Profile of subjects
The initial data in this study were male adults aged between 18-21 years, with a body weight of 45-112 kg, height of 159-180 cm and the BMI distribution is presented in (Fig 1). Fig 1 shows that 6.67% of subjects are underweight, 13.33% are overweight, 6.67% are obese and 73.33% have a normal BMI. BMI variations were primarily influenced by dietary intake and eating frequency. Secondary data indicate that overweight and obese subjects consumed more food and ate more frequently than those with normal BMI. Additionally, these subjects were less physically active, leading to higher calorie intake than expenditure. Excess calorie intake is converted into fat through lipogenesis and stored in adipocytes. Without adequate physical activity, this process repeats, contributing to weight gain. The human body’s evolutionary tendency to store fat as an energy reserve, coupled with modern food abundance, increases the prevalence of overweight and obesity
(Bray and Bouchard, 2020;
Hall and Guo, 2017). Furthermore, sedentary lifestyles exacerbate energy imbalance by reducing calorie expenditure, while diets high in sugar, fat and simple carbohydrates further elevate fat storage risks
(Hill and Wyatt, 2005).
Profile of fecal microflora
Fecal total plate count (TPC) measures viable bacteria in fecal samples, reflecting gut microbial load, including probiotics and pathogens. Lactic acid bacteria (LAB) and Bifidobacteria play a critical role in gut health by balancing harmful bacteria and supporting digestion and immunity. Fig 2 presents TPC, LAB and Bifidobacteria levels in the study subjects’ feces, showing variations likely influenced by diet.
The findings suggest that diverse dietary sources impact TPC levels, including fruits, vegetables, carbohydrates, proteins, fats and fermented milk. Diets high in animal-based protein and fat may favor species like Bacteroides, which efficiently metabolize proteins and lipids
(Rinninella et al., 2019). These results highlight the influence of dietary composition on gut microbiota. While TPC offers valuable insights into microbial burden, further studies are needed to identify specific dietary patterns or nutrients that significantly impact TPC and gut health. Understanding these relationships will help optimize gut microbiota for better digestion, immunity and overall health.
Fecal counts of LAB and Bifidobacteria reflect the abundance of lactic acid-producing bacteria crucial for gut health. These microbes convert carbohydrates into lactic acid, maintaining an acidic pH that inhibits pathogen growth
(Sarkar and Mandal, 2016). Their abundance is influenced by dietary factors, particularly high-fiber diets rich in fruits, vegetables, legumes, whole grains and fermented foods. Prebiotics, such as non-digestible carbohydrates, support their growth by promoting lactic acid and SCFA production. Multivariate analysis showed that frequent consumption of high-fiber foods correlated with higher fecal counts of LAB and Bifidobacteria. Fermented foods, like yoghurt and kefir, directly introduce LAB, enhancing their populations. Bifidobacteria, key anaerobic bacteria, support the immune system, maintain the microbiome and aid digestion
(Slavin, 2013).
Salmonella typhimurium is prevented and the intestinal tract is repaired by a consortium of probiotic fermented milk that contains Bifidobacterium sp. and
Lactobacillus acidophilus (Rathod et al., 2025). Diets rich in fiber and fermented foods are essential for sustaining healthy LAB and Bifidobacteria populations and promoting gut health
(Zheng et al., 2024).
Fecal short-chain fatty acids of subjects
The gut microbiota is pivotal in digesting complex carbohydrates and fibers, fermented into SCFAs like acetate, propionate and butyrate (Table 1). The range of the amount of each of these SCFAs is slightly different from the normal SCFAs range in adults, namely acetic acid, propionic acid and butyric acid in adult feces. However, the average value is generally in the range of acetic acid, around 40-60 µmol/g, propionic acid around 10-20 µmol/g and butyric acid around 5-15 µmol/g feces. However, the total SCFAs range in the study ranged from 44.42-132.83 µmol/g, almost the same as the normal total SCFAs range in adults, which is 50-150 µmol/g feces. Acetic acid is generally the most dominant SCFAs, followed by propionate and butyrate
(den Besten et al., 2013). Similar results were found in the subjects of the present study. The composition of SCFAs can change based on factors such as diet, fiber consumption, gut health status and microbiota composition.
