Featured on Tipcast 34
In our final podcast of 2013, @cgjones91 mentioned beet juice as the big supplement of the year. Since then I’ve had a few questions regarding my comments on both the efficacy and dosage. In addition, @billyjmacdonald wanted to know what supplements have a proven track record. In the first part of a four part series, I’ll explore why beetroot juice appears effective, and how to make the best use of it.
For those involved in weight lifting and body building, nitric oxide (NO) has been purported to be a legal anabolic promoting supplement. However, NO is actually produced in the human body and plays an important role in immune function, muscle contractility and blood flow. This last function is believed to be the key to performance during exercise. Why? In brief, the body’s main goal is to maintain blood pressure/cardiac output (Q), so there is some level of blood flow restriction to the working muscles. If we can increase the blood flow to the muscles, we can deliver more blood and oxygen, while removing more waste products. In other words, performance improves.
Beets are a natural source of nitrates, which are converted to NO. Recent research has lent strong support that an increase in nitrates in the blood leads to a dose dependent significant decrease in blood pressure (BP). The assumption that blood flow increases as BP falls is based on the fact that outside of injury (ie, you get stabbed in gut and are bleeding out), BP is determined by cardiac output and the resistance to flow in the blood vessels. At rest or during steady exercise, Q does not change, therefore a drop in BP must be caused by dilating blood vessels. Dilate the vessels and you increase blood flow. Whew! That was a lot to move through, but now we can move on to the fun stuff.
A number of research papers (see the references for the paper posted here) have shown that BP decreases with consumption of beets and beet juice. Many of these have also shown varying degrees of improved endurance performance. Most recently, Wylie and colleagues (2013) published a paper in the Journal of Applied Physiology – JAP is a very good journal, showing that consumption of the equivalent of 16 oz of beet juice (the authors used a concentrated product) decreased BP as much as drinking the equivalent of 32 oz (1 L for everyone else in the world); incidentally, there was no significant effect from 8 oz (~250 ml). A similar trend was seen for improved exercise performance. Specifically, subjects did alternating bouts of moderate cycling with severe (near VO2 max) cycling, resting between each bout and continuing until exhaustion; translation, they did hard easy cycling until they couldn’t pedal anymore. The 16 oz and 32 oz dosages showed a significant increase in time to exhaustion of about 60 sec, compared to less than 30 sec for the 8 oz dosage.
Another interesting finding, however, was that the highest dosage of NO showed a lower oxygen use during moderate exercise, suggesting higher intakes may still be most beneficial but this is unclear. In contrast, there were NO DIFFERENCES in HR or blood lactate; just in case someone out there has heard that lactic acid levels are influenced.
Why this study matters
The researchers used 10 subjects who performed all sessions in a double blind cross-over design, which is critically important for supplement studies. The study used a common exercise model where high intensity exercise is coupled with moderate intensity exercise to provide an overall exercise bout akin to real competition. Is this ideal? No, but practically speaking, it still answers the question. The benefits to performance, including the reduction in oxygen cost has been shown in other beetroot/NO studies in as little as 2.5 hrs after consumption. A lower oxygen cost is indicative of improved efficiency, thus leaving more “in the tank” when it is needed; the, a penny saved is a penny earned principle. This is actually the first study, though, to show a dose-response relationship, as well as clear blood NO pharmokinetics from time of ingestion and beyond. This matters because we need to know how long it takes before it helps, and how long that improvement lasts; this study suggests that one dose helps from about hour 2 of ingestion to hour 4. Finally, this study strongly supports the consumption of foods high in nitrates for general health, particularly those at risk or with existing high blood pressure. At the highest dosage, BP was decreased nearly 10 points. Added to general dietary changes and regular exercise, hypertensives could see a 20 point or higher drop in BP.
Sometimes translating research like this is difficult. However, the current body of literature indicates that a single bolus of at least 16 oz of beet juice 2 hrs before competition should improve exercise performances lasting from 5 min (my estimate) up to 2 hrs, when levels fall below the threshold of improvement. Additional dosages during competition would maintain NO levels, but research is unclear if this works. Additionally, other research has shown that consuming that 16 oz dosage for about a week before competition also improves performance, at least in the above time range. However, individual responses will vary, so experimentation is needed. What YOU DO NOT NEED TO DO is drink it everyday, unless you are hypertensive.
My advice would be experiment using regular juice first, which is far more cost effective. The concentrated shots are better for race, because they minimize GI issues and diarrhea, not uncommon with beet juice. Compare training sessions with and without beet juice, but there is no need or real advantage to using beet juice everyday if you’re not hypertensive. That being said, consuming beets frequently, especially in the lead up to a goal event could help you achieve your goal.