Page 46 - Today's Dietitian (March 2020)

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A 2011 review by Kau and colleagues can extract additional calories from Role of RDs
suggests that it may not be a specific food. A 2006 study by Turnbaugh and Although much of the research on the
type of bacteria that’s the cause of colleagues found that the balance of gut microbiome and nutritional status
malnutrition, but rather an interaction the two dominant phyla, Bacteroidetes is in its infancy, the potential therapeu-
between these microbes and certain and Firmicutes, was different in obese tic benefits of probiotics are of great
environmental triggers within subjects than in lean subjects. This interest. At this time, there are no spe-
a susceptible host that becomes resulted in an increased capacity to cific evidence-based recommendations
inflammatory, triggering malnutrition harvest more calories from the diet, for the strain or dosage of probiot-
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and other related illnesses. Further causing weight gain and increased fat ics to use to treat malnutrition or obe-
research is needed to identify which deposition. 32 sity. Nevertheless, RDs can make a few
specific bacterial strains increase It’s also unclear whether changes in recommendations.
susceptibility to malnutrition. At this diet over the last 50 years—the overall The first is to suggest the use of pre-
time, there’s an understanding that increase of calorie and refined carbo- biotics for those struggling with diges-
the gut microbiome is just one piece hydrate intake—has modified the gut tive concerns or bacterial imbalance.
of a complex puzzle also involving the microbiome in a way that increases risk These would include fermentable fibers
environment, the host, and diet. of obesity. It’s clear that diet influences such as inulin, galactooligosaccharides,
the composition of the gut microbiome. fructooligosaccharides, and lactulose.
Obesity and the Microbiome A 2013 study by Cotillard and colleagues These foods have been found to shift the
Obesity is a serious health concern found that a calorie-controlled weight composition of the gut microbiome to
affecting almost 40% of the population loss diet increased microbial gene rich- encourage the growth of the most ben-
in the United States, according to ness and lowered systemic inflamma- eficial species. A 2007 study found that
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the Centers for Disease Control and tion. This research suggests that excess when mice on a high-fat diet were given
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Prevention. There are many causes of calories could be an underlying cause prebiotics, the amount of bifidobacte-
obesity, but recent research has found of the low diversity of gut microbiota in ria increased and inflammation to the
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that the microbiome may play a role in obese individuals. Other studies have digestive tract decreased. Foods such
increasing risk. found that the macronutrient composi- as dandelion greens, garlic, and chicory
It’s believed that the gut microbi- tion of the diet is correlated with specific root are high in these beneficial prebi-
ome influences obesity in several ways, bacterial strains, meaning diet likely has otic fibers. These types of foods may be
but the research in this area remains an impact on shaping the microbiome. considered for those with digestive con-
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complex. The first theory is that exces- Given the theory that bacterial cerns who aren’t sensitive to ferment-
sive energy is harvested by gut micro- imbalance and a lack of diversity may able carbohydrates.
biomes, resulting in an increased lead to an increased risk of obesity, The research on specific probiotic
production of short-chain fatty acids. the question arises as to whether strains to improve nutritional
These fatty acids, in turn, promote fat supplementation with probiotics could status still is emerging, so evidence-
deposition, lead to an overexpression reduce obesity. Although this research based recommendations for dietary
of obesity-related genes, or cause an is still in its infancy, a handful of supplements can’t be made. But
increase in the endotoxin lipopolysac- animal studies have shown interesting fermented foods, such as sauerkraut,
charide, which triggers inflammation results. A 2006 study of obese mice kimchi, or yogurt, may be considered as
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and obesity. A combination of these found that Lactobacillus rhamnosus a helpful source of beneficial bacteria
factors working together may increase PL60 reduced weight and adipose for those interested in supporting their
the risk of obesity for people with a spe- tissue without calorie reduction. microbiomes and immune systems. 38
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cific microbiome profile. The exact pro- Another similar study found that a It’s clear that the microbiome has a
file of the “obese” microbiome still is different bacterial strain, Lactobacillus significant influence on human health,
unknown, but there are a handful of paracasei, also decreased fat storage well-being, and nutritional status.
studies with interesting results. by modulating the effects of ANGPTL4, But the relationship is complex and
In a 2009 study by Turnbaugh and which controls triglyceride deposition difficult to discern due to the variety
colleagues, researchers evaluated the into fat cells. These results seem to be of bacterial strains, dietary patterns,
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gut microbiomes of 154 lean and obese strain specific, and there’s no current and environmental conditions. At this
mono- and dizygotic twin pairs and research that has identified which time, there’s simply not enough evidence
their mothers. The microbiomes were particular strains may help reduce to make specific recommendations on
found to be similar among family mem- obesity in humans. Given the diversity strains or dosages. n
bers, but variations among individu- of the microbiome among individuals,
als were identified. Subjects who were research is still many years away from Ana Gabriela Reisdorf, MS, RD, CDE, is
obese had phylum-level changes to their identifying strains to decrease obesity a Franklin, Tennessee–based nutrition
microbiomes and less bacterial diversity across all population groups. consultant and writer.
compared with lean subjects.
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Another theory about how the For references, view this article on our
microbiome influences obesity is that website at www.TodaysDietitian.com.
there are certain types of bacteria that

46 TODAY’S DIETITIAN • MARCH 2020