An avo a day...
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23rd Dec, 2020Quick read

Avocados

 

An avo a day keeps the gut doctor away

 

New evidence suggests eating avocados as part of the daily diet can help to improve metabolic and gastrointestinal health (1). 

The research, published in The Journal of Nutrition, suggests daily avocado consumption can improve the composition and metabolic function of intestinal microbiota in overweight and obese individuals (1). 

Avocados are rich in dietary fibre and monounsaturated fatty acids (MUFAs), nutrients that have been independently connected to the gastrointestinal microbiota and metabolic health benefits (1). Previous studies have found regular avocado consumption is associated with lower body weight (2,3) and can improve satiety and blood lipid concentrations (4,5,6,7). However, the effects on the composition and metabolic function of the intestinal microbiota are not known.

In this 3 month trial, 163 adults between 25 and 45 years who were overweight or obese (BMI ≥ 25 kg/m2) were randomised to an intervention group that received a daily meal with one fresh avocado or a control group that received an isocaloric meal without avocado. Apart from the daily meal replacements, participants consumed their regular diet. Faecal samples were collected throughout the study and analysed for bacterial composition and faecal metabolites, including short-chain fatty acids (SCFAs), bile acids and fatty acid concentration. 

Avocado consumption increased microbiota diversity and enriched Faecalibacterium, Lachnospira, and Alistipes between 26% and 65% compared with the control group.

Faecalibacterium and Lachnospira have the enzymatic capability to utilise fibre to form SCFAs (8,9), and in the current study, faecal acetate concentrations were 18% greater in the avocado group as compared with the control group (P = 0.01) at the end of the intervention.

The avocado group had enhanced fatty secretion and concentrations of stearic acid and palmitic acid were 70% and 98% higher, respectively than the control group. 

Despite reporting higher total fat intake, the avocado group had diminished faecal bile acid concentrations, including 91% and 57% lower cholic acid and chenodeoxycholic acid concentrations, respectively. Concentrations of the secondary bile acids, deoxycholic acid and lithocholic acid, were also lower than in the control group. 

Gastrointestinal microorganisms, as well as dietary fat and fibre intake, are implicated in bile acid regulation. Soluble dietary fibre increases faecal fat excretion, while high-MUFA intake can improve microbial diversity and reduce secondary bile acids (10,11,12)

Conversely, saturated fat intake reduces microbial diversity (13) and increases bile acid synthesis (14), resulting in subsequent intestinal inflammation, and other potential health sequelae. Bile acids not only regulate the digestion of lipids but also act as signalling molecules to regulate systemic metabolism and insulin secretion. Greater bile acid concentrations are associated with obesity and diabetes (15,16).

The current study has several limitations, including reliance on self-administered questionnaires and recall bias and a short follow-up period. Further, participants were overweight or obese adults but without physician-diagnosed chronic conditions and, as such, findings cannot be extrapolated to adults with chronic disease or who are within a healthy weight range. Nevertheless, the results provide valuable insight regarding the impact of avocado intake on the composition and metabolic function of intestinal microbiota. Future trials are needed to investigate the benefits of avocado intake in at-risk populations with metabolic and other chronic diseases. 

