A few weeks ago, I wrote about a study that compared the endurance- and health-boosting benefits of beet juice to those of a supplement containing nitrate, the main active ingredient in beet juice. The message: Isolated supplements don’t produce the same benefits as real foods, because the many micronutrients in foods work together to produce their effects. Beet juice trumped the nitrate supplement.
As it turns out, that study was just the tip of the iceberg. Several studies on related topics are due to be published in the near future, and a particularly interesting one was posted online by the Journal of Nutrition on Wednesday.
Researchers at Maastricht University in the Netherlands, including lead author Kristin Jonvik and senior author Lex Verdijk, compared the effects of beet juice and sodium nitrate with two other vegetable sources of nitrate: spinach and arugula. The conclusion, once again, is that real foods are superior to supplements.
Some quick background on the beet juice phenomenon. Beet juice contains nitrate. Once it’s swallowed, the nitrate is concentrated in your saliva, where friendly bacteria in your mouth convert it to nitrite. The nitrite is swallowed and subsequently converted to nitric oxide, which has a huge number of important effects in the body. From a health perspective, one of the most significant is reducing blood pressure. For endurance athletes, it reduces the amount of oxygen needed to sustain a given pace.
From that description, it may seem logical to forget about beet juice and take straight nitrate, typically in the form of sodium nitrate or potassium nitrate powder. But beets contain other things like vitamin C and various polyphenols that seem to help in the process of converting nitrite to nitric oxide, meaning you get more bang for your nitrate buck from the vegetable.
Of course, even though beets have gotten all the attention, lots of other vegetables contain decent amounts of nitrate. Jonvik’s study looked the nitrate and nitrite response to spinach and arugula, and also measured the change in blood pressure in the five hours after ingestion.
The results are pretty striking. All the doses were equalized to contain 800 mg of nitrate, and as a result, the overall rise in nitrate levels in the blood was similar in all four cases:
The one difference is in the timing: Beet juice and sodium nitrate produce a peak earlier than spinach or arugula (which is referred to by the alternate name of “rocket” in the figure). That may be because of the very large dose of greens (and accompanying fiber) needed to get the same dose of nitrate, which might delay stomach emptying.
The next step in the process in converting to nitrite—and in this case, three were the same, but spinach produced far higher levels of nitrite in the blood:
Spinach itself actually contains more nitrite (as opposed to nitrate) than the other options, which probably leads directly to the observed higher nitrite levels. Is that a benefit? Probably not. A previous study where nitrite was infused directly into the blood didn’t produce the same benefits as nitrite converted from nitrate. Not all nitrite is equally useful, apparently.
The key question, of course, is what actually happens to final outcomes like blood pressure. Here are the observed changes for systolic (C) and diastolic (D) blood pressure for sodium nitrate, beet juice, arugula, and spinach, after 150 minutes (left bars) and 300 minutes (right bars):
There are some big differences there. All the vegetables were effective; in contrast, sodium nitrate had no significant effect on systolic blood pressure, and the smallest effect on diastolic blood pressure. Vegetables win again.
So are spinach and arugula viable alternatives to beet juice? To get 800 mg of nitrate (which is a typical dose used by athletes) from beet juice, they used about one-and-a-half 70 mL bottles of Beet-It concentrated beet juice. The green drinks were prepared by blending the greens into a smoothie-like texture.
It took a lot of spinach to get the same nitrate dose: 365 grams (almost 13 ounces). I have a very big box of fresh spinach in my fridge, and it contains 320 grams. Of course, it’s amazing how much you can consume when it’s blended smooth (or, for that matter, wilted into pasta or other dishes). Arugula was a little more reasonable: 196 grams (7 ounces).
The effects they see here are pretty remarkable: an instant blood pressure drop of more than 5 mmHg just a few hours after downing the juices. Personally, instead of forcing down a whole box of spinach, I’m interested in knowing more about the benefits of maintaining a more modest level of nitrate consumption over longer periods of time. If you eat 400 mg of nitrate per day for months at a time, what does that do to your blood pressure? Or your endurance performance?
The bottom line: Eat food, and don’t limit yourself to beets. Aside from spinach and arugula, there’s some more research coming out in a few months using Swiss chard. And I can hardly wait for rhubarb season!
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