Lowering of blood pressure after nitrate-rich vegetable consumption is abolished with the co-ingestion of thiocyanate-rich vegetables in healthy normotensive males

Dewhurst-Trigg, Rebecca, Yeates, Toby, Blackwell, Jamie R, Thompson, Christopher, Linoby, Adam, Morgan, Paul T, Clarke, Ida, Connolly, Luke J, Wylie, Lee J, Winyard, Paul G, Jones, Andrew M and Bailey, Stephen J (2018) Lowering of blood pressure after nitrate-rich vegetable consumption is abolished with the co-ingestion of thiocyanate-rich vegetables in healthy normotensive males. Nitric Oxide: Biology and Chemistry, 74. pp. 39-46. ISSN 1089-8603

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Abstract

A diet rich in vegetables is known to provide cardioprotection. However, it is unclear how the consumption of different vegetables might interact to influence vascular health. This study tested the hypothesis that nitrate-rich vegetable consumption would lower systolic blood pressure but that this effect would be abolished when nitrate-rich and thiocyanate-rich vegetables are co-ingested. On four separate occasions, and in a randomized cross-over design, eleven healthy males reported to the laboratory and consumed a 750 mL vegetable smoothie that was either: low in nitrate (∼0.3 mmol) and thiocyanate (∼5 μmol), low in nitrate and high in thiocyanate (∼72 μmol), high in nitrate (∼4 mmol) and low in thiocyanate and high in nitrate and thiocyanate. Blood pressure as well as plasma and salivary [thiocyanate], [nitrate] and [nitrite] were assessed before and 3 h after smoothie consumption. Plasma [nitrate] and [nitrite] and salivary [nitrate] were not different after consuming the two high-nitrate smoothies, but salivary [nitrite] was higher after consuming the high-nitrate low-thiocyanate smoothie (1183 ± 625 μM) compared to the high-nitrate high-thiocyanate smoothie (941 ± 532 μM; P <.001). Systolic blood pressure was only lowered after consuming the high-nitrate low-thiocyanate smoothie (−3 ± 5 mmHg; P <.05). The acute consumption of vegetables high in nitrate and low in thiocyanate lowered systolic blood pressure. However, when the same dose of nitrate-rich vegetables was co-ingested with thiocyanate-rich vegetables the increase in salivary [nitrite] was smaller and systolic blood pressure was not lowered. These findings might have implications for optimising dietary guidelines aimed at improving cardiovascular health.