Are nitrate-rich foods, such as beet juice, a good option for increasing muscle strength?
- A new study finds that consuming dietary nitrates before exercise can enhance the amount of force that quadricep muscles can produce.
- Biopsies of study participants revealed that the muscles of people who had ingested a nitrate suspension held more nitrates than the control group. The beneficial action of nitrates in muscles is not yet clear.
- Beet juice is rich in nitrates, suggesting that drinking it may enhance athletic performance without incurring issues increasingly associated with nitrates in meats, processed meats, cheese, and bacon.
In a new randomized, crossover study, researchers demonstrate that the consumption of dietary nitrates improves athletic performance, and they explain why that may be.
The study found that during exercise, participants experienced about a 7% increase in muscle torque, or strength, compared to those who consumed the placebo.
The study comes from researchers at the University of Exeter in the United Kingdom, together with researchers from the University of Queensland, Australia, and the United States National Institutes of Health (NIH).
Its results appear in the journal Acta Physiologica.
What happened in the study?
Ten healthy male volunteers signed up to participate in the study. They consumed either a suspension of potassium nitrate, or as a control condition, a liquid containing a potassium chloride placebo.
Researchers performed muscle biopsies on the participants four times: before ingestion, 1 hour later, 3 hours later, and after participants had performed 60 maximal contractions of knee extensors.
Compared to those who ingested the placebo, individuals who consumed the nitrate solution had elevated levels of nitrates in their vastus lateralis leg muscles, part of the quadriceps.
The increase persisted for a few hours after nitrate consumption.
Nitrates vs. nitrites
The study also looked at how nitrates may have enhanced performance.
Nitrates are naturally occurring chemical compounds that can be beneficial for health, at least in part because they encourage the production of nitric oxide the body needs.
Nitric oxide plays a role in regulating blood pressure, cardiovascular health, the production of mitochondria, the so-called powerhouses of the cell, calcium transport, reducing oxidative stress, and repairing skeletal muscle.
Beet juice, or beetroot juice, contains nitrates and has it can lower blood pressure and enhance physical performance, as previous research has suggested. Nitrates are also plentiful in celery and lettuce.
Nitrates may break down in contact with saliva to form nitrites. Nitrites are similar compounds, although slightly more active than the more stable nitrates. They also promote nitric oxide.
However, nitrates, when exposed to high heat, can also turn into nitrosamines, which are carcinogenic. This is most likely to occur with nitrates that suppress bacterial activity in ham, cheese, bacon, and in processed meats.
How nitrates impact muscle strength
“We show for the first time that nitrate levels in the muscles before exercise is related to the amount of force muscles can produce,” said the study’s corresponding author Dr. Andrew M. Jones, professor of applied physiology at the University of Exeter.
The mechanism behind the increase in torque remains to be fully explained. Dr. Jones hypothesized that “[t]he muscle appears to use the nitrate to improve its ability to contract, we think by converting nitrate to nitric oxide which, in turn, has effects on the contractile apparatus.”
Dr. Paul Arciero, professor in the Human Physiological Sciences Department at Skidmore College in Sarasota, NY, who was not involved in the study, has a different theory.
According to him, “[i]t’s dietary nitrate, not nitric oxide that is showing these enhanced muscle performance effects.”
Dietary nitrate, according to Dr. Arciero, “specifically targets the fast-twitch muscle fibers, possibly through increasing [the] release of calcium, which is necessary for muscle contractions and generating maximal muscle force.”
This would be helpful to athletes who need to quickly accelerate from a starting position, he suggested.
This boost in nitrates would be particularly beneficial during high-performance athletic exertion, and can enhance muscle performance in older people, or those whose movements are affected by disease.
Dr. Jones noted that changes to the way in which one develops muscle after consuming nitrates remain unexplored for now. “But,” he said, “if you can produce more force (lift more weight) and do so repeatedly during a training program, it’s feasible that there could be hypertrophic effects.”
Could beet juice enhance performance?
Although the current study did not investigate the benefits of beet juice, which is rich in nitrates, Dr. Arciero has previously studied its value for enhancing exercise performance.
“Most of the scientific findings suggest that consuming dietary nitrate, and in many cases, beetroot juice 60–90 minutes prior to exercise, are effective nutritional strategies to enhance exercise performance.”
– Dr. Paul Arciero
Specifically, he reported, beet juice can promote continuous endurance during exercise, and the current study’s findings now add that it also supports high-intensity muscular force production as well.
“This study clearly provides compelling new evidence to consider consuming dietary nitrate to enhance maximal torque production, especially of the quadricep muscles,” said Dr. Arciero.
He also noted a range of well-studied proven nutrition strategies to increase the production of power and muscular force. These include the consumption of creatine monohydrate, about which Dr. Arciero has also written.
Dr. Jones said that he hopes for further research with a more gender-balanced set of participants. “Unfortunately, only men volunteered for our study,” he admitted.
He would also like to see investigations into the possible benefits of nitrate consumption among older people with declining muscle strength, noting that this can limit their ability to enjoy life and perform daily living activities.