References
1Thompson SV, Bailey MA, Taylor AM, Kaczmarek JL, Mysonhimer AR, Edwards CG, Reeser GE, Burd NA, Khan NA, Holscher HD. Avocado consumption alters gastrointestinal bacteria abundance and microbial metabolite concentrations among adults with overweight or obesity: a randomized controlled trial. The Journal of Nutrition. 2020 Aug 17.
2Dreher ML, Davenport AJ. Hass avocado composition and potential health effects. Critical reviews in food science and nutrition. 2013 Jan 1;53(7):738-50.
3Heskey C, Oda K, Sabaté J. Avocado Intake, and Longitudinal Weight and Body Mass Index Changes in an Adult Cohort. Nutrients. 2019 Mar;11(3):691.
4Peou S, Milliard-Hasting B, Shah SA. Impact of avocado-enriched diets on plasma lipoproteins: A meta-analysis. Journal of Clinical Lipidology. 2016 Jan 1;10(1):161-71.
5Wien M, Haddad E, Oda K, Sabaté J. A randomized 3x3 crossover study to evaluate the effect of Hass avocado intake on post-ingestive satiety, glucose and insulin levels, and subsequent energy intake in overweight adults. Nutrition Journal. 2013 Dec;12(1):1-9.
6Zhu L, Huang Y, Edirisinghe I, Park E, Burton-Freeman B. Using the Avocado to Test the Satiety Effects of a Fat-Fiber Combination in Place of Carbohydrate Energy in a Breakfast Meal in Overweight and Obese Men and Women: A Randomized Clinical Trial. Nutrients. 2019 May;11(5):952.
7Carranza-Madrigal J, Herrera-Abarca JE, Alvizouri-Muñoz M, Alvarado-Jimenez MD, Chavez-Carbajal F. Effects of a vegetarian diet vs. a vegetarian diet enriched with avocado in hypercholesterolemic patients. Archives of Medical Research. 1997;28(4):537.
8Lopez-Siles M, Khan TM, Duncan SH, Harmsen HJ, Garcia-Gil LJ, Flint HJ. Cultured representatives of two major phylogroups of human colonic Faecalibacterium prausnitzii can utilize pectin, uronic acids, and host-derived substrates for growth. Applied and Environmental Microbiology. 2012 Jan 15;78(2):420-8.
9Bang SJ, Kim G, Lim MY, Song EJ, Jung DH, Kum JS, Nam YD, Park CS, Seo DH. The influence of in vitro pectin fermentation on the human fecal microbiome. Amb Express. 2018 Dec;8(1):1-9.
10Kristensen M, Jensen MG, Aarestrup J, Petersen KE, Søndergaard L, Mikkelsen MS, Astrup A. Flaxseed dietary fibers lower cholesterol and increase fecal fat excretion, but magnitude of effect depend on food type. Nutrition & Metabolism. 2012 Dec 1;9(1):8.
11Mujico JR, Baccan GC, Gheorghe A, Díaz LE, Marcos A. Changes in gut microbiota due to supplemented fatty acids in diet-induced obese mice. British Journal of Nutrition. 2013 Aug;110(4):711-20.
12Holscher HD, Guetterman HM, Swanson KS, An R, Matthan NR, Lichtenstein AH, Novotny JA, Baer DJ. Walnut consumption alters the gastrointestinal microbiota, microbially derived secondary bile acids, and health markers in healthy adults: a randomized controlled trial. The Journal of Nutrition. 2018 Jun 1;148(6):861-7.
13De Wit N, Derrien M, Bosch-Vermeulen H, Oosterink E, Keshtkar S, Duval C, de Vogel-van den Bosch J, Kleerebezem M, Müller M, van der Meer R. Saturated fat stimulates obesity and hepatic steatosis and affects gut microbiota composition by an enhanced overflow of dietary fat to the distal intestine. American Journal of Physiology-Gastrointestinal and Liver Physiology. 2012 Sep 1;303(5):G589-99.
14Di Ciaula A, Garruti G, Lunardi Baccetto R, Molina-Molina E, Bonfrate L, Wang DQ, Portincasa P. Bile acid physiology. Annals of Hepatology. 2018 Apr 20;16(1):4-14.
15Ma H, Patti ME. Bile acids, obesity, and the metabolic syndrome. Best practice & research Clinical Gastroenterology. 2014 Aug 1;28(4):573-83.
16Chávez-Talavera O, Tailleux A, Lefebvre P, Staels B. Bile acid control of metabolism and inflammation in obesity, type 2 diabetes, dyslipidemia, and nonalcoholic fatty liver disease. Gastroenterology. 2017 May 1;152(7):1679-94.