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Discussion (Dietary NO3- safety (Acute GI effects (No reports during study…
Discussion
Dietary NO3- safety
upper level of ADI is 3.7mg (European food safety authority, 2008) :check:
High dietary nitrate has been linked to colorectal cancer (in those with low vitamin C intake), probably from the increased formation of N-nitroso compounds (Dallevalle et al, 2013) :check:
High dietary nitrate has been linked to a reduced risk of gastric cancer (Song et al, 2015) :check:
Week-long supplementation of dietary nitrate had no effect on kidney function at rest or during exercise (Carpentier et al, 2015) :check:
No association between high intake of nitrate-rich veg and chronic kidney disease after 3 years (Mirmiran et al, 2016) :check:
Acute GI effects
No reports during study (Tan et al, 2018) (McQuillan et al, 2017a) (McQuillan et al, 2018) :check:
Tannenbaum et al 1985 has been referenced to warn against the link between dietary nitrate and conversion into N-nitrosamines, and it's subsequent link to gastric cancer, but what was measured was salivary nitrate, rather than dietary nitrate intake :check:
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Effects on VO2
Reduced
during steady state exercise 60% WRmax (Muggeridge et al, 2013)
between 30-120 minutes of moderate intensity exercise (Tan et al, 2018)
during submaximal exercise (45% 65% vo2max)(Cermak et al, 2012a)
only reduces with nitrate on intensities less than or equal to 80% vo2max (larsen et al, 2007)
Didn't Change
50% wmax (MacLeod et al, 2015)
at 70% iPPO (submaximal) (Christensen et al, 2013)
McQuillan et al, 2017 80% VT1 (50-75% vo2 max)
In TT
didnt change
In 4km or 16.1km TT (Lansley et al, 2011))
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reduced
p=0.06, so close for 50 mile TT (Wilkerson et al, 2012)
Discussion Trends
For studies examining bolus dosing, appears to be a trend that for increased VO2 max/peak, decreased improvement :check:
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For the 4 studies examining 4km TTs, there's a trend for a decreased effectiveness of beetroot with increased mean ppt vo2 max :check:
Plasma nitrite change and TT performance #
No correlation between increase in plasma nitrite and TT performance (Muggeridge, 2013) (Kent et al, 2017) - salivary (Cermak et al, 2012) :check:
Correlation between increase in nitrite and performance (Wilkerson et al, 2012) :check:
Conclusions
Bolus
Clearly Support
Significantly effective at simulated altitude of 2500m for 16.1km (Muggeridge et al, 2013)
Significantly effective at 4km and 16.1km distance (Lansley et al, 2011)
Clearly Doesn't Support
In normoxia or hypoxia (10km) (MacLeod et al, 2015)
~1 hr duration (Cermak et al, 2012)
20km (Glaister et al, 2015)
Might Support
Was >0.6% mean improvement, but not statistically significant, 50 mile (Wilkerson et al, 2012)
Chronic
Doesn't Support
4km, 3 days (Tan et al, 2018)
1km and 4km after 6 days (McQuillan et al, 2017a)
4km, 3 days (Callahan et al, 2017)
4km, 3 days (McQuillan et al, 2018)
29.35km, 2 days (Lane et al, 2014)
Harmful
4 day supplementation impaired 1km (McQuillan et al, 2017a)
Might Support
While it wasn't statistically significant, improvement was much >0.6%, so could potentially work (40-64min, 3 days) (Kent et al, 2017)
Wasn't statistically significant, but mean time was improved much >0.6%, 6 days 400kcal (Christensen et al, 2013)
Despite no author acknowledgement of this, mean male TT performance improved by >0.6% (43.84km, 2 days) (Lane et al, 2014)
'Likely beneficial'; only just >0.6% mean, 8 days 4km (McQuillan et al, 2017)
Clearly Supports
Largely significant for 10km, 6 days (Cermak et al, 2012a)
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No correlation between reduction of VO2 and improved TT performance (Muggeridge et al, 2013)
The 'smallest worthwhile change' for elite cyclists in a TT is ~0.6% (Lansley et al, 2011) (Paton et al, 2006) :check:
Conc BJ was used, allowing high dose nitrate without the impracticality of ingesting a larger volume of liquid a few hours before an event (Cermak et al, 2012a)
Changes in proteins caused by NO3- intake are more likely to take multiple days rather than hours to take place (Lane et al, 2014) # :check:
Manufacturer's dosing guidelines: Consume 1-2 shots one to three hours before training and for up to six days prior to competition :check:
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