When we’re faced with the question of which diet is best for our personal health, the answer isn’t easy. The individual response to dietary interventions varies greatly, and the gut microbiota likely plays a major role. However, several factors influence gut microbiota composition such as genetics, long-term dietary habits, hygiene, geographical location, exercise, as well as antibiotic and probiotic use making it a difficult area to study. Personalized nutrition studies aim to predict clinical response to dietary interventions based on the microbial composition, yet few studies have been conducted in humans.
Obesity and irritable bowel syndrome (IBS) represent the best examples of preliminary work conducted in this area of research. More than a third of the global population is overweight or obese, whereas IBS affects 11%. Although the exact mechanisms are not fully understood, researchers believe that the gut microbiota contributes to both health conditions. For example, the gut microbiota has been shown to affect inflammatory responses, triglyceride synthesis and blood sugar levels in obese patients.
The role individual biological and lifestyle factors play in blood sugar control and response to dietary treatments have gained a lot of attention. A recent review analyzed 8 studies that investigated how the gut microbiota composition possibly affects the response to dietary interventions. Specifically, the dietary interventions aimed to improve weight loss or blood sugar levels after consuming a meal in obese patients or reduce symptoms in IBS patients.
The most significant study was performed in 800 participants whose blood glucose was monitored following a low carbohydrate diet (50g carbohydrates/ day) for one week. Elevated post-meal blood sugar levels positively correlated with individuals who had higher levels of specific groups of bacteria such as Proteobacteria, Enterobacteriaceae and Actinobacteria. Interestingly, gut microbiota composition was more predictive of a person’s post-meal blood sugar response than the intake of calorie or carbohydrate alone.
Conversely, the evidence is inconsistent to support the use of ones microbiota composition to accurately predict responses to a low FODMAP diet in IBS patients. A low FODMAP diet restricts the intake of specific fermentable carbohydrates (i.e., oligo-, di-, mono-saccharides and polyols) in the hopes to reduce symptoms such as gas, diarrhea, and constipation. No specific groups of bacteria were consistently found in participants who responded to the diet vs non-responders, suggesting other metabolic factors may be at play in this condition.
As these results show, studies on personalized nutrition are difficult to conduct. Research in personalized nutrition is still in its infancy. However, it is an increasingly important area of research that may one day help us planning better nutritional interventions for patients to better respond to.