Is beetroot good for you ?

What is beetroot

The beetroot is the taproot portion of the beet plant ¹ usually known in North America as the beet, also table beet, garden beet, red beet, or golden beet. It is one of several of the cultivated varieties of Beta vulgaris grown for their edible taproots and their leaves (called beet greens). These varieties have been classified as B. vulgaris subsp. vulgaris Conditiva Group ².

Other than as a food, the juice of the beetroot, has potential antioxidant and blood pressure lowering effect ³. Beetroot contains nitrate, which while in your body changes to a chemical called nitrite and then to nitric oxide in the blood. Nitric oxide is a gas that opens up blood vessels and aids blood flow. In a preliminary study, people with high blood pressure who drank a cup of beetroot juice each day had a 10 mm Hg decrease in blood pressure over the following 24 hours ³.

Beetroots have also been used as a food coloring and as a medicinal plant. Many beet products are made from other Beta vulgaris varieties, particularly sugar beet.

Usually the deep purple roots of beetroot are eaten boiled, roasted or raw, and either alone or combined with any salad vegetable. A large proportion of the commercial production is processed into boiled and sterilized beets or into pickles. In Eastern Europe, beet soup, such as borscht, is a popular dish. In Indian cuisine, chopped, cooked, spiced beet is a common side dish. Yellow-coloured beetroots are grown on a very small scale for home consumption.

The green, leafy portion of the beet is also edible. The wild beet, the ancestor of today’s known beetroot vegetable, was initially grown for the beet greens which to this day tastes delicious, chopped, steamed and drizzled with olive oil and lemon juice. The young leaves can be added raw to salads, whilst the adult leaves are most commonly served boiled or steamed, in which case they have a taste and texture similar to spinach.

Beetroot nutrition facts

Raw beetroot is 88% water, 10% carbohydrates, 2% protein, and less than 1% fat (table 1). In a 100 gram amount providing 43 calories, raw beetroot is a rich source (27% of the Daily Value, DV) of folate and a moderate source (16% DV) of manganese, with other nutrients having insignificant content.

Table 1. Beetroot (raw) nutrition facts

[Source: United States Department of Agriculture Agricultural Research Service ⁴]

Benefits of beetroot juice

In the last 20 years or so there has been renewed interest in the potential of inorganic nitrate (NO3-) to control blood pressure in humans ⁵. Dietary inorganic nitrate is absorbed rapidly and completely in the proximal small intestine with 100% bioavailability ⁶. Approximately 25% of the nitrate circulating in the plasma is then concentrated in the salivary glands and secreted into the mouth where around 20% (or ≈ 5 – 8% of intake) is converted to nitrite (NO2-) by commensal bacteria on the tongue and subsequently swallowed ⁷. Upon reaching the stomach the NO2- is either absorbed directly or reduced to nitric oxide (NO) as a result of the acidic environment of the stomach ⁷, ⁸. Endogenously produced NO and NO2- are vasoprotective agents with the ability to increase vasodilation, decrease blood pressure (BP) and improve cardiovascular function ⁹. Reduced endogenous NO production is associated with hypertension ¹⁰ and there is evidence to support the hypothesis that the NO and NO2- produced as a result of dietary NO3- could induce health benefits ¹¹.

In addition, a potent signaling molecule that affects cell function in many body tissues, NO is endogenously produced by synthesizing nitric oxide from l-arginine oxidation. The molecule has important hemodynamic and metabolic functions ¹², ¹³, being a major vasodilator that can increase blood flow to muscles ¹⁴ and promote oxygen transfer in the muscle. Additional physiological benefits of NO include improved mitochondrial efficiency and glucose uptake in muscle ¹⁵ and enhanced muscle contraction and relaxation processes ¹⁶. Other researchers have reported that NO can act as an immunomodulator ¹⁷ and stimulates gene expression and mitochondrial biogenesis ¹⁸. Given the positive effects of beetroot juice, which are induced by means of NO, this supplement has been proposed as part of the therapeutic approach in people with chronic obstructive pulmonary disease ¹⁹, hypertension ²⁰, heart failure ²¹ and insulin resistance ²².

Figure 1. Exogenous (dietary inorganic nitrate [NO₃⁻] in certain vegetables and fruit & nitrite [NO₂⁻]) and endogenous nitric oxide production

Note: A schematic diagram of the physiologic disposition of nitrate, nitrite, and nitric oxide from exogenous (dietary) and endogenous sources. The action of bacterial nitrate reductases on the tongue and mammalian enzymes that have nitrate reductase activity in tissues are noted by the number 1. Bacterial nitrate reductases are noted by the number 2. Mammalian enzymes with nitrite reductase activity are noted by the number 3. The generation of up to ≈70% of systemic nitric oxide is accomplished by endothelial nitric oxide synthase (eNOS), one of 3 members of the NOS family of enzymes, in the vascular endothelium ²³. These enzymes synthesize nitric oxide from the amino acid l-arginine and molecular oxygen to accomplish vasodilation, blood pressure regulation, inhibition of endothelial inflammatory cell recruitment, and platelet aggregation ²⁴. As a result, the normal production of nitric oxide and nitrite and the ability of the endothelium to respond to these species may prevent various types of cardiovascular disease, including hypertension, atherosclerosis, and stroke ²⁵.

