Data on occurrence of nitrate, nitrite and N-nitrosocompounds in food and drinking water, and on total dietary intakes are reviewed. Metabolic, toxicological and epidemiological studies are surveyed and the implications with respect to safety evaluation are addressed. It is concluded that, on the basis of recent long-term animal studies and of clinical experience in man, the current Acceptable Daily Intake (ADI) allocated to nitrate by the Joint FAO/WHO Expert Committee on Food Additives of 0-5 mg/kg body weight/day (expressed as sodium nitrate) might be increased to 0-25 mg/kg body weight/day. Based on similar criteria, the ADI for nitrite would be 0-0.1 mg/kg body weight/day (expressed as sodium nitrite). In view of the known carcinogenicity of N-nitrosocompounds, exposure to these compounds in food should be minimized by appropriate technological means, such as lowering the nitrite concentration in preserved foods to the minimum required to ensure microbiological safety and use of inhibitors of nitrosation like alpha-tocopherol or ascorbic acid. Further work is needed to define the minimal levels of nitrite in foods needed to inhibit outgrowth of Clostridium botulinum and toxin production.

Nitrates, nitrites and N-nitrosocompounds: a review of the occurrence in food and diet and the toxicological implications.

Nitrate, nitrite and N-nitroso compounds.

Ingested nitrate and nitrite and stomach cancer risk: An updated review

The metabolic fate of a po dose of 35 mmol 15N-labeled nitrate has been investigated in 12 healthy young adults Samples of urine, saliva, plasma, and feces were collected over a period of 48 hr following administration of the dose Subjects received either 60 mg of ascorbic acid, 2 g of ascorbic acid, or 2 g of sodium ascorbate per day An average of 60% of the 15NO3- dose appeared in the urine as nitrate within 48 hr Less than 01% appeared in the feces The 15N label of nitrate was also found in the urine (3%) and feces (02%) in the form of ammonia or urea The fate of the remaining 35% of the 15NO3- dose administered is unknown No effect of ascorbic acid or sodium ascorbate on the nitrate and nitrite levels of plasma, saliva, urine, or feces was observed A one-compartment pharmacokinetic model was used to describe the relationships between intake, plasma concentration, and urinary excretion of nitrate The half-life of nitrate in the body was found to be approximately 5 hr, and its volume of distribution was about 30% of body weight Daily endogenous biosynthesis of nitrate was estimated to be about 1 mmol/day

https://cancerres.aacrjournals.org/content/canres/43/4/1921.full.pdf

Metabolic Fate of an Oral Dose of 15N-labeled Nitrate in Humans: Effect of Diet Supplementation with Ascorbic Acid

The review will encompass the following points: A brief introduction to the role of the gut flora in the toxicology of ingested food components, contaminants, and additives, including known pathways of activation and detoxication of foreign compounds and the implication of the flora in enterohepatic circulation of xenobiotics. The advantages and disadvantages of the various methods of studying the gut flora (classical bacteriological techniques, metabolic and enzymological methods) will be critically discussed with special reference to their relevance to dietary, toxicological, and biochemical studies. Sources of nutrients available to the gut flora will be described including host products (mucus, sloughed mucosal cells, hormones, proteins) and exogenous nutrients derived from diet. An account of the problems involved in studies of dietary modification with special reference to the use of stock laboratory animal diets, purified diets, and human dietary studies. The influence of dietary modification on the flora will be assessed on the basis of changes in numbers and types of bacteria and their metabolic activity, drawing on data from human and animal studies. The effects of manipulation of the quantity and quality of protein, fat, and indigestible residues (fiber) of the diet will be described together with their possible implications for toxicity of ingested compounds.

M.J. Saxby

Papers

Nitrite sources and nitrosamine formation in vitro and in vivo

Nitrosation of food amines lnder stomach conditions.