Dietary patterns and gut health 

The gastrointestinal (GI) microbiome consists of a complex group of microorganisms. An individual’s specific gut microbiota is influenced by diet, age, family genetics, and environmental exposure. When microorganisms are commensal or mutualistic, they play a supportive role in nutrient metabolism, immunity, and endocrine function.

Key metabolites from these microbiota can also help lower chronic disease risk. It is well known that encouraging foods with prebiotics and probiotics can promote gut health in our patients. Recent research demonstrates that dietary patterns can also contribute.    

Microbiota: The good and the bad

Metabolites from food and microbiota diversity determine balance in the gut microbiome.  In a state of symbiosis, microbes present are rich in diversity. This helps to maintain and promote the function of the intestinal mucosal barrier.  Examples of beneficial metabolites and bacteria include:  

• Short-chain fatty acids (SCFAs)  
• Polyphenol metabolites  
• Bifidobacterium  
• Lactobacillus  

In comparison, a greater presence of pathogenic microbes upsets this balance, allows for an influx of harmful bacteria across this barrier, and results in a state of dysbiosis. A shift to this type of environment may show an increase in:  

• Secondary bile acids   
• Trimethylamine N-oxide  
• Proteolytic metabolites  
• Firmicutes  

Foods consumed can positively or negatively impact the gut environment, and certain dietary patterns should be considered when providing patients with individualized nutrition goals.   

Dietary patterns and gut impact

Mediterranean diet   

The Mediterranean diet is a balanced eating approach that focuses on including whole foods and limiting processed foods. Research suggests numerous health benefits from this diet for various chronic conditions, such as diabetes, cardiovascular disease, and early stages of chronic kidney disease.  

Includes:    

This meal pattern endorses a variety of fruits and vegetables, legumes, nuts and seeds, whole grains, lean protein, low-fat or fat-free dairy, and olive oil. Processed foods high in saturated fat, simple sugars, and refined grains are discouraged.   

Impact on gut health:

Due to the wide variety of nutrient-dense foods, the Mediterranean diet supports a diverse and rich microbiota environment with an increased presence of SCFAs and polyphenol metabolites. Given the promotion of gut symbiosis, this diet pattern has been shown to have a positive impact on inflammation, glycemic response, weight management, and immunity. 

Western diet  

The Western diet has evolved over the years to encompass an imbalanced approach of heavily processed food choices. Negative health effects have been associated with this type of diet because of poor diet quality alongside selections high in saturated fat, sodium, and carbohydrates.   

Includes:  

Foods such as red meat, refined grains, high-fat dairy options, beverages with added sugar and alcohol, and ultra-processed foods are often chosen as part of the Western diet. Overall, the diet quality is poor and lacking in nutrient-rich foods like fruits and vegetables.   

Impact on gut health:  

With limited whole foods and fiber, bacterial richness and diversity are limited, resulting in a decrease of SCFAs and polyphenol metabolites. Instead, the accumulation of secondary bile acids and proteolytic metabolites can weaken the intestinal barrier, resulting in increased susceptibility to intestinal permeability, inflammation, obesity, and chronic disease.    

Ketogenic diet  

Initially used for the treatment of epilepsy, the ketogenic diet has more recently grown in popularity as a diet approach for other disease states and weight management. With limited carbohydrate intake, the body shifts into ketosis requiring the use of fat for energy. Research tends to vary on the use of this diet with other disease states.  Most experts recommend against following this diet long-term (unless medically needed) to prevent the risk of nutrient, vitamin, and mineral deficiencies.   

Includes:    

There are different variations of the ketogenic diet, with low carbohydrate, high protein, and high fat being the most consistent macronutrient recommendations. In general, meat, fish, eggs, dairy, nuts and seeds, healthy oils, non-starchy vegetables, and berries can be consumed, with servings determined by patient-specific nutrition goals.   

Impact on gut health:  

Changes in macronutrient contribution with the ketogenic diet have been found to impact the human gut microbiota. One change that occurs is a loss of microbiota count and abundance. With this microbiota alteration, a negative effect has been demonstrated with SCFA production, colonic health, adipose inflammation, and insulin resistance. More research in this area is needed to further determine the short and long-term effects of the ketogenic diet on gut health.   

Vegetarian diet  

The vegetarian diet is a plant-based diet that can offer many health benefits. An individual’s nutrition needs can be easily met by selecting a variety of different foods. Numerous health benefits have been associated with the vegetarian diet because it includes sources that are rich in fiber, vitamins, and minerals and lower in unsaturated fat.  

Includes:   

Depending on the type of vegetarian diet, some individuals may consume fish, eggs, and dairy. More specific plant-based selections with this eating pattern are fruits, vegetables, legumes, nuts, plant-based meat alternatives, and whole grains. The need for supplementation with vitamin B12, calcium, iron, and zinc should be considered on an individual basis.   

Impact on gut health:  

A plant-based approach with diet can result in a more diverse and rich microbiome. Specific examples seen are an increase in SCFAs metabolites, Bifidobacterium, and Lactobacillus.  Health benefits seen with this diet approach include an environment that is anti-inflammatory, anti-pathogenic, and supportive of cardiovascular health.   

Dietitians On Demand is a nationwide staffing and recruiting company for registered dietitians, specializing in short-term, temporary, and permanent-hire positions in acute care, long-term care, and food service. We’re dedicated to dietitians and helping them enhance their practice and excel in the workplace. Check out our job openings, request your coverage, or visit our store today!

References

Hughes R, Holscheer H. The Intestinal Microbiome. In: Health Professional’s Guide to Gastrointestinal Nutrition. 2nd edition. United States: American of Nutrition and Dietetics; 2023:224-253.  

Piccioni A, Covino M, Candelli M, et al. How do diet patterns, single foods, prebiotics and probiotics impact gut microbiota? Microbiol Res. 2023;14:390-408. doi: 10.3390/microbiolres14010030  

U.S. News & World Report. The Ketogenic Diet: A Guide for Beginners. https://health.usnews.com/best-diet/keto-diet.  Accessed October 12, 2024.  

Rew L, Harris M, Goldie J. The ketogenic diet: its impact on human gut microbiota and potential consequent health outcomes: a systemic literature review. Gastroenterol Hepatol Bed Bench. 2022;15(4):326-242. doi: 10.22037/ghfbb.v15i4.2600  

U.S. News & World Report. 6 Types of Vegetarian Diets Explained. https://health.usnews.com/wellness/food/articles/types-of-vegetarian-diets. Accessed October 14, 2024.  

Tomova A, Burkovsky I, Rembert E, et al. The effects of vegetarian and vegan diets on gut microbiota. Front Nutr. 2019;6(47):1-10. doi: 10.3389/fnut.2019.00047