[Source ²⁶]

The individual daily intake of dietary nitrate has been estimated to be ≈81–106 mg/d (not including loses from washing, peeling and cooking) in the typical Western diet, with vegetables contributing approximately 80% of this value ²⁷, ²⁸. The vegetables with the highest nitrate contents (>250 mg/ 100 g fresh weight) are celery, cress, chervil, lettuce, red beetroot, spinach and rocket (see Table 3 below) ²⁸. Green leafy vegetables have recently been shown to be among the foods most beneficial in the prevention of coronary heart disease and ischemic stroke ²⁹, ³⁰. This effect has been postulated to be due to the high inorganic NO3- content of these vegetables ³¹, ³², ³³.

Other food sources nitrates and nitrites

Table 2. Nitrate and nitrite contents of edible components of vegetables

Vegetable types and varieties	Nitrite	Nitrate
	mg/100 g fresh weight	mg/100 g fresh weight
Root vegetables
Carrot	0.002–0.023	92–195
Mustard leaf	0.012–0.064	70–95
Green vegetables
Lettuce	0.008–0.215	12.3–267.8
Spinach	0–0.073	23.9–387.2
Cabbage
Chinese cabbage	0–0.065	42.9–161.0
Bok choy	0.009–0.242	102.3–309.8
Cabbage	0–0.041	25.9–125.0
Cole	0.364–0.535	76.6–136.5
Melon
Wax gourd	0.001–0.006	35.8–68.0
Cucumber	0–0.011	1.2–14.3
Nightshade
Eggplant	0.007–0.049	25.0–42.4

[Source ³⁴]

Table 3. Classification of vegetables according to nitrate content

Nitrate content (mg/100 g fresh weight)	Vegetable varieties
Very low, <20	Artichoke, asparagus, broad bean, eggplant, garlic, onion, green bean, mushroom, pea, pepper, potato, summer squash, sweet potato, tomato, watermelon
Low, 20 to <50	Broccoli, carrot, cauliflower, cucumber, pumpkin, chicory
Middle, 50 to <100	Cabbage, dill, turnip, savoy cabbage
High, 100 to <250	Celeriac, Chinese cabbage, endive, fennel, kohlrabi, leek, parsley
Very high, >250	Celery, cress, chervil, lettuce, red beetroot, spinach, rocket (rucola)

[Source ³⁵]

In addition to the provision of nitrate and nitrite by diet or via the oxidation of nitric oxide to nitrite, vascular and gastrointestinal nitric oxide production can be enhanced through various means based on lifestyle and food choices. Physical activity, commensal bacteria, and dietary factors can influence nitric oxide production. Exercise enhances nitric oxide production in vascular endothelium ³⁶ and post-exercise plasma nitrite concentrations have been proposed as an index of exercise capacity ³⁷. In fact, aging is associated with an impaired capacity of the vasculature to increase plasma nitrite during exercise ³⁸. Strikingly, it has been found that dietary nitrate supplementation, at concentrations achievable by vegetable consumption, results in more efficient energy production without increasing lactate concentrations during submaximal exercise ³⁹.

Beetroot is a rich source of dietary NO3- ²⁸ and a number of studies have investigated its potential for reducing blood pressure in humans ¹¹, ⁴⁰, ⁴¹, which appears to be more potent in men.

In addition, beetroot juice contains antioxidants, including betacyanin, which scavenge free radicals and beetroot contains high levels folic acid. Beetroot is particularly rich in inorganic nitrate content (typically ranging from 110 to 3670 mg nitrate/kg) ⁴² and it has therefore been utilized in several studies as a nutritional strategy to test the effects of inorganic nitrate intake on blood pressure. For example, Webb et al. ⁴³ showed in healthy participants that 24 hour after a single dose of 500 mL beetroot juice, systolic and diastolic blood pressure were reduced by 10.4 and 8.0 mm Hg, respectively.

The BP-lowering effects of inorganic nitrate may derive from increased generation of nitric oxide (NO) ⁴⁴, ⁴⁵, a molecule involved in the vasodilation of large arteries and resistance vessels ⁴⁴, ⁴⁵. Reduced nitric oxide (NO) bioavailability has been associated with impairment of endothelial function and increased risk of hypertension and cardiovascular diseases ⁴⁶, ⁴⁷.

