By Atreyi Mukherji, MD, MPH, FRCPC

Private Practice, Integrative Internal Medicine & Infectious Diseases, Stoney Creek, Ontario

Dr. Mukherji reports no financial relationships relevant to this field of study.

SYNOPSIS: The long-term consumption of a healthy diet, such as the Mediterranean diet or low-fat/high complex carbohydrate diets, may exert a protective effect on the development of type 2 diabetes by changing the gut microbiota, increasing the abundance of Roseburia genera and Faecalibacterium prausnitzii, respectively.

SOURCE: Haro C, Montes-Borrego M, Rangel-Zuniga OA, et al. Two healthy diets modulate gut microbial community improving insulin sensitivity in a human obese population. J Clin Endocrinol Metab 2016;101:233-242.

SUMMARY POINTS

  • Gut microbiota are a complex integrated organ that modulate host metabolism and extraction of nutrients, and help control energy balance.
  • Changes in gut microbiota composition have been linked to the pathophysiology of obesity.
  • The long-term (one-year) consumption of the Mediterranean diet and low-fat/high complex carbohydrate diet (LFHCC) both led to changes in microbiota and improvement in insulin resistance.
  • The LFHCC diet increased Prevotella genera and decreased Roseburia genera, whereas the Mediterranean diet decreased the Prevotella and increased the Roseburia and Oscillospira genera.
  • Although further study is required, this preliminary study raises an interesting hypothesis that changes in microbiota may be one mechanism by which diets can be a useful therapeutic tool for preventing chronic diseases, such as type 2 diabetes.

The objective of the Haro et al trial was to study the changes in gut microbiota after one year of consumption of two healthy diets: the Mediterranean diet (MedDiet) or the low-fat, high complex carbohydrate (LFHCC) diet in 20 obese patients with coronary heart disease (CHD). The study was conducted in a subgroup of the CORDIOPREV study, an ongoing prospective, randomized, open, controlled trial in patients with stable CHD (event-free for six months prior to enrollment). Patients ranged from 20-74 years of age and were excluded if they had severe CHD with life expectancy of less than five years. All patients were on standardized treatments for CHD. The MedDiet composition was 35% fat with 22% monounsaturated fat and the LFHCC diet contained 28% fat with 12% monounsaturated fat. To ensure consistency of diet, all patients in the MedDiet group were provided olive oil. Food packs, including low-fat foods (cereal, biscuits, pasta) of similar costs, were provided to patients in the low-fat group. Plasma and fecal samples were analyzed using various molecular technologies to assess change in microbiota and metabolomic analysis.

The main findings of the study were changes in microbiota. The LFHCC diet increased Prevotella genera and decreased the Roseburia genera, whereas the MedDiet decreased the Prevotella and increased the Roseburia and Oscillospira genera (P = 0.028, 0.002, and 0.016, respectively). Parabacteroides distasonis (P = 0.025) and Faecalibacterium prausnitzii (P = 0.020) were more abundant after consumption of the MedDiet and LFHCC diet, respectively. The increase in Roseburia in the MedDiet group and the increase in F. prausnitzii in the LFHCC diet group also were accompanied by an increase in insulin sensitivity index for both diets (P = 0.019 and P = 0.005, respectively) when measured by oral glucose tolerance test performed at baseline and after one year of dietary intervention. The main metabolic changes noted in the fecal analysis were the profiles of the amino acids, peptides, and sphingolipid metabolism, which could be linked to changes in the gut microbiota. (See Table 1.)

Table 1: Changes in Gut Microbiota

Bacteria

Low-fat/High Complex Carbohydrate Diet

Mediterranean Diet

 

Increased

Decreased

No change

Increased

Decreased

No change

Parabacteroides distasonis

     

+

(P = 0.025)

   

Faecalibacterium prausnitzii

+

(P = 0.20)

         

Oscillospora

   

+

+

(P = 0.001)

   

Roseburia

   

+

+

(P = 0.017)

   

Prevotella

Time X diet interaction
P = 0.028

+

     

+

 

COMMENTARY

This preliminary study showed that long-term (one-year) consumption of two heathy diets (MedDiet and LFHCC diet) was associated with changes in gut microbiota population in the colon, as well as changes in some aspects of the metabolic profile. An improvement in insulin sensitivity also was observed, as measured by the glucose tolerance test in the LHFCC diet, suggesting that these diet patterns may have a protective effect on development of type 2 diabetes.

