Nitrate in diet improves metabolism via nitric oxide
Posted Oct 18 2010 12:00am
iHealthBulletin.com - Dietary nitrates, naturally found in some vegetables, may fight pre-diabetes, reduce blood pressure, and reduce visceral fat gain, if the results of a recent animal study apply to humans as well in future research.
Vegetables that are particularly rich in nitrates include spinach, beet root, and lettuce. A previous study in humans (N Engl J Med 2006; 355:2792-2793) in which subjects were given a dietary supplement of sodium nitrate for 3 days showed a modest decrease in diastolic blood pressure. This effect is thought to be mediated through increased nitric oxide synthesis in the blood vessel lining (endothelium).
Prior research looking at mice that were genetically deficient in the enzyme, endothelial nitric oxide synthase (eNOS), have shown that such mice develop features of the metabolic syndrome, including high blood pressure, decreased insulin sensitivity, and weight gain.
Researchers at the Karolinska Institutet in Sweden set out to examine how chronic but modest dietary nitrate supplementation would affect metabolic and cardiovascular functions in eNOS-deficient mice.
They found that 7 weeks of modest dietary nitrate supplementation led to lower body weight, and reduced visceral fat (fat loss) and triglyceride levels compared to control mice.
Regarding blood pressure, 8 weeks of nitrate supplement led to a sustained reduction in mean arterial pressure over 3 days of observation.
In tests of blood sugar control in the eNOS-deficient mice, nitrate supplementation for 10 weeks virtually normalized the glucose tolerance test, lowered fasting blood sugar, and reduced the hemoglobin A1c (HbA1c, aka glycosylated hemoglobin) compared to the control group.
The authors propose that one possible mechanism for these improvements from dietary nitrate might be through enhanced mitochondrial function that improves insulin sensitivity. Even if changes in glucose regulation are not observed in wild mice [i.e. mice that are not eNOS-deficient], blood pressure benefits through enhanced nitric oxide effects can still be seen in wild mice as a result of nitrate supplementation.
The relative dose of nitrate supplement used in this study is comparable (for humans) to that which can be obtained through a healthy diet that includes spinach, beet roots, and/or lettuce.
Editorial note - At least one dietary supplement company markets a freeze-dried beetroot juice powder that is relatively simple to dissolve, for those that are interested - Dr Zebrun.
The full research study is available free online here:
Source: Mattias Carlström, et al. Dietary inorganic nitrate reverses features of metabolic syndrome in endothelial nitric oxide synthase-deficient mice. PNAS October 12, 2010 vol. 107 no. 41 17716-17720. Published online September 27, 2010. doi: 10.1073/pnas.1008872107
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