I have a five month old baby, breastfed, growing fine. Now I have given him some solid foods. I know that some vegetables (e.g. spinach) are not recommended to babies under 12 months because of high amounts of nitrates. Is it true, that also new potatoes contain too high amounts of nitrates and are not recommended to babies? Are there some safety limits?

Hello,

Nitrates are natural constituents of plants since they are their main source of nitrogen required for growth. The quantities in which nitrates occur vary depending on the type of vegetable, growing temperature, sunlight, soil moisture and the level of nitrogen in the soil. Foods that tend to accumulate large amount of nitrate include spinach, beets, cabbage, broccoli, and carrots. Water, particularly well water, may contain significant amounts of nitrate (mainly from runoff from fertilized farm fields).

Nitrates, per se, are toxic only at levels higher than those found in foods. Nitrate poisoning appears to be associated only with ingestion of nitrate in water rather than with naturally occurring nitrate in foods. The nitrate in food must first be converted to nitrite (prior to ingestion) for poisoning to occur. Nitrates themselves are nontoxic. The potential hazard of nitrate in food or water is its conversion to nitrite either prior to (as for those levels found in food) or after ingestion (as may happen with those levels found in some contaminated water). Once the nitrate is converted to nitrite, the nitrite ion can cause the conversion of the oxygen transporting iron in the blood to a compound called methemoglobin. Methemoglobin is incapable of transporting oxygen. Methemoglobinemia, characterized by cyanosis, is the resulting condition .

In order for methemoglobinemia to occur as a a result of the ingestion of high levels of nitrates certain conditions for converting nitrates to nitrites must exist. Only infants, who have a low stomach acidity, and who harbor nitrate converting bacteria in their upper GI track, develop sufficient concentrations of nitrite to produce methemoglobinemia. Stomach acidity becomes greater as an infant becomes older, which explains the relatively higher incidence of methemoglobinemia in the newborn and young infant. Infants under three months of age are especially susceptible to nitrate toxicity.

THE MOST GENERALLY ACCEPTED STANDARD FOR WATER FOR ALL FEEDING PRACTICES IS 10PPM NITRATE-NITROGEN. So far, it seems that nitrate poisoning appears to be associated only with ingestin of nitrate in water rather than food and current feeding practices are not likely to supply sufficient plant nitrate to cause methemoglobinemia, even to susceptible infants.

Potentially more dangerous than the ingestion of nitrate, is the ingestion of foods whose nitrate was converted to nitrite before consumption. Under some conditions plant nitrates may be converted to nitrite before feeding. If ingested, this nitrite may result in serious methemoglobinemia. Plant foods with high levels of nitrates stored at warm temperatures for several hours with little or no oxygen (i.e. poor storage conditions) are the characteristics of foods with high nitrite levels. A few cases of methemoglobinemia were documented in Germany when young infants were fed spinach pureed in the home and stored under questionable conditions. There have been no documented case of methemoglobinemia from commercially prepared and jarred infant foods due to the optimal storage conditions of the food prior to processing , and the processing procedure itself, which inactivates the enzymes that converts the nitrates to nitrites. To minimize the possibility of infant methemoglobinemia, foods containing high levels of nitrate should not be introduced to the diet of infants younger than 3 months.

Some recommendations for home preparation of high nitrate containing foods are: Freeze vegetables immediately after harvest. Do not use vegetables which have been frozen longer than five months. Thaw vegetables no longer than 15 hours at room temperature. The average level of nitrate in some vegetables follow:

Radishes.................343ppmBeets....................275ppmSpinach..................121ppmString beans ............53ppmPotatoes.................23ppmCarrots..................23ppm

Remember, under the proper growing conditions, any of these vegetables may contain significantly higher levels of nitrates, whose conversion to nitrite can occur under enabling storage conditions. The safest thing to do is to avoid feeding any of these vegetable to infants younger than 3 months. Fortunately, this is in accordance with the common recommendation to not feed solids to infants less than four months. By waiting to introduce solids to four months or older, you avoid the worry of feeding nitrate containing foods.

Thanks for writing.