Beetroot juice and nitrate salt (sodium nitrate/potassium nitrate) supplementation was tested in 17 studies ⁴⁸. The daily amount of nitrate in the beetroot juice consumed varied between 321–2790 mg. The volume of the beetroot juice drinks ranged from 140 to 500 mL/d and the beetroot juice was given as a concentrated solution in 2 studies ⁴⁹, ⁵⁰. The most common side effect reported in the beetroot juice trials was beeturia (red urine) and red stools ⁴³, ⁵¹. Beetroot juice supplementation were associated with a significant decrease in blood pressure, which may potentially have important implications for the primary and secondary prevention of cardiovascular diseases. A systolic BP reduction of at least 5 mm Hg (as observed here) could decrease the risk of mortality due to stroke by 14% and mortality from cardiovascular diseases by 9% ⁵².

In another systematic review and meta-analysis meta-analysis on the medium-term effects of dietary nitrate supplementation on systolic and diastolic blood pressure in adults involving 13 trials ⁵³. The duration of each intervention ranged from 1 to 6 weeks. Ten trials assessed BP in resting clinic conditions, whereas 24 hour ambulatory and daily home monitorings were used in six and three trials, respectively. Overall, dietary nitrate was associated with a significant decline in systolic BP (-4.1 mmHg) and diastolic BP (-2.0 mmHg). However, the effect was only significant when measured in resting clinical settings as no significant changes in BP were observed using 24-h ambulatory and daily home BP monitorings.

A double-blind, randomized, placebo-controlled, crossover study involving fifteen women and fifteen men ⁵⁴ were randomized to receive 500 g of beetroot and apple juice (72% beetroots and 28% apples) or a placebo juice (apple juice concentrate). Subjects ranged in age from 23 – 68 years. Subjects were generally healthy with none of the male subjects and approximately half of the female subjects not medicated. Individual BP changes from baseline after each treatment showed a drop of 4.6 mmHg with 500 g of beetroot (72% beetroots and 28% apples juice) and 3.4 mmHg with placebo apple juice concentrate at 3-h, 6.2 mmHg and 2.2 mmHg respectively at 6-h and 4.5 mmHg and 2.3 mmHg respectively, at 24 hour. Statistically the 6-h difference was a trend overall, with men showing a difference of −4.7 mmHg, and women a difference of −2.5 mmHg. In conclusion, it was demonstrated here that in free-living people consuming an unrestricted diet and a single dose of 500 g of beetroot and apple juice, a trend to lower blood pressure by 4–5 mmHg at 6-h was observed ⁵⁴.

Beetroot Juice Supplementation on Cardiorespiratory Endurance in Athletes

Cardiorespiratory endurance is defined as a health-related component of physical fitness that relates to the ability of the circulatory and respiratory systems to supply fuel during sustained physical activity and to eliminate fatigue products after supplying fuel ⁵⁵. Cardiorespiratory endurance is a performance factor in all sports in which adenosine triphosphate (ATP) is resynthesized, mainly by aerobic metabolism or oxidative processes that produce energy. In these sports, the expended effort typically lasts longer than five minutes, primarily depending on the metabolic level of the oxidative processes involved ⁵⁶. Factors that limit performance in this type of endurance patterns include maximum oxygen uptake (VO2max), ventilatory thresholds (first and second ventilatory threshold) and energy efficiency or economy ⁵⁶, ⁵⁷, ⁵⁸, ⁵⁹.

According to the American College of Sports Medicine ⁶⁰, adequate selection of nutrients and supplements, adjusting intake according to the exercise performed, is necessary for optimal performance in athletes. However, not all supplements have been shown to produce a positive effect on performance. The Australian Institute of Sport ⁶¹, classified supplements to which athletes have access, with the goal of categorizing nutritional supplements based on the level of evidence for impact on an athlete’s performance (Table 4). However, the effectiveness of supplements also depends on dosage and type of effort, because the potential ergogenic effect may differ by the specific type of sport ⁶².

Table 4. Classification of nutritional supplements, based on performance effect. Adapted from Australian Institute of Sport ⁶¹ and Burke ⁶³

Category	Sub-Categories	Supplements
High level of evidence	Will improve athletic performance with adequate dosing and specific types of effort	β-alanine
		Sodium bicarbonate
		Caffeine
		Creatinine
		Beetroot juice
Moderate level of evidence	May improve performance, under specific dosing and effort conditions, although additional research is needed	Fish oils
		Carnitine
		Curcumin
		Glucosamine
		Glutamine
		HMB
		Quercetin
		Vitamins C and E
		Tart cherry juice
Low level of evidence	No demonstrated beneficial effects	Supplements not found in other categories
Prohibited supplements	May result in positive doping tests and therefore are prohibited	Substances on the list published annually by the World Anti-Doping Agency (WADA)

[Source ⁶⁴]

Beetroot juice is used as a supplement because of its high inorganic nitrate (NO3−) content, a compound found naturally in vegetables. Athletes use nutritional supplementation to enhance the effects of training and achieve improvements in their athletic performance. Beetroot juice increases levels of nitric oxide (NO), which serves multiple functions related to increased blood flow, gas exchange, mitochondrial biogenesis and efficiency, and strengthening of muscle contraction. These biomarker improvements indicate that supplementation with beetroot juice could have ergogenic (performance enhancing) effects on cardiorespiratory endurance that would benefit athletic performance.

