Habitual Dietary Nitrate Intake in Highly Trained Athletes

Abstract

Although beetroot juice, as a nitrate carrier, is a popular ergogenic supplement among athletes, nitrate is consumed through the regular diet as well. We aimed to assess the habitual dietary nitrate intake and identify the main contributing food sources in a large group of highly trained athletes. Dutch highly trained athletes (226 women and 327 men) completed 2-4 web-based 24-hr dietary recalls and questionnaires within a 2-to 4-week period. The nitrate content of food products and food groups was determined systematically based on values found in regulatory reports and scientific literature. These were then used to calculate each athlete's dietary nitrate intake from the web-based recalls. The median [IQR] habitual nitrate intake was 106[75-170] mg/d (range 19-525 mg/d). Nitrate intake correlated with energy intake (ρ = 0.28, p < .001), and strongly correlated with vegetable intake (ρ = 0.78, p < .001). In accordance, most of the dietary nitrate was consumed through vegetables, potatoes and fruit, accounting for 74% of total nitrate intake, with lettuce and spinach contributing most. When corrected for energy intake, nitrate intake was substantially higher in female vs male athletes (12.8[9.2-20.0] vs 9.4[6.2-13.8] mg/MJ; p < .001). This difference was attributed to the higher vegetable intake in female vs male athletes (150[88-236] vs 114[61-183] g/d; p < .001). In conclusion, median daily intake of dietary nitrate in highly trained athletes was 106 mg, with large interindividual variation. Dietary nitrate intake was strongly associated with the intake of vegetables. Increasing the intake of nitrate-rich vegetables in the diet might serve as an alternative strategy for nitrate supplementation.

Effects of nitrate supplementation in trained and untrained muscle are modest with initial high plasma nitrite levels

“…In turn, the consistent finding of higher NO − 3 plasma levels in endurance athletes relative to less trained individuals 11,[29][30][31] which was also observed in the present study, and the general lack of effect from NO − 3 supplementation in endurance athletes 7-12 could be speculated to relate to higher NOS content 5 and/or higher daily dietary intake of NO − 3 due to increased energy intake. 35 There is evidence to suggest that a NO − 3 dose and physiologic response relationship exists; 34 however, the NO − 3 dose used in the present study (9 mmol) is similar to or higher than the doses used in previous studies reporting significant effects on energy expenditure and blood pressure following an acute dose in moderately trained subjects 16 and kayakers. 36,37 Furthermore, a quite large dose (19.5 mmol) 8 failed to lower submaximal VO 2 in highly trained runners indicating that subjects not responsive to NO − 3 supplementation, similar to those in the present study, will not benefit from a more aggressive supplementation strategy.…”

Micronutrient Intakes in 553 Dutch Elite and Sub-Elite Athletes: Prevalence of Low and High Intakes in Users and Non-Users of Nutritional Supplements

“…The study was performed between February 2012 and June 2015 as described by Wardenaar et al [ 24 ] and others [ 25 , 26 ]. A total of 1800 athletes were informed about the study.…”

No longer beeting around the bush: a review of potential sex differences with dietary nitrate supplementation

“…However, it is important to consider the possibility that non-sex-specific differences may be driving these responses. For example, Jonvik et al (2016) found that highly trained females had greater dietary NO 3 intake compared with males. Furthermore, little is known regarding differences in other dietary and lifestyle factors that may influence plasma NO 3 and NO 2 levels.…”