Table 2

Nitrate knowledge in the overall cohort and when stratified by participant qualification status

QuestionOverall (%)Highest qualification (%)P value
Health and performance effects of dietary inorganic nitrate
 1. Have you heard of inorganic nitrate?*0.001
  Yes 71417886
 2. In your opinion, is dietary inorganic nitrate a primarily beneficial or harmful nutritional component?0.002
 3. For each of the following variables, please specify if it is increased or decreased by dietary inorganic nitrate:
  Sports performance*0.017
   Increase 59357164
  Blood pressure*0.016
   Decrease 54415369
  Glucose levels0.409
  Lung function0.179
  Cancer risk0.697
  Cognitive function0.113
  Kidney function0.619
Current and recommended intake values for nitrate
 4. In the general population, what is the average daily intake of dietary inorganic nitrate of an individual?*0.017
  ≤10 mg/day67100
  11–50 mg/day107173
  51 200  mg /day 1531428
  201–500 mg/day3350
  501–750 mg/day0000
5. Do you know what is the acceptable daily intake (ADI) of dietary inorganic nitrate?*0.302
  Currently no ADI1114136
  0.2 mg/kg body mass/day2303
  3.7  mg/kg body mass/day 2172428
  14.8 mg/kg body mass/day2320
  29.6 mg/kg body mass/day1300
6. In your opinion, does the ADI for dietary inorganic nitrate require revision?0.828
  Yes—it should be higher15101518
  Yes—it should be lower2323
Dietary sources of inorganic nitrate
7. For the following foods, do you think they typically have a low (<50 mg/100 g fresh-weight) or high (>100 mg/100 g fresh-weight) dietary inorganic nitrate content?
   High 70557478
   Low 46385442
   Low 51384864
   High 69457681
   Low 43383658
   Low 42385131
   High 42314350
   High 52355564
8. Which of the following factors do you think modify the inorganic nitrate content of food?
   Yes 59466853
   Yes 58545469
  Soil conditions*0.05
   Yes 79648089
  Use of fertiliser*0.176
   Yes 71577278
  Storage conditions*0.698
   Yes 47395047
   Yes 41295134
 9. How much dietary inorganic nitrate is there, on average, in drinking water?*0.711
  < 50  mg/L 40354439
  51–100 mg/L4726
  101–200 mg/L0000
  201–300 mg/L0000
Methods of evaluating inorganic nitrate intake
 10. Which biomarker would you choose to evaluate dietary inorganic nitrate intake?0.155
  Urinary nitrate32313628
  Salivary nitrite5753
  Plasma nitrite27173425
  Exhaled nitric oxide73514
Nitrate metabolism
 11. In the body, which of the following compounds is dietary inorganic nitrate converted into?*†<0.001
  0 point2341229
  1 point 65597160
  2 points 120731
 12. Which one of these mechanisms is involved in the conversion of nitrate into nitrite in the mouth?*0.012
  C reactive protein2323
  Salivary Amylase19142711
  Bacterial reductases 36213158
  • ≤BSc=highest qualification is an undergraduate degree or below, MSc=Highest qualification is a master’s degree or equivalent, PhD=highest qualification is a PhD or equivalent. Italicised answers are those identified as correct and awarded a point on the Nitrate Knowledge Index. For question 3, only sports performance and blood pressure were included in the Nitrate Knowledge Index, as evidence was deemed to be ambiguous for other physiological effects. All other questions (2, 6 and 10) were viewed as reflecting beliefs rather than knowledge ofinorganic nitrate.

  • *Questions which were included in the construction of the Nitrate Knowledge Index (ie, those where clear evidence exists for a correct answer).

  • †Potential answers were nitric oxide, nitrosamines, nitroglycerine, carbon dioxide, adrenaline, glucose and unsure. Correct answers were nitric oxide and nitrosamines. If participants identified correct and incorrect answers, their score was capped to 1 point.