Nitric oxide (NO) induces several physiological mechanisms that influences O2 utilization during contraction skeletal muscle (Domínguez R, Cuenca E, Maté-Muñoz JL, et al. Effects of Beetroot Juice Supplementation on Cardiorespiratory Endurance in Athletes. A Systematic Review. Nutrients. 2017;9(1):43. doi:10.3390/nu9010043. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5295087/)). Physiological mechanisms for NO2− reduction are facilitated by hypoxic conditions, therefore, nitric oxide (NO) (vasodilator) is produced in those parts of muscle that are consuming or in need of more O2. This mechanism would allow local blood flow to adapt to O2 requirement providing within skeletal muscle an adequate homogeneous distribution. This physiological response could be positive in terms of muscle function, although it would not explain a reduced O2 cost during exercise ⁶⁵. Another probable mechanism is related to nitrite (NO2−) and nitric oxide (NO) as regulators of cellular O2 utilization ⁶⁵.

Peak NO2− concentration in blood is obtained within 2–3 h of NO3− supplementation ⁶⁶ and the ergogenic effects of supplementation with beetroot juice can be observed at 150 min after ingestion ⁶⁷. Oral antiseptic rinses should not be taken with beetroot juice supplementation, as these can prevent the desired increase in NO2− levels after NO3− ingestion ⁶⁸. Although the majority of studies show ergogenic effects of beetroot juice at a supplementation dose of 6–8 mmol NO3−, it is possible that high performance athletes might require a slightly higher dose. For example, in high performance kayakers, the ergogenic effect of supplementation with beetroot juice was 1.7% in a 500-m test after ingestion of 9.6 mmol of NO3− but a 4.8 mmol dose did not significantly improve results in a 1000-m test ⁶⁹.

Acute supplementation with beetroot juice may have an ergogenic effect on reducing VO2 at less than or equal to VO2max intensity, while improving the relationship between watts required and VO2 level, mechanisms that make it possible to enable increase time-to-exhaustion at less than or equal to VO2max intensity. In addition to improving efficiency and performance in various time trials or increasing time-to-exhaustion at submaximal intensities, chronic supplementation with beetroot juice may improve cardiorespiratory performance at the anaerobic threshold and VO2max intensities.

However, not all studies show a positive effect to acute beetroot supplementation indicating that the efficacy of acute nitrate supplementation will be attributed to several factors such as the age, diet, physiological and training status, and other parameters as the intensity, duration, endurance modality and environment conditions ⁷⁰. Although most of the studies determine a supplementation dose of 6–8 mmol NO3−, it is unclear that this supplementation dose can be effective to improve cardiorespiratory performance in sports modalities such as kayaking or rowing. The dose should possibly be increased in sports modalities where muscular groups of upper limbs are implicated. Endurance athletes should take the dose of NO3−, approximately 90 min before the competition without oral antiseptic. Acute supplementation with beetroot juice is not sufficient to induce mitochondrial biogenesis, suggesting that mitochondrial adaptations could only occur after longer supplementation protocols. In chronic supplementations with beetroot juice, it appears that the benefits in cardiorespiratory performance might be produced in longer intake protocols of about six days ⁷¹, ⁷². Time-to-exhaustion at several intensities (between 70% and 100% VO2max, VT1) and the load at anaerobic threshold could be enhanced while aerobic energy expenditure could be diminished. Longer-term beetroot supplementation (15 or more days) could be effective, although it would be necessary other studies analyzing the mitochondrial biogenesis to corroborate whether mitochondrial adaptations depend on endurance training and/or beetroot supplementation. To date, this assumption is unknown.

The scientific literature shows discrepancies regarding the improvement of the cardiorespiratory performance induced by the supplementation of beetroot juice under hypoxic conditions. NO3− could mitigate the ergolytic effects of hypoxia on cardiorespiratory in endurance athletes ⁷³.

Apparently, the effects of supplementation with beetroot juice might not have a positive interaction with caffeine supplementation, mitigating the effects of beetroot juice intake on cardiorespiratory performance, however, more work is needed to confirm the results of these investigations because the number of studies analyzing the effects of the combination of beetroot juice with other supplements, such as caffeine, is limited ⁶⁴.

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