Dietary intake of inorganic nitrate in vegetarians and omnivores and its impact on blood pressure, resting metabolic rate and the oral microbiome

Ann Ashworth, Craig Cutler, Garry Farnham, Luke Liddle, Mia Burleigh, Ana Rodiles, Carla Sillitti, Michele Kiernan, Melanie Moore, Mary Hickson, Chris Easton, Raul Bescos

Research output: Contribution to journalArticle

Abstract

Vegetarian diets are commonly associated with lower blood pressure levels. This has been related to greater consumption of inorganic nitrate, since vegetables are the main source of this anion. Dietary nitrate is reduced to nitrite by commensal bacteria in the mouth, which in turn leads to increased circulatory nitrite availability. Nitrite can form nitric oxide by several pathways promoting a reduction in the vascular tone and lower blood pressure. This study tested whether vegetarians have higher concentrations of nitrite in saliva and plasma, and lower blood pressure and resting metabolic rate (RMR), due to higher intakes of nitrate, compared to omnivores. Following a non-randomized, cross-over and single-blinded design we measured dietary nitrate intake, blood pressure and RMR in young and healthy vegetarians (n= 22) and omnivores (n= 19) with similar characteristics after using placebo or antibacterial mouthwash for a week to inhibit oral bacteria. Additionally, we analyzed salivary and plasma nitrate and nitrite concentrations, as well as the oral nitrate-reduction rate and oral microbiome in both groups. Dietary nitrate intake in vegetarians (97 ± 79 mg/day) was not statistically different (P > 0.05) to omnivores (78 ± 47 mg/day). Salivary and plasma nitrate and nitrite concentrations were similar after placebo mouthwash in both groups (P > 0.05). The oral nitrate-reducing capacity, abundance of oral bacterial species, blood pressure and RMR were also similar between vegetarians and omnivores (P > 0.05). Antibacterial mouthwash significantly decreased abundance of oral nitrate-reducing bacterial species in vegetarians (_16.9 %; P < 0.001) and omnivores (_17.4 %; P < 0.001), which in turn led to a significant reduction of the oral nitrate-reducing capacity in vegetarians (-78%; P < 0.001) and omnivores (-85%; P < 0.001). However, this did not lead to a significant increase in blood pressure and RMR in either groups (P > 0.05). These findings suggest that vegetarian diets may not alter nitrate and nitrite homeostasis, or the oral microbiome, compared to an omnivore diet. Additionally, inhibition of oral nitrite synthesis for a week with antibacterial mouthwash did not cause a significant raise in blood pressure and RMR in healthy, young individuals independent of diet.
Original languageEnglish
Pages (from-to)63-72
Number of pages10
JournalFree Radical Biology and Medicine
Volume138
Early online date10 May 2019
DOIs
Publication statusPublished - 31 Jul 2019

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Basal Metabolism
Microbiota
Blood pressure
Nitrates
Nitrites
Blood Pressure
Mouthwashes
Nutrition
Vegetarian Diet
Plasmas
Bacteria
Vegetarians
Placebos
Diet
Vegetables
Saliva
Anions
Blood Vessels
Mouth
Nitric Oxide

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Ashworth, Ann ; Cutler, Craig ; Farnham, Garry ; Liddle, Luke ; Burleigh, Mia ; Rodiles, Ana ; Sillitti, Carla ; Kiernan, Michele ; Moore, Melanie ; Hickson, Mary ; Easton, Chris ; Bescos, Raul. / Dietary intake of inorganic nitrate in vegetarians and omnivores and its impact on blood pressure, resting metabolic rate and the oral microbiome. In: Free Radical Biology and Medicine. 2019 ; Vol. 138. pp. 63-72.
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Dietary intake of inorganic nitrate in vegetarians and omnivores and its impact on blood pressure, resting metabolic rate and the oral microbiome. / Ashworth, Ann; Cutler, Craig; Farnham, Garry; Liddle, Luke; Burleigh, Mia; Rodiles, Ana; Sillitti, Carla; Kiernan, Michele; Moore, Melanie; Hickson, Mary ; Easton, Chris; Bescos, Raul.