Roseburia genera and F. prausnitzii are butyrate-producing bacteria that are found to be low in patients with type 2 diabetes. Roseburia could play an important role in gut health10 and is known to have an anti-inflammatory effect on the gut.10-12 An antimicrobial effect through inhibiting Bacillus subtilus in the colon is another mechanism by which Roseburia genera have been shown to affect the gut microbial population in the colon.13 F. prausnitzii, along with other butyrate-producing bacteria, previously have been shown to increase in people with metabolic syndrome on the MedDiet, but not the LFHCC diet.14 The increase in Prevotella in the LFHCC diet is thought to be an adaptation of the microbiota to enhance extraction of calories from carbohydrates that escape digestion in the small intestine and are fermented in the gut.15 This also is born out in a study with Prevotella abundance with long-term diets rich in carbohydrates.16

In conclusion, the observations in this present study findings are provocative and suggest the development of a new hypothesis about changes in gut microbiota being one mechanism by which dietary interventions could be a therapeutic tool for chronic disease. Further studies are required to assess the effect of these findings in clinical practice. Perhaps a potential exists for a more customized (personalized) approach to the implementation of dietary interventions based on the disease and the individual patient. In the interim, clinicians should continue to utilize evidence-based dietary interventions such as the MedDiet for chronic disease, including cardiovascular disease and breast cancer.

REFERENCES

  1. Turnbaugh PJ, Ley RE, Mahowald MA, et al. An obesity-associated gut microbiome with increased capacity for energy harvest. Nature 2006;444:1027-1031.
  2. Tremaroli V, Kovatcheva-Datchary P, Backhed F. A role for the gut microbiota in energy harvesting? Gut 2010;59:1589-1590.
  3. Caesar R, Fåk F, Bäckhed F. Effects of gut microbiota on obesity and atherosclerosis via modulation of inflammation and lipid metabolism. J Intern Med 2010;268:320-328.
  4. Bays HE, González-Campoy JM, Bray GA, et al. Pathogenic potential of adipose tissue and metabolic consequences of adipocyte hypertrophy and increased visceral adiposity. Expert Rev Cardiovasc Ther 2008;6:343-368.
  5. Cani PD, Delzenne NM, Amar J, Burcelin R. Role of gut microflora in the development of obesity and insulin resistance following high fat diet feeding. Pathol Biol (Paris) 2008;56:305-309.
  6. Ley RE. Obesity and the human microbiome. Curr Opin Gastroenterol 2010;26:5-11.
  7. Blaser MJ, Falkow S. What are the consequences of the disappearing human microbiota? Nat Rev Microbiol 2009;7:887-894.
  8. Ghanim H, Sia CL, Korzeniewski K, et al. A resveratrol and polyphenol preparation suppresses oxidative and inflammatory stress response to a high-fat, high-carbohydrate meal. J Clin Endocrinol Metab 2011;96:1409-1414.
  9. Ghanim H, Sia CL, Upadhyay M ,et al. Orange juice neutralizes the proinflammatory effect of a high-fat, high-carbohydrate meal and prevents endotoxin increase and Toll-like receptor expression. Am J Clin Nutr 2010;91:940-949
  10. Karlsson FH, Tremaroli V, Nookaew I, et al. Gut metagenome in European women with normal, impaired and diabetic glucose control. Nature 2013;498:99-103.
  11. Qin J, LiY, CaiZ, et al. A metagenome-wide association study of gut microbiota in type 2 diabetes. Nature 2012;490:55-60.
  12. Aminov RI, Walker AW, Duncan SH, et al. Molecular diversity, cultivation, and improved detection by fluorescent in situ hybridization of a dominant group of human gut bacteria related to Roseburia spp.or Eubacterium rectale. Appl Environ Microbiol 2006;72:6371-6376.
  13. Hatziioanou D, Mayer MJ, Duncan SH, et al. A representative of the dominant human colonic Firmicutes, Roseburia faecis M72/1, forms a novel bacteriocin-like substance. Anaerobe 2013;23:5-8.
  14. Haro C, Garcia-Carpintero S, Alcala-Diaz JF, et al. The gut microbial community in metabolic syndrome patients is modified by diet. J Nutr Biochem 2016;27:27-31.
  15. Flint HJ, Bayer EA, Rincon MT, et al. Polysaccharide utilization by gut bacteria: Potential for new insights from genomic analysis. Nat Rev Microbiol 2008;6:121-131.
  16. Wu GD, Chen J, Hoffmann C, et al. Linking long-term dietary patterns with gut microbial enterotypes. Science 2011;334:105-108.