for information re the possible toxicity of nitrates in our foods. >From net.cooks come the following: >> You'll be interested to find that certain delicacies >> have inedible parts or seasons. Also, that beet and turnip greens store >> toxic levels of potassium nitrate if grown in soils too rich in it. Warning: >> the book's main subject is livestock rather than primate poisoning. >> >> Sukie Crandall >The question re potassium nitrate is possibly a serious one. Does anyone have >any factual information on permissible levels of nitrates in foods? >I understand that there are Federal guidelines for permissible levels of >nitrates in drinking water--something like 40 ppm--but that similar >levels do not apply to foods. According to some farmers/gardeners, nitrate >levels in green vegetables exceed 40 ppm in many vegetables, >organic and not, due to the immaturity of the plants when picked. This >is a result of the nitrates necessary for growth not being completely utilized >by the plants if they are picked early. Concentrations are apparently >higher in vegetables which come from another region since they must be >picked prematurely in order to avoid early wilting. The levels are also >highest in the white parts of the vegetables, e.g., the center of iceberg >lettuce, since photosynthesis changes the nitrates. Is there >a possible danger in consuming high levels of nitrates, and what are >permissible levels in our foods? In some cases nitrates do convert to >nitrites. What determines this? > >If anyone has any information on this please either post or respond. I heard nothing which may imply no one has any further information or interest in this topic. I have since discovered additional information which may pique your curiosity on this topic. The average person in Japan consumes ~300 mg of nitrate per day from foods. Americans ~100 mg nitrates. The biggest difference is from the large amount of sea vegetables consumed by the Japanese. For Americans, 86.3% of all nitrates comes from vegetables. Of this, the vegetables which contain significant nitrates are as follows: NITRATE & NITRITE CONTENT (ppm) Vegetable Edible Portion Leaf Stalk ---------------------------------------------------------------------- NO2 NO3 NO2 NO3 NO2 NO3 ______________________________________________________________________ Cabbage 0.58 185.00 0.80 72.00 0.72 513.00 Chin. Cab. 0.61 2.56 0.50 1.86 0.73 2.317 Spinach 0.41 2.39 0.43 1.12 0.24 4.38 Celery 0.44 2.97 0.35 2.67 0.44 3.06 Lettuce 0.05 521.00 0.05 347.00 0.26 992.00 Parsley 0.70 4.995 0.56 3.68 1.04 9.81 Scallion --- --- 0.24 801.00 0.05 468.00 Root vegetables also contain high levels of nitrate, although figures are not immediately available. Nitrates are used for protein synthesis, and nitrates accumulate as plants grow. In the body, nitrates may convert to nitrites. This occurs in the intestines due to the presence of a certain bacteria whose name escapes me, but this bacteria descends lower as we age. Thus in adults, it is rare for any nitrites to be absorbed through the gut, but in children, up to adolescence, it is possible that enough nitrate will be converted to nitrites high enough in the gut to be absorbed into the blood stream. References on this are available. Please let me know if you are interested. I would still like to know what more is known about this phenomenon. And still not certain how serious this problem actually is. -- Len Jacobs East West Journal harvard!bbnccv!ewj01!lj