In: Free Radical Biology and Medicine, Vol. 138, 31.07.2019, p. 63-72.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Dietary intake of inorganic nitrate in vegetarians and omnivores and its impact on blood pressure, resting metabolic rate and the oral microbiome

AU - Ashworth, Ann

AU - Cutler, Craig

AU - Farnham, Garry

AU - Liddle, Luke

AU - Burleigh, Mia

AU - Rodiles, Ana

AU - Sillitti, Carla

AU - Kiernan, Michele

AU - Moore, Melanie

AU - Hickson, Mary

AU - Easton, Chris

AU - Bescos, Raul

PY - 2019/7/31

Y1 - 2019/7/31

N2 - Vegetarian diets are commonly associated with lower blood pressure levels. This has been related to greater consumption of inorganic nitrate, since vegetables are the main source of this anion. Dietary nitrate is reduced to nitrite by commensal bacteria in the mouth, which in turn leads to increased circulatory nitrite availability. Nitrite can form nitric oxide by several pathways promoting a reduction in the vascular tone and lower blood pressure. This study tested whether vegetarians have higher concentrations of nitrite in saliva and plasma, and lower blood pressure and resting metabolic rate (RMR), due to higher intakes of nitrate, compared to omnivores. Following a non-randomized, cross-over and single-blinded design we measured dietary nitrate intake, blood pressure and RMR in young and healthy vegetarians (n= 22) and omnivores (n= 19) with similar characteristics after using placebo or antibacterial mouthwash for a week to inhibit oral bacteria. Additionally, we analyzed salivary and plasma nitrate and nitrite concentrations, as well as the oral nitrate-reduction rate and oral microbiome in both groups. Dietary nitrate intake in vegetarians (97 ± 79 mg/day) was not statistically different (P > 0.05) to omnivores (78 ± 47 mg/day). Salivary and plasma nitrate and nitrite concentrations were similar after placebo mouthwash in both groups (P > 0.05). The oral nitrate-reducing capacity, abundance of oral bacterial species, blood pressure and RMR were also similar between vegetarians and omnivores (P > 0.05). Antibacterial mouthwash significantly decreased abundance of oral nitrate-reducing bacterial species in vegetarians (_16.9 %; P < 0.001) and omnivores (_17.4 %; P < 0.001), which in turn led to a significant reduction of the oral nitrate-reducing capacity in vegetarians (-78%; P < 0.001) and omnivores (-85%; P < 0.001). However, this did not lead to a significant increase in blood pressure and RMR in either groups (P > 0.05). These findings suggest that vegetarian diets may not alter nitrate and nitrite homeostasis, or the oral microbiome, compared to an omnivore diet. Additionally, inhibition of oral nitrite synthesis for a week with antibacterial mouthwash did not cause a significant raise in blood pressure and RMR in healthy, young individuals independent of diet.

AB - Vegetarian diets are commonly associated with lower blood pressure levels. This has been related to greater consumption of inorganic nitrate, since vegetables are the main source of this anion. Dietary nitrate is reduced to nitrite by commensal bacteria in the mouth, which in turn leads to increased circulatory nitrite availability. Nitrite can form nitric oxide by several pathways promoting a reduction in the vascular tone and lower blood pressure. This study tested whether vegetarians have higher concentrations of nitrite in saliva and plasma, and lower blood pressure and resting metabolic rate (RMR), due to higher intakes of nitrate, compared to omnivores. Following a non-randomized, cross-over and single-blinded design we measured dietary nitrate intake, blood pressure and RMR in young and healthy vegetarians (n= 22) and omnivores (n= 19) with similar characteristics after using placebo or antibacterial mouthwash for a week to inhibit oral bacteria. Additionally, we analyzed salivary and plasma nitrate and nitrite concentrations, as well as the oral nitrate-reduction rate and oral microbiome in both groups. Dietary nitrate intake in vegetarians (97 ± 79 mg/day) was not statistically different (P > 0.05) to omnivores (78 ± 47 mg/day). Salivary and plasma nitrate and nitrite concentrations were similar after placebo mouthwash in both groups (P > 0.05). The oral nitrate-reducing capacity, abundance of oral bacterial species, blood pressure and RMR were also similar between vegetarians and omnivores (P > 0.05). Antibacterial mouthwash significantly decreased abundance of oral nitrate-reducing bacterial species in vegetarians (_16.9 %; P < 0.001) and omnivores (_17.4 %; P < 0.001), which in turn led to a significant reduction of the oral nitrate-reducing capacity in vegetarians (-78%; P < 0.001) and omnivores (-85%; P < 0.001). However, this did not lead to a significant increase in blood pressure and RMR in either groups (P > 0.05). These findings suggest that vegetarian diets may not alter nitrate and nitrite homeostasis, or the oral microbiome, compared to an omnivore diet. Additionally, inhibition of oral nitrite synthesis for a week with antibacterial mouthwash did not cause a significant raise in blood pressure and RMR in healthy, young individuals independent of diet.

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