It is also well-known, that the gut microbiota plays an imperative role in human health. The gut microbiota plays a very strong role in the regulation of the metabolic and immune system. (Wang et al.) When we think about this fact we understand quickly, how important a balanced composition of our gut microbiota is. And when we talk about gut microbiota we have to know the intrinsic and extrinsic aspects shaping our microbial features. Especially environmental factors like diets, health condition and lifestyle are having a strong influence on the gut microbiota. Changes and the composition of our diet is known to modulate the metabolic function of our gut bacteria rapidly. (Wang et al.)

Dysbiosis of the gut microbiota is often seen with decreased bacterial richness and diversity, as well as a disturbed compositional balance between commensal and putatively pathogenic species. Dysbiosis is linked to enterobacteria-dependent disorders like allergic reaction, depression, hypertension, diabetes mellitus and inflammatory bowel disease. (Wang et al.)

Red beetroot (Beta vulgaris L.) is rich in phytochemicals like fiber, polyphenols and betalains. The main betalain in red beetroot is betanin, a betacyanin. The gut microbiota produces enzymes like ß-glucosidases and glycoside hydrolases, which can metabolize phytochemicals into SCFAs. Consuming red beetroot has been shown to regulate the gut microbiota metabolism and the SCFA production. As especially bacteria like Bifidobacterium and Bacteroides produce the specific enzymes to metabolize betalains, the response to red beetroot may depend on the gut enterotype. (Ko et al.)

Enterotypes are defined by different clusters of the human gut microbiota. Those are categorized based on core bacteria like Bifidobacterium, Faecalibacterium, Bacteroides, etc. Recent research implicaits that individuals may show different metabolic responses to the same diet, because of a different enterotype. This hows again, how important a personalised nutrition in healthy individuals and also in therapeutic settings is. (Ko et al.)

It’s well known, that the gut microbiota has a huge influence on the communication between GI tract and the central nervous system through biochemical metabolites like serotonin, SCFAs and tryptophan. Lower levels of SCFAs has been observed in individuals with depressions (Verma et al.). Existing literature also suggests, that the gut micriobiota may also influence the hypothalamiy-pituarity-adrenal (HPA) axis. The HPA-axis coordinates the adaptive stress response and an impaired function seems to lead to anxietyand depressive disorders, often associated with elevated levels of cortisol and inflammatory mediators (Simpson et al.).

In the past years several studies aimed to investigate the influence of red beetroot on the gut microbiota.

Wang et al. investigated 2022 gut microbial changes, following a 14-day period of red beetroot consumption, in healthy humans. 18 healthy participants (13 females, 5 males) were recruited. Two weeks before the study initiation, participants were asked to avoid the consumption of betalain-containing food. During the 14-days intervention period the participants consumed 30mL of beetroot concentrate everyday. Stool samples were collected at the baseline (BL), after 3 days (D3) and 14 days (D14). Anthropometric measurements were performed at the initial visit. The study indicated no significant changes in alpha- and beta-diversities between BSL, D3, D14 samples. But there were marked changes observed in abundance of specific taxa (e.g. Romboutsia and Bacteroidales) and also the enrichment of A. munciniphila (inversely associates with obesity, inflammation and metabolic disorders) and a decrease in B. fragilis (potentially enterotoxigenic leading to inflammatory diarrhea) popultaion.

They also observed an increased production of total SCFAs, especially (iso)butyric acid in stools. Surono et al. investigated the effect of red beetroot on the gut microbiota of prediabetic indonesian individuals during weight loss. A randomized double-blind cross-over trial was conducted with 15 (6 males, 9 females) prediabetic (fasting blood glucose of 100–125 mg/dL; random blood glucose of 140–199 mg/dL; BMI 25–27 kg/m2) volunteers.

They were provided with:

1.) 50% taro flour + 50% wheat flour

2.) these products + probiotic L. plantarum

3.) the products of 1.) with beetroot adsorbed for a period of 2 weeks with 2 weeks wash-out in between. Stool and blood samples were collected before and after two-week interventions for each type of treatment. The total study duration was 14 weeks.

The results showed a highly interindividual variability in the response of the gut microbiota. In the end the individual could be divided into those with a more resilient microbiota and those with a microbiota more prone to nutritional changes.

Ko et al. investigates the effects of red beet powder (RP) and betanin production based on enterotype. Therefore they used a gastrointestinal digestion and fecal fermentation model. For the enterotype analysis they recruited 30 healthy Korean participants (17 men and 13 women). They could divide the participants in the subgroups of predominating enterotype:

Phocaicole, Prevotella and Bifidobacterium. Feces were collected from one representative subject of each subgroup and fermented with red beet powder or betanin pigment. The effect RP and BP as prebiotics on the gut microbiota depended on the enterotype of the 3 selected subjects. Only in the S3-Bifidobacterium sample a significant change in the richness of microbial taxa was detected. Also the S3-Bifidobacterium cluster showed a different trend in gut microbiota changes compared to the other samples.

Each enterotype (with and withoutRP/BP fermentation) showed a different metabolic activity related to SCFA production. The greatest increase in SCFA production was found in the S3-Bifidobacterium sample, whereas the S2-Prevotella sample showed a smaller change in SCFAs. The results of this study indicate that RP and BP have enterotype-specific responses in the gut microbiota and SCFA production.

Adekolurejo et al. performed a study regarding the problem of microbiota disruption due to weaning. 48 piglets were randomly allocated to one of four diets for 14 days, after a period of 28 days of weaning. There was a basal control-diet (con), one with 300mg/kg zinc oxid (ZNO), and two different diets containing Red beetroot. RB2 and RB4 were obtained by adding 2 (20g/kg) and 4% (40g/kg) pulverized whole red beetroot to the basal diet.

The results showed the potential of beet root to modulate the gut microbiota (of weaned pigs) by increasing species richness and enhancing lipid metabolism.

Calvani et al. discovered beneficial effects of beetroot juice intake on the gut microbiota in adults with long covid. They included 25 participants in their study (15 juice, 10 placebo), after supplementation for two weeks the participants who ingested beetroot juice had a greater abundance of bacteria with well-known beneficial effects compared with the placebo group.

Several studies aimed to investigate the influence of red beetroot on our gut microbiota and in conclusion on our health. All in all they couldn’t show significant changes in alpha- and beta-diversity. But significant changes in specific taxa were discovered, as well as an increase in SCFA production. It was also shown, that human microbiota can be divided in different enterotypes, which seem to react more or less sensitive to the ingestion of red beetroot. The highest increase in SCFA production after red beetroot consumption was observed in the Bifidobacterium enterotype, which seemed to be the most sensitive enterotype to red beetroot consumption. Unfortunately the studies show multiple limitations, as they all have a small number of participants and just short-term results were observed.

The studies showed the potential of red beetroot consumption by increasing SCFA production and by a beneficial modulation the gut microbiota. Both may lead to variable health benefits and might prevent the host of inflammatory diseases like inflammatory bowel disease and syndrome, as well as of depression, diabetes mellitus and a huge amount of different metabolic disorders. Further research needs to investigate long-term effects of red beetroot on the gut microbiota (especially on different enterotypes) and the physiological consequences for the gut and host organism.