Why Supplements Aren’t the Same as Foods

I’ve written lots about the potential endurance-boosting effects of beet juice over the last few years. The secret to its powers, according to the research, is its high levels of nitrate.

So why not just take straight nitrate (or, more specifically, a nitrate salt like sodium nitrate)? That way, you avoid issues like the taste and (ahem) digestive challenges that sometimes arise after large doses of beet juice.

A new study in the journal Applied Physiology, Nutrition, and Metabolism, from researchers at several institutions in Switzerland, takes this question on. The researchers put 12 “well-trained’ volunteers through a series of tests with three different doses of nitrate (3, 6, and 12 mmol), obtained either from beet juice or from straight sodium nitrate dissolved in water.

The big benefit of beet juice, from the perspective of endurance athletes, is that it makes exercise more “economical”—that is, it costs less oxygen to sustain the same pace. Sure enough, the results showed that the middle dose of beet juice reduced the oxygen cost of cycling at 80 percent of VO2max by about 4 per cent. (There were similar results at the higher dose and at moderate intensity, but they didn’t reach statistical significance.)

In contrast, the sodium nitrate didn’t produce a significant improvement in cycling economy. Similarly, beet juice reduced blood pressure more than sodium nitrate.

So we have a puzzle here. The earlier studies compared regular beet juice with specially prepared beet juice that had the nitrate stripped out of it. The fact that the nitrate-free juice didn’t work suggests that nitrate is what matters, and all the other wonderful things that beet juice contains—antioxidants, polyphenols, and so on—don’t matter.

And yet the new results suggest that nitrate alone doesn’t do the trick, and all the other stuff is what makes the difference.

What does this tell us? When I put the question to Andy Jones, the University of Exeter researcher most closely associated with beet juice for athletes, on Twitter, he suggested that it’s the “cocktail” that matters.

In the new paper, the researchers cite previous research suggesting that the polyphenols and antioxidants in beet juice may play a role in transforming nitrite in the gut into nitric oxide. (When you ingest nitrate, it’s first converted in the body to nitrite, and then to nitric oxide, which is what is believed to produce the beneficial effect.)

In other words, you need the whole package. There may be (in fact, there almost certainly are) other ways in which the various ingredients in beet juice work together to produce their effects. Maybe we’ll figure them all out someday, so that we can develop a pill that has the exact same effects. If we do, I suspect that pill will look a lot like… a beet.

I should note that this was a small study, with just 12 subjects, and the differences observed were pretty small. It’s certainly a question that I hope other researchers will return to in greater depth, to verify the findings.

Still, it seems to me a pretty powerful illustration of what I think is a very familiar phenomenon: Trying (and failing) to replace complex foods that we’ve co-evolved with over millennia with a few isolated nutrients from those foods. It’s a mug’s game. Stick with the real thing.

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