NITRATE AND NITRITE IN HUMAN NUTRITION

Studies were conducted to investigate nitrate and nitrite in human nutrition. Normal urinary nitrate response to intake of nitrate was evaluated using 24-hour composites. Nitrate excretions from human subjects consuming a free choice diet were compared to excretions when subjects consumed a free choice diet plus spinach, a high nitrate containing food. When diets contained high nitrate levels, additional nitrate from spinach increased nitrate excretion, but not in the same proportion as when spinach was added to diets normally low in nitrate. Nitrate excretion was also evaluated in humans after 5 weeks of adjustment to a controlled low nitrate diet. From 3 weekly composites, urinary nitrate fluctuated as much as 100% for any one subject. When urinary nitrate excretions during pre- and post free choice diets were compared to excretions during the controlled diet periods, nitrate excretion increased with increased nitrate consumption. The effect of fiber on urinary nitrate excretion was evaluated using weanling rats. Purified diets varying in amounts of nitrate and cellulose and a diet using spinach as a source of nitrate and fiber were fed. When nitrate was not fed, urinary nitrate was not detected. Urinary nitrate and nitrite excretions were lower (p \u3c .05) when spinach was fed than when the purified diets containing similar amounts of nitrate were fed. Higher urinary nitrite values were observed when the purified diet containing nitrate plus cellulose was fed than when the nitrate supplement was fed alone suggesting that cellulose might enhance conversion of nitrate to nitrite. Home extension club members in 4 counties of Nebraska were surveyed to investigate knowledge, attitude and practices concerning nitrate and nitrite issues. Level of knowledge was low but concern was expressed by the majority of respondents. Nitrate or nitrite were not avoided. No correlations were found among knowledge, attitude and practice nor between any of these scores and demographic characteristics. Recommendations for further education programs were made