PUBLIC HEALTH
BACTERIA: THE GOOD, THE BAD AND THE UGLY More and more research is delving into the area of gut bacteria and its impact on health and disease, but whatâ&#x20AC;&#x2122;s good bacteria and whatâ&#x20AC;&#x2122;s bad and are probiotics the answer? As humans are born, their individual gut microbiota develops and is affected by the birthing process and early life. For example, whether an infant is breastfed or formula-fed, or whether the mother has taken antibiotics during pregnancy or lactation, it has been shown to result in a different balance of microbiota in the infantâ&#x20AC;&#x2122;s gut.3,4 Furthermore, differences in gut microbiota have been identified between those born via the vaginal canal or by caesarean section, though arguably other factors may be driving these differences, as critically discussed by Stinson et al.5 A multicentre European study by Fellani et al, found that breastfed infants had significantly higher proportions of Bifidobacteria (40.7% vs 29.2%, P<0.001) than formula-fed infants.6 Additionally, this study found that country of origin effected gut microbiota balance post weaning: infants from northern European countries had a higher proportion of Bifidobacteria, whereas infants from southern European countries had higher proportions of Bacteroides and Lactobacilli.6 It could be considered that the types of foods an infant is weaned on and their overall dietary intake will help determine which bacteria dominate for life. It is the foods eaten long term, along with other factors, such as environmental temperature and individual physiology,2 that play key roles in gut microbiota development. Once developed, the microbiota of an individual is quite stable for life. However, there are some factors that can lead to gut flora changes, for
example, antibiotic use, ageing, changes in diet such as drastic calorie changes, or altering macronutrient balance. Also, high-fibre diets are associated with increased diversity of microbiota.7 TYPES OF GUT BACTERIA
Numerous types have been identified in the human gut. However, the main two phyla are the Bacteroidetes and the Firmicutes.2 These two phyla differ in the efficiency of their metabolism. For example, a study by Turnbaugh et al showed that obese individuals and mice with a higher proportion of Firmicutes bacteria had a higher capacity to harvest energy.8 The study also showed that when the microbiota was transplanted from obese mice to germ-free mice, they rapidly gained fat mass, despite a decrease in food consumption. In another study, the abundance of Bacteroidetes was shown to increase as obese individuals lost weight on different low-calorie diets with a correlation that was significant.9 With obesity being a challenging and multifaceted health concern, it is important to address gut microbiota, as it may be a contributing factor, together with genetics, diet and lifestyle. Throughout the human gastrointestinal tract, the microbiota increases in both number and diversity, being affected by factors such as pH, transit time and nutrient availability.10 As the colon has the slowest transit time, a favourable pH and has plentiful available nutrients, the collection of microbiota is most varied and populated here. The intestinal microbiota has several beneficial roles:
Priya Tew Freelance Dietitian, Dietitian UK Priya runs Dietitian UK, a freelance dietetic service that specialises in social media and media work, consultancy for food companies and private patient work.
Naomi Leppitt Dietitian Naomi is newly qualified, working as a Community Dietitian in Windsor.
REFERENCES Please visit the Subscriber zone at NHDmag.com
www.NHDmag.com October 2019 - Issue 148
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