A recent study published in the journal Proceedings of the National Academy of Sciences of the United States of America (PNAS) provides some evidence that dietary nitrates may not be as bad as we are often told and may actually reverse metabolic syndrome.
The article, written by a group of Swedish scientists, reports the experimental effects of feeding inorganic nitrate on metabolic syndrome using a mouse model of the disease.
Metabolic syndrome describes a series of changes to one’s physiology and metabolism that increase the risk for heart disease and type 2 diabetes. Some indicators of metabolic syndrome include increased insulin levels, insulin resistance, glucose intolerance, high blood pressure, gout, and obesity. They are all inter-related and stem from changes in the metabolism of insulin, the key hormonal regulator of fat, carbohydrate and protein metabolism.
The pre-diabetic mice used in this study were deficient in the enzyme endothelial nitric oxide synthase (eNOS) and had high blood pressure, high levels of fat in their blood, insulin resistance, and obesity. Thus they are thought to be an animal model useful for studying metabolic syndrome. Previous research has suggested that nitric oxide metabolism and bioavailability might be involved.
Nitric oxide (NO) can be oxidized to inorganic nitrate but the reverse is also true, nitrate can be reduced to nitrite which can be reduced to NO and other bioreactive nitrogen oxide compounds, even in vivo.
Two groups of eNOS-deficient mice were fed a comparable diet that differed only in whether or not inorganic nitrate was included in their drinking water. Those mice fed nitrate ultimately lost weight and visceral (abdominal) fat, and had lower levels of fat in their blood. They also had lower levels of fasting blood glucose and passed a glucose tolerance test.
The authors discuss the interesting possibility, yet to be tested, that the dietary nitrate effect might involve the activities of commensal bacteria that inhabit the mouth and/or the rest of the gastrointestinal tract.
The amount of nitrate responsible for the observed dietary nitrate effect, translated into human proportions, are easily achievable with a normal diet. Real foods naturally rich in nitrates include beets, fennel and green leafy vegetables such as spinach and lettuce.
Carlström M, FJ Larsen, T Nyström, M Hezel, S Borniquel, E Weitzberg, and JO. Lundberg. 2010. Dietary inorganic nitrate reverses features of metabolic syndrome in endothelial nitric oxide synthase-deficient mice. PNAS 107: 17716-17720.
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