According to
Koh et al., (2016), SCFAs, primarily acetate, propionate and butyrate, are metabolites produced by gut microbiota fermentation of dietary fibers, including LAB. LAB primarily produces lactic acid through the fermentation of carbohydrates and this lactate can serve as a substrate for other gut microbes to produce SCFAs, particularly butyrate. This process often involves cross-feeding interactions within the gut microbiota
(Louis and Flint, 2009). Bifidobacteria are known for their beneficial effects on human health, including their ability to produce SCFAs. Bifidobacteria produce SCFAs primarily through the fermentation of dietary fibers and prebiotics, such as inulin, oligofructose and other prebiotics and resistant starches as substrates for fermentation. The fermentation results in the production of lactate, which can be further converted to acetate
(Louis and Flint, 2009). Short-chain fatty acids (SCFAs), such as acetate, propionate and butyrate, are produced by various microbes other than LAB and Bifidobacteria. These microbes are TPCs that play an essential role in the gut ecosystem and produce SCFAs that support gut health and overall human metabolism. Adequate production of SCFAs is associated with numerous health benefits, including reduced risk of colorectal cancer, improved gut health and better metabolic profiles. Conversely, reduced SCFAs production has been linked to inflammatory diseases, metabolic syndrome and other health issues
(Blaak et al., 2020).
The blood total cholesterol, glucose and uric acid of subject
The relationship between blood cholesterol, glucose, uric acid and gut microflora is a growing research focus. Fig 3 shows blood cholesterol, glucose and uric acid levels in non-fasting male subjects, with 93.33% having normal cholesterol. Bivariate analysis found no correlation between cholesterol and gut microflora, likely due to similar diets and environments. At ages 18-21, hormonal peaks, such as testosterone, influence efficient cholesterol metabolism, which increases HDL and reduces total cholesterol
(Robinson et al., 2021). Probiotics, particularly Bifidobacteria, may lower cholesterol by binding it in the intestines and promoting fecal excretion
(Brown et al., 1999; Pato et al., 2004, 2005). Soluble fibers in the dietary food bind to bile acids in the intestine, preventing their reabsorption. Since bile acids are made from cholesterol, their increased excretion forces the liver to use more cholesterol to synthesize new bile acids, thereby reducing circulating LDL-cholesterol levels. The viscous gel formed by soluble fibers can trap cholesterol and other lipids, reducing their absorption in the small intestine
(Gunness and Gidley, 2010). These findings underscore the potential of probiotics in managing cholesterol and highlight the need for further exploration of gut microbiome-metabolism interactions.
Consuming meals high in fiber, such as soluble fibers and resistant starch, is crucial to increasing the production of SCFA. Additionally, fermented foods may provide healthy bacteria that support the synthesis of SCFAs. The gut microbiota ferments complex carbohydrates and fibers into SCFAs, such as acetate, propionate and butyrate, influencing blood glucose regulation. All subjects had normal blood glucose levels (<140 mg/dL), but bivariate analysis showed no correlation between blood glucose and fecal microbes (TPC, LAB and Bifidobacteria). Other gut microbes, including Bacteroides,
Akkermansia muciniphila and
Faecalibacterium prausnitzii, regulate glucose metabolism through SCFA production and improving insulin sensitivity
(Cani et al., 2007; Duncan et al., 2009; Everard et al., 2013; Qin et al., 2012). Regarding uric acid, 70% of subjects had normal levels, while 30% had elevated levels, likely due to high-purine diets. Bivariate analysis showed a correlation between Bifidobacteria and uric acid levels, suggesting their role in uric acid metabolism. Bifidobacteria produce enzymes that degrade uric acid into allantoin, preventing crystal formation
(Cao et al., 2017; Wang et al., 2021). SCFA levels in this study were within normal ranges, with acetic acid (71.89 µmol/g), propionic acid (3.99 µmol/g) and butyric acid (3.47 µmol/g). SCFA production is influenced by fiber intake, gut health and microbiota composition, with LAB and Bifidobacteria contributing to butyrate and other SCFAs
(Louis and Flint, 2009). SCFAs benefit health by reducing inflammation and improving metabolism
(Blaak et al., 2020; Lopez-Siles et al., 2017). Additionally,
Akkermansia muciniphila and Ruminococcus spp. produce acetate and propionate, enhancing metabolic health
(Derrien et al., 2010; Flint et al., 2012).