Beetroot juice has long been hailed as a workout aid by some fitness aficionados. It’s rich in nitrates that are thought to help improve blood flow and therefore muscle function.

But it appears workouts are not exactly where beet juice's value lies.

Researchers had people drink either regular beetroot juice or beetroot juice from which the nitrates had been extracted. Everyone in the study did handgrip exercises, during which blood flow to the lower arm was measured.

If you’re in the habit of downing beetroot juice before workouts, you may want to rethink the ritual.

Even though the study did confirm that the nitrates were getting converted to nitric oxide, a compound known to relax blood vessels, there was no difference between the two groups in terms of blood flow during exercise.

There was, however, a slight difference when the participants muscles were at rest — the arteries of the people who’d consumed regular beetroot juice were more relaxed, meaning that blood flow was slightly improved.

There are two reasons for the ho-hum effects found in the study, the Penn State researchers point out. One is that the people in the study were all young and were already in excellent shape with good cardiovascular function. It’s possible that older people or those who are less fit may see a larger effect.

The other possibility is that since the intensity of activity in the current study was relatively low, larger effect on blood flow to the muscles might be seen under different, more strenuous conditions.

“It is possible that any blood flow enhancing effect of dietary nitrate will only be apparent during higher intensity and fatiguing work intensities; conditions within the muscle that favor the conversion of nitrite to nitric oxide,” study author, David Proctor, said in a news release.

So if you’re in the habit of downing beetroot juice before workouts, you may want to rethink the ritual. On the off chance that you just like the taste of it, it’s probably safe to carry on, since the effects don’t seem to be very strong in either direction.

But ask your doctor before beginning any new supplement, including one that seems harmless, since even the most “natural ” supplement can have biological effects we don’t always anticipate.

The study is published in the journal Applied Physiology, Nutrition, and Metabolism.