Following the much-vaunted Dietary Approaches to Stop Hypertension (DASH) diet, which produces beneficial reductions in blood pressure, results in an intake of nitrate of 550 per cent the World Health Organization’s Acceptable Daily Intake (ADI), according to findings published in the American Journal of Clinical Nutrition.
“These data call into question the rationale for recommendations to limit nitrate and nitrite consumption from plant foods; a comprehensive re-evaluation of the health effects of food sources of nitrates and nitrites is appropriate,” wrote the authors, led by Norman Hord from Michigan State University.
About 80 per cent of nitrates in the diet come from vegetables, while nitrites sources include vegetables, fruit, and processed meats. Nitrites are added to meat to retard rancidity, stabilise flavour, and establish the characteristic pink colour of cured meat. Studies and recommendations by health and governmental organisations ensure the safety of such products.
However, observational studies, including data from the third National Health and Nutritional Examination Survey (NHANES) on 7,352 subjects over the age of 45, have suggested that increased consumption of nitrites from cured meat could increase the risk of lung disease.
In collaboration with Yaoping Tang and Nathan Bryan from the University of Texas Health Science Center, Hord quantified levels of nitrites and nitrates in high-nitrate or low-nitrate vegetable and fruit choices based on the DASH diet.
The nitrate concentrations in these patters ranged from 174 to 1,222 mg, with the upper level equivalent to 550 per cent the WHO’s ADI for a 60-kg adult.
“The strength of the evidence linking the consumption of nitrate- and nitrite-containing plant foods to beneficial health effects supports the consideration of these compounds as nutrients,” wrote the researchers.
In an accompanying editorial, Martijn Katan from the Institute of Health Sciences, VU University, Amsterdam said that, while it is “undisputed” that nitrates benefit arteries, “evidence is still scant that nitrate in the amount present in vegetables lowers blood pressure”.
“Therefore, indications that dietary nitrate or nitrite reduces cardiovascular disease risk are insufficient to relax standards for nitrate in drinking water and foods.”
Katan called for a trial in which subjects are fed high and low nitrate-containing foods.
“A trial to investigate whether nitrate in vegetables is healthy is thus feasible. It would require a few months, a few hundred subjects, and less money than the bonus of a second-tier banker. Such a trial urgently needs to be conducted,” he concluded.
The study was funded by the Michigan Agricultural Experiment Station, Michigan State University, and the American Heart Association.
Source: American Journal of Clinical NutritionPublished online ahead of print, doi:10.3945/ajcn.2008.27131 “Food sources of nitrates and nitrites: the physiologic context for potential health benefits”Authors: N.G. Hord, Y. Tang, N.S. Bryan
Editorial: American Journal of Clinical NutritionPublished online ahead of print, doi: 10.3945/ajcn.2009.28014 “Nitrate in foods: harmful or healthy?”Author: M.B. Katan