Key takeaways: More is better. Peak levels arrive about 2-3 hours after ingestion, and are approaching baseline again by 12 hours later.
So what results does this boost in nitrate produce? From a health perspective, an interesting one is that systolic blood pressure dropped by 5, 10 and 9 mmHg for the three doses (from smallest to biggest); the decrease in diastolic blood pressure was a bit smaller (no change, 3, and 4 mmHg).
The amount of oxygen required to maintain a given level of moderate exercise decreased after taking beet juice; in other words, it took less energy to cycle at the same pace. The best results came from the highest dose, which decreased oxygen consumption by about 3%. They did the tests 2.5 hours after ingesting the beet juice, since that seems to be the peak nitrite level.
They also did a cycle test to exhaustion; here are those results:
The dark bar is how long they lasted with a placebo drink (nitrate removed), and the light bar is how long they lasted with proper beet juice. In this case the middle dosage produced the best result, for reasons that aren’t entirely obvious. Given that beet juice is anecdotally reported to be associated with port-a-potty stops, there’s a pretty high incentive to use the lowest dose that produces good results — so the apparent saturation of benefits is worth bearing in mind here. It’s also worth noting that you tend to see much bigger changes in time-to-exhaustion tests that you would in races or time-trials; the authors estimate that the 12-14% boosts seen here would likely translate to 1-2% reduction in race time.
So what are these doses? The researchers used a product called Beet-It, which is a British company that makes concentrated beet juice. Using the concentrated form may help get the beet juice down without subsequent digestive woes. Beet-It is sold in 70 mL shots, each of which is roughly equivalent to 300 mL of regular-strength beet juice in terms of nitrate content. The three doses used in the study were 1 shot, 2 shots, or 4 shots — corresponding to 300 mL, 600 mL, or 1200 mL of regular juice (which would be pretty ridiculous!). In the past, I’ve talked to athletes who’ve used 500 mL of regular juice a few hours before races; based on this study, I’d say that’s pretty close to the sweet spot. Many athletes now use the shots, which are easier to get down. In that case, I’d say this study suggests that there may be potential benefits to experimenting with up to two shots, since the individual responses in the study varied quite a bit.