Smoothies and the Gut Microbiome

The University of Minnesota recently conducted an interesting study in which 34 subjects provided detailed dietary records of all food and beverages consumed daily for 17 days and daily fecal samples used for microbiome sampling (also for 17 days)(Johnson et al., 2019). The researchers correlated daily microbiome samplings with personalized diet records, showing that diet is indeed associated with gut microbiome flora and diversity in humans.

The main findings of the study were:

  1. Daily microbiome variation is related to food choices, but not to conventional nutrients.
  2. Daily microbiome variation depends on at least two days of dietary history.
  3. Similar foods have different effects on different people’s microbiomes.


One of the things I find most interesting about this study was that unbeknownst to the researchers until after study completion, 2 of the 34 study participants (#s 11 and 12, student volunteers at the U of MN) reported diets consisting primarily of “a nutritional meal replacement beverage in 4 different flavors (Soylent, Rosa Foods).”

Soylent is a plant-based (vegan) meal replacement shake with 20g of protein and a full spectrum of vitamins, minerals, and nutrients (ingredient list below). Though Soylent beverages do not include sugar, I would not typically recommend them to my clients (or use them myself) due to their inclusion of maltodextrin – a lab-manufactured artificial sweetener that can be highly inflammatory, hard on the kidneys/liver to filter, & highly activate the reward system- to induce addiction responses (Lauds et al., 2019; Arnold & Chassaing 2018). 

Despite the inclusion of the GI-stressor maltodextrin, the research found the two participants whose diets consisted mostly of Soylent still had beneficial microbial diversity in their gut microbiome with good flora (though an n of two lacks statistical power, so more follow-up research is certainly warranted). 

SOYLENT INGREDIENTS: Soy Protein Isolate; Vegetable Oil (Canola And/Or Sunflower); Maltodextrin; Isomaltulose; Soluble Corn Fiber; Modified Food Starch; Vitamin And Mineral Premix; Cellulose; Natural Flavors; Soy Lecithin; Salt; Xanthan Gum; Sucralose.

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