Specific dietary modifications have been an area of focus to treat a myriad of diseases such as obesity and IBS. However, the individual response to dietary interventions can vary greatly, partly due to our unique gut microbiota compositions.
Personalized nutrition is a promising area of research that aims to predict physiological response to dietary interventions based on a person’s gut microbial composition, yet few studies have been conducted in humans. Besides this, diet, genetics, hygiene, geographical location, exercise, and antibiotic use affect microbiota composition making it a complex field of study. Obesity and irritable bowel syndrome (IBS) represent the best examples of recent research conducted in the area of personalized nutrition.
Despite a lack of a clear definition of a “healthy microbiota”, general characteristics include stability and resistance to change which enables protection against pathogens and necessary metabolic and immune functions to be carried out. Researchers believe that the gut microbiota contributes to both obesity and IBS, though the exact mechanisms are unknown. For example, the gut microbiota has been shown to affect inflammatory responses, triglyceride synthesis and blood sugar levels in obese patients. On the other hand, studies have reported IBS patients to present instability and a lower abundance of Bifidobacterium in response to dietary change compared to healthy controls.
A review analyzed recent clinical trials and predictive modeling analyses that used the gut microbiota to predict weight loss in obese and overweight patients, glycemic response in healthy subjects and the effect of a low FODMAP diet in IBS patients.
The most significant study was performed in 800 healthy participants whose blood glucose was monitored for one week after consuming the first meal of the day which consisted of a standardized meal plan that contained 50g of carbohydrates. Elevated postprandial glycemic response positively correlated with individuals who had higher levels of specific groups of bacteria such as Proteobacteria, Enterobacteriaceae and Actinobacteria, whereas Clostridia and Prevotellaceae were associated with a lower postprandial glycemic response in participants. Interestingly, gut microbiota composition was more predictive of a person’s post-meal blood sugar response than calorie or carbohydrate content alone.
Two non-randomized controlled trials aimed to use baseline microbiota to predict weight loss in obese patients prior to a low calorie dietary intervention. One reported an association between greater baseline gene richness and reduced fat tissue and systemic inflammation. The other study showed that elevated baseline abundance of Akkermansia muciniphila, which has been shown to improve host metabolism, was associated with improved insulin sensitivity. On the other hand, a modeling study predicted that the likelihood of weight loss in 78 obese adults consuming a high-fiber diet was related to the amount of the group of bacteria Firmicutes prior to a high fiber diet intervention.
Conversely, the evidence is inconsistent to support the use of gut microbiota composition to accurately predict responses to a low FODMAP diet in IBS patients suggesting other metabolic factors may be at play in this condition. Moreover, the authors found several limitations in the studies analyzed such as differences in study design, length, microbial sampling and quantification, and varying adhesion to a strictly low FODMAP diet which all affect data interpretation. In fact, many researchers believe that the low FODMAP diet should only be implemented short-term because it may reduce beneficial bacteria.
Although some evidence exists, the authors conclude there is still inconsistent evidence to support the existence of signature gut microbiota compositions that accurately predict clinical response to dietary interventions in obese and IBS patients. Personalized nutrition studies remain challenging to test due to several factors that affect gut microbiota composition as well as analysis technology limitations. Though personalized nutrition research is still in its infancy, these studies pave the way for future research that could improve the patients’ response to therapeutic diets.
Biesiekierski JR, Jalanka J, Staudacher HM. Can Gut Microbiota Composition Predict Response to Dietary Treatments?. Nutrients. 2019; 11(5). doi:10.3390/nu11051134.