Vasodilatazione: Nitriti e nitrati

[mr oat]

The vasodilating properties of dietary nitrates are irrefutable. The clinical use of nitrates indicate that they [significantly] enhance systemic vasodilation. Both nitrate and nitrite can be recycled to produce nitric oxide in a variety of ways. They provide a NOS-independent source of NO, and release NO in an extremely wide distribution of tissues. Nitrite has been investigated as a vasodilator for over 125 years and is a by-product of organic nitrate metabolism.

Based on studies by Tannenbaum 1994; Kelm and Yoshida 1996, nitrates remain in circulation and significantly enhance NO production for around 10 to 16-hours post-administration. Enhanced systemic NO distribution increases blood flow to the muscle itself, thereby enhancing muscle force production/growth/repair.

Dietary nitrate has been shown to reduce diastolic blood pressure in healthy volunteers [Larsen, Ekblom et al. 2006]. Kleinbongard/Dejam et al. 2006, demonstrated that plasma nitrite levels progressively decrease with increasing cardiovascular risk load [risk factors included age, hypertension, high blood cholesterol, and smoking]. It has been proposed that a continuous intake of dietary nitrate may help to maintain tissue levels of nitrite and NO at adequate levels [even when endogneous enzymatic synthesis of NO is disturbed].

[mr oat]

Acta Physiol (Oxf). 2007 Sep;191(1):59-66. Epub 2007 Jul 17.
Effects of dietary nitrate on oxygen cost during exercise.
Larsen FJ, Weitzberg E, Lundberg JO, Ekblom B.
Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden.

AIM: Nitric oxide (NO), synthesized from l-arginine by NO synthases, plays a role in adaptation to physical exercise by modulating blood flow, muscular contraction and glucose uptake and in the control of cellular respiration. Recent studies show that NO can be formed in vivo also from the reduction of inorganic nitrate (NO(3) (-)) and nitrite (NO(2) (-)). The diet constitutes a major source of nitrate, and vegetables are particularly rich in this anion. The aim of this study was to investigate if dietary nitrate had any effect on metabolic and circulatory parameters during exercise. METHOD: In a randomized double-blind placebo-controlled crossover study, we tested the effect of dietary nitrate on physiological and metabolic parameters during exercise. Nine healthy young well-trained men performed submaximal and maximal work tests on a cycle ergometer after two separate 3-day periods of dietary supplementation with sodium nitrate (0.1 mmol kg(-1) day-1) or an equal amount of sodium chloride (placebo). RESULTS: The oxygen cost at submaximal exercise was reduced after nitrate supplementation compared with placebo. On an average Vo(2) decreased from 2.98 +/- 0.57 during CON to 2.82 +/- 0.58 L min(-1) during NIT (P < 0.02) over the four lowest submaximal work rates. Gross efficiency increased from 19.7 +/- 1.6 during CON to 21.1 +/- 1.3% during NIT (P < 0.01) over the four lowest work rates. There was no difference in heart rate, lactate [Hla], ventilation (VE), VE/Vo(2) or respiratory exchange ratio between nitrate and placebo during any of the submaximal work rates.

CONCLUSION: We conclude that dietary nitrate supplementation, in an amount achievable through a diet rich in vegetables, results in a lower oxygen demand during submaximal work. This highly surprising effect occurred without an accompanying increase in lactate concentration, indicating that the energy production had become more efficient. The mechanism of action needs to be clarified but a likely first step is the in vivo reduction of dietary nitrate into bioactive nitrogen oxides including nitrite and NO.

[max_power]

Sinceramente preferisco avere un po' meno resistenza nell'allenamento che aumentare il margine di rischio di patologie anche maligne al colon retto.

[brosgym]

Sinceramente preferisco avere un po' meno resistenza nell'allenamento che aumentare il margine di rischio di patologie anche maligne al colon retto.

In effetti...visto che hanno la "cattiva abitudine" di convertirsi in nitrosammine.......

[Rik_the_Dog]

In effetti...visto che hanno al "cattiva abitudine" di convertirsi in nitrosammine.......

[max_power]

In effetti...visto che hanno la "cattiva abitudine" di convertirsi in nitrosammine.......

Già. Brutta storia.