Recently in the news, several news aggregators picked up the results of a new study published in the Journal of Nutrition, Dietary Nitrate Intake Is Positively Associated with Muscle Function in Men and Women Independent of Physical Activity Levels.
The study suggests that eating one cup of leafy vegetables a day can boost muscle function and strength because they contain nitrates. This is the type of study that news sites love as they report “a simple, low-effort dietary strategy will lead to demonstrable muscle and strength building effects.” Well, as much as I love greens, it sounds too good to be true, so I dug deeper so that you could have the truth.
The researchers took data from the diets of approximately 3,700 Australians over a 12-year period, and found that those with the highest regular nitrate consumption, through leafy green, showed 11% stronger leg strength than those with the lowest consumption of nitrates. In addition, the top group was able to walk 4% faster than the bottom group.
The study participants were all non-athletes and their baseline age was 48.6 years, +/- 11.1 years. As such, this study does not apply particularly well to those of us who train regularly or participate in athletic endeavors of some kind. In addition, the study used food questionnaires to obtain data, and this methodology has proven, time after time, to the extremely unreliable. Therefore, there are issues with the study design.
Nevertheless, there are a number of previous studies (some involving athletes) that show a positive correlation to strength and endurance from increasing dietary intake of nitrates, although usually from beets, not greens. In fact, the collective evidence appears to be sufficiently strong to suggest that regular consumption of a bowlful of leafy vegetables may have positive strength effects on younger athletes.
Benefits of Nitrates
In order for nitrates to work their magic on human physiology, the body first has to convert the nitrates to nitric oxide, a chemical that helps increase blood flow to muscles. Increased blow flow has been shown to reduce muscle fatigue. In addition, there is strong evidence that increased nitric oxide levels improve skeletal muscle excitation-contraction coupling (which means that it increases the speed and intensity of muscle contractions) and high-energy phosphate metabolism (increasing muscle endurance).
Which Vegetables Contain Nitrates?
Among leafy greens, arugula is THE nitrate powerhouse, followed by cabbage, kale, spinach, and Swiss chard. Beets are also nearly as high as arugula.
Perhaps the best advice is to include a wide variety of mixed greens in your salads, making sure to include arugula, and then top it off with some beets. If you consistently eat this type of salad over time, you may improve athletic performance over time, but don’t expect the same results that the study participants got.