Just Beet It: Nitrate-Rich Beetroot Juice Boosts Brain Health, Blood Flow, and Better Oral Bacteria
Over the past twenty or so years, research on the gut microbiome — the vast collection of bacteria in our gastrointestinal tracts — has exploded, linking this multitude of microscopic species to numerous diseases. While the word ‘microbiome’ has been becoming more mainstream in recent years, most people associate the term solely with the gut. However, our bodies also have a rich and diverse ecosystem of bacteria living on many more surfaces and organs than just our intestines — including our mouths, the under-recognized beginning of our entire digestive tract.
With the second largest collection of microbes in the body after the gut, the oral microbiome harbors over 700 species of bacteria. Being the first point of entry to what we consume, ranging from the foods we eat to the airborne bacteria we breathe in, the oral microbiome is particularly vulnerable to the invasion and proliferation of unwanted bacterial species — just ask your dentist!
But, undesirable changes to the oral microbiome (also known as dysbiosis) don’t just affect your teeth and gums — recent research has also linked oral microbial imbalances to impaired cardiovascular, cognitive, and metabolic health. While it’s been relatively unknown how exactly these oral microbial changes modulate human health, a new study authored by Vanhatalo and colleagues provides evidence that the missing link to this puzzle is the compound nitric oxide — and boosting its levels may be as easy as sipping on beet juice.
The Brain-Boosting and Blood Flow Benefits of Nitric Oxide
Nitric oxide is a gaseous signaling molecule necessary for the proper flow of blood, nutrients, and oxygen throughout the body. This nitrogen- and oxygen-containing compound is a vasodilator, meaning it relaxes and opens blood vessels to increase blood flow and circulation. These vasodilating properties benefit cardiovascular, metabolic, and cognitive health, as proper blood flow is crucial to maintaining these systems.
There are two known pathways to produce nitric oxide. First, the compound can be produced inside the body from the amino acid L-arginine, which then gets converted into nitric oxide. However, this process diminishes with age, leading to low nitric oxide bioavailability and an increased risk of disorders related to poor blood flow, including high blood pressure and cognitive decline.
The second nitric oxide synthesis pathway is exogenous — meaning, through external sources, like food. Dietary nitrates first get converted into an intermediate called nitrite, which then gets reduced into bioactive nitric oxide in the blood and tissues. While this nitrate-to-nitrite conversion can occur in the stomach, the preferred route is through specific oral bacteria that reduce nitrate to nitrite. Having oral dysbiosis, or low amounts of these nitrate-reducing bacteria with higher amounts of unhealthy bacteria, will reduce the amount of available nitric oxide for the body to improve blood flow.
Thus, increasing nitric oxide synthesis through the consumption of nitrate-rich foods presents a therapeutic opportunity for attenuating the cardiovascular, metabolic, and cognitive declines commonly seen with advancing age. In this study, the research team uses nitrate-rich beetroot juice to modulate the oral microbiome and improve markers of heart and brain health in a small study of 30 older adults. "Previous studies have compared the oral bacteria of young and older people, and healthy people compared to those with diseases, but ours is the first to test nitrate-rich diet in this way,” states lead author Vanhalato.
Telling Bad Bacteria to Beet It
The 30 adults, ranging in age from 70 to 80, were randomized to drink beetroot juice that supplied 750 mg of nitrates per day or a placebo drink for ten days. As it was a crossover-designed study, each participant then consumed the other treatment a few days after completing the first 10-day round. They found that consuming the nitrate-rich drink significantly shifted the oral microbiome, boosting the abundance of beneficial bacterial species and reducing the prevalence of harmful bacteria.
Specifically, the beetroot juice tripled levels of Neisseria lactamica and more than doubled Rothia mucilaginosa, two species linked to improved cognition and reduced mean arterial pressure (a measure of the flow, resistance, and pressure in your arteries), respectively.
The researchers also clustered together some bacterial species that tend to coexist under certain conditions and exhibit similar functions. Referred to as microbial modules, one such cluster called Prevotella-Veillonella, which is linked to inflammation and cognitive decline, was reduced by about half after beetroot treatment. Similarly, the nitrate intervention decreased Clostridium difficile (C.diff), a common infection-causing bacteria in older adults, to about one-fifth of its original levels.
In addition to shifting the oral bacterial makeup from harmful to helpful, the beetroot juice treatment significantly boosted plasma levels of nitric oxide, which increases blood flow, and enhanced exercise efficiency. In terms of cardiovascular and cognitive health markers, the nitrate-rich juice reduced systolic blood pressure by 5 points — a reduction of this amount has been linked to a 10% reduction in the risk of cardiovascular-related events, like stroke or heart attacks.
Lastly, the beetroot treatment boosted performance on a cognitive test that measures sustained attention. As deficits in sustained attention are a common first sign of cognitive decline, these results suggest that adding nitrate-rich foods to the diet may be a simple measure for preventing or delaying cognitive decline.
A Beet a Day Keeps the Doctor Away?
In this study, Vanhatalo and colleagues show how quickly a short dietary intervention can manipulate the oral microbiome to produce more nitric oxide and, with it, improve outcomes related to cardiovascular and cognitive health. Consuming a diet rich in nitrates in older age may substantially impact both oral and vascular health, reducing the risk of hypertension, heart disease, and cognitive decline.
This study’s results open up new potential opportunities for using targeted probiotic therapies combined with dietary nitrates for older adults or those with poor vascular function. Although beetroot juice is the richest source of dietary nitrates (the one used in this study provided 750 mg in less than 5 ounces), you can also find the nitric oxide precursors in whole beets, celery, spinach, arugula, kale, parsley, and turnips. While additional research in more diverse groups is warranted, as this study only included generally healthy older adults, these results are promising for the future use of nitrate-rich foods to mitigate the harmful effects of impaired nitric oxide production with age.
As summarized by Vanhatalo, "Our findings suggest that adding nitrate-rich foods to the diet — in this case via beetroot juice — for just ten days can substantially alter the oral microbiome for the better. Maintaining this healthy oral microbiome in the long term might slow down the negative vascular and cognitive changes associated with ageing.”
Vanhatalo A, L'Heureux JE, Kelly J, et al. Network analysis of nitrate-sensitive oral microbiome reveals interactions with cognitive function and cardiovascular health across dietary interventions [published online ahead of print, 2021 Mar 5]. Redox Biol. 2021;41:101933. doi:10.1016/j.redox.2021.101933