Our microbiome is formed through childhood and reaches its adult composition by the age of two. It develops and adapts with us throughout our lives and alters its own composition in response to our changing environmental conditions [1].

Several environmental factors influence the microbiome, but dietary intake may be one of the most immediate and controllable factors [2].

While the microbiota has been shown to be relatively stable over time, changes related to weight loss and diet composition continue to subtly alter the composition and relative abundance of our gut bacteria.

Therefore, the diet has a significant impact on the development of our gut microbiome throughout adulthood [3].

This can perhaps be seen best in the elderly population where changes in the microbiome are typically associated with a decrease in diversity.

This was originally thought to be part of the aging process but has since been associated with dietary changes often seen in the elderly population.

Studies have shown that elderly people consuming a moderate fat and high fiber diet had a much greater bacterial diversity in their digestive tract than elderly people consuming high fat and low fiber diet [3].

The high fiber diet has been shown to be beneficial for adults of all ages because it provides prebiotics from foods like bananas, onions, asparagus, and wheat bran. Prebiotics are “food” for probiotics; they feed the good bacteria already in your gut, helping them grow.

In addition, fiber increases transit time which reduces the time that potentially unhealthy bacteria are in contact with the walls of the intestines; it essentially moves them through faster.

While the fiber content is important, the macronutrient composition of the diet may have a greater impact in determining the composition of the microbiota.

Resistant starch and oligosaccharides present in high fiber diets are utilized in the large intestine by bacteria to produce Short Chain Fatty Acids (SCFAs).

These have been shown to play a role outside of the gut by providing energy, preventing overgrowth of pathogenic bacteria, enhancing insulin sensitivity, and decreasing inflammation.

They also play a role in producing B vitamins like vitamin K and folate and may play a role in appetite regulation.

It has been suggested that the high fat, low fiber Western Diet has created a widespread microbial imbalance that has contributed to the increase of many lifestyle-related conditions such as Metabolic Syndrome and Obesity [4].

Therefore, consuming a diet that minimizes processed and high-fat foods, particularly animal fats, and maximizes the intake of fruits, vegetables, and whole grains can significantly impact our microbial diversity and therefore our overall health and well-being, not just today but throughout our lives.


  1. Ley, R.E. et al. Evolution of mammals and their gut microbes. Science.2008: 320;1647–1651.

  2. David LA, Maurice CF, Carmody RN, et al. Diet rapidly and reproducibly alters the human gut microbiome. Nature. 2014;505(7484):559-563. doi:10.1038/nature12820.

  3. Voreades N, Kozil A, Weir TL. Diet and the development of the human intestinal microbiome. Frontiers in Microbiology. 2014;5:494. doi:10.3389/fmicb.2014.00494.

  4. Jeffery IB, O’Toole PW. Diet-Microbiota Interactions and Their Implications for Healthy Living. Nutrients. 2013;5(1):234-252. doi:10.3390/nu5010234.

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